PROCEDURES FOR EVALUATING PERFORMANCE OF WASTEWATER TREATMENT PLANTS A Manual Prepared for Environmental Protection Agency Office of Water Programs Washington, D.C. Under Contract No. 68-01-0107 by URS RESEARCH COMPANY Environmental Systems Division •••Qj San Mateo, California 94402 ------- ABSTRACT This manual establishes a procedure for the evaluation of the performance of wastewater treatment plants. Jt furnishes the informa- tion necessary to identify and classify vari- ous types of treatment plants. This manual details the processes commonly utilized in wastewater treatment. The common problems affecting plant operation are identified and described. The description first states the problem and then identifies the indicators of the problem, which are listed in order of their relative importance. The type of lab- oratory tests which should be performed are listed, along with other evaluation tech- niques. Finally, operational, maintenance, or other corrective measures are listed in order of their effectiveness. References are given for an in depth review of unit and process operation and for addi- tional information (where applicable). A glossary is also included. 111 ------- CONTENTS Section Page INTRODUCTION 1 I PLANT EVALUATION PROCEDURES 3 Preparation for Site Visit 5 On-Site Inspection 7 Procedures for Problem Evaluation 9 Total Plant Evaluation 10 II WASTEWATER TREATMENT SYSTEMS OPERATIONAL DATA 17 Pretreatment and Primary Treatment Data 19 Secondary Treatment Data 21 Secondary Treatment Data - Activated Sludge Process 23 Advanced Waste Treatment Data 25 Solids Treatment Data 27 Common Solids Treatment Data 29 III SAMPLING AND TESTING Introduction 31 General 31 The Sampling Program 32 IV COMMON OPERATING PROBLEMS AND SUGGESTED SOLUTIONS Introduction 41 Pretreatment 49 Primary Treatment 59 Secondary Treatment 64 Advanced Treatment 82 Disinfection 89 Metering 109 Solids Handling 111 iv ------- Appendix Page A CLASSIFICATION OF WASTEWATER TREATMENT PLANTS A-l Classification by Function A-l Operator Classification A-2 Location of Temperature Zones in the United States A-3 Common Processes and Operational Units A-4 B PERSONNEL REQUIREMENTS B-l General Skills B-l Manpower and Work Scheduling B-2 C PRIMARY TREATMENT MODE (Background Information) C-l General C-l Pretreatment C-3 Chemical Precipitation C-10 Chlorination C-10 D SECONDARY TREATMENT D-l General Background of a Biological Reactor D-3 Trickling Filters D-4 Activated Sludge D-6 Stabilization Ponds and Lagoons D-8 Intermittent Sand Filters D-9 Secondary Clarification D-10 Package Aeration Plants D-ll E ADVANCED WASTEWATER TREATMENT E-l General Background E-l Chemical/Physical Treatment E-2 Carbon Adsorption E-3 Ammonia Stripping E-4 Electrodialysis E-5 Reverse Osmosis E-6 ------- Appendix Page F SOLIDS TREATMENT AND DISPOSAL F-l General Background F-l Treatment of Sludge F-2 Sludge Thickening F-3 Sludge Conditioning F-4 Sludge Dewatering F-5 Disposal of Sludge F-6 G CONTROL AND METERING SYSTEMS G-l Control Systems G-l Flow Measurement G-2 H MAINTENANCE DATA SYSTEM H-l J REFERENCES J-l K GLOSSARY .. K-l VI ------- INTRODUCTION ------- INTRODUCTION ------- INTRODUCTION The purpose of this manual is to provide technical guidance for persons conducting evaluations of wastewater treatment plants and serve as a model which can be used by state regulatory agencies. It furnishes the information needed to facilitate identification and classification of various types of treatment plants. It also details the processes commonly utilized in wastewater treatment. The common prob- lems affecting plant operation are identified and described. Several aspects of each problem are covered: exactly what is the problem; how it is detected, what are the possible causes, and what solutions are feasible. It is assumed that the manual user has a general familiarity with both typical wastewater treatment plant design and operation, as well as a tech- nical background in sanitary engineering. In addition, the user should complete a training program which includes the evaluation of a series of wastewater treatment plants using this manual and other evaluation methods. As wastewater treatment technology is changing rapidly, this manual will be reviewed and updated routinely in order to maintain its effective- ness as a plant evaluation tool. MANUAL FORMAT In order for the manual to be an effective tool in the evaluation of wastewater treatment plants, familiarization with its structure as well as its advantages and limitations is necessary. Like any other tool which is being used for a particular purpose, the manual can be utilized best by familiarization with.: • TABLE OF CONTENTS - so material can be quickly and easily located. • GLOSSARY - to understand the manual terminology. • 'PLANT OPERATIONAL DATA - to become familiar with operational parameters, loading rates., and support systems used with each unit operation. 1 ------- • PLANT CLASSIFICATIONS - to give background information on the schemes, their processes, and their relation to a treatment system. • PLANT EVALUATION PROCEDURES - to become familiar with the steps required in performing a plant evaluation. • DATA FOR EVALUATION - an in-depth review of the data required in conducting a plant evaluation. This manual contains four principal sections and several supplemental appendixes: SECTION I Procedures for Plant Evaluation. This section of the manual contains a step-by-step procedure for organizing information before the plant is visited and for performing the on-site evaluation. SECTION II Wastewater Treatment Systems Operational Data. This section of the manual contains data on the common operating parameters, loading rates, waste products accumulated from process operation, and the support systems which are used in the various unit operations and processes. SECTION III Sampling and Testing. This section of the manual contains information on the type of sampling to be done, location of sampling points, and analyses to be performed for the particular treatment system. SECTION IV Common Operating Problems and Suggested Solutions. This section of the manual is to properly identify problems which frequently occur in wastewater treat- ment plants and delineate which corrective measures should be implemented. APPENDIX A These appendixes supply the background information through on the various treatment systems; how they are APPENDIX G classified, personnel requirements, maintenance data programs, and information on the various unit operations. ------- PROCEDURES ------- I PLANT EVALUATION PROCEDURES ------- Section I PLANT EVALUATION PROCEDURES The evaluation of a wastewater treatment plant consists of an in-depth analysis of the following basic elements: • Plant performance • Operational problems • Operating personnel • Sampling and testing program • Laboratory facilities • Maintenance data program. Information and data for each element are gathered and analyzed in four interrelated phases, namely 1. Preparation for site visit 2. On-site inspection 3. Problem identification 4. Total plant evaluation. The estimated evaluation time will depend on the size and complexity of the plant, the amount of preparation on the part of the investigator(s), and the willingness of the plant personnel to cooperate with the investigator(s). For planning purposes the following table gives values which can be used for the initial evaluation. The estimate of the times required to perform a treatment plant evaluation will vary with the complexity of the treatment facility and other factors; this variation could be as great as 50 percent. ------- TREATMENT PLANT EVALUATION PERIOD (days) Preliminary Preparation On-Site Investigation • Visual Inspection • Record Analysis • Problem Evaluation and Solution Written Report 1 1/4 1/4 1 1 1/2 Plant Size (MGD) 10 1 : 1/2 2* J 0 to 3 1 100 Lj to 2^ 1 to l£ l\ to 4 0 to 4 1 Total Days (maximum) 13 ------- PREPARATION FOR SITE VISIT Preparation for the on-site inspection should include compilation and review of information which provides a description of the plant's physical setting, plant design details, plant operating personnel, and any available performance records, previous inspection reports, compliance orders, etc. Reference material relevant to the type of plant being evalu- ated should also be reviewed (see Section II and the Appendixes). The following are specific steps suggested for use in preparation for the on-site visit: 1. Compile and Review Information on Plant's Physical Setting Information describing the physical location of the plant will be required in the evaluation. The information should include the following: (a) Classification of Treatment System • Type of plant (see Appendix A) • Contributory population (domestic, industrial, etc.) • Wastewater system (sanitary, combined, etc.) • Geographic-climatic effects (see Appendix A) to determine if extreme geographic-climatic areas could have an effect on plant performance. This should include both extremes of temperature and precipitation • Determine, if possible, the characteristics of the plant's influent and effluent. This should include both values of the parameters measured by the plant (BODg, pH, 001} temperature, etc.), and flow quantity and variations with time. (b) Identification of Discharge Requirements For a particular plant location, this might consist of allowable COD, pH, BOD,-, etc. , or any special controlling conditions such as a minimum DO and chlorine residuals. If the official data are not readily available from the plant, then try contacting local and/or state health departments and state, regional, and municipal pollutional control agencies. These agencies may be able to supply the needed information. These data should then be compared to the matrix, Table A-2 of Appendix A, which contains expected effluent quality criteria for various treatment systems. ------- 2. Compile and Review Information Describing the Plant and Staff This should be accomplished in advance of the plant visit, recognizing that most state agencies will have some sort of records and previous evaluations which can be used as a comparison between the past, existing, and optimum operation of the plant. The information required to make this comparison includes: • Size of plant (design, average daily flows, peak flows) • Type of unit operations • Historical operating data • Size of staff, their qualifications, and distri- butions of time spent between unit operations • Review all relevant plant documents such as design drawings, operating manuals for various pieces of major equipment, and summary (or monthly) operating reports. This information should be compared with sections of the manual or other sources which give information on the following: • Wastewater treatment systems operational data (use design specifications, where available, or see Section II of this manual) • Personnel requirements (see Appendix B) • Classification of wastewater treatment plants (see Appendix A). 3. Prepare a Pre-Visit Evaluation Data Sheet Data will be needed prior to the evaluation to insure adequate data- gathering at the time of the on-site visit. The pre-visit evaluation guide should include a summary of all background information. ------- ON-SITE INSPECTION* The inspection of the plant should be accomplished in several phases with each phase being progressively more detailed. The visit(s) would typically consist of two phases: Phase One—a general orientation and overview of the plant and its operation, including: • Meet initially with plant engineer or chief operator. Have him describe the plant and its principal operating charac- teristics, on a schematic basis (this and the following steps are to help orient you to the plant, but also to give you an indication of how well the staff understands the system). • Interview plant staff members, starting with plant super- intendent and other supervisory personnel and working progressively through the appropriate operating personnel. • Determine routine plant performance and compare this with design performance and norms section of the manual (see matrix, Table A-2, Appendix A). Phase Two—problem identification with an evaluation as to effect on overall plant performance. This phase also includes the pro cedure for laboratory evaluation. .^ tf&U&UM X*^ Problem identification begins wifrfa k tour of the facility./ Have the plant engineer or operator give you a complete tour of the facilities. Watch for and inquire about: • Excessive particles and/or floe flowing over overflow weirs • Excessive grease and scum buildup • Any unusual equipment such as special pumps, chemical feeders, temporary construction on structures or other jury-rigged systems which are being used to correct problems (or possibly causing them) • Evidence of flow in by-pass channel to parallel units because problems have come up in normal operating units * Always contact the plant manager in advance to set up an appointment; avoid ill-will from arriving unannounced. ------- DDE • Excessive odors • Abnormal color of wastewater in various process stages. If any special plant modifications were made, determine: • Purpose • Physical makeup • Effect on the other treatment processes by comparing old operational data with data after modification. REVIEW RECORDS In general, all records should be analyzed and compared with the information in the manual and/or other sources for consistency, method of calculation and to verify that recorded values are within the range recommended by this manual or other sources. The following records should be reviewed: FLOW Hydraulic' data are reviewed for: • Consistency with the design flow and with present population served • Over- and under-loading of the various treatment units. • Meter calibration UNIT OPERATIONAL DATA (BOD, COD, Suspended Solids, etc.) are reviewed for: • Consistency with design specification and values indicated in the manual or other sources • Extreme values for the daily flows. -^ POWER CONSUMPTION records should be reviewed for values above or below normal. These records would tend to indicate the following: • Operating heads lower than the pump's rating • Specific gravity or viscosity of liquids being pumped is too high. POWER CONSUMPTION AND FLOW RECORDS. Analyses of the FLOW data in combination with POWER might indicate the following: • Output of each pump separately and pumps collectively • Unusual operating conditions which are in effect or have occurred • Changes in efficiency of pumps by comparison of gallons pumped/ kilowatt hour over an extended period of time. ------- * MAINTENANCE DATA . The maintenance program is usually a good indi- cator of operational quality; this can be indicated by checking: • Manufacturer's maintenance schedule for components • Type of routine being used for maintenance scheduling (as compared with Appendix H) • Personnel qualifications for the type of maintenance work being performed. PROCEDURES FOR PROBLEM EVALUATION In general, the problems detailed in the manual are those most commonly encountered. However, these procedures can be used for any type of problem evaluation. The f j.rst step in problem evaluation is to deter- mine if the plant is meeting design performance standards by comparing its effluent quality and overall removal efficiencies with those specified by the design (if design specifications are not available, compare the plant's performance against the guidelines given, see Appendix A). If the plant does not routinely meet performance specifications, it will be neces- sary to determine whether the deficiency is due to problems wtiich fall into two categories: PROBLEM DEFINED—If the treatment plant operator has defined the problem: a. Verify general area of problems, such as related to process, maintenance or design, sampling, etc. b. For common process problems, refer to that section of the manual dealing with the problem (see Section IV). c. Develop sampling and testing program to provide additional data, if needed (see Section III). PROBLEM UNSPECIFIED—If effluent discharge does not meet required standards and no definite problem area has been established: a. Review flow and process records again in greater detail. b. Recheck sampling and testing procedures required (see Section III). c. Compare sampling and testing program against recom- mended programs in the manual. d. Recommend a modified testing and sampling program to furnish additional data for evaluation (see Section III). * Refer to 0 & M manual requirements. ------- e. Compare the data with the problem indicators detailed in the manual (see Section IV) to see if there is a solution offered. f. For those problems not specifically covered in the manual, and if the evaluator's experience does not suffice, should be recommended that a consultant be hired. MAINTENANCE PROBLEM—Refer to sample maintenance program (see Appendix H) and compare with actual plant program; recommend new program where needed. TOTAL PLANT EVALUATION This should include the following: 1. TOTAL EVALUATION OF PLANT—utilizing the Evaluation Guide materials at the end of this section (a) Modification of initial evaluation, if appropriate (b) Differences in existing plant performance and operational data with design and/or manual operational or performance data (c) Personnel needed for adequate operation (d) Type of sampling program required to give needed data (e) Maintenance system needed (f) Laboratory equipment needed (g) Problems encountered • Those corrected by visit • Those that need outside help to correct • Proposed solutions. FINAL REPORT—should contain the following elements: (a) Summary of on-site visit (b) A list of problems encountered (c) Solutions recommended (d) Proposed action. * See EPA Staffing Guides. 10 ------- Pre-Visit Evaluation Guide Plant Identification (Name, Owner, etc.) Plant Location, Operator in Charge. Date of Evaluation. Evaluation by Date of Plant Construction Name of Design Firm Regulatory Agency of Concern Stage Operating Permit? Background Informatic 1. Type of Plal Schematic oj Contributor] Domestl •obtain prior to visit 2. 3. Low Route to Unit jpulation Industrial (P Other 4. Type of Wast] Combii Saniti iwa' Indus 5. Geographic Clin ftic Effects ,o Ranges ( F) Rainfall Extremes (in.) to to 11 ------- 6. Plant Wastewater Characteristics Nitro- gen Sus- pended Solids (mg/£) COD Flow (MGD) Dis- solved Oxygen a. b. Plant influent Plant effluent Overall perform- ance (%) Design and/or manual recommended performance values (%) Existing receiving water quality Required receiving water quality 7. Possible Problems a. Identified from/g^M^ITting reports b.Identified from/previous inspection reports c. Complaints 12 ------- On-Site Evaluation Guide 1. Flow Design (actual). Daily Average Peak Note any variation or erratic flow patterns. 2. Process Units Employed and All Pertinent Information Unit Process Operational Parameters Existing Plant Values Design and/or Recommended Manual Values Lsting >lant Values Loading Rates Design and/or Recommended Manual Values 3. Historical Operational Data Organize data to see if following occurred: Equipment failure - when, what type failure, how long out of service Extreme weather conditions Exdessive loadings on plant: Flow — when, how long, results of Organic - when, how long, results of 13 ------- Changes in process operation, such as: Increasing air flow to activated sludge units Decreases in detention times What caused changes? Are changes still in effect? Why? 4. Plant Personnel Size of Staff for Daily Average Flow Handled Qualifications Types of Shifts (hours) Existing Plant Recommended Manual and/or Other Sources Existing Personnel Recommended Manual and/or Other Sources Exist- ing Recom- mended Manual 5. Laboratory Evaluati Type of 1 Treatment Type Pests Perfo ; System Ev Frequency rmed/for aluajbed Location Testing Procedures and Equipment Used Type of Tests Performed for Treatment System as per Manual 14 ------- Guide for Overall Evaluation Yes No I. OPERATING PROBLEMS Are there problems affecting the performance of this plant? Can they be solved without major construction? Are the skills to solve the problem available among the staff? Was a solution suggested by the evalua^ Is it a permanent solution? II. THE SAMPLING AND BESTING PROGRAM • Are the sa noting locations suitab Are testin j procedures Is testing process co equency adequ ol? III. LABORATORY FACILI Is the labofra\pry apparently fun\tio Is there enough all the nefessarj Is the eq irgdfiized and is intended? knt to perform 3tS? eing properly used? IV. PERSONNEL - Planf Operators (including lab personnel) Is the st^t^eKiequate in size? • Are theyfqualified? State certified? • Is thera an operator training program? • Are the/shifts adequate and balanced? 15 ------- Evaluation Guide - page 2 V. OVERALL PLANT PERFORMANCE Is it operating to its design specifications? Is it meeting discharge requirements for its location? Even if adequate, can plant performs be improved by simple and/or inexper changes? Yes No Evaluator: If any of' taken: 1. Submit a • Sumnu • A lis • Solu^ • Prop^ 2. Discuss plant s1 answers are ollowing steps should be Ivisit bins encountered lions! rqqMmended ctlon. ^commendations with treatment In cooptJtaf ion with the plant operator (and local officials, if necessary), decide on a course of action fo solve the problem(s). After af suitable period of time, revisit the plant fo make a re-evaluation. 16 ------- OPERATIONAL DATA ------- II WASTEWATER TREATMENT SYSTEMS OPERATIONAL DATA ------- Section II WASTEWATER TREATMENT SYSTEMS OPERATIONAL DATA This section of the manual contains data on the common operating parameters, loading rates, waste products accumulated from process opera- tion, and the support systems which are used in the various unit operations and processes. Once the plant has been classified and the type of unit operations and processes have been determined, the information in this section will serve as a guide to evaluation of the overall plant operation. If operating and performance data are largely different, investigation of plant processes should be made to determine if the problem is with equipment or process failure. These should be noted, and if remedial solutions can be deter- mined by use of this manual (Problem-Solution Section IV, this manual), they should be suggested to the plant operator. Where problems are beyond the scope of this manual, or experience of the evaluator, it should be suggested that the operator take the necessary steps to get proper outside help. In the total evaluation of the plant, a list of problems encountered should be made and the steps that are being taken or were suggested to cor- rect them. A return visit should be made after the operator has had suf- ficient time to correct the problems and a new evaluation made. 17/18 ------- OPERATIONAL DATA ON PRETREATMENT AND PRIMARY TREATMENT OF WASTEWATER ------- Table II-l PRETREATMENT AND PRIMARY TREATMENT DATA Unit Operations or Process Racks o coarse o medium o fine o mechanically cleaned Grit Chambers o Air injected Cutters-Shredders ( comminuters) Pre- Aeration Sedimentation Primary sedimentation before activated sludge Primary sedimentation tanks before trickling filters Intermediate sedimentation between multistage trickling filters Final sedimentation after activated sludge Final sedimentation after standard trickling filters Final sedimentation after high-rate trickling filters Chemical Precipitation Chlorination S/ Type of wastewater or effluent : Raw wastewater, depending on strength and stale- ness Settled wastewater Chemically precipitated wastewater Trickling filter effluent Activated sludge plant effluent Intermittent sand filter effluent Operational ^ ^^ Parameters 2/ Bar Spacing in Inches— 1-2 1/2 - 1 1/32 - 1/4 As small as 5/8 - Flow Velocity: Mteh of Gritf Overflow Rate 0.75 to to\Be Removed gal/sq ft/ day 1.0 ft/sec \35 / 73,000 \g/ 51,000 sX 38,000 V"0\ 25,000 / Ai^j Requirement : / .025 to .05 cu ft/gal Capacities: , / 0.35 to 25 MGD- _*— — — — — 650-5,200 lb/hr£ ,. *~"~* Detention Time: Air Requirement: I/ 15-45 min. .005 to .2 cu. ft/gal or 25 - 40 psi Overflow Rates: I/ 2000-6000 gal/day/sq.ft 2/ Detention Time- Overflow Rates (hr) gal/day/sq ft 0.75 - 1.0 1,500 - 1,000 2.5 600 2.0 - 2.5 600 - 900 2.0 1,000 2.0 800 2.0 800 2.0 800 Weir loading rates: *-l MGD; 10,000 gal/linear f t - >1 MGD; 15,000 gal/linear^f t \ 2/ Chlorine Probable Chlorine Chlorinator— residual : Requirements Capacities 2 mg/1 Ib/day „ ^ ^ _ mg/1 per 1,000 mg/1 lb/1,000 Contact time : - persons * persons * 6-25 5-21 30 25 5-20 4-17 25 20 3-20 3-17 25 20 3-20 3-17 25 20 2-20 2-17 25 20 1-10 1-3 15 12 Accumulated Material (Sludges, etc. ) I/ Cubic feet/MG 3/4 - 3 3-8 5-30 Cubic feet/MG 2-8 Volume of skimmings: 0.1 to 6 cu.ft/MG or 200 cu.ft/ 1000 person/yr Sludge accumula- tion is approxi- mately .038 cu ft/ capita or 3,500 gal/mg of flow sSludge contains chemical high water conteiffc^nd is twice the volumexproduced from plain sedi- mentation ^^^ Scum and grease accumulated in contact chamber. Support Systems Power for mechanically cleaned racks, conveyor belts, grinders Power for mechanical cleaning, cyclone operations, and for pumps to supply air. Conveyor system to remove grit. Power : "•""iTi to 3.5 hp motor Cleaning units for dif f users, power supply for air supply. Cleaning mechanism for units without mechanical scrapers and skimmers. Sludge pumps and power supply for those with pumps and mechanical skimmers. Dosing, mixing, f locculation; and sedimentation units; where existing sedimentation units are not being used. Chlorinators, chlorine leak detection equip- ment; baffled contact tank unless adequate contact time is provided in a waste- water outfall or conduit. Safety equipment : Scott air packs, cylinder repair kits, ventilation system. Chlorine residual anal- yzer scales, evaporators, CPRV * For background information see Appendix C ** For wastewater flow of 100 gpcd *** For approx. specific gravity of 2.31 I/ Steel 2/ Imhoff-Fair 3_/ 10-State Standards, 1971 edition 4' ASCE Std Manual 5/ Local requirements should prevail 19/20 ------- OPERATIONAL DATA ON SECONDARY WASTEWATER TREATMENT ------- Table II-2 SECONDARY TREATMENT DATA * Unit Operations or Processes Trickling Filters t xOperat ionaV— >~^^ t^'S ' Parameters-^ ^N, y ' Recirculation Rate for Maximum BOD of Settled Wastewater \ \ Loading Rates Low Rate gal/day/sq ft 25-100 High Rate Filter 200-1,000^ Support Systems = -\ v Dosagin£>tanks -Recirculation BOD mg/1 Ratio 130 1:1 170 2:1 220 3:1 260 4:] ' million gal/acre/day 1.1-4.4 Organic Loading lb/1,000 cu ft/day 5-25 Ib/acre ft/day 220-1,100 8.7-44 >elcjfc>e'pui power supply 25-300 ,100-13,000 Intermittent Depth of sand 3J-4 ft Sand Filters Head on filter, 5 ft Stabilization Pond or Lagoon^ Detention Concen- 4/ 1. Large holding reservoir (days)** Depth tration — - -tabili-ntion oond (months) (ft) (mg/1) (a) Facultative 7-30 2-5 10-50 (b) High rate 2-6 J-l 100 3. Aerated lagoons 1 or 2 - 14 6-15 4. Anaerobic 30-50 8-10 Final clarification Following Low-rate trickling filters High-rate trickling filters Activated sludge (over 2.0 mgd) Activated sludge (under 2.0 mgd) Loading 75,000-125,000 gal/acre/day Solids 2 lb/5 sq ft/day Ib/acre/day 20-50 100-200 300-500 Overflow Data 3 g/ gals/day/sq ft — *~ 800-1,000 800 /"Vs. *-**T j 800-1,000 ^— ^ 800 C Dosing siphon of ) flow distributor ) ~ Aerators Sludge pumps, power supply for mechanical sweepers , pumps reclrculatlon pump Detention Tine (hrs) for Overflow Rates & Depth of Tank—' Overflow Rate Depth ^*^ 600 2.1 2.4 3,/0 Package Aeration Plants 800 1,000 Flow Rate : 1.6 1.8 .X2.25 1.25 1.4/ 1.75 .