United States
                    Environmental Protection
                    Agency
Industrial Environmental
Research Laboratory
Research Triangle Park NC 27711
                    Research and Development
EPA-600/S2-84-081 May 1984
&EPA         Project  Summary
                    Characterization  of  Operating and
                    Maintenance  Practices  for
                    Wastewater  Treatment  Systems
                    in  the  Iron  and  Steel  Industry
                    Richard T. Price, William F. Kemner, William E. Gallagher, and
                    Gopal Annamraju
                     The purpose of this study was to
                    document effective  operations  and
                    maintenance  (O&M) practices  for
                    wastewater treatment systems in the
                    iron and steel industry and to ascertain
                    how their application might affect  per-
                    mit parameters and operational upsets.
                     The wastewater generating processes
                    selected  for study  were byproduct
                    cokemaking, ironmaking  (blast  fur-
                    naces), steelmaking (basic oxygen  fur-
                    naces), hot forming, and acid pickling.
                    Selections were based on pollutant
                    loadings, system complexity, control
                    costs, and commonality among most in-
                    tegrated steel mills.
                     Information was gathered from sev-
                    eral sources: a literature  search  for
                    wastewater-related O&M  practices in
                    the iron and steel industry, discussions
                    with state and regional agency person-
                    nel to identify major areas of concern
                    and effective O&M practices, review of
                    agency files, discussions with waste-
                    water treatment equipment vendors  and
                    chemical additive manufacturers,  and
                    discussions  with  industry  represen-
                    tatives.
                     Various steel mills were visited,  and
                    treatment  plant operators and  en-
                    vironmental staff members were inter-
                    viewed. The information produced by
                    these visits  includes typically  en-
                    countered problems and their solutions,
                    troubleshooting efforts, extent of  op-
                    erator training, efforts to minimize  the
                    effect of operational upsets, and preven-
                    tive maintenance practices.
  The study produced a report that: pro-
vides a better understanding of waste-
water problems in the iron and steel
industry, helps agency inspectors to be
more effective in evaluating the effect
of O&M practices on wastewater treat-
ment performance, and provides infor-
mation that will assist plant personnel
in practical  and cost-effective fine-
tuning of their systems.
  This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Research  Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering infor-
mation at back).

Introduction
  Effective O&M practices at a wastewater
treatment system are those that can keep the
system operating at its optimum perfor-
mance with minimal downtime.
  It is management's responsibility to initiate
and maintain an O&M plan. Although such
O&M practices as communication, operator
training, staffing, recordkeeping, preventive
maintenance,  and treatment system audit-
ing/evaluation are probably implemented in
some degree at all plants, their effectiveness
depends on the degree to which they are
practiced, how carefully they are practiced,
and whether they are fine-tuned periodically
(if necessary)  to achieve optimum results.
  The plant visits made during this study
showed that the management organization
for water pollution control has much to do

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with successful communications and with
obtaining the cooperation necessary to solve
problems expeditiously.  Generally,  the
management structure at the plants visited
was:
  • The utilities (power and fuels) depart-
    ment is responsible for operating the
    wastewater treatment systems.
  • The process department, responsible for
    the steel mill process operations, as-
    sumes at least part of the responsibility
    for proper handling of the wastewater.
  • The environmental department keeps all
    pertinent personnel informed of current
    and expected water regulations that will
    have an impact on the plant. This de-
    partment is a go-between for the plant's
    pollution control section of the utilities
    department and the regulatory agencies
    and is responsible for all correspondence
    with the agencies.
  The wastewater  generating  processes
studied were byproduct cokemaking, iron-
making (blast furnaces), steelmaking (basic
oxygen furnaces), hot  forming,  and acid
pickling.  The  report discusses  the  O&M
problems  and practices of each process
separately and also presents general obser-
vations regarding the components of effec-
tive industry-wide O&M practices.


Management-Based  O&M
Practices
  These  management-based practices in-
clude communications, operator training,
logs/recordkeeping, staffing, and treatment
system auditing.

Communications
  Good communication is essential to effec-
tive O&M. Figure  1 illustrates effective and
ineffective communication structures, both
of which are found in the industry. Usually,
the utilities supervisor is the key person in
making a communications system  work.
Only through effective communication ties
between operators, supervisors, and main-
tenance personnel can problems be brought
to the attention of the necessary parties, and
alternate solutions  discussed and  imple-
mented.