^ ,-*400 gpc/dwelling or 100 gpc/day Organic load: 10-20 Ib BODs/1,000 cu ft of areation tanks/day Power supply sludge pumps Detention Time for: aeration tank 24 hrs clarifier 4 hrs Air Supplied: 2,100 cuft/lb BCD/day Recirculation rate: 1:1 Activated sludge System & ponds (see table) For background information see App. D. Unless otherwise noted I/ Now parallel systems £/ After 1960, Eckenfelder, O'Connor 3/ ASCE STD manual 4/ Algae concentration in suspension 5/ 10-State Standards 1971 21/22 ------- Unit Operations or Processes Tyjjes of Process Table II-3 I — In QPTTYNTIA DV TPITATTWITTMT HATA APTY VATTTn QT ITnm? OPHP'C'QQ " - Operational Parameters Loading Rates Support Systems 2/ Loading- Detention Time- Percentage Recycled Ibs BODs/ Type of Mixing Flow Scheme (hr) Sludge Ibs MLSS Air Requlrements- Plug Complete Aeration Aeration & Uulti Stage Flow Mixing Only Sludge Return Aeration & Sludge Return Modified Aeration (or high rate) Conventional Contact Stabilization scheme 1 scheme 2 A tO PWO Stage Aeration I Extended Aeration Step Aeration x x 3 or less 10-sc£ 1 or more .41 ft3/gal x x 1-6 15-755/ 0.2-0.5 .4-1.5 ft3/gal or , 768-1000 ft3/lb BOD x x .5-1.0 50-1502/ 1 0.15-0.2 \ (750 ft3/lb BOD 'N P°wer s"PPly x x Contact range 1-4 1 0.15-0.2 \ V removed / sludge pumps Stabilization tank ] \ ^^» ^S air compressors -^ ' ^-^^^.^ ™~ ~" alr control x x Contact range f 0.07-0. 15% system 1.5-3.0 \ ^^^a&' sludge Stabilization tank v— — __— — aeration f 6-9 ^__ tanks x x 24 hr 50-200- C /*0. 01-0. 07 •* J 3-8 20-7^ .2-0.5 of /tf500-700/f t3/lb 1\ 50 Ibs/lOOOft3 V^TjaDD^removed J Completely mixed 3 or more 20-10O- 2-.5 C./ SOOft^lbTOD ) Oxidation Ditch (Passover Ditch) Due to limited data at this tine, no ranges for operational parameters or loading rates are possible. I/ Ib of BOD Ib mixed liquor suspended solids unless otherwise stated. American City, October 1971 2/ Steel, 1961. Manual for EPA "Up Grading Wastewater T.P." 3/ Minimum air requirement, according to 10-State Standards, Is 1500 cu ft air/lb BODs except extended aeration which Is 2000 4/ Steel 5/ 10-State Standards, 1971 ------- OPERATIONAL DATA ON ADVANCED WASTE TREATMENT ------- Table I1-4 ADVANCED WASTE TREATMENT DATA* ffl V X Unit Operations or Processes Operational Parameters Accumulated Material Support Systems \VV^\ Chemical/Physical If Treatment ^ Capacities as for primary or secondary clarifiers From 200 to 900 mg/1 of additional sludge (for phosphorus removal) Mixing basin for dis- persion of added chemicals, pH measurement and control equipment Carbon Absorp- tion Contact time: 15 to 45 minutes. Flow , rates: 5 to 10 gpm/ft' From 50 to 120 mg/1 of organic materials Regeneration furnace Filtration equipment (where needed) to on Ammonia Stripping Air temperatures above 32°. pH between 10.8 and 11.5 Ammonia is carried off into atmosphere. AJ2-- Soma carbonate scale ind sludge buildup. Power for forced draft. A Coupling with phosphorus removal. Recarbonation equipment Electrodialysis Flow rate: up to 10 MOD. More A efficient at higher \ temperatures Brine stream 10-25% of feed stream Electric power for stacks Brine disposal system Reverse Osmosis Flow rate: up to 50 MGD. More effici- ent at higher temperatures Brine stream 10-25% of feed stream Power for high pressure pumps (600 psi) Brine disposal system *For background information, see Appendix E. ------- OPERATIONAL DATA ON SOLIDS TREATMENT ------- Table I1-5 * SOLIDS TREATMENT DATA* Operational Parameters Support Systems Unit Operations or Processes 6.8-7.2 85-95°F 30 days 12 cu ft/lb volatile matter reduced Anaerobic Digestion PH Temperature Detention Gas production Heat exchangers Loading of Heated Tanks,** Ib volatile solids per cu ft per montj Circulation pumps o Gas o Sludge Sludge produced/ for Anaerobic Digestion by Plain sedimentation Plain sedimentation and trickling fi>tfatlpn """"^-^ f Low-rate operation \ V High-rate operation * and activated sludge High-rate operation Conventional operation Aerobic Digestion Sludge Thickening Gravity thickener o Secondary sludge o Activated sludge- Flotation Sludge Drying Beds for: o Primary precipitation o Standard-rate filter!/ o High-rate filter 2/ o Activated sludge!/ o Chemical precipitation #-' r/s fjS 9 9 £ 4.4 9 3.6 7 Dissolved oxygen 1.0-1.5 mg/1 Detention times 20-30 days Overflow Loading gal/sq ft/day Ibs/sq ft/day 400 8 500 8 Area in sq ft per capita Open beds Covered beds 1.00 0.75 1.25 1.00 1.50 1.25 1.75 1.35 2.00 1.50 QLG4. -JjJtLvLMA. U ' »irv4j <^Ju------- CO o Table II-6 COMMON SOLIDS TREATMENT DATA* ffl Amounts of Chemicals Commonly Unelutriated Sludge and Yields Condi- tioner, % of dry sludge solids Type of Sludge CaO FeCl O Plain sedimen- tation (primary) 1. Fresh sludge 10 3 2. Digested sludge 10 2 0 6 Plain sedimen- tation and low- rate trickling filtration 3. Fresh sludge mixture 12 3 4. Digested mixed sludge 12 2 0 7 Plain sedimen- tation and con- ventional acti- vation 5. Fresh activated sludge 0 6 6. Fresh settled sludge mixture 0 6 7. Digested mixed sludge o 8 Dry Solids Ib per 1,000 persons daily 143 89 78 183 117 99 71 195 129 Filter Capacity Ib per sq ft per Cake hr, dry Solids basis % 5 32 6 32 6 28 4 28 6 30 6 26 2.5 20 4 22 2.5 22 Employed in of Vacuum Required Filter Area, sq ft per 1,000 persons daily 1.2 0.6 0.5 1.9 0.8 0.7 fl I D 1.2 *^ 2.1 2.1 Conditioning Sludge Filters Condi- Sludge tioner, Cake, Ib per Ib per 1,000 1,000 persons persons daily daily 450 280 280 650 390 380 350 880 580 CaO FeCl, O 12 3.6 7.5 1.5 0 4.5 18 4.4 11 1.9 0 6.7 0 4.1 0 11 0 9.7 Support System Dosing equipment Power supply Sludge pumps Elutriation tanks Chemical storage *Adapted from Imhoff-Fair, 2nd edition. For background information, see Appendix F. ------- SAMPLING/TESTING ------- Ill SAMPLING AND TESTING ------- Section III SAMPLING AND TESTING INTRODUCTION The sampling and testing program described in this section is designed to determine » the type of sampling to be done • the locations of sampling points • the analyses to be performed for the particular treatment system. In addition, recommended storage temperatures and durations are given, as, well as a list of the laboratory equipment that will be needed to perform •- the various analyses. Sample forms are included which are intended as aids for the systematic recording of the results of the various analyses. The information in this section can be used with the problem/solution section of this manual (Section IV) either to establish a sampling and testing program to solve a particular problem involving a particular process, or to institute an adequate sampling program at a plant lacking such a program. A comparison of the type and frequency of tests needed to control the various processes with the sampling program actually being performed at the plant site can help evaluate the process control system of the plant. In the overall evaluation of the plant, this comparison would be used in ratings of the sampling and testing program, and. the laboratory facility to" perform necessary tests. GENERAL / (j/4X^us/tf"1 ' ' <--^ w- yjjr. ^ur* The characterization of waste, whether it be domestic or industrial in J ju^ ^ origin, beg_inswithsampling. A wastewater treatment plant consists of various components which make up the treatment system. A program of sampling and testing which measures influent, effluent and'individual process units on a scheduled basis not only means better plant performance but can also indicate problems quickly so that immediate Corrective measures can be taken. ^^ \)------- facilities. The treatment plant should be provided with adequate laboratory facilities for the performance of tests necessary for the proper operation >f the plant. Some more sophisticated treatment plants are provided with instrumenta- tion which allows for constant monitoring of certain treatment processes and it is customary for this information to be telemetered and recorded at some convenient location within the plant control building. Telemetered information can include, but not be limited to, primary effluent pH, final effluent chlorine residual, aeration tank dissolved oxygen, and sludge density. Even though the instruments performing these monitoring functions can be highly reliable, it is recommended that their performance be checked periodically by analyzing concurrent and identical samples. THE SAMPLING PROGRAM A well-organized, effective sampling program must consider several factors: • Type and scheduling of sampling needed for the specific analyses to be made • Quantity of samples needed • The most effective sampling locations • Handling and storage procedures (between sampling point and testing site) • Types of sample testing to be done. Tables III-l and III-2 indicate the common constituents which are analyzed from the flows of various treatment processes. The matrix (Table III-2) also indicates points in the treatment system where samples should be taken. The indicated sampling frequencies are minimum values and are dependent on or can vary with size of plant and staff, complexity of the system, the nature of the waste handled, and on the effluent require- ments placed on the facility. The test indicated should be performed as frequently as indicated in accordance with the prevailing requirements of the agency governing waste discharge within the area in which the plant is located. Every effort should be made to perform the tests in accordance with their scheduled frequency. A test with a "weekly" frequency should be run at a regular hour and day of the week. 32 ------- Table III-l PROCESS TESTING GUIDE* PROCESS A/&A/VAJ aA )°£ii AI/W Removal f ^ • P R I y / Primary Sedimentation TEST l %J),4 ------- "» Table III-2 EQUIPMENT TESTSSG MATRIX* EQUIPMENT NEEDED •* * '11 r ^Y* 4 CONSTITUENTS 'tt| ^J TO BE ANALYZED U ^ \ Volatile Solids I Total Solids ' ^Settleable Solids Total Sulfides < Biochemical Oxygen Demand Chemical Oxygen Demand •^ Suspended Solids Dissolved Oxygen *X Chlorine Residual ell-fa'* W MPN Coliform Volatile Acids Alkalinity Gas Analysis Grease Total Organic Carbon Turbidity Volatile Suspended Solids Total Phosphorous MBAS Sludge Filterability Ash Analysis Jar Test Apparent Density Iodine Number f—t~erc~ — ^hSfheTms— Calcium Content Ammonia Nitrogen Organic Nitrogen Nitrate Nitrogen Heavy Metals / «J Atomic Absorption. 600° C Muffle Furnace 103° C Drying Oven Analytical Balance Imhoff Cone 3 • • • • • • • • • • • • • • • • • • A-^ ^ * ^ Is V i }; ~4 \ O t» C fc .5 £ J -s co v_J LO i; co • '•#' • • • i. Turbidity Meter Carbon Adsorption Unit Desiccator Spectrophotometer ,3 OHlllny CHuiuiiicnt U&^t. U^t- • • • • • • « _. " . • "*: S ^^ ^ t" I! 1 | | 0 • • • • • • • • *The equipment specified in this matrix is subject to plant size and com plexity of processes and the degree of ------- Types of Sampling Sampling can be either of two types: 1. Grab. This type of sample is taken when wastewater does not flow continuously, when appearance of discharge, changes rapidly, and when making sure that the composit sample isn't masking extreme conditions of the—was /''/y \ It is also used when test samples cannot b^ inaxedj such as when testing for residual chlorine, dis^soi-vea oxygen, or pH. 2. Composite. With the widely varying characteristics of waste, this type of sampling provides a representation of wastewater over a period of time and can be composited on the basis of proportional flo,w or the same amount being collected at every internal during the sampling period. Composites^ should bo/corrected as specified in Standard Methods. Location of Sampling Points • ' > -n. J ^ Samples should be taken only jfhere the wastewater is well mixedM \t large particles are found in the/sample, they should be broken up to make a more homogeneous sample. Dejrosits or growths of floating material which have formed at the samRiing point should not be included in the sample. Quantity of Sample ^, In order to determime the correct^amount of sample to be collected, the past flow records of the plant should be analyzed to determine the daily average flow. The amount of the composite sample to be collected at a given period should/be proportional to flow of wastewater at that time. Then determine thar quantity of sample needed for analysis; 1 liter is usually sufficient; never try to work with less than about 200 ml. Handling and SJrorage of Samples Samples sfhould be tested as soon as possible. If testing must be delayed, th/n adequate storage must be provided. Table II1-3 recommends appropriatiS storage temperature and duration in terms of the test to be performed/on the stored sample. 35 ------- Table II1-3 STORAGE TEMPERATURE AND TIMFP I/ ANALYSIS Total solids Suspended solids Volatile sus- pended solids COD BOD TEMPERATURE 4°C 4 C 4°C TIME/ / Up /o several d/ays /Up to several days Up to several days Up to one day in com- posite sampling systems TEMPERATURE <^ 0°C f o°c o°c TIME f^l No storage No storage Unlimited Lag develops, must use fresh sewage seed Source: Agardy, F.J., aria M. L. Kiado, Effects of Refrigerated Storage on the Characteristics of Waste, 21st Industrial Waste Conference, Purdue Univer/ity, May 3-5, 1966. I/For more .detailed preservation techniques, see Analytical ~" Quality^Control, EPA Chemical Methods, or Standard Methods Test Records In order that the data developed through the plant sampling program can be properly utilized to gage plant performance, it is necessary that it be systematically recorded and filed for ready reference. The most practical means of satisfying this requirement is to prepare convenient forms on which these data can be recorded. These forms should be prepared to fit the particular operating conditions at each individual plant. The data should be recorded chronologically on these forms and should be organized so that each set of data can be utilized to evaluate a particular aspect of the treatment process. Proper recording of sampling data will allow for more efficient and expedient solution of operational problems. Several examples of operational forms are included at the end of this section which can be utilized for the recording of analytical data pertinent to the treatment process. 36 ------- In addition to recording the data on forms, graphing of pertinent operating parameters may be appropriate and desirable for visual presenta- tion. For additional information on sampling and testing, see: State of Washington Wastewater Plant Operator's Manual Operation of Wastewater Treatment Plants: A Field Study Training Program, EPA Effects of Refrigerated Storage on the Characteristics of Waste, 21st Industrial Waste Conference, Purdue University Standard Methods, 13th Ed Collection, Storage, Transportation and Pretreatment of Water and Wastewater Samples by Sanitation and Radiation Laboratory, California State Dept. of Public Health MOP 11 MDP 18 37 ------- SAMPLING PROGRAM FREQUENCY AND LOCATION PARAMETERS TO SAMPLE PROCESSES PRE TREATMENT GrU Removal PRIMARY TREATMENT Sedimentation SECONDARY TREATMENT Activated Sludge Trickling Filler- Single Stage Trickling Filter -Two Stage Oxidation Ponds Final Sedimentation Package Aeration Plants Imhoff Tanks DISINFECTION Chlorination SOLIDS HANDLING Thickening Digestion Centrifuging Vacuum Filter* Incineration ADVANCED WASTE TREATMENT GREASE ©®* , See Tab See Tafal I a. ©©»• mm, ©o ©d ©d ©©©„ ©©" ©< @®» ©< , Ml-l. e Ill-l. 1 -t ©d ©d ©G@d ©@" ®- ©y / O § ©O". ©" I ©- CHLORINE RESIDUAL ®d ®.' ©d ©d ©d ©d FREQUENCY daily d weekly w monthly no biweekly b-w bimonthly b-m when in operation q SAMPLING POINT Q raw sewage (2) final effluent ^ proceo effluents @ primary effluent (V) secondary effluenl NOTE: Thi* ii a minimum channel with plant :diote effluent ® i»l © c(orifi«d efflu«i ®/filt.red effluent .fluent r® inlluent or .Fflu.nl ing program and U subject to ind operational problemi. ^§) digestor effluent © row.ludo. (Tg) primary sludge (f|) secondary sludge © above tludge blanket Qj) digested sludge @ receiving water ------- SAMPLE FORMS TO BE USED WITH A SAMPLING AND TESTING PROGRAM ANALYSIS AND EVALUATION Forms to be developed and inserted by field inspectors. 39 ------- PROBLEMS/SOLUTIONS ------- IV COMMON OPERATING PROBLEMS and SUGGESTED SOLUTIONS ------- COMMON OPERATING PROBLEMS and SUGGESTED SOLUTIONS INTRODUCTION There is a. variety of common operating problems which may occur period- ically and prevent the proper processing of wastes by a treatment plant. The purpose of this section is to properly identify the problem by defining the indicators. Once the problem has been identified, certain monitoring, analyses and/or inspections must be performed prior to making a decision as to which corrective measures should be utilized. In some cases, the data-gathering process can be a simple visual observation and in other cases it can involve rather intricate sampling and laboratory pro- cedures. The resulting information should then be systematically utilized to make a determination on which of the corrective measures should be implemented. The problems discussed in this section are those which occur rather frequently in practice and the suggested solutions have been, for the most part, accepted procedure in the industry. There may be times when the suggested corrective measures do not correct the problem, or a problem may exist which does not fit into the common category. In a case such as this, it is prudent to seek expert advice on the subject prior to under- taking any course of action. The information utilized in development of the indicators and solutions reflect the present state-of-the-art; as information from new technical advances becomes available, this section will be updated. 41 ------- PROBLEM INDEX Page I. PRETREATMENT PUMPING PLANTS AND INFLUENT SEWERS Surging of plant influent 49 Accumulation of solids or scum in wet wells 51 Odor source in wet wells ~52 SCREENING AND SHREDDING Accumulation of rags and debris for disposal 53 Excessive grit in bar screen chambers 54 Odor source in grit chamber ^—•66- Shredded screenings clogging pumps 56 GRIT HANDLING AND REMOVAL Grit removed has high organic content 57 GENERAL Industrial waste is inadequately pretreated 58 II. PRIMARY TREATMENT PRIMARY SEDIMENTATION TANKS Floating, gaseous, or septic sludge in tanks 59 Low settleable solids removal efficiency 60 Erratic operation of sludge collection mechanism 61 Low scum (grease) removal 62 Tank contents turn septic 63 43 ------- Page III. SECONDARY TREATMENT ACTIVATED SLUDGE PROCESS Sludge bulking 64 Erratic sludge volume indexes 65 Difficulty in maintaining balanced mixed liquor dissolved oxygen 66 Excessive foam in aeration tanks 67 Digester supernatant and/or centrifuge centrate upsetting activated sludge process 68 Unable to maintain balanced food/micro-organism ratio in aeration unit 69 Facilities inadequate for disposal of waste activated sludge 70 Uneven hydraulic and solids loading of aeration tanks 71 TRICKLING FILTERS Ice buildup on media 72 Filter odors 73 Fly nuisance in vicinity of filter 74 Clogging and ponding of filter media 75 Clogging of distributor nozzles causes uneven distribution of flow on the filter surface 76 OXIDATION PONDS Excessive weeds and tules 77 Pond odors 78 Low pond dissolved oxygen 79 FINAL SEDIMENTATION Sludge or pin floe flowing over weirs 80 Erratic operation of scraper mechanism 81 44 ------- Page IV. ADVANCED TREATMENT CHEMICAL COAGULATION AND FLOCCULATION Chemical coagulants utilized for settling or dewatering sludges through recycling cause floating sludges in primary sedimentation tanks 82 AMMONIA STRIPPING Freezing in ammonia stripping tower 83 Formation of calcium carbonate scale on ammonia stripping tower fill and structural members 84 FILTERS Filter backwash wash water hydraulically overloads and upsets clarifiers 85 MICROSCREEN Fouling of fabric with grease and solids 86 Microscreen effluent exhibits higher suspended solids content than influent 87 ACTIVATED CARBON Mechanical fouling of columns 88 V. DISINFECTION CHLORINATION Insufficient chlorine gas pressure at the chlorinator with all cylinders connected to gas phase. 89 Insufficient chlorine gas pressure at the chlorinator 90 There is no chlorine gas pressure at the chlorinator, when apparently full chlorine cylinders are connected to the chlorine supply system. 91 45 ------- Page Impossible to operate chlorinator because rotameter tube ices over and feed rate indicator is extremely erratic. Chlorine supply is from ton containers connected to the gas phase. 92 Chlorinator will not feed any chlorine even though all systems appear normal. 93 Chlorine gas is leaking from vent line connected to external chlorine pressure reducing valve (CPRV) 94 Inability to maintain chlorine feed rate without icing of chlorine supply system between external chlorine pressure reducing valve and chlorinator. (Equipment consists of evaporator, external CPRV and the chlorinator.) 95 Chlorination facility consisting of evaporator- chlorinator combination with external chlorine pressure reducing and shut-off valve is unable to maintain water-bath temperature sufficient to keep external chlorine pressure reducing valve in open position. 96 Inability to obtain maximum feed rate from chlorinator or chlorinators with adequate chlorine gas pressure at chlorinator. 97 Inability to maintain adequate chlorine feed rate 98 Inability to obtain maximum or proper feed rate from chlorinator with adequate gas pressure at chlorinator. 99 Excessive chlorine odor at point of application 100 Chlorinator will not feed enough chlorine to produce a proper chlorine residual at the sampling point. 101 Wide variation in chlorine residual in effluent as determined by hourly chlorine residual determinations. 102 Chlorine residual analyzer recorder controller does not appear to control the chlorine residual properly. 103 46 ------- Page Chlorination system consists of either compound-loop control or direct residual control and system does not appear to be controlling properly. 105 Coliform count does not meet the required disinfection standards set by regulatory agencies. 106 Coliform count does not meet the required standards for disinfection. 107 Plant effluent does not meet toxicity requirements because chlorine residual to achieve proper disinfection is at too high a level. 108 VI. METERING Plant meter unreliable 109 VII. SOLIDS HANDLING SLUDGE THICKENERS Odor from thickener 111 Thickener contents do not settle 112 Sludge pumped from thickener has low solids concentration 113 SLUDGE DIGESTION (Anaerobic) Scum blanket in tank 114 No digester gas production 115 Increase in volatile acid/alkalinity ratio in digester 116 Foam in digester 117 Low reduction of volatile solids in digester 118 High percent solids in digester supernatant 119 CENTRIFUGING Low solids recovering rate 120 47 ------- VACUUM FILTERS LowOsolids cove] INCINERATION Abnormally high temperature in furnace Abnormally low temperature in furnace High oxygen level in furnace stack exhaust Low oxygen level in furnace stack exhaust SLUDGE LAGOONING Excessive solids carried over from lagoon supernatant to plant influent Odors from sludge lagoons Page 121 122 123 124 125 126 127 48 ------- »sx»VjA l^Ci . I. PRETREATMENT - Pumping Plants SURGING OF PLANT INFLUEN Intermittent flooding of.'weirs and structures. Monitoring, Analysis and/or .If a main sewage lift station pumps ck for frequent starting and stopping of pumps or more than one pump operating at one time (out of phase) during a pumping cycle. -fg|» L/tAttLJ (& (fn^&fb M"ff/j/^^ ,-^M~- ||j~— ^ | n»t lAAf If influent flows to the plant by gravity through a main trunk, check depth of flow in connecting sewers if channel iSK uniform or monitor flow with a portable flow If surging occurs during rainfall, record relation of surging to duration of rainfall; and record or obtain rainfall intensity if possible. Surging from gravity influent line indicates a major 'pump/station discharge into a connect/ng sewer. Review •water depth and/or/portable flow meter data to determine so/rce of flow. ' Intermittent starting and stopping or recycling of main influent pump station or stations indicates improper wet well sensor adjustment fy^ tha_t±he hydraulic capacity of the station has been exceeded.^ Adjust level sensors for 'a more desirable pumping cycle. If possible, install variable speed pumps units for uniform flow into treatment plant; or install surge tank. Heavy surging or hydraulic loading of treatment plant ^treating waste from a separated system during periods of rainfall indicates illegal-connections to system s catch basins, yard drain, or roof downspouts. "Smoke bomb" sanitary sewer system to determine source of illegal connections. Heavy surging or hydraulic loading of treatment plant during period of heavy rainfall is caused primarily by flooding of street areas and water, entering the system through manholes, broken lines, etc. Seal all manhole covers in high risk flood areas and patch all cracks in manhole structures with an epoxy water resistant compound. 49 ------- I. PRETREATMENT - Pumping Plants and Influent Sewers Problem SURGING OF PLANT INFLUENT Indicators nitoring. Analysis and/or Inspection Corrective Measures 1. Intermittent flooding of weirs and structures. 2. Pl_ant efficiency treating wastewater drops sharply for short period of time. 3. Flow meter records intermittent high and low peak flows. 4. Excessive suspended solids in overflows. 1. If a main sewage lift station pumps effluent to plant, check for frequent starting and stopping of pumps or more than one pump operating at one time (out of phase) during a pumping cycle. 2. If influent flows to the plant by gravity through a main trunk, check depth of flow in connecting sewers if channel is uniform or monitor flow with a portable flow meter. 3. If surging occurs during rainfall, record relation of surging to duration of rainfall; and record or obtai rainfall intensity if possible. Surging from gravity influent line indicates a major pump station discharge into a connecting sewer. Review water depth and/or portable flow meter data to determine source of flow. Intermittent starting and stopping or recycling of main in- fluent pump station or stations indicates improper wet well sensor adjustment or that the hydraulic capacity of the sta- tion has been exceeded. Adjust level sensors for a more desirable pumping cycle. If possible, install variable speed pump units for uniform flow into treatment plant; or install surge tank. Heavy surging or hydraulic loading of treatment plant treat- ing waste from a separated system during periods of normal rainfall indicates illegal connections to system such as catch basins, yard drain, or roof downspouts. "Smoke bomb" sanitary sewer system to determine source of illegal connections. Heavy surging or hydraulic loading of treatment plant during period of heavy rainfall is caused primarily by flooding of street areas and water entering the system through manholes, broken lines, etc. Seal all manhole covers in high risk flood areas and patch all cracks in manhole structures with an epoxy water resistant compound. 50 ------- Problem Indicators I. PRETREATMENT - Pumping Plants and Influent Sewers /I ,\ K " ^ ACCUMULATION OF SOLIDS OR SCUM IN WET WELL &> r$r Monitoring, Analysis and/or Inspection Corrective Measures Scum blanket in wet well t ^Pffiffi iment «/ A teWf * mproper operation ofl\level sensingf/equipment 1. Sound wet well with a pole to determine solids level. 2. Measure/owet well draw .downd pumping cycle. 3. Ascertain relation or pump suction piping to floor of wet well. 4. Determine elevation of inlet piping. 