Operator Training
  Proper and adequate training of operators
is critical to the  effective operation of  a
wastewater  treatment  system.  Operators
need to know:
  • How their systems operate and how to
    handle routine problems.
  • What pollutants are being removed and
    where they are destined to go  (sinter
    plant, landfill, recycle, etc.).
  • Where the treated  water goes.
                  Agency
            Environmental
             Supervisor

                Utilities
              Supervisor.
       Polymer
    Representative
 Process^
Supervisor
           Maintenance
                              Operator
        Process Department  Treatment Plant

                    Ineffective


                 Agency FN
           Environmental
            Supervisor ,'
                             Utilities
  Process  p-fl/        i

ProTees7Departmentg)''/"\^^w'SOA
                                  |  Lab
                                  Results
       Representative /
            Maintenance      Operator
                  Treatment Plant
                     Effective

 Figure  1.    O&M communication structure.


   • How the steel mill depends on their per-
     formance (directly for return of needed
     water, or indirectly to avoid potential
     regulatory action).
   • What daily routines must be followed.
   • What to do in emergencies.
   It is important to keep subsequent genera-
 tions of operators as well trained as those
 who were there during system start-up and
 had the benefit of receiving thorough train-
 ing from the equipment manufacturers.
   One  useful aid that some operators have
 developed involves the  use of simplified
 schematics of their equipment and/or overall
 treatment scheme. These schematics  are
 usually much less complex than those in the
 O&M  manuals provided  by the  design
 engineers.

 Logs/Recordkeeping
   Good recordkeeping is an effective O&M
 tool. The plant visits made during this study
 indicated that current practice varies from
 maintaining essentially no records to record-
 ing numerous operating parameters every 2
 hours.  Although the extent and frequency
 of recordkeeping vary greatly from plant to
plant, it was obvious that the operators of
the well-operated systems made a practice
of logging key operating parameters on a
periodic basis. In addition, the operating
supervisors at these plants reviewed the logs
for abnormal conditions and initiated re-
quired followup action. In other words, the
logs were used,  not just filed away. (See
Figure 2.)
                                                 Wrong
                        Treatment Plant
                        Bulletin Board


                            Right
Figure 2.    Effective use of records.
Staffing
  Proper operation of a treatment system re-
quires enough operators (and assistants and
helpers) with clearly defined job functions.
The plants visited were  generally well
staffed. At one plant, however, one operator
had to devote all of his time to manually con-
trolling  the  treatment  system  (filtration
plant).  Had this operator been responsible
for  areas other than the filtration plant or
were he less efficient, the filters would have
plugged and  the system might have been
damaged or the amount of filter effluent
might have increased greatly.

Treatment System Auditing
  Results of this study indicate that most
plants have proceeded from permit negotia-
tions, to system design, to routine operation
without ever having stepped back to over-
view their situation. Some type of periodic
formal  O&M  audit would be  beneficial to
provide such an overview.
  It is  suggested that audits or self-evalu-
ation programs by a plant team or an out-
side consultant be implemented periodically
(e.g., annually). When such  evaluations
reveal less-than-optimum conditions, correc-
tive action  should be taken, with followup
to ensure that approved suggestions have
been carried out.

Cokemaking—O&M Practices
  Treatment  systems  and  component ar-
rangements for treating coke plant waste-
waters vary throughout the industry,  but
most  plants  have equipment specifically
designed to remove two pollutants —  am-
monia  and  phenol.

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  About two-thirds of the plants with coke-
 making facilities have  ammonia stills and
 treatment systems for removing phenol. All
 of this group have free ammonia stills, and
 about 85 percent also have fixed ammonia
 stills. About half of the plants that remove
 phenol  have dephenolizers; the rest are
 equipped with oxidation systems (primarily
 bio-oxidation). Figure 3 shows the compo-
 nent arrangement at one plant.
 Major Anas of O&M Concern
   Improper handling of or lack of attention
 to any of the following items can cause an
 upset in the bio-oxidation system ranging
 from minor to major proportions.
   • Monitoring  the performance of  am-
     monia stills
   • Controlling biological basin pH
   • Controlling basin  temperature
   • Adding nutrient
   • Aeration
   • Maintaining  adequate dilution  water
     (where practiced)
   • Introducing intermittent, experimental,
     or toxic material
   • Monitoring key parameters
   • Communicating
   • Operator attention and know-how, and
     good supervisors
Some Effective O&M Practices

Ammonia Still
  1)  Maintaining adequate storage of crude
      liquor to allow the coke batteries to
      continue operating without interrup-
      tion during still shutdowns.
  2)  Monitoring the return liquor  flows
      from the lime legs to the stills. One
      plant monitors and  records the flow
      rate every  2 hours.
  3)  Properly adjusting the steam flow to
      the  lime leg discharge to ensure an
      adequate supply of steam to strip the
      ammonia from the liquor. Operators at
      one plant  use an easily read chart
      showing proper steam/return  liquor
      flow ratios.
  4)  Regular monitoring  and recording of
      still pressure, noting changes and call-
      ing them to the attention of the main-
      tenance department.

Lime Slaker
  1)  Periodic checking of the  level of the
      lime storage bin or tank and reporting
      low levels  to the foreman.
  2)  Controlling slaker feed water. Feed to
      the slaker should be steady and rela-
      tively uniform  in size. Lime  mixing
      spray should be inspected for block-
      ages. Also, lime quality  should  be
                                                         f Waste
                                                           Liquor
                                                          ''Holding
                                                            Tank
                                                                      Splitter
                                                                       Box
 Overflow to
   Settling
   Lagoon
(330.000 gpd*)
           Sludge
        Recirculation
           Pump


Figure 3.    Biological plant flow diagram.
           Liquor
      —  Tar Sludge and
           Lime Waste
 ———~ Activated Sludge

   (*)    1 gpd (gallon per day)
       = 3.79m'
     closely controlled; e.g., lime size as
     received (about 80 percent less than
     !/4-in. or 0.635 cm) and lime  slurry
     temperature (90 to 95°C). Carefully
     controlling these parameters improves
     dissolution of lime into the  slaker
     water and reduces lime consumption
     considerably.
  3)  Controlling pH of the still effluent to
     control  the amount of lime  water
     being fed to the lime legs for reaction
     with the crude liquor. Because of in-
     herent plugging problems, a pH con-
     troller  with  pH probes  is  not
     dependable in a lime-based system;
     therefore, effective O&M practices are
     required to back up (or substitute  for)
     pH control. At one plant the operators
     check the pH of the effluent and of the
     liquor from the lime leg every 2 hours.
  4)  Preventive  maintenance;  e.g.,  fre-
     quent   inspections,   scheduled
     cleaning.

Biological Treatment Systems
  1)  Controlling pH in aeration basin. The
     most effective  practice observed is
     monitoring the  basin  pH and  its
     sources. At one plant, operators take
     samples every 4 hours  from  the
     equalization tank effluent,  secondary
     storage tanks' influent and effluent,
     basin inlet sump, and basin  outlet
     sump. The pH's are analyzed  and
     recorded on  a daily log  sheet.  At
     another plant, wastewater treatment
     plant operators take bihourly waste-
     water samples from the ammonia stills
     and  daily  samples from  the  basin
     wastewater feed  and clarifier over-
     flow. These samples are analyzed for
     pH and recorded. These practices per-
     mit early detection of pH  deviations
     and allow the immediate implementa-
     tion of corrective action to protect the
     system  and  effluent  quality  (e.g.,
     diversion to an emergency storage
     tank, if  necessary).
  2)  Controlling basin temperature.  Micro-
     organism activity  diminishes  if  the
     wastewater becomes too  cold, and
     microorganisms  can  be killed if
     wastewater temperatures get  too
     high. Plants are equipped with moni-
     tors, control valves, and recorders on
     control  panels,  but operators  still
     should manually record temperatures
     at the source and log this information
     to ensure good temperature control.
  3)  Checking nutrient addition. All of the
     systems visited use phosphoric acid as
     a nutrient.  Some plants check  the
     phosphate residual daily. One effective
     practice is to observe the addition of