5. Look for dead spots in corners and structural cracks ' ^J&L i where sludge can^ccumulate, * fad ^^a^/Lob^^ i. Start pumps manually, being careful not to break suction, and pump wet well down to lowest possible elevation while breaking scum blanket with a high pressure water hose. 2. Check pumping level and determine if more of a drawdown can be allowed for in order to remove more of the ^floatable materials. If one or more influent line^come in at a higher elevation than the pump suction inlet, set level sensor so drawdown will allow for spillage of fresh wastewater onto the scum blanket. The resultant turbulence could assist in breaking the blanket. 4. If this is a persistent problem install air diffusers in wet well with comp-ressors--wixed_^jo_Qpe^aj;.e-^in—t-andeiifwi't-h- the—pumps.. Diffused air will assist in placing the solids in suspension ^and c/urtail thf development of a scum blanket. /fD A £) \ ^ * 51 ------- I. PRETREATMENT - Pumping Plants and Influent Sewers Problem Indicators ODOR SOURCE IN WET WELL i 2. 3. Monitoring, 1 Analysis and/or Inspection 3. 4. 5. 6. 7. Corrective 1. Measures 3. 4. Odors of hydrogen sulfide origin Corrosion of iron work and concrete Black color observed in liquid or solids I Hang hydrogen sulfide (lead acetate) indifl tiles in wet well. (}W»-£- \X) V- Mf-we-tv wgfi ah(i analyze for total Check for floating solids in wet well. / Run dye test on influent sewer or sewers to determine velocity of waste flow and travel time to wet well. Check temperature of wastewater in wet well. Check pump invert position and condition. Check passage time in the interceptors at flow velocities. Low velocities (less than 2 ft/sec) are an indication that solids are being deposited in influent sewer and sulfides are being formed and released in the wet well. increased in the sewer or influent must be continuouslyCreated upstream with chlorine or copperous to pi?olT±bi-fe~fefee**aevelopment of hydrogen sulfide gas. If the source of hydrogen sulfide is in the wet well and not the influent sewer, increase pumping cycle for more frequent removal of solids. Install air diffusers in wet well to keep wastewater fresh. Install blower and gas scrubber for the oxidation of the gases and exhausting to the atmosphere. Dose wet well with£hyperchloride)on' a periodic basis to suppress the formatiotf"•crC-irygrogen sulfide. 52 ------- I. PRETREATMENT - Screening and Shredding Problem Indicators Monitoring, Analysis and/or Inspection ACCUMULATION OF DEBRIS FOR DISPOSAL Large amount' of rags and debris*accumulated-.on plant site gives off obnoxious odors and attracts \flies and other insects. . stimate volume '(cubic feet) of rags and debris removed eacB day-in PE9.pprjtJ.oii to flow. ine v_ ^ exposed material Ts allowed to accumulate Check disposal method used. Corrective 1. Arrange for local refuse or garbage company to pick up Measures rags and debris on a daily basis and dispose of them in a sanitary fill. ' .——"^ 2. Store rags and debris in closed containers whenever possible. \ 3. If incineration facilities are available on plant site or at some other convenient location, burn them. Care must be taken to see that /the emission from the incinerator meets location air pollution control requirements. 4. Rags and debris can be disposed of on the plant site if sufficient land is available for a fill and cover tion. If none of the abokve debris can be grou equipment and retu should only shrejdded and i thods pro up by instal d"'to the pla a last re ay cause p: feasible, rags and the proper flow. This method since ground or in pumping 53 ------- I. PRETREATMENT - Screening and Shredding Problem Indicators Monitoring, Analysis and/or Inspection EXCESSIVE GRIT IN BAR SCREEN CHAMBERS Surging * in chamber-due — l-r-TrSurging <2tAj8j incr i-h waterVJLevel. 2. I/ow removal off grit by degritting equipment -i y oJ— 1. Sound chamber with flat board at end of pole to determine depth of grit. 2. Determine velocity in chamber by timing a dye release from one end of chamber to the other. 3. Check plans and probe bottom of chamber to determine whether there are any irregularities in chamber bottom slope. 4. Check channel when dewatering for regularly scheduled maintenance. Corrective Measures 1. 2. 3. If velocity in chamber is less than 2 ft/sec, flush chamber regularly with high pressure water hose. If slide gates are available at inlet end of chamber, throttle gates to jet flow along chamber bottom. Remove irregularities or reslope chamber bottom; if possible, to increase velocity. 54 ------- I. PRETREATMENT - Screening and Shredding Problem ODOR SOURCE IN GRIT CHAMBER Indicators 1. Odors of hydrogen sulfide origin 2. Corrosion of metal work and concretx Monitoring, Analysis and/or Inspection 3. 1. 2. 4. Corrective Measures 6. 7. 1. 2. 3. Hang hydrogen sulfide (lead acetate) tiles in chamber Check velocities through grit chamber Check volatile solids content of the grit. and/3inaly/6fe foi\to,ckl arid /dijfsSlteedy siW tide.------- I. PRETREATMENT - Screening and Shredding Problem Indicators Monitoring, Analysis and/or Inspection SHREDDED SCREENINGS, CLOGGING PUMPS 1. Rope-like rags and debris wrapped around pump impellers. 2. Pump suction lines plugged with "bundles" of rags. vy 3. Excessive pump or drive treating and power requirements. 4. Appearance of chunks larger in size than usual in the shredder discharge. 1. Install pressure gages on discharge side of pump and check pressure daily. 2. If pump discharge line visible, check flow daily. 3. Check power input, bearing heat pressures on inlet and discharge sides. 4. Check driver speed and power train for power use and delivery to the shredder. Do not shred screenings and return them to flow. Remove them either mechanically or manually and dispose of them bv burial. Check cutters periodically on all barminutors, comminutors, and other shredding equipment for sharpness. Back flush pumps, periodically if possible. If necessary, modify pump type, inlet protection or prior protective devices to avoid recurred plugging. Upgrade screening and grit removal operation. 56 ------- I. PRETREATMENT - Grit Handling and Removal Problem Indicators Analysis and/or Inspection Corrective Measures GRIT REMOVED HAS HIGH ORGANIC CONTENT 1. 2. 3. Monitoring, 1. 2. 3. 4. 3. 4. Grey color Odors from Greasy fe with^excessive components I Run volatile solids test on grit daily. Check discharge pressure on cyclonic grit removal equipment. Check velocities with dye releases in grit chambers. If grit chamber is aerated, check air flow rate to chamber. Visual examination of grit and identification of origin of grit materials. Keep pressure on cyclonic grit removal equipment at an acceptable range (usually between 4 and 6 psi) by governing pump speeds. Increase velocities in grit chambers by whatever means possible. Adjust air accordingly. Check inlet and outlet controls, baffles and mechanical equipment; adjust and repair and keep clean. 57 ------- I. PRETREATMENT - General Problem INDUSTRIAL WASTE IS INADEQUATELY PRETREATED. Indicators 1. Discoloration of influent iSterTTrTZtftionJof biological treatment. esses 3. Digester upsets .4. Change in influent odbi 5. Unusual amounts of solids in influent Monitoring, Analysis and/or Inspection 1. Constantly monitor influent for pH above 8.0 or below 6.0 2. Check pH of raw sludge. 3. Run heavy metal tests on influent. 4. Check influent temperature. 5. Run settleable solids test. 6. If toxic flow is constant, attempt to trace source upstream of treatment plant. 7. Run C.O.D. test on contaminated effluent and compare results with normal plant loading. Bypass all biological treatment processes to parallel units as soon as contaminant has been detected. Isolate and dispose of all contaminate sludges. If digesters show increases in volatile acids because of contaminated sludges, see Section VII(b) for corrective measures. If activated sludge process has become contaminated, dispose of floe and restart process. Institute program of source control (industrial waste ordinances). 58 ------- II. PRIMARY TREATMENT - Primary Sedimentation Tanks Problem Indicators Monitoring, Analysis and/or Inspection FLOATING. GASEOUS. OR/SEPTIG SJLUDGE V . Mr. t Corrective i. 2. loating material! in ta deadspots ortin sgum troughs igin Dewater tanks and check sludge collector mechanism (flights, chains and scrappers) for wear and tear. If total solids of raw sl&dge analyzed a cycle is over 2%, increase duration of pumping cycle, preferably with a timer. If sludge collector mechanism shows signs of wear during 'inspection, repair or replace. Certain chemicals \ sutin\ as alum, used in\chemical treatment, .cause floatine sluage afVthis chemical is recirculated tW the, primajjy sedimentation rcanks. Change operating/procedures or chemicaMis usedyl Long detention in sludge hoppers favors production of a sludge that readily slips. 59 ------- II. PRIMARY TREATMENT - Primary. 'S«Mn.mentation Tanks Problem Indicators LOW SETTLEABLE SOLIDS JlEMfcVAL EFFICIENCY! ^ A iAtj-A™ ^-rj^ £R 2. Percent settleable solids removal below 95% Monitoring, Analysis and/or Inspection Corrective Measures 6. 1. 2. 3. Run settleable solids test (Imhoff Cone) during times of day where there are appreciable changes in plant flow. Check raw sludge removal pumping cycles and duration of pumping period. Dismantle and/or inspect raw sludge pumps an collection mechanism for wear and tear. Check tank inlets with relation to the tank ^outleYs. If baffles have been installed on the inlets, dewater the tanks and check their condition. Calculate theoretical detention time, weir overflow rates, and surface loading rates and compare all data with design criteria. h v . - ft * lu/j Try a dye test to estim^reWlow^trfrougntime. Check for density stratification due to significant tempera-f ture or density difference top sto bottom If efficiency*of removal drops during peak or increased plant flows, the hydraulic capacity of tanks has probably been exceeded. Refer problem to operating agency engineering staff. Repair all worn raw sludge pumps, parts and sludge collector mechanism. Damaged or missing inlet line baffles could cause tank short circuiting whereby increased velocities from one end of the tank to the outlet end cause settleable matter to remain in .suspension. Tleplace or repair baffles. 60 ------- II. PRIMARY TREATMENT - Primary Sedimentation Tanks- Problem ERRATIC OPERATION OF SLUDGE COLLECTION MECHANISM Indicators Monitoring, Analysis and/or Inspection Corrective Measures 1. 2. Frequent replacement of broken sheer pins on chain driven collector mechanisms. Frequent torque switch activated alarms on concentric driven clarifier equipment. Visible slippage or "stuttering" collection mechanisms. of clarifier sludge Check all drives for gear wear. Dewater tank and check chains and sprockets for wear see that chains have not come off sprockets. &JC4£> Check to see that rags and debris have not entwined themselves around sludge collector mechanism. Check dewatered tanks for excessive bottom deposits of sand, rocks and other inorganic material. Sound bottom for excessive^ accumulation o£ sludge. . .^ _ , V> /lAs&Ot Repair all worn sludge collector equipment and drives. If rags are a problem, make provisions for removal of all rags and debris as part of the pretreatment process. If sand and rock deposits on the tank bottom are a problem, provide adequate screening and grit removal as a part of the pretreatment process. If sludge accumulation is a problem, increase frequency of pumping raw sludge from tanks. 61 ------- II. PRIMARY TREATMENT - Primary Sedimentation Tanks Problem Indicators LOW SCUM (GREASE) REMOVAL Monitoring, Analysis and/or 1. 2. 1. 3. 4. 5. Visible grease particles being discharge/ effluent * serve if wooden flights making a return travel on tank surface carry grease particles adhered to them under scum troughs at the discharge end of the tanks. ickup wiper blades. If possible, lower return wooden flight to beVLow wateh surface so grease particles do not adhere to them. Install surface surface |rays to direct grease particles on tank !m troughs. Water spray should not break n on water surface. If scum removal is done manually and intermittently, continuous removal equipment should be installed. Excessive water in scum pits should first be removed by pumping from bottom of pit to plant headworks and then the concentrated scum can be pumped to a digester or an incinerator. Efficiency of scum removal in plants receiving a high grease loading can be increased by the addition of flotation or evacuator equipment. Since grease particles normally in suspension tend to agglomerate into larger particles after being dosed with chlorine, chlorine contact tanks should be provided with grease removal equipment. Pump scum pits down on a regular basis so as not to cause scum overflows back into the clarifier. Clean and replace all worn wiper blades. f/ 62 ------- II. PRIMARY TREATMENT - Primary Sedimentation Tanks Problem TANK CONTENTS TURN SEPTIC Indicators 1. Tank contents are a dark color r 2. Hydrogen sulfide odors emitted from tanks Monitoring, Analysis and/or Inspect / \ RuA to±al/antf Idis^bJved^ulfi taAk/Kj/fuent teib Run DO test. Check quantity and total solids of all inflows into tank from other plant processes such as digesters supernatant, thickener overflows, centrifuge con- centrates, etc. f tank influent contains high dissolved and totalj sulfides, influent is septi< oorroot-problom.. a4~&g>u-pee.. If tank influent pH is below 6 or above 8, toxic waste is being discharged yit^O|Dlant a^nd mpfctlbe oprMkcted a the source. M tyUtAwijtf /$A^4[U4AA H?P If discharges rrdmSother nJWfnt processes contain excessive total soli&sa«ncl exceed 5% of the daily tank .1)inflow, the sedimentp^ba».^ank is being overloaded. If \possible, reduce n^re of precede flows to sedimentation tanks or pretre-er flows by aerating <•>]- fhinri patjng them If possible divert or find other means of disposal for supernatant or centrates. tX? 63 ------- III. SECONDARY TREATMENT - Activ 3. Filamentous growths in mixed liquor Monitoring, Analysis and/or Inspection 1. 2. 3. 4. Check mixed liquor for low pH and low dissolved Check sludge age, food/micro-organism ratio, or mean cell residence time. Run settleability test and check for separation of floe in graduated cylinder or use Mallory Direct Reading Settleometer. Check aeration period. •"lir rli' fnr TOPI ind-jff Corrective Measures If possible, reduce organic loads on aeration tanks affected. Add digested sludge (that has been aerated for some time) to aeration tanks. Dose the aeration tanks with alum or ferric chloride together with lime. TeTOrTT activated sludge. sludge age and air rate -jrg^stojj ^nili'lf icatjxnr; Increase sludge age by regulating waste sludge rate. Increase or correct low dissolved oxygen or pH in aeration tank. Increase aeration period by placing another aerator operation if possible or reduce the return sludge te by thickening the return sludge concentration by coagulation. Control filamentous growth by increasing sludge age or supplementing nutrient deficiencies. inimum 64 ------- III. SECONDARY TREATMENT - Activated Sludge/Process ERRATIC SLUDGE VOLUME INDEXES Indicators 1. Pin floe visible in final clj^ifiers overflow 2. Poor settling characterisj^cs of mixed liquor lids in each aerat Monitoring, Analysis and/or tleability test in each aeration Inspection the point floe is a recurrent result of toxicants. Determine^whe situation or Regulatsr wasting to decrease suspended solids mixed Xiquor . Chlflfrinate return activated sludge. crease-solids loading to aeration tanks. Make appropriate adjustments to obtain a less oxidized sludge. 65 ------- III. SECONDARY TREATMENT - Activated Sludge Process Problem Indicators DIFFICULTY IN MAINTAINING BALANCED MIXED LIQUOR DISSOLVED OXYGEN AN AERATION^TANK Monitoring, Analysis and/or Inspection Corrective Measures N? \ Intermittent sludge bulking 2. Loss of sludge blanket in secondary clarifier 3. Dark color in the aerator contents 1. Check D.O. concentration in different areas of aeration tanks during changes in daily flow. 2. Check suspended solids in mixed liquor at different periods during the day. 3. Run suspended solids test on aerator influent and mixed liquor to check sludge age. 4. Monitor rate of flow to aeration tanks. 5. Check daily flow variation in loading for excessive peak demand periods. 1. Lower D.O. concentrations occurring during changes in plant flow are an indication of excessive loading of aeration tanks. Increase air supply to tank if possible by placing another blower into service, etc. 2. Decrease loading to aeration tanks by placing more tanks into service if possible. 3. Provide controlled air supply to aeration tanks by interlocking blower speeds to tank D.O. monitoring equipment. 4. Increase inflow could hydraulically overload the \ secondary treatment systt Aportion oiVthe V ,i-*i If possible, bypass a he primary sed ns to normal ------- III. SECONDARY TREATMENT - Activated Sludge Process Problem EXCESSIVE FOAM IN AERATION TANKS Indicators 1. Frothing in aeration tanks Monitoring, Analysis and/or Inspection 1. Check influent for radical temperature changes. 2. Run M.B.A.S. test on influent. 3. Check suspended solids concentration in aeration tanks. 4. Check D.O. concentration in aeration tanks. Corrective Measures 1. 2. 3. 4. If practical, increase mixed liquor suspended solids by decreasing wasting rate. Install or operate reclaimed water sprays in aeration tanks. Utilize defearning agent. i**Fr " Lower air supply while being careful to maintain a safe dissolved oxygen concentration in aeration tanks. 67 ------- III. SECONDARY TREATMENT - Activated Sludge Process Problem DIGESTER SUPERNATANT AND/OR CENTRIFUGE CENTRATE UPSETTING ACTIVATED SLUDGE PROCESS Indicators 1. Mixed liquor changes from a light to a dark brown 2. Mixed liquor suspended solids decrease sharply during operation of centrifuge or when sludge is being pumped to digester 3. Final clarifier effluent increases in turbidity 4. Mixed liquid DO decreased. Monitoring, Analysis and/or Inspection 1. Run total solids and pH tests on supernatant or centrate being returned to plant headworks. 2. Check mixed liquor suspended solids during discharge of centrate or supernatant. 3. Continuously check mixed liquor D.O. 4. Check volume of concentration of recycle flows relative to total plant flow. Corrective 1. Program discharges of supernatants or centrates so they Measures do not coincide. 2. Pump centrates to digester whenever possible. 3. If centrates have high solids content, use flocculants in the operation of the centrifuge. 4. If supernatant have high solids content, experiment with supernatanting from a different level in the digester. 5. If possible, pre-aerate centrate and supernatants prior to discharging them to the activated sludge process. 6. Avoid discharging supernatants from septic digesters to activated sludge process. 7. If possible, release only small amounts of supernatant or centrate during periods of low inflow and increase return activated sludge rates if necessary. 8. Program recycles so that the return load does not exaggerate peak loading. 68 ------- III. SECONDARY TREATMENT - Activated Sludge Process Problem UNABLE TO MAINTAIN BALANCED FOOD/MICRO ORGANISM RATIO IN AERATION UNIT Indicators 1. Fluctuation in S.V.I. 2. Fluctuation in sludge age. Monitoring, Analysis and/or Inspection 1. Check S.V.I, at least daily. 2. Check mixed liquor suspended solids at least daily. 3. Check suspended solids in influent and effluent at least daily. 4. Monitor plant flow, return activated sludge rate, and waste activated sludge rate. Corrective 1. Select and operate secondary treatment system by either MeasuresMean Cell Residence Time, Solids Retention Time, food/micro organism ratio, or sludge age. 69 ------- FACILITIES INADEQUATE FOR DISPOSAL OF WASTE ACTIVATE \ (HIGH SUSPENDED SOLIDS IN THE CLARIFIER OVERFLO^) SECONDARY TREATMENT - Activated Sludge Process 1. High suspended solids in mixeiL_ii£LuJor 2. Increased turbidity in final clarifier effluent '\ 3. High solids concentration in digester supernatants and sludge thickener effluents Monitoring, Analysis and/or Inspection 1. Check S.V.I, at least daily. 2. Run C.O.D. and suspended solids of plant influent with and without supernatant and thickener return flows. 3. Check blanket depth level or high and low load periods. 4. Check inlet and outlet baffling for possibility of short circuiting. Corrective Measures" 1. sludge lS~n«JL_ae.t±*iTi"g '±~n flnw-nf mini — mirier rn rTii rlrrnrr~nr thj^skenorj inrrra dose thickener inflow with coagulants. 3. Re-aerate waste sludge prior to pumping to thickeners or~ discharging to primary clarifiers. 4. Change operation mode of aeration tanks to contact stabilization if possible. 5. If the sludge doesn't settle satisfactorily, coagulate with iron or aluminum , but adjust pH *f jmrr>n-nt£% to keep aerator pH within 6.0-8.5. 70 ------- III. SECONDARY TREATMENT - Activated Sludge Process Problem UNEVEN HYDRAULIC AND SOLIDS LOADING OF AERATION TANKS Indicators 1. Mixed liquor suspended solids in each aeration tank varies considerably. 2. Dissolved oxygen in each tank varies considerably. Monitoring, Analysis and/or Inspection Corrective Measures 1. Run S-.V.I-. "T.n each tank at least daily. 2. Run mixed liquor suspended solids in each tank at least daily. 3. Run dissolved oxygen in each tank at least daily. 4. Run suspended solids on influent and effluent. 1. Adjust valves and tanks when operating u 2. Equalize air flow air discharge line es to equalize flow to all conventional mode. tanks by throttling valves on 71 ------- III. SECONDARY TREATMENT - Trickling Filters Problem Indicators Monitoring, Analysis and/or Inspection Corrective Measurete H -• '' '•''<£ ^ ICE BUILDUP ON MEDIA 1. Visible ice formation on filter media 1. Check air temperature. Jr 2. Check recirculation rate to filter. 3. Check flow through filter orifices. 4. Check temperature of wastewater flow to filter. 5. Check filter surface for even distribution of flow. 1. 2. 3. 5. By regulating amount of recirculation rate, adjust. flow\ -, to filter to proMbit the formation of ice. AX\£/\ 1 \* \ ]'//••'/ ' " n Adjust flows from orifices and splash plates to reduce spray effects. Cover filter to reduce heat loss.es or install a windbreak to reduce chill factor. Manually break up and remove major ice formations. . If possible, add hot water or steam to filter influent. 72 ------- III. SECONDARY TREATMENT - Trickling Filters Problem Indicators Monitoring, Analysis and/or Inspection FILTER ODORS / o 1. Orlnrfl nf tiydrnfrn nrtilfirir nrif-in present il/ ack slime visible on surface of 1. Ch^Bk^dTssolved and total sulfide of 2. Check filter dj-aiois for stoppages or growths. &tA/y %{* 3. Check rate (of recireulation to filter..^ U QM^ 4. Check ,-for Miter, overflow or jSplashjLr 0 Corrective «," 1. If flow to filter is septic, correct in upstream system Measures \ . "" for l™--~ by aerationor controlled prechlorination ation. | ...,_. »«^ Vr.""2. Clear under drain system of all stoppages. A° I* 3. Force air into filter drain system to increase ventilation* '\ V tk^ through filter media. rJv"' \ . f\ ff- ' \ 4. Increase recirculation rate to filter to increase|D.fO. and to, slpuglxvc&f f'.feurfaoe "Slime. jSM | | 1 **" |,AA { ^ ( t •( i 5. Keep areas around filters clean of slimes- and growths. 6. Cover filter wi ^h J1Hejrt'i»rna't:p'>"i.fll^air'f1^fixhaust air into ------- III. SECONDARY TREATMENT - Trickling Filters Problem FLY NUISANCE IN VICINITY OF FILTER Indicators 1. Tiny gnat sized flies becoming a nuisance in plant area and in neighboring area Monitoring, Analysis and/or Inspection Corrective Measures 1. Inspect grounds for tall grass, weeds and other sanctuaries for filter flies. » 1. Increase rate of recircuJLation .to .filter^ to waslj. fly larvae out of filter. \ \ aslj. f V* 2. If possible, flood filter for approximately 24 hrs. to prevent completion of life cycle of flies. Apply a low dosage of chlorine being careful not to sterilize filter media. V/'2-Maintain grounds so as not to provide sanctuaries for f * flies. I 74 ------- III. SECONDARY TREATMENT - Trickling Filters Problem Indicators Monitoring, Analysis and/or Inspection CLOGGING AND PONDING OF FILTER MEDIA 1. 2. 1. 2. 3. 4. 5. Ponding on filter surface Intermittent flooding of filter Check size of filter media for uniformity Check for cementing or breaking up of media. Check for fi or snails in slime growths, trash, insect larvae, r media voids. Check organic loading on filter. Check hydraulic load on filter. Corrective 1. If filter media is non-uniform and the smaller pieces Measures fill the voids, replace the media. 2. Jet problem areas in filter media with a high pressure water s/pray fron^a stationary distributor. y to lessen or remove any Flood filter media ccumuiations. growth poasttTTet 75 ------- III. SECONDARY TREATMENT1- Trickling Filters Problem CLOGGING OF DISTRIBUTOR NOZZLES CAUSES nfj TTITT F.TTTTOT] Indicators Monitoring, Analysis and/or Inspectien Corrective 1. 2. 1. 2. Uneven sprays from distributor nozzles Ponding on certain areas of the filter media with concurrent drying of other areas ttempt to identify types OT solieqf clogging nozzles. Check for visible grease particles in waste being pumped to filtej .emove and clean all nozzles and thoroughly flush distributor piping. Improve primary clarifier skimming to prevent grease carryover to filter. Increase detention settleable and suspend \ primary tanks to prevent olids carryover to filter. 76 ------- III. SECONDARY TREATMENT - Oxidation Ponds Problem EXCESSIVE WEEDS AND TULES Indicators -1-. Excessive weed and tule growths 2. Mosquito problems in neighborhood of ponds 3. Poor pond circulation Monitoring, Analysis and/or Inspection Corrective Measures 1. Check water depths in selected areas of the pond Deepen all pond areas shallower than three feet. Remove all weed and tule growths as soon as they are visible. every 10 days. varY liquid level in the pond 77 ------- III. SECONDARY TREATMENT - Oxidation Ponds Problem POND ODORS Indicators 1. Odors of hydrogen sulfide origin from pond 2. Other objectionable odors Monitoring, Analysis and/or Inspection 1. Check for blue-green algae growths in pond. 2. Check for scum accumulation in pond. 3. Analyze for total and dissolved sulfides in pond and pond influent. 4. Check pond pH and pond influent pH. 5. Check DO content in pond at several locations. Corrective 1. If pond influent is septic, correct situation upstream Measuresby aeration or controlled prechlorination. 2. If possible, aerate pond with mechanical aerators. 3. Remove or break up all scum accumulations. Sir 5. If pond is septic, divert flow from aerobic pond to or pump high D.O. make up water to it. 6. Add sodium nitrate to pond. 78 ------- III. SECONDARY TREATMENT - Oxidation Ponds Problem Indicators LOW POND DISSOLVED OXYGEN 1. Low algae growth in pond 2-, Traoo hydge§eB-&u3^£d.de..odor. Monitoring, Analysis and/or Inspection 3. Grey color of pond Check all areas in pond for adequate D.O. 2. Monitor flow into pond and calculate average daily detention time in pond. 3. Check pH of pond influent and pond contents. Run total and dissolved sulfides in pond influent. 5. Check pond loading rate (Ib BOD/acre). t~i c '"weedHT""*' aq Corrective 1. Increase detention time in ponds to at least 5ive days ~~~~ by placing ponds in parallel. 2. In the absence of adequate D.O. in the pond, aerate pond contents or pond influent. I ' 4. Physically remove floating weeds/£0 increase light penetration. 79 ------- III. SECONDARY TREATMENT - Final Sedimentation Problem Indicators Monitoring,^ Analysis and/or Inspection SLUDGE OR PIN FLOC FLOWING OVER WEIRS 1. Particulate material rising to surface in clarifier 2. Effluent clarity poor Corrective Measures discharged from clarifier Attempt to determine height of sludge blanket in clarifier with depth sampler TIT I rnl uirnfTlm pi>\p Ktm/s>u^peni*ed sp4J:5Js>el<^^ eck all sludge uptake piping to see that they are flowing freely nntl from.Di 6. Check pump rates and schedules of sludge withdrawal pumps. 'N x-\ ^^ -1-udge ly at the periphery of th tank. 8. Determine if the weir overflow rate is equal for the entire weir. P 1. Increase pumping rate for greater removal of sludge from clarifier. 2. Wash down or clean all sludge uptake piping. 3. Repair or replace all damaged sludge scraper mechanism. 4. Level the weir. 5. If uneven weir overflow rate is caused from wind, install a windbreak. 6. Persistence of this problem would indicate a mal- function in the secondary treatment process. 80 ------- III. SECONDARY TREATMENT - Final Sedimentation Problem ERRATIC OPERATION OF SCRAPER MECHANISM Indicators 1. Frequent torque switch activated alarms on concentric driven clarifier equipment 2. Visible slippage or "stuttering" of clarifier sludge collection mechanisms Monitoring, Analysis and/or Inspection 1. Check all drives for gear wear. 2. Dewater tanks and check for true travel of scrapper mechanism. Corrective .Measures 1. Repair all worn sludge collector equipment and drives. 81 ------- IV. ADVANCED TREATMENT - Chemical Coagulation and Flocculation Problem CHEMICAL COAGULANTS UTILIZED FOR SETTLING OR DEWATERING SLUDGES THROUGH RECYCLING CAUSE FLOATING SLUDGES IN PRIMARY SEDIMENTATION TANKS. Indicators 2. 3. Floating and gaseous sludge floating in primary sedimentation tanks during periods of chemical treatment Poor settling characteristics in the sludge Poor sludge dewatering characteristics. Monitoring, Analysis and/or Inspection Determine types and amounts of chemicals used. Check the dosing sequence, the rapid mix energy, and flocculation energy. Corrective Measures Correct the dosage of coagulants and alkalinity in line with process requirements on the basis of phosphorus content and a coagulant metal/phosphorus ratio of about 2/1. Institute a regular phosphorus determination and product turbidity control. Correct coagulant concentrations and dose points to favor efficient chemical usage. Make sure that sufficient rapid mix energy (800-1000 G) is applied for 1/2 to 2 minutes after dosage to mix substrate and coagulant. Follow with lower energy flocculation to agglomerate fines. Adjust coagulant dosage in line with flow and concentra- tion variations in the plant inflow. Monitor the treated overflow turbidity by the hour. 82 ------- DUB IV. ADVANCED TREATMENT - Ammonia Stripping Problem FREEZING IN AMMONIA STRIPPING TOWER Indicators 1. Ice formation on outside face of tower 2. Drop in ammonia removal efficiency Monitoring, Analysis and/or Inspection 1. Monitor ammonia removal 2. Check out water temperature for maximum and minimum values. 3. Check air circulation rate and distribution. Corrective 1. Use large flow distribution orifices at the outside face Measures of the tower thus concentrating a curtain of warm water where the cold air first enters the tower. 2. Reverse draft fan to blow warm inside air outward to melt the ice. 3. If ammonia removal efficiency drops below 30%, take the tower out of operation. 83 ------- IV. ADVANCED TREATMENT - Ammonia Stripping Problem FORMATION OF CALCIUM CARBONATE SCALE ON AMMONIA STRIPPING TOWER FILL AND STRUCTURAL MEMBERS Indicators 1. Visible scale deposits in tower Monitoring, Analysis and/or Inspection 1. Check pH of tower influent (ph has to be 10.5 or greater. Corrective Measures 1. Hose off scale with water jet at periodic intervals. 2. Install water sprays in tower for jetting off scale at frequent intervals. 3. Clean tower with light solution of sulfuric acid. 84 ------- IV. ADVANCED TREATMENT - Filters Problem FILTER BACKWASH WASH WATER HYDRAULICALLY OVERLOADS AND UPSETS CLARIFIERS Indicators 1. Surging of clarifier during filter backwash operation 2. Higher turbidity in the treated flow Monitoring, Analysis and/or Inspection 1. Determine amount and rate of filter backwash water being recycled to clarifiers. 2. Increase drum speed, backwash pressure or temperature, and backwash rate. Corrective 1. Collect backwash wastes in a storage tank and recycle Measures at a controlled rate to clarifiers. 85 ------- IV. ADVANCED TREATMENT - Microscreen Problem FOULING OF FABRIC WITH GREASE AND SOLIDS Indicators 1. Loss of microscreen efficiency 2. Visible solids and grease on fabric Monitoring, Analysis and/or Inspection 1. Run suspended solids test on influent to screen. 2. Check for upset in activated sludge process, if any. Corrective Measures 1. Increase speed of drum. 2. Increase backwashing pressure. 3. Adjust backwashing cycles. 4. Backwash with hot water. ( 5. Backwash with an approved degreasing agent. 86 ------- IV. ADVANCED TREATMENT - Microscreen Problem MICROSCREEN EFFLUENT EXHIBITS HIGHER SUSPENDED SOLIDS CONTENT THAN INFLUENT. Indicators 1. Increased suspended solids and turbidity on discharge side of screens. Monitoring, Analysis and/or Inspection 1. Determine colloidal solids in the influent to microscreens. 2. Determine total solids removal efficiency of microscreens. 3. Determine C.O.D. removal efficiency of microscreen. Corrective 1. Convert colloids in microscreen influent to suspended Measuressolids by adjusting the pH accordingly or by the addition of coagulants. 87 ------- IV. ADVANCED TREATMENT - Activated Carbon Problem MECHANICAL FOULING OF COLUMNS Indicators 1. The flashing of aciCumulated /Jlids from ^rbon columns is followed by ajy abrupt increase in th^ rate of absorption ' / / 2. Pressure rises in downflow columns 3. Decrease in flow rate. Monitoring, Analysis and/or Inspection Corrective Measures Run suspended solids and total organic carbon of column influent and effluent. 3 1. 2. 3. Check columi operating routine and backwash records. Bypass column ^ifluent with large amounts of suspended matter. Flush columns frequently. Consider upflow operation, filtration, or larger carbon grain size. 88 ------- Monitoring, Analysis and/or Inspection V. DISINFECTION - Chlorination INSUFFICIENT CHLORINE GAS PRESSURE AT THE CHLORINATOR ITH ALL CYLINDERS CONNECTED TO GAS PHASE Chlorine pressure gage at chlorinator is reading too low. Chlorine supply lines from cylinders are either very cold or are icing. ne cylinders or cylinder show a frost line. o about one-tenth the Reduce feed rate on chlorinator rotameter capacity. '/* hlorine gas pressure risesmJ^ that the rate of feed ft/^ ded If after a short period the appreciably it can be cone through the chlorinator \f greater than the evaporation rate of the chlorine cyynders or cylinder at the prevailing ambient temperature. Corrective 1. Connect enough cylinders to the supply system so that Measures the chlorine feed rate does not exceed the withdrawal rate of the cylinders. For 150 Ib. cylinders the withdrawal rate at room temperature is 40 Ibs. per day per cylinder; for ton containers it is 400 Ibs. per day. At lower temperature it is less. 2. If insufficient cylinder capacity exists, do not try to apply heat directly to the cylinders, and do not heat the chlorine storage room with a space heater unless the control equipment (chlorinator) room can be brought to the same temperature. 3. The chlorine cylinder should always be kept cooler than the control equipment if possible; otherwise reliquefaction of chlorine may occur at the chlorinator. 89 ------- V. DISINFECTION - Chlorination Problem INSUFFICIENT CHLORINE GAS PRESSURE AT THE CHLORINATOR Indicators 1. Chlorine pressure gage at chlorinator is reading too low. 2. Chlorine supply lines from cylinders are either very cold or are icing. 3. There is icing or considerable cooling at one point in the chlorine header system between the cylinders and chlorinator. Monitoring, Analysis and/or Inspection Reduce feed rate on chlorinator to about one-tenth the rotameter capacity. If icing condition or cooling effect does not disappear, mark the point wh\ere cooling begins and secure the chlorine supply system at vhe cylinders, but let the chlorinator continue to operate\ Corrective Measures When chlorine gas pressure at chlorinator reaches zero and with chlorinator still operating, disconnect flexible connection to one chlorine cylinder. (This will allow chlorinator to evacuate residual chlorine in header system by replacing chlorine with air.) Disassemble chlorine header system at point where cooling began. A stoppage or a flow restriction will be found at or near this point. After the stoppage has been found it can be cleaned with a solvent such as tri-chlorethylene. For massive build-up in black steel pipe header systems, the pickling process should be used. This consists of isolating the header system by disconnecting it from the cylinders at one end, the chlorinators at the other, and flushing with cold water until the water coming out is clear. The header then has to be dried with steam or hot air and final air drying to a dew point of -40 F. 90 ------- V. DISINFECTION - Chlorination Problem THERE IS NO CHLORINE GAS PRESSURE AT THE CHLORINATOR, WHEN APPARENTLY FULL CHLORINE CYLINDERS ARE CONNECTED TO THE CHLORINE SUPPLY SYSTEM. Indicators Chlorinator gas pressure gage is at zero, inlet valve is open, all valves beginning with chlorine cylinder valve to the chlorinator are open. Monitoring, Analysis and/or Inspection Check the external chlorine pressure reducing valve installed just downstream of the chlorine cylinders. Corrective 1. If normal chlorine pressure appears at the chlorinator Measuressecure all the main chlorine cylinder valves, and start ventilating fans if available and arrange for maximum ventilation. 2. Put on a gas mask and gingerly break one flexible connection joint to release the gas in the header system. 3. Place a bottle of ammonia on the floor near the connection to be broken and when a white vapor appears leave the area as fast as possible and return only when the vapor disappears. 4. Repair the reducing valve which is probably plugged from the inherent impurities in chlorine gas. These units should be put on bi-annual overhaul. 5. Install a chlorine gas pressure gage upstream of the pressure reducing valve. 91 ------- \Indicators. V. DISINFECTION - Chlorination IMPOSSIBLE TO OPERATE CHLORINATOR BECAUSE ROTAMETER TUBE ICES OVER AND FEED RATE INDICATOR IS EXTREMELY ERRATIC. CHLORINE SUPPLY IS FROM TON CONTAINERS CONNECTED TO THE GAS PHASE. Monitoring, Analysis and/or Inspection Corrective- Measures There is sufficient chlorine gas pressure and injector vacuum and the chlorine is at room' temperature but the rotameter tube that indicates chlorine feed rate is nearly completely iced over. The entire chlorine supply line back to the cylinder is also iced over, but cylinders are at about ambient temperature. Inspect the chlorine cylinder area to see if they are connected properly. (This problem is specific to. ton containers.) tv Shut off main outlet valve on all cylindersAand evacuate chlorine in header system until gage pressure at chlorinator reads zero. Disconnect the cylinder that had ,. ,, _ , , , connection to the outlet valve and^rotate it 180 Jand ^reconnect to ,toji_QiLLlet valve and witn j'otner cylinders closed7place this one in operation. Tag cylinder so that packager can identify it as defective with possible broken dip tube but allow cylinder to remain in1 use until empty.. ------- V. DISINFECTION - Chlorination Problem CHLORINATOR WILL NOT FEED ANY CHLORINE EVEN THOUGH ALL SYSTEMS APPEAR NORMAL. Indicators Chlorinator feed rate indicator shows little or no indication of chlorine flow when chlorine control valve is moved from closed to wide open position. The chlorine pressure gage in the chlorinator is normal but the injector vacuum gage shows an abnormally high vacuum. Monitoring, Analysis and/or Inspection Check for an obstruction in the chlorine gas line near or at the inlet cartridge of the chlorine pressure reducing valve inside the chlorinator by shutting off chlorine supply system at chlorinator; chlorine pressure gage remains the same or moves downward in pressure at a very slow rate, i.e., one division per five minutes. Corrective Measures Shut off chlorine supply at the cylinders and try to let the chlorinator drain off all the chlorine gas pressure in the chlorine supply line. If this cannot be done, turn on the ventilating equipment in the chlorine container space, if any, open all windows, don a gas mask and break a connection in the chlorine supply header but be absolutely sure that all chlorine cylinders have been secured. When the gas has sufficiently cleared itself from the working area, disassemble the chlorinator chlorine pressure reducing valve to remove inlet cartridge and clean stem and seat with a soft cloth. If this situation occurs regularly during hot weather, the source of the trouble usually is a result of the chlorine cylinders being hotter than the chlorine control apparatus. Inspect cylinder area to see if anything can be done to make the area cooler. Do not connect a new cylinder if it has been allowed to sit in the sun. Install an external chlorine pressure reducing valve adjacent to the last chlorine cylinder connected to the supply system. Precede the reducing valve by a combination chlorine filter and sediment trap. 93 ------- V. DISINFECTION - Chlorination Problem CHLORINE GAS IS LEAKING FROM VENT LINE CONNECTED TO EXTERNAL CHLORINE PRESSURE REDUCING VALVE (CPRV). Indicators 1. There is no visible indication of a malfunction. 2. Chlorine escaping from CPRV vent line. 3. Chlorine gas pressure, chlorine feed rate and injector vacuum are all normal. Monitoring, Analysis and/or Inspection 1. Confirm leak by placing ammonia bottle near the termination of the CPRV vent line. Corrective The symptom described indicates that the main diaphragm of the CPRV has been ruptured. Remove the external CPRV after evacuating header system and replace with a jumper tube for temporary operation while valve is being repaired. Disassemble valve and replace diaphragm. Inspect the ruptured diaphragm to see if failure is from corrosion, improper assembly or just fatigue from length of service. Consult manufacturer for expert opinion. If failure is from corrosion the chlorine supply system should be inspected for moisture intrusion. 94 ------- V. DISINFECTION - Chlorination Problem INABILITY TO MAINTAIN CHLORINE FEED RATE WITHOUT ICING OF CHLORINE SUPPLY SYSTEM BETWEEN EXTERNAL CHLORINE PRESSURE REDUCING VALVE AND CHLORINATOR. (EQUIPMENT CONSISTS OF EVAPORATOR, EXTERNAL CPRV AND THE CHLORINATOR.) Indicators 1. Noticeable cooling of gas line to chlorinator beginning at outlet of external chlorine pressure reducing valve. 2. Evaporator water bath temperature is normal: 160 to 180°F. 3. Further cooling at point of pressure reduction in chlorine pressure reducing valve in chlorinator assembly. 4. Deposit of "gunk" on chlorinator feed rate indicator tube and what appears to be droplets of an amber color liquid. Monitoring, Analysis and/or Inspection Reduce feed rate on chlorinator to about 75 percent of evaporator capacity. If this or further reduction of feed rate eliminates the above symptoms, the difficulty is most likely to be insufficient evaporator capacity. If chlorine gas temperature is available, calculate the superheat. If there is less than 5°F of superheat, there is very little reserve capacity in the evaporator. This is the result of an accumulation of sludge in the bottom of the liquid chlorine vessel of the evaporator. Corrective 1. Check for stoppage in the external CPRV cartridge if Measuressuperheat cannot be measured. 2. Take the evaporator out of the system, flush and clean it with cold water and dry it in accordance with the manufacturer's instructions utilizing an "Evaporator Cleaning Kit." All evaporators should be routinely cleaned after passage of 250 tons of liquid chlorine. 95 ------- V. DISINFECTION - Chlorination Problem CHLORINATION FACILITY CONSISTING OF EVAPORATOR-CHLORINATOR COMBINATION WITH EXTERNAL CHLORINE PRESSURE REDUCING AND SHUT-OFF VALVE IS UNABLE TO MAINTAIN WATER-BATH TEMPERATURE SUFFICIENT TO KEEP EXTERNAL CHLORINE PRESSURE REDUCING VALVE IN OPEN POSITION. Indicators 1. External chlorine pressure reducing valve shuts off intermittently until water bath temperature is raised above 150°F. 2. Intermittent operation of chlorination equipment 3. Insufficient heat being supplied to evaporator water bath. Monitoring, Analysis and/or Inspection 1. Check evaporator water bath temperature. Corrective After evaporator has been in operation sufficiently long enough to bring heating elements to operating temperature, shut down power supply and remove and replace heating elements. 96 ------- V. DISINFECTION - Chlorination Problem INABILITY TO OBTAIN MAXIMUM FEED RATE FROM CHLORINATOR OR CHLORINATORS WITH ADEQUATE CHLORINE GAS PRESSURE AT CHLORINATOR Indicators Chlorinator is placed into manual control and control valve is opened wide but chlorine feed rate will not go beyond 70 to 80 percent of maximum. Check injector vacuum gage to see if reading is less than minimum recommended by manufacturer. Check for injector vacuum reading below ten inches Hg. Monitoring, Analysis and/or Inspection 1. Reduce feed rate on chlorinator. 2. If the injector vacuum reading increases then increase the injector water pressure. 3. Verify whether or not inlet water pressure to the injector is the same as when the installation was first installed. 4. Check injector water pump pressure against the manufacturer's operating data. Corrective Measures Disassemble injector and see that the throat and tailway are clear and without any abnormal deposition of iron or manganese, and clean the injector parts by soaking in nuriatic acid, rinse in fresh water and replace. 97 ------- V. DISINFECTION - Chlorination Problem INABILITY TO MAINTAIN ADEQUATE CHLORINE FEED RATE Indicators Inspection of chlorinator reveals that chlorinator cannot feed as much as previously noted even though chlorine supply pressure is adequate. Monitoring, Analysis and/or Inspection If effluent is used check the injector operating water supply for deterioration in supply pump performance. Corrective 1. In the case of a centrifugal pump the only solution is Measuresa complete overhaul. 2. If a turbine pump, close down on the needle valve to maintain the proper discharge pressure. 3. If the turbine pump has worn sufficiently and it requires operation with the needle valve in the fully closed position, the pump should be thoroughly overhauled. 98 ------- V. DISINFECTION - Chlorination Problem INABILITY TO OBTAIN MAXIMUM OR PROPER FEED RATE FROM CHLORINATOR WITH ADEQUATE GAS PRESSURE AT CHLORINATOR Indicators With chlorinator in manual control and chlorine control valve is manipulated to very the feed rate, the change of feed rate response seems sluggish and chlorinator will not achieve maximum feed rate. The injector vacuum reading is borderline, and when feed rate is reduced the injector vacuum does not increase appreciably. Monitoring, Analysis and/or Inspection 1. Check the chlorinator vent system for a small vacuum leak in the chlorine control apparatus by disconnecting the vent line at the chlorinator and while observing the chlorinator operation (feed rate and injector vacuum), place a hand over the vent connection to the vacuum relief device on the chlorinator. If this action produces more injector vacuum and more chlorine feed rate, it signifies that air is entering the chlorinator via this mechanism (vacuum relief device) because the springs have become weak due to normal metal fatigue. 2. Moisten all joints subject to a vacuum with ammonia solution or put paper impregnated with orthotolidine at each of these joints. With chlorinator operating at maximum feed rate, close the injector discharge line as rapidly as possible. If there is a vacuum leak in the chlorinator system it will be detected by either the ammonia or the paper. Corrective 1. If the vacuum leak is in the vacuum relief device, Measuresdisassemble the mechanism and replace all the springs. 2. Repair all other vacuum leaks by tightening a joint, replacing gaskets, replace tubing and/or compression nuts. 99 ------- V. DISINFECTION - Chlorination Problem EXCESSIVE CHLORINE ODOR AT POINT OF APPLICATION- Indicators 1. Air cover above area of chlorine diffuser reacts with ammonia solution to produce typical white wisps of "smoke" indicating escaping molecular chlorine. Monitoring, Analysis and/or Inspection 1. Scattering ammonia indicator solution onto the wastewater stream over the area of the diffuser produces white fumes at the surface. 2. Check chlorine solution strength. Corrective 1. Add enough injector water to bring the chlorine solution Measuresstrength down to 3500 ppm chlorine at maximum expected :chlorine feed rate. 2. If the chlorine diffuser is situated below the injector which leads to a negative head in the solution line, install a special diaphragm protected chlorine solution pressure gage in the highest point of the chlorine solution discharge line and regulate the injector water flow so that there is a 2 to 3 psi positive pressure at this point. 100 ------- V. DISINFECTION - Chlorination Problem CHLORINATOR WILL NOT FEED ENOUGH CHLORINE TO PRODUCE A PROPER CHLORINE RESIDUAL AT THE SAMPLING POINT. Indicators A routine spot check sampling shows that at some hours of the day there is an adequate residual but there are times during the day when there is no residual. If there is a chlorine residual analyzer the chart will show periods during the day of insufficient chlorine residual. Monitoring, 1. Ascertain that if the chlorination equipment is being Analysisused for disinfection that it is equipped to proportion and/or the chlorine feed rate in accordance with the flow of Inspection the wastewater. 2. If it is flow proportional, check to see if the meter capacity on the chlorinator matches the pl'ant flow meter capacity. 3. Disconnect the flow proportional control and by manual control test the chlorinator to see if it will pull maximum feed rate. 4. Determine if solids have settled to the bottom of the contact chamber. Corrective Measures The automatic control features of the chlorinator should be repaired by the manufacturer's field service per- sonnel- who are equipped to simulate the various types of electric and pneumat'ic signals commonly used for chlorinator control. If neede'd'', clean the chlorine contact chamber. 101 ------- V. DISINFECTION - Chlorination Problem WIDE VARIATION IN CHLORINE RESIDUAL IN EFFLUENT AS DETERMINED BY HOURLY CHLORINE RESIDUAL DETERMINATIONS Indicators Inability to adjust dosage so that there is reasonable agreement of chlorine residual throughout a 24-hour period as determined by occasional chlorine residual analysis at each shift. Monitoring, Analysis and/or Inspection While in flow proportional operation the feed rate of the chlorinator should be plotted on a piece of graph paper against the flow meter reading. The plots of wastewater flow versus chlorine feed rate should yield a straight line. Corrective Measures If the feed rate plots do not follow a reasonably straight line, it is well to recheck the zero and span of the flow proportional control device on the chlorinator. First make the zero check and then the span check in accordance with the manufacturer's instructions. If this does not correct the difficulty, it may be necessary to replace operating parts within the controller to achieve satisfaction. If after the flow proportional control system on the chlorinator has been corrected the irregular chlorine residual reading continues, then it is recommended that a continuous chlorine residual analyzer be installed. 102 ------- V. DISINFECTION - Chlorination Problem CHLORINE RESIDUAL ANALYZER RECORDER CONTROLLER DOES NOT APPEAR TO CONTROL THE CHLORINE RESIDUAL PROPERLY. Indicators 1. Recorder draws a poor line on the chart that seems not to bear any relation to the "set point." Monitoring, Analysis and/or Inspection 1. First check the loop-time in the system. This is best accomplished by turning off the gas supply to the chlorinator and determining the length of time required to show a sharp drop in the residual on the analyzer chart. 2. Disconnect the analyzer cell output leads from the cell and apply a simulated signal to the recorder mechanism from a manually controlled external signal generator. (Authorized chlorinator repair personnel carry such a device as part of their tool kits.) 3. Check buffer additive system to see if pH of sample going through the cell is maintained at 5 or less. 4. Check electrode bombardment system and see that electrodes are clean, particularly the noble metal electrode (Pt. or Au.). Do not disturb the copper electrode unless it is fouled with grease. 5. If residual analyzer is being used to measure total residual, check to see if sufficient potassium iodide is being added for the amount of residual being measured. 6. Reconnect cell output leads and make a zero, span and temperature check by following the manufacturer's procedure for a routine calibration. 103 ------- Corrective 1. If the loop time is found to be in excess of 5 minutes, Measures satisfactory operation will not be achieved until the loop time is brought down to 5 minutes or less. This can be accomplished by moving the injector closer to the point of application, increasing the velocity in the sample line to the analyzer cell, by moving the cell closer to the sample point, or by moving the sample point closer to the point of application. 2. If the line on the chart indicates proper operation when subjected to a simulated signal, this signifies that the equipment between the cell and the readout of the pen is satisfactory. The erratic or poor line can either be caused by poor mixing of chlorine at the point of application or faulty operation of the cell. Poor mixing can be verified by setting the chlorine feed rate for a constant dosage (proportional to flow) and analyzing a great many grab samples over a ten minute period as quickly as possible. A poor mix will show rapid wide swings of the recorder pen. Consider mixing the point of application and/or install some type of mixing device to cause turbulence at the point of application. 3. If poor mixing is not the cause, and if the electrodes are clean, and if the pH and KI additive system is normal, then the difficulty must be in the cell and it should be replaced. 4. If when the simulated signal is applied to the recorder mechanism and the recording system does not respond properly, the difficulty lies in the electrical components of the recorder mechanism. Authorized service personnel should be summoned to correct the difficulty. 104 ------- V. DISINFECTION - Chlorination Problem CHLORINATION SYSTEM CONSISTS OF EITHER COMPOUND-LOOP CONTROL OR DIRECT RESIDUAL CONTROL AND SYSTEM DOES NOT APPEAR TO BE CONTROLLING PROPERLY. Indicators Chlorine residual line on analyzer chart appears normal but does not track close enough to set point. Monitoring, Analysis and/or Inspection If the chlorine residual analyzer is operating properly, check the chlorinator system to see that it is functioning properly over its entire range of feed rate. Check to see if the chlorination system is feeding enough chlorine to satisfy the maximum demand; also check to see if the rotameter tube range is sized so that incremental corrections in feed rate by the residual controller are not too large. These two factors would cause wide swings in the chart line, or not allow the chlorine applied to ever actually "catch up" with the set point. Corrective Measures If the chlorination system will not feed enough chlorine, consult the corrective measures described previously under the problem of chlorination control equipment unable to feed enough chlorine. If the chlorinator rotameter tube range gives too large or too small an incremental change, replace with a proper range of feed rate. 105 ------- V. DISINFECTION - Chlorination Problem COLIFORM COUNT DOES NOT MEET THE REQUIRED DISINFECTION STANDARDS SET BY REGULATORY AGENCIES. Indicators 1. Routine analysis of effluent or receiving waters shows MPN coliform organism to be in excess of that required by regulatory authorities. Monitoring, 1. Check capacity of chlorination equipment as follows: For Analysis primary effluent chlorinator capacity should be from 175 and/or to 200 Ib per MG. For secondary effluent 100 to 125 Ib Inspection per MG and for tertiary effluent 75 to 100 Ib per MG unless nitrogen removal is required. For the latter or for those plants requiring free residual chlorine, equipment capacity must be 10 mg/1 of chlorine for each mg/1 ammonia nitrogen in the effluent. 2. All chlorination equipment used for disinfection of waste- water effluent should have at the very least control propor- tional to the effluent flow. The capacity of the chlorina- tor should also be based on the maximum reading of the flow meter. 3. Continuously record the residual in the effluent with an amperometric type chlorine residual analyzer. N 4. Check for short circuiting in contact chamber. Corrective 1. Chlorination equipment should be brought up to optimum capac- Measures ity requirements. The necessary equipment should be installed to provide flow proportional control. In plants where only an influent meter exists, it may be required to install an effluent meter. After the proper primary meter is installed then the chlorinator can be modified by adding a chlorine ori- fice positioner to be operated either ( electrically or pneu- matically from the primary meter. 2. A chlorine residual analyzer should be installed to properly monitor the chlorine control system. Using this apparatus to automatically control the chlorine dosage is optional; how- ever, experience shows that the change in chlorine demand of most domestic wastewaters is significant enough to warrant the small added expense to accomplish automatic dosage control. 3. Install additional baffling in contact chamber. 4. If needed, install a mixing device in contact chamber. 106 ------- V. DISINFECTION - Chlorination Problem COLIFORM COUNT DOES NOT MEET THE REQUIRED STANDARDS FOR DISINFECTION. Indicators Monitoring, Analysis and/or Inspection Corrective Measures 1. Routine analysis of effluent or receiving waters shows MPN of coliform organisms to be in excess of the required standards. 1. Check to see if chlorine capacity is adequate, control system is functioning properly and effluent is being . monitored with a continuous chlorine residual analyzer. 2. Check the chlorine contact time at low flow, average flow and maximum flow to determine the optimum residence time of the process. With this as a basis analyze five replicate samples for each hour around the clock on Monday, Wednesday^ Friday and Sunday for coliform MPN after the following treatment: samples are to be taken from the effluent prior to point of application of chlorine and dosed in the laboratory with the same amount of chlorine as that applied by the Chlorination equipment. The chlorine for this procedure should be taken from the plant chlorine solution line, standardized according to Standard Methods and added to one liter replicate sample of effluent. Upon addition the chlorine solution should be rapidly and thoroughly mixed, then allowed to stand for the amount of time determined previously at the optimum residence time. At the expiration of the residence time one portion of the samples should then be analyzed for chlorine residual using the iodometric back titration procedure while another portion should be dechlorinated and analyzed for coliform MPN in accordance with Standard Methods. 3. If the resulting coliform MPN from the above analysis is satisfactory, it is then reasonable to assume that the mixing at the point of application is at fault , because stirring chlorine in a batch process described above results in ideal chemical mixing. 4. Check for solids buildup in contact chamber. 1. If the difficulty is too low a residual raise feed rate and increase contact time if possible. 2. If poor mixing is the problem install a mixing device of high turbulence such as exists in an hydraulic jump or a combination of turbulent flow and mechanical mixer. 3. Clean contact chamber to reduce solids buildup. 107 ------- V. DISINFECTION - Chlorination Problem PLANT EFFLUENT DOES NOT MEET TOXICITY REQUIREMENTS BECAUSE CHLORINE RESIDUAL TO ACHIEVE PROPER DISINFECTION IS AT TOO HIGH A LEVEL. Indicators 1. Toxicity level is too high as determined by present bio-assay procedures. Monitoring, 1. Chlorine residual as determined by iodometric method Analysis using back titration method is deemed toxic to fish and and/or other aquatic life in the receiving waters. Inspection Corrective 1. Install a dechlorination facility to operate in Measures conjunction with the Chlorination system. 108 ------- Problem Indicators Monitoring, Analysis and/or Inspection VI. METERING PLANT. METER UNRELIABLE A. . Drop or sharp increase in totalized .dry weather If meter operates on a float, check float well obstructions. If meter operates on bubbler, check bubbler tube for damage. Also check air pressure gage to see that meter is getting proper air flow. Bypass measuring weir or f to see if meter Zespos.. Check height lof flow over weir or in/ flume at dlfd time intervals and, using the weir or flume characteristics formulas calculate flow and compare with flow meter data. Compare water surface elevation immediately behind weir or flume with elevation of water in float or bubbler well. Ascertain the fact that none of the plant's process return flows (centrate, supernant, waste activated sludge, etc.) are discharged upstream from the meter. Install a portable flow meter in the weir or flume and compare results with If metered flow discltarges/iinto a wet well or other chamber which has.,* known volume and outflow can be shut off, record time' of measured rise in chamber and calculate infl<6w rate. Compare calculated data with 109 ------- If wastewater treated at the plant is supplied by one or more utilities and the total amount of water used is metered, compare area water consumption with plant flow. During fall or early winter months, water consumed is approximately 10% more than wastewater discharged. 10. Check magnetic *Aow meter cores for grease bui.M-uB.Q estrictions. . . Corrective 1. Keep all floats and bubbler wells clean and free of Measures grease by periodic maintenance. 2. Differences between inside and outside or bubbler well water surface elevations are due to extreme velocities in the immediate area of these wells. If possible, move wells to a more quiescent area behind the weir or flume. 3. Clean all foreign matter off weir plates. 4. If problem appears to be in the meter, recording or telemetering equipment, a qualified technician should be called in to repair and calibrate the metering equipment. 110 ------- VII. SOLIDS HANDLING - Sludge Thickeners Problem ODOR FROM THICKENER Indicators Monitoring, Analysis and/or Inspection 1. Odors of hydrogen sulfide origin 2. Floating or gaseous sludge in thickener 3. Corrosion of thickener concrete structure and metal work 1. 2. 3. 4. Run/Total and ffluent. ^solved test of thickener Check pumping rate and frequency of pumping raw sludge from thickener. Run total solids test on raw sludge pumped. Dewater thickener and check operation of a scrapper and/or stirrer arms and sludge removal equipment. 5. Determine sludge blanket depth. Corrective Measures 1. Adjust pumping rate to remove solids at a frequent rate and at not less than 3% total solids. 2. Repair or replace all damaged sludge collector mechanisms. 3. Cover thickener and exhaust gases to an odor control scrubber. Ill ------- VII. SOLIDS HANDLING - Sludge Thickeners Problem Indicators Monitoring, Analysis and/or Inspection THICKENER CONTENTS DO NOT SETTLE 1. Floating sludge on thic 2. Floe in thickener effluent \^/Xlny3^reased^\oadi*lgs~^n P/"Vnar y^sedinrenVarciW^fanics and secoh43«ry treatment p**°cess*/ \s 4.. Excessive sludge solids in the overflow 5. Poor concentration of underflow. Run tota1J'ssolids on thickener effluent. Run total solids in raw sludge withdrawn from thickener. Run total solids of all thickener inflows and compare to thickener design capacity. Run 30 minute settleability test of waste activated sludge inflow to thickener. Corrective Measures If thickener effluent contains high solids and the raw sludge withdrawn low solids, dose thickener with polymers or other coagulants. If solids loading exceeds thickener design capacity, partially bypass thickener, if possible, by pumping raw sludge from the primary sedimentation tanks directly to the point of disposal, digester, or incinerator. If waste activated sludge pumped to thickener does not ^readily settle, re-aerate or treat with coagulants. 112 ------- VII. SOLIDS HANDLING - Sludge Thickeners Problem SLUDGE PUMPED FROM THICKENER HAS LOW SOLIDS CONCENTRATION Indicators 1. Thin or watery sludge discharged to point of disposal Monitoring, Analysis and/or Inspection 1. Run total solids of raw sludge pumped from thickener. 2. Check pumping cycle and rate of pumping raw sludge from thickener. 3. Check rate of inflow to thickener. 4. Run total solids of thickener inflow. 5. Determine depth of the sludge blanket. Corrective 1. Adjust pumping rates and cycles, preferably with Measures timers, and remove raw sludge from thickener at a density not less than 3% total solids. 2. Adjust thickener inflows to apply total solids to thickener of not less than 2%. 3. In gravity thickness adjust pumping cycles to maintain 3 to 4 ft sludge blanket. 113 ------- VII. SOLIDS HANDLING - Sludge Digestion (Anaerob Problem Indicators SCUM BLANKET IN TANK Monitoring , Analysis and/or Inspection . 1. 2. 3. 4. 1. Decrease in dige'ster gas production 2. Crust visible through sight glasses in digester roof g * 3. Unable to supernate from upper level of digester Core blanket through digester thief holes to thickness. Check digester temperature. Check daily digester gas production. Determine gallons of scum pumped to digester daily. Corrective Measures If possible, recirculate digested sludge from bottom of digester to top of scum blanket. If digester has a gas mixing system, run system continuously while increasing digester temperature to not more than 105°F with the incremental increases not exceeding 1°F per day. If digester has mechanical mixers with draft tubes , degassify digester, break up scum with a high pressure water jet and direct to draft tubes. Clean digester and find alternate means of scum disposal. If digester has gas mixer system, place temporary gas diffusers in thief holies and pipe compressed digester gas /to them. 114 ------- VII. LIDS HANDLING,- Sludge Digestion (Anaerobic) DIGESTERGAS PRODUCTION Indicators Monitoring, Analysis and/or Inspection Corrective Measures 2. 3. 4. 2. 3. 4. 5. 6. 7. 8. Gas produced hafe sen^fic Gas producedyrfoes ifot ignite^ Increase in^ligearcer volatile acids Increase ±y vol^ile acid/alkalinity Determing digester volatile acid, alkalinity, and pH of digested sludge together with trend of volatile acid/alkalinity ratio. Check gas meter and piping for restrictions. Monitor volume of raw sludge pumped to digester daily. Determine total solids, volatile solids, and pH of raw sludge pumped to digester. Check digester temperature. Sound digester to determine depth of scum blanket and grit residue on bottom. Calculate volatile matter reduction in digester. Check for toxic material i digeste If volatile acjra to alkalinity 0.2 and pH billow 6.5 add/lime volatile a/ld/alkalin/i r Do not fe^a digestejr raw than 7. If volatil decrease, Do not solids disconti greater than decrease pH. ranges (less 50% pH rises eefci djAest'ej5xrawvSi3jJ4ge— with average volatile l3S' x an-^75%. If possible transfer digested sludge with a volatile acid/alkalinity ratio of 0.2 from another digester to affected digester. If scum blanket and/or grit deposits comprise more than 50% of the effective volume of the digester, clean the ( tank. * iJf^ijjJti AAMW^A Keep digester temperature at 98 F. (vflM/TUA** r*'v'rw I r o r • Clean all restrictions in gas lines and/or meters. v_ If toxic material has killed digester, clean digester and determine source of toxicity to prevent recurrence. ------- VII. SOLIDS HANDLING - Sludge Digestion (Anaerobic) INCREASE IN VOLATILE ACID/ALKALINITY RATIO IN DIGESTER Indicators 1. Drop i/i digestenrgas production 2. Hydr/gen sulfd^fle odoijr from digegrter superna Monitoring, Analysis and/or Inspection Corrective Measures 1. 2. 3. 4. 1. 2. 3. 4. 5. 6. 7. Determine volatile acid, alkalinity and pH sludge at least twice daily. Check digester temperature. Check pH of raw sludge pumped^to cfigester. Check mixing in digester. If digester pH is below 6.5, add lime to digester If volatile acid/alkalinity ratio is greater than 0.4 decrease or discontinue feeding digester and add lime. Do not feed digester raw sludges with pHs lower than 6.8. Do not let digester temperatures drop below 90°F. If possible, transfer sludge with low volatile acid/ alkalinity ratio content from another digester to affected digester. Keep contents of digester well mixed. Decrease sludge withdrawal rates from digester. 116 ------- VII. SOLIDS HANDLING - Sludge Digestion (Anaerobic) Problem FOAM IN DIGESTER Indicators 1. Foam discharged from upper level supernatant lines 2. Froth visible through sight glasses in digester roof Monitoring, Analysis and/or Inspection 1. Determine total and volatile solids of sludge being pumped to digester and volume pumped. 2. Determine pH of digester contents. 3. Check digester temperature daily. 4. Monitor withdrawal rate of sludge from digester. 5. Ascertain depth and/or thicknesses of grit deposits and/or scum layers. 6. Check digester mixing program and effectiveness of mixing equipment. Corrective 1. Maintain digester pH between 6.8 and 7.2 and volatile Measures acid/alkalinity ratio below 0.2 by adding lime. 2. Reduce or discontinue pumping raw sludge to digester. 3. Maintain digester temperature constant and at least at 95°F. 4. Attempt to thoroughly mix digester by recirculation or by available digester mixing equipment. 5. Break up scum layers or, if not possible, clean digester. 6. If possible, add digested sludge from a healthy digester. 117 ------- VII. SOLIDS HANDLING - Sludge Digestion (Anaerobic) Problem LOW REDUCTION OF VOLATILE SOLIDS IN DIGESTER Indicators 1. Volatile reduction calculates to less than 50% Monitoring , Analysis and/or Inspection 1 3 4 5 Determine total solids of digested sludge and/or raw sludge being pumped to digester. Monitor solids loading to digester daily. Monitor solids withdrawal from digester. Check total solids in digester supernatant. Ascertain depths and/or thickness of grit deposits and/or scum layers. 6. Determine volatile acid/alkalinity ratio and pH of digested sludge. 7. Monitor digester gas production. Corrective Measures 2. 3. 4. 5. If total or volatile solids daily loading of digester exceeds design loading, reduce the amount of sludge pumped to the digester daily. Keep digester temperature above 95°F. Raw sludge pumped to digester should contain more than 50% volatile solids. Recirculate and mix digester. Prolong periods of withdrawing digested sludge until volatile reduction is above 50%. Lower volatile acid/alkalinity ratio and raise pH above 6.5 by adding lime to digester. If supernatant contains high solids content, let digester settle. 118 ------- VII. SOLIDS HANDLING - Sludge Digestion (Anaerobic) Problem HIGH PERCENT SOLIDS IN DIGESTER SUPERNATANT Indicators .1. Supernatant very dark and thick 2. If supernatant is circulated to plant headworks, primary and/or secondary treatment processes efficiency drops severely. Monitoring, Analysis and/or Inspection 1. Determine total solids of digester supernatant while supernating from different levels in the digester. 2. Determine total solids of digested sludge. 3. Monitor amount of raw sludge, activated sludge, and scum pumped to the digester daily. 4. Check pH of digester supernatant. 5. Determine length of time of digester mixing. Corrective 1. If supernatant contains more than 1% solids, do not mix Measures digester and feed alternate digester if possible. 2. Supernate from digester level which gives the least solids in the supernatant. 3. Supernate from one digester into another if possible. 119 ------- VII. SOLIDS HANDLING - Centrifuging Problem LOW SOLIDS RECOVERING RATE Indicators 1. Centrifuge efficiency falls below 60% 2. Solids in centrate exceed 3%. 3. Centrate very dark in color. 4. If centrate is recirculated to the plant headworks, the efficiency of primary and secondary treatment processes are directly affected. 5. Cake appears thick and quite wet. Monitoring, Analysis and/or Inspection 1. Calculate centrifuge efficiency. 2. Monitor sludge feed rate to centrifuge and percent solids in sludge. 3. Monitor coagulant, if any, feed rate to centrifuge. 4. Check centrifuge for mechanical wear. 5. Check pool depth. Corrective Measures 1. Decrease sludge feed rate to centrifuge. 2. Increase chemical coagulant dosage, if any. 3. Repair or replace all worn centrifuge parts. 4. Increase pool volume and bowl speed. 5. Reduce conveyor speed. 120 ------- VII. SOLIDS HANDLING - Vacuum Filters Problem LOW SOLIDS RECOVERY Indicator 1. High solids in filtrate 2. Poor clarity filtrate Monitoring, Analysis and/or Inspection 1. Calculate filter efficiency. 2. Monitor coagulant, if any, feed. 3. Check filter mesh for blindings or coarseness. Corrective Measures 1. Increase chemical coagulant feed rate. 2. Clean filter media. 3. Install fine mesh filter media. 4. Check sludge washing (elutriation) process. 5. Check filter drum speed and operation cycle. 6. Change types of coagulants being used. 121 ------- VII. SOLIDS HANDLING - Incineration Problem ABNORMALLY HIGH TEMPERATURE IN FURNACE Indicators Temperature indicator exceeds limit of maximum operating temperature. High temperature alarm activated. Monitoring, Analysis and/or Inspection 1. Check rate of fuel consumption to determine if excessive. 2. Check to determine if fuel feed is off and temperature is still rising. Greasy solids may be present. 3. Check temperature indicator to see if it reads all the way up on the scale. Corrective Measures Decrease fuel feed rate, if excessive, in relation to sludge feed rate. If temperature rises without supplementary fuel feed, greasy solids may be present in sludge. (This occurs infrequently when 100% primary sludge is incinerated.) To lower temperature, raise air feed rate while holding sludge feed rate constant. If air feed rate is at maximum, reduce sludge feed rate slightly. If temperature indicator is all the way up the scale, this is an indication that the termocouple well is burned out. Replace thermocouple with spare unit, repair or replace thermowell with spare. 122 ------- VII. SOLIDS HANDLING - Incineration Problem ABNORMALLY LOW TEMPERATURE IN FURNACE Indicators 1. Temperature indicator shows low on scale. Monitoring, Analysis and/or Inspection 1. Check calorific value of sludge to determine if it is decreasing. 2. Check moisture content of sludge to determine if it is increasing. 3. Determine level of excess oxygen in stack. Corrective Measures If calorific value of sludge is low, or if sludge moisture content is high, increase the supplementary fuel feed rate. If excess oxygen is abnormally high in stack exhaust, reduce the air feed rate slightly or increase sludge feed rate. 123 ------- VII. SOLIDS HANDLING - Incineration Problem HIGH OXYGEN LEVEL IN FURNACE STACK EXHAUST Indicators 1. Oxygen analyzer (recorder chart) indicates excessive oxygen in stack exhaust Monitoring, 1. Determine total and volatile solids of sludge fed to Analysis furnace. and/or Inspection 2. Check to determine if sludge is being fed to incinerator. Corrective 1. If sludge being fed to furnace is low in solids, increase Measures the speed of sludge pump which feeds centrifuge. If the air feed rate is low and the sludge rate at a maximum and the exhaust oxygen is still high, shut down. The sludge supply to the furnace is inadequate. 2. If sludge is not being fed to incinerator, check for blockage of sludge in feed chute and check sludge feed pump stator. Unplug chute or repair stator if not in good condition. 124 ------- VII. SOLIDS HANDLING - Incineration Problem LOW OXYGEN LEVEL IN FURNACE STACK EXHAUST Indicators 1. Oxygen analyzer (recorder chart) indicates low oxygen in stack exhaust. Monitoring, Analysis and/or Inspection 1. Check volatile content of sludge fed to furnace to determine if increasing. 2. Check sludge for grease content to determine if increasing. 3. Check to determine if air flow to furnace is restricted. Corrective 1. If the volatile content of the sludge is increasing or Measures if the grease content of the sludge is increasing, increase the air feed rate. If the air feed rate is at maximum decrease sludge feed rate. 2. Remove any restrictions or blockages in air conduits. . 125 ------- VII. SOLIDS HANDLING - Sludge Lagooning Problem EXCESSIVE SOLIDS CARRIED OVER FROM LAGOON SUPERNATANT TO PLANT INFLUENT Indicators 1. Dark supernatant discharged from sludge lagoons 2. Solids removal efficiency of plant treatment processes is lowered. Monitoring, Analysis and/or Inspection 1. Determine total and suspended solids of lagoon supernatant. 2. Measure depth of sludge in lagoons. 3. Check for broken dikes between lagoons. 4. Check rate and volume of application of digested sludge to lagoons. 5. Determine total solids of sludge being applied to lagoons. Corrective 1. Reduce volume of sludge applied to lagoons thereby Measures reducing depth of sludge in lagoon. 2. Repair all broken dikes between lagoons. 3. Delay release from lagoons of supernatant with heavy solids content until sludge is allowed to settle. 126 ------- VII. SOLIDS HANDLING - Sludge Lagooning Problem ODORS FROM SLUDGE LAGOONS Indicators 1. Obnoxious odors from sludge lagoons. Monitoring, Analysis and/or Inspection 1. Determine volatile acid/alkalinity ratio and pH of digested sludge being applied to lagoons. 2. Determine total and dissolved sulfide of lagoon supernatant. Corrective 1. If volatile acid/alkalinity and pH tests indicate a sour Measures digester, attempt to correct problem at source. 2. Apply lime to surface of lagoon. 3. Install peripheral odor control system. 4. Flood lagoon with heavy chlorinated water. 127 ------- ------- CLASSIFICATION OF WASTEWATER TREATMENT PLANTS ------- Appendix A CLASSIFICATION OF WASTEWATER TREATMENT PLANTS This section of the manual contains information for the classification and identification of wastewater treatment plants by various designations. These include: • Definitions of the classes of plants by function • Operator classification • Geographic location and climatic conditions • Common processes and operational units Also included is a matrix by which treatment systems are clas- sified by their unit operations, removal efficiencies and expected effluent quality. This section is used by: • Isolating treatment system (by various classification) • Determining the units which fall into that general system • Learning the performance capabilities of the system. This information, along with operational .data for the particular system from Section II of this manual, is compared to the performance and operational data of the plant being evaluated and is to be considered in the overall evaluation of the plant. CLASSIFICATION BY FUNCTION Following are generalized definitions of classes of treatment plants according to their functions: 1. Primary treatment - Those wastewater treatment plants that employ methods which remove or reduce a high percentage of the suspended and floating solids but little or no colloidal and dissolved matter. 2. Secondary treatment- Those methods which remove or reduce fine suspended colloidal, dissolved solids, and cause the reduction of organic material by biological oxidation. 3. "Advanced waste treatment - Those methods which remove or reduce nutrients, residual organics, residual solids and pathogens by, but not limited to, sand filtration,chemical treatment, carbon absorption, ammonia stripping, electrodialysis or reverse osmosis. A-l ------- OPERATOR CLASSIFICATION The classification system used in the area of the plant being evaluated should be reviewed to see if the proper personnel are being utilized for the existing treatment system. Table A~l shows the diversification of wastewater treatment plant classifications as denoted by their type, design flow and population served, contrasted with the class of operator which should be capable of operating them. These classifications have been established by the California Water Pollution Control Association and the California State Water Resources Board. Evaluators should be aware that most states will have their own classification system. Table A-l OPERATOR AND TREATMENT PLANT CLASSIFICATION California Water California* Pollution Control Operator Treatment Process Association Classifications Design Flow Population (MGD) Served IV III II I la I Stabilization Pond Primary II Primary Biofiltration III Primary Biofiltration Activated Sludge Tertiary IV- Primary Biofiltration Activated Sludge Tertiary V Biofiltration Activated Sludge Tertiary All 2000 1 or less 1-5 2000 to 1 or less 10,000 5-20 10,000 to 1-10 40,000 5 or less 1 or less 20 & over 40,000 10-30 5-20 1-10 30 & over 20 & over 10 & over *Classification adopted by the State Water Resources Control Board A-2 ------- Temperature zones and their approximate sphere of influence, along with probable effects on operating efficiencies , are defined below. 1. Cold Zone - average January air temperature of 30 F or less will cause a decrease from 4 to 5 percent in operating efficiency 2. Temperate Zone - average January air temperature of 35 to 45 F will cause a decrease of 4 to 5 percent at the 35 F range but normal operation at the higher temperature 3. Warm Zone - average January air temperature of 50 to 70 F allows normal operation at the low temperature and a possible 4 to 5 percent increase in efficiency at the higher range. The following sketch delineates the approximate climate zones in the United States. Alaska Hawai i LOCATION OF TEMPERATURE ZONES IN THE UNITED STATES 'A-3 ------- COMMON PROCESSES AND OPERATIONAL UNITS The purpose of this subsection will be to identify all of the opera- tional units and processes common to wastewater treatment plants operating in the primary, secondary and advanced waste treatment mode. While every treatment plant can be considered unique, it is obvious that most treatment plants will have many operations and processes in com- mon. Below is a list of the most common units used in various treatment modes. Pretreatment To remove or reduce floating solids and coarse suspended solids, use: Racks Medium screens Grit chambers Skimming tanks Primary Treatment To remove or reduce fine suspended solids, use: Fine screens Sedimentation a. Plain sedimentation tanks, with or without mechanical sludge-removal devices b. Septic tanks (biological action also takes place) c. Imhoff tanks (biological action also takes place) d. Chemical precipitation tanks Secondary Treatment To remove or reduce suspended colloidal and dissolved solids , oxidize with Filters - intermittent sand filters contact filters trickling filters Aeration - activated sludge contact aerators (as used in aerated lagoons) Chlorination Oxidation ponds Disinfection Chlorination Ozone Advanced Waste Treatment Chemical/physical treatment methods Carbon absorption Ammonia stripping Electrodialysis Reverse osmosis or desalting Microscreening A-4 ------- Ultimate Wastewater Disposal Discharge into receiving waters Irrigation or disposal on land by a. Application to surface b. Subsurface irrigation c. Groundwater recharge Treat by advanced treatment system and reuse for industrial water supply or possibly a fire protec- tion system Treatment and Disposal of Wastewater Solids Screenings a. Treatment (1) Medium - shred and digest (2) Fine - digest b. Disposal (1) Medium - burial or incineration (2) Fine - burial or incineration Settled Solids (sludges) a. Treatment (1) Sludges from primary and secondary treatment by: (a) Digestion (b) Thickening (by gravity or flotation; may or may not be conditioned by elutriation or chemicals) 1) Vacuum filtration 2) Drying on beds or in kilns 3) Centrifugation b. Disposal (1) Wet sludges - dumping at sea or piping to sea (where still permitted) (2) Dried or dewatered sludges - incineration or use as soil conditioner or deposit in a landfill A-5 ------- Performance of Treatment Systems Table A-2 is a classification matrix of treatment systems by their unit operations, removal efficiencies and expected effluent quality. It indicates the percentage removal of constituents (based on process effluent to process influent) and ranges of effluents of treatment systems which are employed in the wastewater treatment.• Most of the systems shown have some form of pretreatment, in combination with primary, secondary or advanced, unit operation which would provide the influent quality that can be handled by the treatment system. In order for plants to approach the effluent ranges indicated, each unit operation would have to be examined and evaluated to determine what operation could be improved without affecting other plant operations. A-6 ------- UNIT OPERATIONS PRIMARY® illilill •sssliisl ^— By Aaaonlm Stripping Tower SECONDARY h *- £ S 1 a 1 | i | — • Physical -Chemical Sand Filtration > Carbon Adsorption > 9 Sludge Treatment A. Disposal •BE— TREATMENT SYSTEM PRIMARY TREATMENT ACTIVATED SLUDGE . Conventional . Contact Stabilization . Completely Mixed . Two Stage Activated Sludge TRICKLING FILTERS . Low Rate . High Rate STABILIZATION PONDS PACKAGE AERATION PLANTS ADVANCED WASTE TREATMENT . Reverse Osmosis . Activated Carbon . Microscreening . Deep Bed Sand Filtration (Rapid sand filtration) . Phosphorous Removal (Chemical treatment) . Ammonia Stripping CD . Electrodlolytii EFFL o 2 15-65 er* in Z | 70 TITUEr e-ch bo *, bott c 1 60-S5 W-95 <1 •ITS r - am in * | Z £ i 50-80 <5 n « 5 1 90-99 70-8\$ 2-4 <5 Suspended Solidl 1 <5-75 85-90 20- JO 60-80 80-100 74-94 17-29 100 60-80 < 7 30-80 3-5 60-85 <1 @ & 3 100 90 <5 1 60-100 80 1 MUTUAL SCCTIOff flicJtoround Ops Oita Probleam L-l to C-JJ 11-19 IV 43-63 D-7 to D-9 11-22 IV 64-71 D-5 to D-6 11-21 IV 72-76 D-9 to D-ll 11-31 IV 77-79 D 13-14 11-31 C-l to E-8 11-24 VI 82-il ^-V function of pH and temperature ®Not all operations are used in all plants In color units All percent removals are based on process effluent to process influent Table A-2 Classification Matrix of Treatment Systems by Their Unit Operations, Removal Efficiencies and Effluent Quality A-7 ------- B ------- PERSONNEL ------- Appendix B PERSONNEL REQUIREMENTS This section of the manual contains information on personnel require- ments for effective treatment plant operation. It lists the minimum skills required for the various duties which are performed at treatment plants. A manpower and work schedule is included to delineate the numbers of per- sonnel and hours needed to perform the required work. Table A-l (Appendix A) of this manual indicates the classification of operator for plant size and treatment system. This data, along with the information presented in this section, should be compared against personnel information for the plant being evaluated to see if adequate staff (both in numbers and qualifications) is being utilized. This should be included in the overall evaluation rating given to the plant. GENERAL SKILLS The skill requirements outlined below are minimal for successful per- formance of specific required duties. These are only a guide; additional requirements for the particular plant location should be checked. • Supervisory Personnel (level of ability depends on size and type of plant) - high school education or equivalent, should display better than average ability to: 1. Use and manipulate basic arithmetic and geometry. 2. Think in terms of general chemistry and physical sciences. 3. Understand biological and biochemical actions. 4. Grasp meaning of written communications. 5. Express thoughts clearly and effectively, both verbally and in writing. In addition, supervisory personnel are often responsible for: 1. Public relations 2. Bookkeeping 3. Analysis and presentation of data 4. Budget requests 5. Report writing 6. Personnel B-l ------- 7. Safety educational program 8. Contracts, specifications and codes 9. Estimates and costs 10. Plant library • Laboratory Technicians - require training in laboratory pro- cedures and mathematics • Operating Personnel - require training in: 1. Fundamentals of wastewater treatment processes, including chemistry and biology. 2. Mathematics (including geometry). • Maintenance Personnel - must be familiar with and capable of: 1. Mechanical repairs 2. Electrical and electronic repairs. MANPOWER AND WORK SCHEDULING • Day-Shift Operators. 225 days/year at 6 hours/day = 1,350 hours/ year. Attempts to schedule workloads and staff plants on this basis indicates that 5-1/2 hours/day is more realistic. This value will drop as the number of phone calls, visitors , inspectors, and emergencies increase. • Night-Shift Operators. 7 hours/man/shift (fewer interruptions and work is of the routine inspection and recording nature). Table B-l shows ranges of the number of personnel which would be re- quired to operate various modes of treatment systems. Each plant may have its own particular operating mode, depending on the number of components which make up liquid and sludge treatment, along with administrative and general plant functions. The advanced waste treatment plants were not included in this table because of the lack of reliable manpower estimates for this classification. B-2 ------- Table B-l PLANT MANPOWER REQUIREMENTS* Type of Plant Average Capacity (MOD) 13 5 10 20 35 50 65 80 100 Primary 4.5-6 6.5-7.5 7.5-9 10-13 15.5-19 22-27 29-34 34-41 40-49 50-59 Secondary (including 6-7 7.5-9.5 9.5-11.5 13-16 19.5-24 28-34 37-44 45-53 53-61 63.5-76.5 Trickling Filter) Secondary (including 7-8 9.5^10.5 11.5-13 15-18 23-26 33-38 43-49 51-59 61-69 71-82 Activated Sludge) *Based on a preliminary study performed by Black and Veatch for the EPA. B-3 ------- ------- PRIMARY TREATMENT MODE (Background Info) ------- 7046 Appendix C PRIMARY TREATMENT MODE (Background Information) This section of the manual contains background information on processes generally used in preliminary and primary treatment of wastewater. It describes the basic mechanisms of the various processes and how they fit into the overall treatment scheme. A list of references for each process is included for additional information. The tables located in Section II of this manual list the common preliminary and primary treatment operating parameters, loading rates , material accumulated during process operation, and support systems which are used in conjunction with each process. If a general review of preliminary and/or primary treatment is desired, review this section plus the applicable tables in Section II, and the pertinent problems and solutions in Section IV. GENERAL Pretreatment of raw wastewater includes the removal of large pieces of debris by passing it through a bar screen to remove large solids and then a grinder (comminution) to reduce particle size of the remaining solids to protect plant equipment and prevent plugging of pipes. This treatment also includes degritting by sedimentation. After degritting, the wastewater goes to the primary treatment where a sedimentation process removes a portion of the suspended solids (SS) and the settleable solids, along with related biochemical oxygen demand (BOD). Figure C-l shows a pre- and primary treatment system. There are many configurations that can be representative of this form of treatment, with units being added or deleted on the basis of the degree of treatment required, economics and space availability. References shown after each description of a process provide additional information on that particular process. C-l ------- 7046 If no cutters or shredders screenings Hauled to sanitary landfill or incinerator i 1 1 Chemical addition ' I , ... I i for precipitation | Influent \ From combined system or sanitary system By Pass Prechiorination wet well Weir for flow control CUTTERS SHREDDERS COMMINUTOR PP.EAEPAT1OM *-* r.r • rr o r%r\/ \^l\l_/-VJi- (Ji v-*Lyv CONTROL FINE SCREENS SEDIMENTATION LAGOONS -fc sludge DIGESTER CHLORINATION & CONTACT CHAMBER 1 Secondary system Effluent discharge r* VACUUM FILTER, ^Periodically ' scraped, hauled Hauled or incinerated Discharge Fig. C-l. A Primary Treatment System C-2 ------- 7046 PRETREATMENT Flow Regulators Local conditions will determine the hourly variations in quantity and strength of the wastewater. The regulation and metering of flow through the treatment plant is accomplished by use of weirs and flumes for open channel sections, and the venturi tube, orifice plate, Dahl flow tube and magnetic flow meter for pipe flows. Devices which measure flow in an open channel all operate with a head loss. The parashall flume has the smallest head loss of all the commonly used open channel flow meters and is the one commonly used. Some plants utilize electronic sensors coupled with servo control units that operate valves or other mechanisms for flow control or diversion to various parallel units. Racks and Screening Devices Racks and screens are designed to remove floating matter and larger suspended solids (mainly inorganic). Commonly used screening systems include racks, coarse or medium, having either: 1. Fixed bars, either hand or mechanically cleaned, or 2. Movable racks, such as the cage rack. / //]/ trough rack a) Fixed Bar Rack b) Mechanically Cleaned Rack Fig. C-2. Fixed Bar Racks C-3 ------- 7046 Figure O2a shows a cross-section of a fixed medium bar rack. This rack, like the coarse rack, is primarily used to protect pumps. The medium rack also removes floating material which will form a heavy and troublesome scum in sedimentation basins. For additional information see: Chapter 4 of ASCE Sewage Treatment Plant Design and Chapter 22 of Water Supply and Sewage-Steel. Grit Chambers Grit chambers are installed prior to sedimentation and usually after bar racks to remove dense mineral matter such as sand, gravel, egg shells or cinders. Grit removal helps prevent problems in pumping sludge. Grit chambers are also used to avoid the cementing effects on the bottom of the sludge digester and in the sludge blanket of the primary settling tank. They also are installed to prevent reduction of active digester capacity and help prevent damage to mechanical equipment. These units are usually installed in plants with combined flow; however, many of the newer plants are designed with grit removal systems as common practice. Figure C-3 shows a plan and a section view of the most common configuration of a grit chamber. PLAN SECTION Fig. C-3. Grit Chamber C-4 ------- 7046 Removal mechanisms generally fall into one of four types: 1. Flow rate control which is maintained at 0.75 to 1.0 ft/sec by proportional weirs, by controlling the depth of flow. 2. Clarifier-like mechanisms, sized to cause grit to fall out. The grit is then cleaned by washing and the organics are returned to the wastewater flow. 3. Hydraulic cyclone, removes grit by centrifugal force which tends to force the heavier grit particles to the outside of rotating flow stream. - 4. Injection of diffused air produces a spiral flow velocity causing particles to settle out. The average cleaning interval is every two weeks. In wet weather, and particularly with combined wastewater flow, the accumulation of grit may be enormously increased, necessitating rapid or continuous cleaning to keep the unit operating efficiently. For additional information see: Ch. 23 of Steel; Ch. 4 of Imhoff- Fair; and ASCE Sewage Treatment Plant Design, Ch. 5. Cutters , Shredders (comminutors) Cutters and shredders are usually located after grit removal to prevent excessive wear on cutting edges and before the sedimentation unit so the shredded particles can be added back to the wastewater treatment stream and removed by sedimentation. Generally, fine racks and fine screens have been replaced by the cutting screens of communutors. These units are found in a variety of sizes, capacities, and configurations. Those include up and down moving cutting edges on bar racks and units that function like a kitchen sink garbage disposal with rotating cutter edges. For additional information see: Ch. 22 of Steel; Ch. 3 of Imhoff- Fair. Fine Screens Fine screens are used in old plants where cutters and comminutors were not installed and in newer plants as partial treatment of certain industrial wastes (e.g., cannery, brewery, distillery or packing house). They are usually located after the grit and pre-aeration units and before the sedimentation unit. C-5 ------- 7046 Fine screens may be made up of a series of disk screens with a frustum of a cone superimposed upon it. It rotates slowly, with brushes sweeping the screenings from the part above the wastewater flow to a conveyor belt or hopper. Drum screens are of several types. Basically, screenings are accumulated on the outside of a drum as it rotates or on the inside of a drum as the flow passes through. Conveyors and collectors then handle the retained solids. For additional information, see: Ch. 22, Steel; Ch. 3, Imhoff-Fair; Ch. 4, ASCE Sewage Treatment Plant Design. Aeration and Chlorination Aeration and Chlorination are utilized to minimize odor and grease problems. Chlorine added to wastewater causes grease to coagulate. This process also reduces the finely divided suspended solids load on the primary sedimentation and biological treatment units. The cohesive force of the wastewater is reduced by the diffused air bubbles that buoy up the grease and suspended solids which are then skimmed off. This unit may follow the grit chamber and cutters. It usually precedes the fine screens and/or primary sedimentation unit. For additional information, see: Ch. 20, Fair & Geyer; Ch. 6, ASCE Sewage Treatment Plant Design; Ch. 3, Imhoff-Fair. Sedimentation Sedimentation (in primary treatment) usually follows grit removal, screening and pre-aeration. It precedes final Chlorination and/or discharge to the receiving waters or other effluent disposal areas. It reduces the suspended solids and organic loading on subsequent secondary and advanced waste treatment units. Sedimentation tanks may be constructed with or without mechanical devices for continuous removal of sludge. Tanks are classified by • Primary - in which raw wastewater is settled • Secondary of Final - in which mixed liquors or activated sludge plants or trickling filter effluents are clarified C-6 ------- 7046 • Intermediate - when used between filters in a two-stage trickling filter plant • Septic tanks - combine sedimentation and sludge digestion in the same compartment • Imhoff tanks (two-story tanks) - combine sedimentation and sludge digestion but are designed so that the processes are carried on in separate compartments arranged one above the other Municipal wastewater contains both granular and flocculent solids. Based on this condition, the required capacity of primary settling tanks is both a function of surface loading and of volume loading or detention period. A number of factors affect the performance of sedimentation tanks and the designs are influenced by those parameters which have the greatest impact on the desired results. Some of the commonly considered parameters are: • Variation from 16-hour average flow • Temperature variation (of the wastewater, as it affects the density and viscosity of the liquid) • Density currents • Solids concentration • Solids removal The mechanism of sedimentation is based on the settling velocity of particles. A particle in a still fluid of less density will move vertically downward because of gravity. The time required for the optimum percentage of these particles to drop out is the theoretical detention time of the settling basin. This time varies with what the next treatment mode is. Fig. C-4 shows the removal of suspended solids and BOD from wastewater in primary settling tanks (after Imhoff and Fair) as it varies with detention time. A secondary mechanism affecting the performance of the sedimentation tank is its overflow rate. A case in point is a high overflow rate with overflow velocities which exhibit a high scouring and solids-carrying capacity in wastewater effluent. The allowable values of overflow rates are dependent on the next mode of treatment. 07 ------- DDDB 7046 3 4 Tims, hours Fig. C-4. Percent of Suspend Solids and BOD5 Both of these mechanisms are influenced by changes in the temperature of the wastewater. By increasing the temperature, it reduces the viscosity and density of the fluid, thereby increasing the settling velocity of the particles and reducing the detention time required. Along with this, characteristics of effluent quality over the overflow weir would be changed. Figure C-5 shows the various types of sedimentation tanks and their sludge collection systems. For additional information, see: URS Project 7032; Ch. 9 & 23, Steel; Ch. 4, Imhoff-Fair; Ch. 3, ASCE Sewage Treatment Plant Design. C-8 ------- o REPRESENTATIVE LONGITUDINAL-FLOW SETTLING TANKS Rectangular, hand-cleaned tank with sludge hopper Tank a provided with track- mounted sludge scraper (Mieder tank) Rectangular, hopper- bottomed tank with hydrostatic sludge removal :-^^-—---ri Square tank with cross flow (d) and rotary sludge scraper (Dorr Co.) ,'v^ Rectangular tank with sludge ^i scraper and scum collector (Link-Belt Co.) MODIFIED IMHOFF TANKS WITH SMALL SLUDGE SUMPS Horizontal flow Vertical and radial flow REPRESENTATIVE VERTICAL & RADIAL-FLOW SETTLE TANKS Hopper-bottomed, circular or square tank with hydrostatic sludge removal (Dortmund tank) — Tank i equipped with sludge scraper Tank -J O c^i7.\i Tank e with cross collector lilpJ! for sludge and scum (Link-Belt Co.) ;_> Circular tank with sludge collector to which scum collector can be added (Dorr Co. ) Fig. C-5. Settling Tanks ------- 7046 CHEMICAL PRECIPITATION Chemical precipitation processes obtain effluent quality which is in the range between primary sedimentation and the biological oxidation processes. The most effective use of chemical precipitation is under the conditions of seasonal variations in volume, strength or degree of treatment required of the wastewater. In plants that are not specifically designed for chemical precipitation, it is not uncommon for chemicals to be added prior to primary or secondary sedimentation to aid in the settling process. The process of chemical precipitation functions under one of three mechanisms or under all three at the same time: • Mechanical entrapment - heavy metal salts (such as alum or ferric chloride), plus an alkaline material, produce large volumes of precipitates which settle out true and colloidal suspension in wastewater • Particle charge - colloidal particles with electrical charges, plus chemicals with opposite charges (polyelectrolytes) , neutralize each other and settle out • Physical - insoluble chemicals (such as activated carbon) with large surface areas either absorb or act as nuclei for the colloids and start settling As in primary sedimentation, detention time under quiescent conditions is an important part of the processes, with detention times similar to primary sedimentation. For additional information, see: Ch. 9, ASCE Sewage Treatment Plant Design; Ch. 9 & 23, Steel. CHLORINATION Final chlorination is used to disinfect (destroy the pathogenic organisms harmful to man or animals) treated effluents before they are discharged to the final receiving waters. To accomplish disinfection, enough chlorine is added to satisfy the chlorine demand of the waste while leaving a chlorine residual to destroy the pathogenic organisms. The amount of chlorine required for disinfection is largely dependent upon the organic matter present. The performance of the chlorination process is affected by the quantity of chlorine used, waste characteristics, where the chlorine is applied and how well it is mixed. The contact chamber should have a cleaning and flushing system to prevent buildup of sludge due to solids carry-over from the final settling tank and grease. Figure C-6 shows a typical baffled C-10 ------- Chlorine Contact Tank Baffle Baffle A U Flow Control Weir Final Effluent to Receiving Water Weir Scum Baffle Mixing Baffle ' Chlorine Diffuser Influent from Final Treatment Processes Chlorine Source PLAN VIEW Baffle Mixing Baffle Flow Control Weir " Chlorine Diffuser SECTION A-A Fig. C-6. Final Chlorination System C-ll ------- 7046 chamber. To be most effective, the contact time should be not less than 15 minutes at maximum flow. There are some State health departments which require a residual of 2.0 mg/1 after 15 minutes. All such requirements should be checked before plants are inspected. There is a secondary benefit of proper effluent chlorination. At the point where orthatoline residual is produced, each mg/1 of chlorine absorbed will satisfy and remove approximately 2 mg/1 of BOD in the treated effluent. C-12 ------- ------- SECONDARY TREATMENT MODE (Background Info) ------- 7046 Appendix D SECONDARY TREATMENT This section of the manual contains background information on pro- cesses now being used in the secondary treatment process of wastewater. It delineates the basic biological mechanism which takes place in the various biological reactors, a description of these reactions and how they fit into the treatment scheme, and a list of references for each process for additional information. The tables located in Section II of this manual list the common secondary treatment operating parameters, loading rates, and support sys- tems which are used in conjunction with each process. This information, along with this section and the common problems and solutions for secondary treatment (Section IV of this manual), should be reviewed for a general background to expedite the plant evaluation and help in finding solutions to process problems in this area. As in pre- and primary treatment, there are many configurations that can be representative of secondary treatment. The unit operations which are shown in Figure D-l make up the basic secondary mode of treatment. In secondary treatment, flow is received from the primary treatment system. This flow then enters a biological reactor where biological growth occurs. This growth "fixes" most of the remaining organic materials in a biological mass (biomass). This biomass is then removed by sedimenta- tion in the secondary clarifier. Some of the sludge (settled biomass) is returned to the inlet of the biological reactor and is mixed with the incoming primary effluent so that organisms with increased assimilation capacities can work on the waste. The effluent from the secondary clarifier is then chlorinated and discharged to the receiving body. The biological reactors which are in common use in wastewater treat- ment were listed in Appendix A of this manual. They can be operated in many modes, depending on plant area limitations or treatment desirability. In many cases the only prior requirement to the use of a biological reactor is primary treatment. D-l ------- to Wastewater I Pre-Treatment Secondary Clarifier 1 1 1 1 1 1 1 1 1 > — - c ' 1 1 » Primary Sedimentation f f Biological Reactor -7 — r 1 1 11111111 i i x i i / i I llil Lf-^ ©*- ^"^ 1 Slud •- - 1 — Dinr Trea —— Ff fluent ge stion & Irnent — ^ Sludge Wastewater Effluent To Final Receiving Body MM ^^ «M^ ^^m «^^ Chlorine Contact Chamber 1 1 Sludge J Final Sludge Disposal o ^ CD Chlorination Fig. D-l. Flow Diagram of a Secondary Treatment System ------- 7046 GENERAL BACKGROUND ON A BIOLOGICAL REACTOR In nature, bacteria and other microorganisms break down organic materials (the substrate) found in wastewater into simple, more stable substances. A biological (aerobic) reactor provides a place where organic waste is brought into contact with the surface, contact, or interfacial forces of biological slimes, or films, zoogleal aggregates, activated sludges or activated surfaces to remove suspended and finely divided solids and dissolved organic matter by the mechanisms of adsorption and coagulation, and enzyme complexing. Whatever the individual operation of the biological reactor, the microorganisms which stabilize the wastewater must have a continuous supply of substrate (food) , an adequate supply of oxygen (aerobic systems only) and a suitable supporting film of floe. The reactions involved in the reduction of organic material in the wastewater during biological oxidation can be interpreted as a three-phase process: 1. an initial removal of BOD on the contact of a waste with a biologically active sludge or film which is stored in the cells of the organism as a reserve food source 2. removal of BOD in direct proportion to biological sludge or film growth 3. oxidation of biological cellular material through endogenous respiration. For additional information, see: Ch. 2, Eckenfelder & O'Connor; Ch. 1, Rich Unit Process; Ch. 6, Imhoff-Fair. D-3 ------- 7046 TRICKLING FILTERS A trickling filter is a fixed bed system over which wastewater is intermittently or continuously discharged and contacted with biological films on the filter media. Through this contact nonsettleable suspended matter and colloidal and dissolved organic matter are removed from settled wastewater by the organisms to be used as food. A schematic representation of mechanism involved in the trickling filter processes is shown in Figure D-2. The largest portion of the waste- water applied to the surface of the filter passes rapidly through the filter, and the remainder slowly trickles over the surface of the slime growth. The reduction of organic loading occurs in two stages: • the wastewater passes rapidly through the filter and removal occurs by biosorption and coagulation • soluble constituents are removed from the remaining portion of flow due to the substrate utilization by the organisms. WASTEWATER AIR AIR \ I -n m — ^5 j> m \\X\\\\\\\\\\\\\\\\\\\\\\ H2S ORGANIC ACIDS ANAEROBIC EFFECTIVE FILM DEPTH -* h *• BOD °2 co2 AEROBIC WASTE 1 1 i i AIR Fig. D-2. Trickling Filter D-4 ------- 7046 Classification of Trickling Filters Filter classification is based on applied hydraulic and organic (BOD) loadings (Section II of this manual shows typical loading rates). • Low-Rate (Standard or Conventional Filter) - Low-rate filters usually operate with intermittent dosing. The wastewater is applied to the filter surface and passes through the filter with its effluent going to the secondary clarifier without recirculation. The filter depth is usually greater than for high-rate filters. • High-Rate - Wastewater is applied much in the same manner as in the low-rate filter. However, the hydraulic loading is five to fifteen times as great, with the organic loading being four to five times greater. Along with the higher loading rates , the high-rate filter is characterized by the recirculation of a portion of the wastewater. • Roughing Filter - Roughing filters are used to reduce the organic load applied to subsequent filters of activated sludge units. They are designed on the basis of the volume of liquid applied to filter. They will also handle a greater organic loading than low- or high-rate filters, but with reduced removal efficiencies. Trickling filters , like most biological reactors, are followed by a final sedimentation process to remove any biomass which is lost from the reactor. This final sedimentation process is figured in total process efficiency when it is calculated. For additional information, see: Ch. 6, Eckenfelder-O'Connor; Ch. 24, Steel; Ch. 6, Washington State Waste- water Plant Operation Manual; WPCF Publication No. 14, Sec. 15, Ch. 11, ASCE Treat- ment Plant Design. D-5 ------- 7046 ACTIVATED SLUDGE The activated sludge process is based on the utilization of a floe made up of microorganisms, non-living organic matter and inorganic materials. These are brought into contact with primary treated wastewater (in most cases) in the presence of dissolved oxygen. A high degree of mixing causes the removal of settleable solids, nonsettleable suspended solids, colloidal solids and dissolved organic matter. The basic process flow includes: • Aeration of pre-primary treated wastewater for a period of time • Final clarification for the separation of solids and liquids at the end of the contact time • The return of a percentage of the separated solids to the reactor for mixing with influent wastewater • Discharge of the liquid wastewater fraction as process effluent. Classification of Activated Sludge Processes • Conventional (plug flow). All primary- introduced at one end of the reactor a] sludge. The length of the reactor width. The diffusers are located i tank so that the diffused air bull rolling motion on an axis parallel £to th.e/*4hMh of the tank. This class of activated sludge process prtoviWes insufficient dissolved oxygen content at the influent part of the reactor. • Modified (high-rate). This process utilizes short aeration periods and low activated sludge concentrations. It is characterized by low BOD removals (40-70) and a low percentage of sludge return (10%). Also associated with this process is a high solids accumulation due to insufficient time for significant oxidation of cellular mass and the retention of influent inerts. • Step Aeration. Primary treated wastewater enters this reaction at a number of different points along one side of the reactor, but with the returned sludge being introduced at the point of first entry, with or without a portion of the incoming wastewater. The greatest concentration of sludge solids in the mixed liquid is where the final amount of waste is introduced and decreases as more waste is introduced at subsequent points. By entering the waste in this manner, a more uniform aeration of the waste occurs, and a decrease in detention time is possible. D-6 ------- 7046 Tapered Separation. Basically the same concept as step aeration except that the air is added in stages along the reactor instead of the wastewater. The air requirements are staged to give maximum amount at the inlet of the raw waste with the rest regulated to meet oxygen utilization in other sections of the reactor. This process is supposed to provide better control in meeting shock loadings. Kraus Process. This is a modification of conventional activated sludge where incoming wastewater (primary treated water) has insufficient amount of nutrients (usually nitrogen) available to provide a stable activated sludge process. These nutrients are provided by the recycling of digester mixed liquor to the activated sludge system by means of a nitTTrfica- tion tank where a mixture of supernatant and returned activated is aeratec/f24yhours and returned to the activated sludge unit? Jfeiek),.fromVTrtyppiying the needed nutrients , there are other beneficial effects from this process: it provides an oxygen reserve in the form of nitrates and also tends to weight the sludge thus providing better settling characteristics. Completely Mixed Reactor. The primary treated waste is completely mixed throughout the reactor as quickly as possible. The process provides for immediate distribution for all incom- ing waste, and the oxygen requirement throughout the tank is uniform. This process minimizes the effect of slug loadings of very strong waste or short term, high volume wastes (shock loadings). Contact Stabilization. Incoming primary-treated wastes (some new plants omit primary sedimentation) are mixed with returned sludge in a contact basin for a period of 30 minutes to one hour in which most of the absorption of solids is accomplished. This short contact permits solubilization of the absorbed organic solids before the absorption by microorganisms in the activated sludge of the soluble organics. This process is also affected by a highly variable influent flow rate which reduces the adsorption time causing high effluent BOD. Two Stage Aeration. This is basically the same as contact stabilization except that the contact time is six times as long, providing enough time for absorption, solubilization, absorption and the synthesis of cellular material. The aeration time of the second reactor is long enough to provide for the oxidation of a large portion of the synthesized cell mass. D-7 ------- 7046 Extended Aeration. This type of system is usually provided for a small-sized treatment facility. This system is completely mixed with a low food/microorganisms (F/lW) loading rate for a given population, which allows for almost complete oxidation of synthesized cell mass. It is also characterized by low oxygen uptake rate. For additional information, see: Ch. 2, 3 & 6, Eckenfelder- CD 'Connor; Ch. 6, State of Washington Wastewater Plant Operators Manual; Ch. 25, Steel; Ch. 10, ASCE Sewage Treatment Plant Design. STABILIZATION PONDS AND LAGOONS The operation of stabilization ponds and lagoons that are aerobic depends on oxidation and reduction by microorganisms, sedimentation, bio- flocculation and anaerobic digestion of bottom sludge. The oxygen utilized in this process is obtained from the algae growth present or mechanical and diffused aerators with additional oxygenation being provided by wind and wave action. Some ponds operate anaerobically in much the same way as a digester with sufficient depth to create anaerobic conditions due to poor oxygen transfer to the deep parts of the pond. ! The effluent from this treatment process is disposed of by percolation (where ground water regulations permit), evaporation, transpiration from irrigation of cover crops or discharged to a receiving body. Classification of Stabilization Ponds and Lagoons The classification of stabilization ponds and lagoons may be according to: depth, main source of oxygen, rate of waste loadings (Ib of BOD per acre per day), inlet, flow-through, and inlet and outlet arrangements including load distribution, recirculation, and effluent disposal. In general, stabilization ponds and lagoons may be classified into three types: » Large Holding Reservoirs. These are characterized by long detention times (months, usually) with the oxygen being supplied by surface aeration and dilution of the wastewater with clean water. The removal of organics is accomplished by bio-flocculation, oxidation, and reduction with an aerobic digestion of bottom sludge taking place. D-8 ------- 7046 o Stabilization Ponds. The rate of oxidation of organic matter by microorganisms exceeds the rate of natural surface aeration and the algal growths must supply the additional oxygen required. Since solar energy is required for photo- synthesis, the depth of the ponds is limited. Location is also a limiting factor as climatic parameters are very important. The detention times in stabilization ponds range from less than a week up to six weeks , depending on the type. a. Facultative Ponds. This type of pond is characterized by the aerobic and anaerobic processes occurring simultaneously. The removal of organic material is accomplished by sedimentation, bio-flocculation and aerobic oxidation. The primary source of oxygen is obtained from algae growth with a second source supplied by wind and wave action. b. High Rate Ponds. This pond is characterized by its shallow depths for extreme solar energy penetration; it is fully mixed and completely aerobic. The organics iii this system are oxidized by microorganisms utilizing oxygen generated by algal growths. o Aerated Lagoon. This system is characterized by the use of mechanical aeration to supply the required oxygen supply directly, causing sufficient mixing to supply additional oxygen from surface aeration, so that the lagoon remains aerobic. For additional information, see: Ch. 6, Eckenfelder-O'Connor; Ch. 12, ASCE STP Design Ch. 21, Steel. INTERMITTENT SAND FILTERS Intermittent sand filters are being phased out of secondary waste treatment mode due to the large area requirements. Because of the high quality effluent produced, they may be used in advanced waste treatment modes on a smaller scale to polish secondary treatment effluent. The basic mechanism of this process is a straining effect produced by sand grains which trap suspended solids. The intermittent dosing (twice during a 24-hr period) permits air to enter the bed to allow micro- organisms to reduce the organic load aerobically. It should be noted that work done by Grantham, Emerson and Henry in Florida indicates that sand D-9 ------- 7046 size affects the percentage of organic material removed. For additional information, see; Ch. 12, ASCE STP; Ch. 24, Steel. SECONDARY CLARIFICATION This unit follows the biological reactor (such as the trickling filter of activated sludge). Its primary functions are to retain the biological growths produced by the reactor for recycling and to produce clarified liquid in the overflow and thickening on the bottom of the tank. This depends on the physical and chemical nature of the sludge and the hydraulic characteristics of the clarifier. The clarifiers can be rectangular or circular in shape. In both types of clarifiers, their size is related to one of the following factors: • Surface of clarifier area over the M.L.S.S. concentration • Surface area and volume of clarifier for producing thickening and underflow of a desired concentration • Volume for retention of settled sludge Along with these requirements, the velocity of the density currents are critical in the clarifier. If these velocities are increased, the critical value for separation of solids could be exceeded causing bottom scour with the possibility of carryover of low density particles in the effluent. For additional information, see: Ch. 4, Rich, Unit Operations of Sanitary Engineering; Ch. 5, Eckenfelder-O'Connor; Paper by Clair Sawyer - Final Clarifiers, and Clarifier Mechanisms (MIT); Ch. 8, ASCESTD. D-10 ------- 7046 PACKAGE AERATION PLANTS This type of treatment system is characterized by • low daily flow • no primary sedimentation • 20-24 hour aeration period • long final sedimentation period • limited flow control between processes due to close proximity of operations. The basic mechanism of the process is to keep the microorganisms predomi- nantly in the endogenous growth phase (organisms are using all material in absence of organic material growth) through long detention time and a low food-to-microorganism ratio in the aeration tank. Two systems in common use consist of: • aeration tank and final sedimentation tank plus chlorination • mixing chambers, sedimentation tank, and sludge reaeration tank plus chlorination. Both of the systems utilize aerated digestion of the activated sludge. Critical to successful operation of these plants is a program of effective solids removal from the system. For additional information, see: "Aeration Plant in Florida", ASCE Jour, of Sanitary Eng., Vol. 88; "Field Evaluation of the Performance of Extended Aeration Plant", J. WPCF, Vol. 41, July 1969, p. 1299. D-ll ------- ------- ADVANCED TREATMENT MODE (Background Info) ------- 7046 Appendix E ADVANCED WASTEWATER TREATMENT Advanced wastewater treatment processes are described in this section of the manual. It delineates how the process works, the various organic and inorganic constituents which are removed by the processes, removal percentages which can be expected, and references for additional information. The tables in Section II of this manual list the common advanced waste treatment operating parameters, a range of materials accumulated due to process operation, and support systems which are used in conjunction with each process. This operating information, together with the common problems and suggested solutions , should be reviewed with the information in this section to provide background data against which an advanced waste treatment plant can be evaluated. GENERAL BACKGROUND In the past few years the United States has experienced rapid popula- tion growth, concentration of people in urban areas, and the appearance of ever larger industrial establishments. All of these factors have contributed to increased pollutional loads on streams, rivers, and other receiving waters. The result has been that conventional primary and secondary treat- ment processes are not always able to provide adequate removal of pollutants. For this reason, advanced waste treatment processes have been developed to remove pollutants not handled by conventional (primary and secondary) treatment. Advanced waste treatment is intended, therefore, to alleviate pollution of a receiving watercourse. It may also, however, be used to provide a water quality adequate for reuse, since the population expansion and increased water demand mean that more and more people have water supplies that must be used more than once for industrial and domestic purposes. It should be pointed out that certain materials to be removed by advanced waste treatment are normally removed to a great extent by secondary treatment (e.g. , 90 to 95 percent of suspended solids are removed in an efficient secondary plant). Advanced waste treatment, which is important whenever upsets occur in such a secondary plant, is physical-chemical treatment. This process, due to its reliability, could also be used in cases where direct water reuse is anticipated and 90 to 95 percent removal is inadequate. Advanced waste treatment is more commonly used, however, for materials which are not efficiently removed by primary or secondary treatment (e.g., phosphates and nitrates). E-l ------- 7046 In general, advanced waste treatment is applied to effluent from conventional secondary processes for the purpose of removing one or more of the following constituents: soluble organic compounds, soluble inorganic compounds (nitrogen and phosphorus), particulate solid material, and pathogenic organisms. The following paragraphs examine selected advanced waste treatment unit operations to provide descriptions of the processes involved and present references of interest for additional detailed information. CHEMICAL/PHYSICAL TREATMENT Chemical precipitation and sedimentation is a treatment method combining chemical and physical elements to achieve removal of soluble inorganic compounds (such as phosphorus) or removal of suspended solids in a colloidal state. A mineral or synthetic polymer is added to the wastewater and chemically reacts with one or more constituents of the wastewater to produce a precipitant. This precipitant is then coagulated or flocculated by means of the mechanical action of mixing or the addition of a coagulation/ flocculation aid. The precipitant is subsequently removed by sedimentation. In this process, constituents of the wastewater are removed in several ways: • chemical reaction with the material added and sedimentation of the resulting precipitant • physical capture of suspended solids by the descending precipitant • adsorption of particles and dissolved constituents by the precipitant. Removal of phosphorus is typically obtained by addition of calcium, aluminum, or iron salts (e.g., lime, alum or ferric chloride). Phosphorus removals vary from about 70 to 95 percent. Chemical/physical treatment can be applied to secondary effluent or to primary effluent. In an activated sludge plant, efficient removals have been achieved by mineral addition before primary settling, after primary settling, in the aeration tank, or near the mixed liquor exit point. In a trickling filter plant, the precipitation is usually accomplished in the primary sedimentation tank. Final chlorination and discharge to receiving water follows chemical/physical treatment after it is used in secondary or advanced waste treatment. Chemical/physical treatment is basically a sedimentation process and has associated with it the same type of equipment and performance parameters as in primary or secondary sedimentation. Additional equipment is, however, required to store and feed the required additional materials into the sedimentation tank. Specialized equipment and instrumentation are necessary E-2 ------- 7046 since slurries often are involved and pH control is critical. For additional information, see: Ch. 2, Gulp and Gulp Ch. 26, 29 and 30, Fair, Geyer and Okun Advanced Waste Treatment Research Series AWTR-2, -12 Advanced Waste Treatment Seminar, Session II (Oct. 1970) CARBON ADSORPTION Carbon adsorption is a treatment method used to remove residual dissolved and suspended organic material from wastewater treatment plant effluents. These organic pollutants are typically responsible for the color, odor, taste, and froth problems of wastewater. In carbon adsorption, the wastewater is continuously run through a bed or column of activated carbon which removes the organic materials by adsorption. When the adsorption capacity of the columns is exhausted, the wastewater is rerouted through another bed of carbon and the exhausted carbon is regenerated for use again. In actual plant experience (South Tahoe) , the carbon adsorption process has yielded the influent entering it the following removals: BOD - 70+%; COD - 50+%; TOC - 75%; color - 75%. In pilot plant tests, removals of suspended solids have run up to 90% and removal efficiencies even greater than those shown above have been experienced. Conventional primary and secondary treatment removes organic matter to a great extent. The difficult-to-remove organics (refractory organics) are handled by carbon adsorption. Carbon adsorption, therefore, follows secondary treatment and precedes chlorination. The activated carbon must be of the proper type to adsorb materials present in the existing wastewater. Many different types are available, and the actual type and quantity to use depend on the kind and concentra- tions of pollutants to be removed. In addition to variations in the adsorption characteristics, activated carbon also varies in physical form from powdered to granular. Since the carbon is stressed during regenera- tion and transported between generations, it must be durable to such stresses and still maintain performance. The granular carbon is generally optimum from an overall cost performance, endurance, and recovery point of view. The carbon columns may run from 8 to 12 ft in diameter and 24 to 60 ft tall. Usual operation is to run the wastewater through from two to four columns in series. The most important factors in column operation are E-3 ------- 7046 contact time, pretreatment, and flow conditions within the column itself. For regeneration, the spent carbon is transported from the column in water slurry and fed by screw conveyor into a regeneration furnace where intense heat burns off accumulated material, opening the interstices of carbon for additional adsorption. Makeup carbon is added as needed and the regenerated carbon is returned to the column (again in the slurry). For additional information, see: Ch. 7 and 8, Gulp and Gulp Ch. 26, Fair, Geyer and Okun Advanced Waste Treatment Research Series 9, 10, 11 and 16 Advanced Waste Treatment Seminar, Section III. AMMONIA STRIPPING Ammonia stripping is a treatment method for specific removal of nitrogen in the form of ammonia. The process is one in which the wastewater is cas- caded down a stripping tower and air is forced up through the tower. The air strips the dissolved ammonia from the water and carries it off into the atmosphere. Removal efficiencies up to 90% have been achieved. Neither conventional primary nor secondary treatment removes significant amounts of nitrogen, but the biological process does convert nitrogen com- pounds in the wastewater into ammonia. Ammonia stripping, therefore, follows secondary treatment and precedes chlorination. Effective ammonia stripping requires a high pH and high air-to-liquid loadings. Both of these factors are temperature dependent, such that when air temperatures are lower, the corresponding pH and air loadings must be higher to give the same ammonia removal. Normal operation calls for a pH of above 11 and air rates of from 200 to 500 cfm/gpm. Actual ammonia stripping towers are very similar to forced-draft type cooling towers. The pH adjustment takes place before entry of the waste- water to the stripping tower. In a typical operation, the pH adjustment, using lime and a phosphorus removal step, takes place in a clarifier just before feeding the wastewater to the stripping tower. After passage through the tower, recarbonation is performed to readjust pH as needed to prepare the wastewater for filtration, carbon adsorption, chlorination, or final discharge. In the recarbonation process, an intermediate reaction or settling basin exists between the two recarbonation basins. In the settling basin, a dense floe rich in calcium carbonate is formed, and this is a source of material to reclaim lime for reuse. E-4 ------- 7046 In an advanced waste treatment scheme, therefore, the secondary effluent proceeds through a chemical/physical treatment for phosphorus removal, then ammonia stripping, carbon adsorption, and finally filtration and/or desalting. Two problems that may occur with ammonia stripping are: 1) the inability to operate at air temperatures below 32 F; and 2) the deposition of calcium carbonate scale on stripping tower surfaces. For additional information, see: Ch. 4 and 5, Gulp and Culp Ch. 28 and 31, Fair, Geyer and Okun Advanced Waste Treatment Seminar, Session 1. ELECTRODIALYSIS Electrodialysis is a membrane desalting process for removal of dis- solved inorganic ions from wastewater. In the process, membranes are used which are permeable to charged ions and impermeable to ions of the opposite charge. A pair of opposite membranes has a direct current potential applied across them and the wastewater is pumped between them. Positive and negative ions, therefore, permeate out of the wastewater, and a product with lower dissolved minerals results. In addition, a brine stream very concentrated in dissolved minerals also results. Electrodialysis is capable of yielding product water with up to 85% of the total dissolved solids removed. In this process , nitrogen removal is about the same as total dissolved solids , but phosphorus and CO do not show the same high removal. A typical system will yield about three gallons of product water and one gallon of brine for every four gallons of feedwater treated. Conventional primary and secondary treatment does not remove significant amounts of dissolved inorganics. Electrodialysis usually follows carbon adsorption which removes constituents capable of fouling the electrodialysis membranes (non-ionic particles). Normal operation of electrodialysis requires pH control, chemical control of scale formation, and routine flushing and cleaning of membrane surfaces. Proper disposal of the brine stream is important and this may consist of ocean dumping (where it is still permitted), evaporation pond utilization, or deep well injection. E-5 ------- 7046 For additional information, see: Ch. 21 and 30, Fair, Geyer and Okun Advanced Waste Treatment Seminar, Section IV. REVERSE OSMOSIS Reverse osmosis is a membrane desalting process for removal of dissolved inorganic materials from wastewater. In the process, membranes are used which are permeable to pure water, but nearly impermeable to dissolved salts when operated at high pressure. Product water with lower dissolved minerals is forced through the membrane, and a brine stream very concentrated in dissolved minerals is rejected by the membrane. Reverse osmosis is capable of yielding product water with up to 85% of the total dissolved solids removed. In this process, phosphorus, COD, and ammonia- type nitrogen are removed about as efficiently as the total dissolved solids, but nitrate-type nitrogen is less efficiently removed. A typical system will yield about three gallons of product water and one gallon of brine for every four gallons of feedwater treated. Conventional primary and secondary treatment does not remove signifi- cant .amounts of dissolved inorganics. Reverse osmosis usually follows carbon adsorption in an advanced waste treatment scheme so that fouling of membranes is avoided. Normal operation of reverse osmosis requires pH control, chemical control of scale formation, and routine flushing and clearing of membrane surfaces. Proper disposal of the brine stream is important, and this may consist of ocean dumping, if still permitted, evaporation pond utilization, or deep well injection. For additional information, see: Ch. 21 and 30, Fair, Geyer and Okun Ch. 10, Gulp and Gulp Advanced Waste Treatment Seminar, Section IV. E-6 ------- ------- SOLIDS TREATMENT AND DISPOSAL ------- Appendix F SOLIDS TREATMENT AND DISPOSAL This section of the manual supplies background information on the various processes involved in handling and treating of solids accumulated during the wastewater treatment process. Sludges are characterized by their percentage water content, volatile matter, and the various processes by which they are produced. In addition, this section explains the methods available for final solids disposal. A comparison of operational parameters and loading rates (design specifica- tion) with those presented in this manual or in other sources will facili- tate an evaluation of the solids treatment and disposal system. Deviations from normal will reveal any problem areas. A check of the common operating parameters, loading rates, and support systems which are generally used in solids handling (Tables II-5 and II-6 in Section II) should also be made. These tables, along with the common problems in solids handling (Section IV), and a review of this section will supply information needed for a general evaluation of the solids handling program carried on at the wastewater treatment plant. GENERAL BACKGROUND The solids accumulated from the various wastewater treatment processes can be grouped into one of two categories: those trapped on medium and fine screens in pretreatment, and those formed from processes in the primary, secondary and advanced treatment modes. Large-size material trapped by racks, such as glass bottles, rags, or pieces of wood, is collected and usually buried in a sanitary landfill. The solids from medium screening are shredded and treated by anaerobic digestion, along with fine-screen solids. Settled solids (from primary and secondary treatment) can be treated by combinations of thickening, anaerobic and aerobic digestion, condition- ing elutriation; or with chemicals, vacuum filtration and drying on beds or in kilns. The final disposal of wet sludge is accomplished by dumping or piping it to sea or by incineration; dried or dewatered sludges are also inciner- ated, used as soil conditioners, or buried in sanitary landfills. F-l ------- TREATMENT OF SLUDGE The water content of sludge is the controlling factor as to the volume of sludge produced. Sludge can be characterized by the type of process by which it was produced. The following table characterizes sludges produced by the various processes. Table F-l SLUDGE CHARACTERISTICS Process Producing Sludge Percent Water Content Volatile Matter as Percentage of Dry Solids Primary sedimentation sludge 94 - 96* Activated sludge 95 - 97.5 High rate Trickling filter 96 - 97 Chemical precipitation 95 Digested sludge (well digested) • Primary 88 - 94 • Primary and activated 94 - 96 • Primary and trickling filter 90 - 94 70 45-70 32-45 * Steel, Water Supply and Sewage, pp. 574-575 The Digestion Process Anaerobic organisms break down complex molecular structures of the solids and release much of the bound water, while obtaining nutrients and energy from the conversion of the raw solids into more stable organic and inorganic solids. Anaerobic sludge digestion takes place in three phases: a Acid fermentation. Soluble or dissolved solids are broken down into simple organic acids (volatile acids) with a decrease of pH. F- 2 ------- • Acid regression. The organic acids and nitrogenous compounds are decomposed with an increase in pH. • Methane production. This occurs simultaneously with the first two phases. Methane bacteria reduce the organic acids and other products of the first and second phases to produce methane and carbon dioxide gases. Sludge digestion accomplishes the following: • Reduces organic matter into simple compounds • Reduces sludge volume • Releases the remaining water more easily • Reduces the coliforms by 99.8 percent in 30 days Aerobic Sludge Digestion This particular process functions in much the same way as an activated sludge unit, with the feed to the aeration tank being sludge from the primary and secondary sedimentation basins. This process requires adequate mixing and a dissolved oxygen level range of 1.0 to 1.5 mg/1. The deten- tion time required for treatment of sludge is from 20 to 30 days with removals of supernatants and sludge from the digester to maintain a consis- tent feed rate. For additional information, see: Ch. 6, Washington State Treatment Plant Operator's Manual Ch. 1 and 7, Eckenfelder-O'Connor Ch. 14, ASCE STP Design Ch. 26, Steel Ch. 12, Imhoff-Fair SLUDGE THICKENING This process, usually found in the larger treatment plants, precedes digestion, vacuum filtration, or kiln drying. Sludge thickening is used to reduce the liquid volume of the sludge solids which have to be pumped to other treatment units. These treatment units then can be smaller because they do not have to handle the excess liquid. F-3 ------- There are two major types of sludge thickening operations: • Gravity thickening. Sludge and aerated secondary effluent are introduced into a basin, much like a stirred sedi- mentation basin except deeper, which allows the concentration of solids from flocculation by interfacial contact and compaction by the weight of the overlaying water. This method can produce a solids content of 8% or greater. Not all sludge combinations will work in a gravity thick- ener, and testing of sludge produced by the treatment process will be necessary. In some cases, the addition of chemical flocculant will aid in the concentration of the sludge. « Flotation thickening. This is usually used on sludges formed by biological reactors. This process combines sludge with a liquid which has been exposed to high pressure and contains large amounts of dissolved oxygen. Under less pressure in the thickening tank, air bubbles from the liquid attach themselves to the sludge particles and rise to the surface where the sludge is collected for further treatment. For additional information, see: Ch. 15, ASCE STP Design Ch. 6, Washington State Treatment Plant Operator's Manual Ch. 26, Steel Ch. 14, Imhoff-Fair SLUDGE CONDITIONING The basic processes which are used in sludge conditioning are elutriation and chemical conditioning. • Elutriation consists of mixing thoroughly 1 part of sludge with 2 parts of water and allowing separation of about 6 hours, followed by decanting the resulting elutriate and drawing off the sludge. • Chemical conditioning consists of the addition of cer- tain chemicals to coalesce particles in sludge which facilitates moisture removal by filtration. Some of the chemicals commonly used are: F-4 ------- DOE Ferric chloride Ferric sulfate Lime and ferric chloride Chlorinated coppeas Aluminum sulfate Chemical solutions Polyelectrolytes Activated silicates Inorganic polyelectrolytes For additional information, see: Ch. 15, ASCE STP Ch. 26, Steel Ch. 14, Imhoff-Fair SLUDGE DEWATERING Some common methods for sludge dewatering are vacuum filtration, centrifuging, and sludge drying. • Vacuum Filtration is widely used in the separation of liquids from concentrated suspensions, sludges, and slurries. The basic mechanism of this process is the passing of a cylindrical drum which rotates partly submerged through a container of sludge. The solids in the container are agitated to keep them in suspension. A vacuum which is applied between the drum deck and filter media causes the water to be removed while sludge is held on the filter media. Following this process, the sludge is buried in a sanitary landfill or incinerated. The supernatant can be disposed of by returning it to the elutriation tank or returned into the influent of the plant. e Centrifuging removes water by centrifugal force which tends to force the heavier solids to the outside of the rotating flow stream much like the spin dry cycle of a washing machine. • Sludge Drying is best suited for sludges which have been digested. The mechanism is that of a shallow sand filter for draining the sludge and air for drying in beds. The supernatant may be disposed of in the same manner as vacuum filtration liquids. F-5 ------- For additional information, see: Ch. 7, Rich - Unit Operations of Sanitary Engineering Ch. 26, Steel Ch. 15, ASCE STP Design Ch. 14, Imhoff-Fair DISPOSAL OF SLUDGE The final disposal of sludge is influenced by many factors: • The character, and composition of the sludge • Availability of land for dumping of sludge cake or lagooning of wet sludge • Whether or not regulatory agencies allow piping (deep water sludge outfall) or barging of sludge • Local market possibilities for its use as fertilizer. Coastal cities can dispose of sludge through barging or piping to sea, where still allowed. On land, it may be buried in swamps, abandoned quarries, and other lands which have no present use. Incineration of raw or digested dewatered sludge is gaining popularity. At present, only larger cities are utilizing this process because of its added expense. In general, incineration of sludge is a wet combustion process in which sludge in solution or suspension goes through chemical oxidation processes under pressure. For additional information, see: Ch. 14, Rich - Unit Processes of Sanitary Engineering Ch. 15, ASCE STP Design Ch. 26, Steel Short Course - Theory and Design of Advanced Waste Treatment Processes, U.C. Berkeley Extension F-6 ------- ------- CONTROL AND METERING SYSTEMS ------- 7046 Appendix G CONTROL AND METERING SYSTEMS Various control and metering systems which are in common use in waste- water treatment plants are described in this section. It also indicates the uses and the limitations of these devices. The limitations are a function of physical/chemical makeup of the wastewater, the type of treatment units employed, sophistication of the plant personnel, economics, and the plant's maintenance program. A comparison of devices indicated in this section should be made with those that will be encountered at the treatment plant to see if they are types which will supply the data needed and required to maintain proper plant performance. The section on Problems and Solutions indicated the various problems which are commonly encountered with existing metering devices to help with solutions. CONTROL SYSTEMS Wastewater treatment plants use a variety of treatment processes. These processes usually fall into four categories: physical, biological, chemical, and electrochemical. In most plants, the processes are affected by temperature, weather, and day-to-day load variations. The nature of wastewater being high in solids' content and the inability of sensors to withstand fouling due to these solids makes total automation (computer control of the process) infeasible at the present time. Most treatment plants in existence today use instrumentation which involves the measurement of physical variables, such as flow, level, pressure, and temperature. These controls are electric and pneumatic mechanisms in conjunction with hydraulic equipment. These controls can be divided into two basic types: • On-off - used for the activation of pumps, alarms, etc. • Modulating - where the regulation of valves or other equipment is accomplished in proportion to a measurement (ratio control). The treatment systems utilize these controls to regulate or determine recirculation rates or controllers that set recirculation flow at a ratio to some other variable. The greatest present use for instruments and controls is in the treatment of sludge, where the use of density monitoring equipment to maintain optimum raw sludge density in the digester is becoming common. G-l ------- 7046 Other examples of automated control include: temperature control, gas volume sampling, and sludge level measuring equipment. What most systems lack is redundancy; there are no built-in back-up systems for emergency failures. A second shortcoming is the lack of an information feedback system. If a switch on the operating console activates a pump, there is no return loop which indicates to the operator that the pump has in fact been activated and is working. FLOW MEASUREMENT Differential Measuring Devices and Instruments Devices which measure flow and are used with differential measuring instruments are all descendants of the Venturi tube and are considered pri- mary devices. Most of the devices require very little head and can handle flows which contain suspended solids. Larger differential (high-head recovery) devices, such as the Dall tube, amplify a small, purely static change in head to a value which can be conveniently measured with secondary instruments. The high-head recovery, Venturi-type devices are not applicable to "dirty" fluids (high solids content) except in conjunction with a purging system. Other exceptions are the flow nozzle and the Lo-Loss tube. Orifice plates were originally developed for use on gas flows, but have been applied for use in the masurement of water which contains little or no solids in suspension. In general, wastewater can be successfully metered with the long- and short-type Venturi tube, flow nozzle, and Lo-Loss tube. It must be realized that an orifice that is too small produces large permanent pressure drops and is uneconomical. On the other hand, a too-large orifice measurement can be affected by inlet flow disturbances. The choice of device has to be care- fully considered. Secondary Instrument System These instruments measure the differential produced by the primary devices and convert the result into a signal for transmission or into a motion for indication recording or totalization. These instruments include mercury manometer, diaphragm meter, and various types of force-balance and motion-balance pneumatic and electronic transmitters. Other Flow Metering Devices • Magnetic devices utilize Faraday's Law to measure flow in a magnetic field. With a.steady magnetic field, the volume of flow G-2 ------- 7046 rate is directly proportional to the generated voltage; a voltmeter calibrated in volume flow units is then read for the flow measure- ment. The basic advantages: it has no head loss; it handles solids in suspension; it has no liquid connections; and it has an electronic output ready for in-plant transmission. • Propeller meters utilize the velocity head and convert it into mechanical power which is linear and translatable into velocity. This type of system is useful where frequent totalization readings are necessary. • Open Channel Devices - Weirs are of two basic types: rectangular and V-notch. In weir measurement water abruptly flows through a precise cross section. The nappe, or profile of water over the weir, must be completely aerated in order to have precise flow measurement with a minimum head loss. Flumes , a modification of the basic weir concept, are designed primarily to reduce head loss that occurs in weirs. This is accomplished by having the sides of the channel vary gradually to the desired cross section. Open-channel flow nozzle is a combination of flume and weir; this device can handle solids effectively but does not have the head recovery characteristic of the in-line flume. In general, the flow-through of a weir- or flume-type device is a function of fluid level. The three basic devices for measuring this level are float-and-cable, the in-flume float, and the bubble tube. In determining if the type of measuring device is suitable for the location in the treatment system, the following should be considered: • Probable flow range • Acceptable head loss • Required accuracy • Fouling ability of wastewater The diversity of instruments for measuring the various parameters precludes their individual description in a broad overview. The level of sophistication of these instruments is rapidly increasing. Devices which are available and are used for pressure, level, temperature, and analytical measurements consist of: Pressure • Bourdon tube • Spiral and helical elements G-3 ------- 7046 • Bellows and diaphragm elements • Wire strain gauges Level • Bubble tube • Diaphragm box Temperature • Mechanical (filled thermal) system • Electrical systems Analytical Measurement Type of Measurement • pH; oxidation-reduction potential (OKP) (although many ions can be measured with selective ion electrodes) • Residual chlorine; DO • Turbidity; color • Conductivity Type of Electrical Signal Voltage or amperage Amperage or resistance Resistance For additional information, see: Instrumentation and Control in Water Supply and Wastewater Disposal by Russell H. Babcock, P.E. ; Introduction to Chemical Process Control by Daniel D. Perlmutter; Ch. 19, ASCE Treatment Plant Design; Ch. 11, Operation of Wastewater Treatment Plants, EPA. G-4 ------- H ------- MAINTENANCE DATA SYSTEM ------- Appendix H MAINTENANCE DATA This section of the manual describes the basic components of a main- tenance system. It describes the type of filing system which could be employed for maintenance data, how to set up such a filing system, and the type of information it should contain. By comparing the maintenance records at the treatment plant with this guide and manufacturer's maintenance schedule, the plant's maintenance pro- gram can be evaluated. It is imperative that a record be kept of the service requirements of every piece of major equipment in the plant and when and how frequently service is required. Therefore, a system is needed to keep a complete record of maintenance requirements. Such a system should provide a permanent record of all maintenance work together with the advanced scheduling of preventive maintenance for an entire year. The system should also provide the maintenance work schedule for any given day. To be efficient, the system should contain the following five files: (1) preventive maintenance records (2) the preventive maintenance schedule for each piece of equipment (3) specifications on each major piece of equipment, the supplier, and where spart parts can be purchased, (4) spare parts inventory, and (5) instructions for operation and maintenance of each item of major equipment. As a first step in setting up any maintenance record system, each struc- ture and each major piece of equipment should be assigned a file number. A simple means of doing this is assigning each area or each structure within a treatment plant a block of 1000 numbers; and each equipment item in each area or structure requiring maintenance can be assigned an individual number within the block of 1000. Therefore, sufficient open numbers remain to provide for any additional equipment which may be required within that area or structure in the future. The assigned numbers will serve to identify each item of equipment in all of the plant records described above and should also be used to catalog spare parts. The file of preventive maintenance requirements mentioned in Item 1 above should contain one sheet for each item of plant property which requires periodic attention or maintenance, filed numerically. Listed thereon should be all pertinent requirements with respect to periodic H-l ------- maintenance including frequency, number of men required, and the estimated time of performance. These sheets are to be filed numerically as recommended above and maintained as a reference file. The file for preventive maintenance scheduling as mentioned in Item 2 above should show the equipment number and the key information given on the preventive maintenance sheet, together with a specific day for the performance of each item of work. Space should be provided on each equipment card for the operator to know the work items performed and the date of performance. A systematic means of pulling these cards on the dates on which maintenance work is required should be devised. The equipment data file mentioned in Item 3 above should contain cards with complete nameplate data for each item of equipment. These cards may also be used to show the type of lubricant required, together with the nature of any special service requirement. The cards should also be filed numeric- ally in accordance with the recommended system. The operation and maintenance instruction file mentioned in Item 4 above should contain information relating to maintenance, operation, and servicing of each item of equipment. This information should be filed numer- ically in accordance with the recommended system. Specifically, the file should contain all maintenance and operation manuals furnished by equipment manufacturers, parts lists, dimension drawings, and other informative literature. In order to maintain an effective maintenance program it is recommended that the maintenance record system be kept up to date faithfully and consist- ently. Service requirements should be modified as equipment ages and flow rates increase. All modifications to major plant equipment should be recorded in the maintenance record system. A complete set of the as-built drawings of the wastewater treatment plant should be available for the ready use of the plant operators. The plant operators should record on these plans all changes that are made in the plant piping, equipment, and electrical circuitry. The original drawings of the treatment plant should be updated at least yearly in accordance with the changes made on site. For additional information, see: Ch. 11, Operation of Wastewater Treatment Plants, EPA. H-2 ------- REFERENCE ------- REFERENCES ------- Appendix J REFERENCES 1. Advanced Wastewater Treatment Seminar, Session I to III and Section IV, October 1970. 2. 'Aeration Plants in Florida," ASCE Journal of ganitary Engineering, Vol. 88, SAG, November 1971. 3. Agardy, F.J., and M.L. Kiado, Effects of Refrigerated Storage on the Characteristics of Waste, 21st Industrial Waste Conference, Purdue University, 3-5 May 1966. 4. Babcock, Russel H., Instrumentation and Control in Water Supply and Wastewater Disposal, R.H. Donnelley Corp., 1968. 5. Gulp, Russell and Gordon L., Advanced Wastewater Treatment, Van Nostrand Reinhold Environmental Engineering Series, 1971. 6. Eckenfelder, W.W., and D.J. O'Connor, Biological Waste Treatment, Pergamon Press, 1961. 7. Fair, Gordon M., John Geyer, Water Supply and Wastewater Disposal, John Wiley & Sons, 4th edition, 1961. 8. Fair, Gordon M., John Geyer, and Daniel A. Okum, Advanced Waste Treatment, Research Series, AWTR-2 to 12, 1962-1964^ 9. "Field Evaluation of the Performance of Extended Aeration Plant," WPCF, Vol. 41, July 1969, p. 1299. 10. Imhoff, Karl, and Gordon M. Fair, Sewage Treatment, John Wiley & Sons, 2nd edition, 1956. 11. Operation of Wastewater Treatment Plants, A Field Study Training Program, Environmental Protection Agency, Office of Water Programs, Division of Manpower and Training, 1971. 12. Perlmulter, Daniel D., Introduction to Chemical Process Control, John Wiley & Sons, 1965~ 13. Rich, Linvil G., Unit Operations of Sanitary Engineering, John Wiley & Sons, 1961. 14. Rich, Linvil G., Unit Process of Sanitary Engineering, John Wiley & Sons (to be published 1972). J-l ------- 15. Sawyer, Clair, "Final Clarifiers and Clarifier Mechanisms," ASCE STD, MIT, 1962. 16. "Sewage Treatment Plant Design," ASCE Manual of Engineering Practice, No. 36, WPCF Manual of Practice No. 8, 1959. 17. Short Course - Theory and Design of Advanced Waste Treatment Processes, University of California Extension, Berkeley, Calif., 1971. 18. Standard Methods for the Examination of Water and Wastewater, 13th edition, APHA, AWWA, WPCF, 1971. 19. Steel, Ernest W., Water Supply and Sewage, McGraw-Hill, 4th edition, 1960. 20. Waste Heat Utilization in Wastewater Treatment, URS 7032, URS Research Co., San Mateo, Calif., (to be published 1972). 21. Waste Water Plant Operators Manual, Coordinating Council for Occupational Education, State of Washington, Division of Vocational Education. 22. Wastewater Treatment Plant Operator Training Course Two, WPCF No. 14, 1967. J-2 ------- GLOSSARY ------- GLOSSARY ------- Appendix K GLOSSARY The terminology used in the glossary of this manual reflects particular meanings of those words and definitions which clarify the basic informa- tion compiled from the various texts, journals and technical papers used. BIOCHEMICAL OXYGEN DEMAND (BOD) BIOLOGICAL OXIDATION BY-PASS CHLORINE CONTACT CHAMBER CHLORINE DEMAND COMBINED AVAILABLE RESIDUAL CHLORINE The quantity of oxygen used in the biochemical oxidation of organic matter in a specified time, at a specified temperature, and under specified conditions. It is not related to the oxygen requirements in chemical combustion, being determined entirely by the availa-. bility of the material as biological food and by the amount of oxygen utilized by the microorganisms during oxidation. The process whereby living organisms in the presence of oxygen convert the organic matter contained in wastewater into a more stable or a mineral form. A pipe or conduit which permits wastewater to be moved around a wastewater treatment plant or any unit of the plant. This is usually found in plants which receive combined flow or high infiltration rates and is utilized to prevent flooding of units, or in case of shutdown for repair work, flow can be moved to parallel units. A detention basin where chlorine which has been dif- fused through the treated effluent is being held a required time to provide the necessary disinfection. The difference between the amount of chlorine added to the wastewater and the amount of residual chlorine remaining at the end of a specific contact time. The chlorine demand for given water varies with the amount of chlorine applied, time of contact, temperature, pH, nature and amount of impurities in the water. That portion of the total residual chlorine remaining in water or wastewater at the end of a specified contact period which will react chemically and biologically as chloramines, or organic chloramines. K-l ------- 7046 COMBINED RESIDUAL CHLORINATION The application of chlorine to water, wastewater, or industrial wastes in an amount to produce directly or through the distribution of ammonia, or of cer- tain organic nitrogenous compounds, a combined chlorine residual. COMBINED SEWER SYSTEM A transport system which carries both sanitary wastewater and storm or surface water runoff. DENITRI- FICATION EFFLUENT ENDOGENOUS RESPIRATION FOOD TO MICROORGANISM RATIO HYDRAULIC LOADING INFILTRATION INFLUENT MIXED LIQUOR Chemically-bound oxygen in the form of either nitrates or nitrites is stripped away for use by microorganisms This produces nitrogen gas which can bring up floe in the final sedimentation process. It is an effective method of removing nitrogen from wastewater. Wastewater or liquid - raw, partially or completely treated; flowing from a basin, treatment process, or treatment plant. An auto-oxidation of cellular material that takes pla'ce in the absence of assimilable organic material to furnish energy required for the replacement of worn-out components of protoplasm. An aeration tank loading parameter. Food may be expressed in pounds of suspended solids, COD, or BOD added per day to the aeration tank, and microorganisms may be expressed as mixed liquor suspended solids (MLSS) or mixed liquor volatile suspended solids (MLVSS) in the aeration tank. The flow (volume per unit time) applied to the surface area of the clarification or biological reactor units (where applicable). The flow (volume per unit time) applied to the surface area of the clarification or biological reactor units (where applicable), Groundwater that seeps into pipes through cracks, joints, or breaks. Wastewater or other liquid - raw or partially treated; flowing into a reservoir, basin, treatment process or treatment plant. A mixture of activated sludge and wastewater under- going activated sludge treatment in the aeration tank. K-2 ------- 7046 ORGANIC LOADING OVERFLOW RATE OXYGEN UPTAKE RATE POSTCHLORINATION PRECHLORINATION RAW SLUDGE RECIRCULATION RATE SANITARY SEWER SYSTEM SLOUGHINGS SLUDGE AGE Pounds of BOD applied per day to a biological reactor One of the criteria for the design of settling tanks in treatment plants; expressed in gallons per day per sq ft of surface area in the settling tank. The amount of oxygen being utilized by an activated sludge system during a specific time period. Application of chlorine to the final treated wastewater or effluent following plant treatment. Chlorination at the headworks of the plant; influent chlorination prior to plant treatment. Settled sludge promptly removed from sedimentation tanks before decomposition has much advanced. Frequently referred to as undigested sludge. The rate of return of part of the effluent from a treatment process to the incoming flow. A sewer intended to carry wastewater from homes, businesses, and industries. Storm water runoff sometimes is collected and transported in a separate system of pipes. Trickling filter slimes that have been washed off the filter media. They are generally quite high in BOD and will degrade effluent quality unless removed. In the activated sludge process, a measure of the length of time a particle of suspended solids has been undergoing aeration expressed in days. It is usually computed by dividing the weight of the suspended solids in the aeration tank by the daily addition of new suspended solids having their origin' in the raw waste. SLUDGE DENSITY INDEX A term also used in the expression of settling characteristics of activated sludge 100/S.V.I. K-3 ------- 7046 SLUDGE VOLUME INDEX (SVI) SUSPENDED SOLIDS (SS) WASTED SLUDQS WET WELL A numerical expression of the settling characteristics of activated sludge. The ratio of the volume in milliliters of sludge settled from a 1000 ml sample in 30 minutes to the concentration of mixed liquor in milligrams per liter multiplied by 1,000. Solids that either, float on the surface of, or are in suspension in, water, wastewater, or other liquids, and which are largely removable by laboratory filtering. The portion of settled solids from the final clarifier removed from the wastewater treatment processes to the solids' handling facilities for ultimate disposal. A compartment in which a liquid is collected and held for flow equalization and then pumped (by systems' pumps for transmission through the plant). K-4 -------