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     phosphoric acid to the primary clarifier
     every 2 hours. This was not difficult
     at one  plant, as the addition point is
     about 1 ft (30 cm) above the water
     level. At one plant the phosphoric acid
     tank is on stilts, above the primary
     clarifier (which returns sludge to the
     basins); this allows the acid to flow by
     gravity into the clarifier's sludge recy-
     cle pump. Gravity always works, and
     the operators can visually check the
     flow of acid.
  4)  Ensuring adequate aeration. The prac-
     tice at one plant is to make an occa-
     sional check of the dissolved oxygen
     content of the basin water  and to
     make a physical check of the aerators
     twice per shift to see if they appear to
     be  operating  properly.  Instead  of
     regularly monitoring the dissolved oxy-
     gen content, one plant  has installed
     ammeters in a pump house, which are
     connected to the aerator motors. Nor-
     mal readings are 25 to 30 amps. The
     operators observe these readings bi-
     hourly, and enter a check on the log-
     sheet if the readings are in this range;
     if not, the actual reading is recorded,
     and if the deviation is more than a cou-
     ple of amps outside the normal range,
     the operating supervisor is notified.
     The amp readings correlate well with
     cell  wastewater dissolved  oxygen
     levels of  1 to 2 ppm. One plant that
     recently  had a problem with strat-
     ification of the  dissolved oxygen in-
     stalled air lances for use at these times
     to promote better localized mixing.
     The  lances also serve as a backup
     when an aerator fails or is taken out
     of service for a maintenance check.

Blast Furnace—O&M  Practices
  Blast furnace treatment systems do not
vary much from plant to plant. They gener-
ally consist  of recycle systems  with   a
thickener/clarifier for solids removal, a cool-
ing tower, and a chemical treatment system
for deposit or scaling control. Several plants
use alkaline chlorination for removal of am-
monia and cyanide for blowdown water.

Major Areas of O&M Concern
  • Controlling pH
  • Removing phenol
  • Removing cyanide
  • Removing ammonia
  • Controlling scaling by dissolved solids
  • Handling sludge
  • Maintaining a tight recycle for hydraulic
    balance
  • Temperature of recycle water
  • Adding chemicals
Some Effective  O&M Practices
  O&M concerns at the operating level
focus primarily on the condition of the equip-
ment and the parameters used for daily
monitoring of the system. Effluent water
quality, on the other hand, is the concern of
the environmental department. The follow-
ing O&M practices were observed:

Controlling pH
  1)  Daily inspection of oxidation reduction
     potential (ORP) and pH  probes for
     scaling problems and cleaning as nec-
     essary. Maintaining spare probes and
     experimenting  with  new types of
     probes as they become available.
  2)  Manually checking pH readings. One
     plant checks the pH of the blowdown
     twice a shift and the pH at several
     other locations in the system once a
     shift.
  3)  Using standard solutions of 6 and 9 pH
     to calibrate pH probes rather than the
     usual standards, which are outside of
     this control range.

Controlling Scaling by
Dissolved Solids
  1)  Maintaining chemical feed in a tight
     recycle system. Some experiments
     with softening have been reported.
  2)  Monitoring hardness, alkalinity, and
     conductivity on each shift.
  3)  Adding a deposit control agent at the
     hot well of the cooling tower.
  4)  Adding an antifoulant and dispersant
     at the main recirculation sump.
  5)  Long-term  analysis  of hardness,
     alkalinity, and conductivity, and using
     graphical plots versus time to detect
     and correct scaling trends.

Handling Sludge
  1)  Scheduled preventive  maintenance,
     which includes:
     a)  Changing gear box oil every 6
         months.
     b)  Checking and lubricating all pumps
         and other moving equipment every
         week.
  2)  When a pump fails to work:
     a)  Operator checks to  see if suction
         line is  plugged; if so, cleans  line
         and replaces it.
     b)  If problem  is more major (e.g., a
         badly worn impeller), maintenance
         department repairs the pump.

Basic Oxygen Furnace—
O&M Practices
  A  basic oxygen  furnace  (BOF)  shop
typically  has two furnaces. Each  has a
separate scrubber, but both share a common
water treatment system. The primary pollu-
tant of concern is suspended solids. Since
the water is recirculated, the concerns of
dissolved solids and scaling are similar to
those in blast furnace systems.

Major Areas of O&M Concern
  Focus is primarily on BOF systems that
have  recycle loops  because many plants
have recirculation systems and because this
technology is emphasized in the guidelines
for  steel mill effluent limitations.
  • Controlling dissolved solids
  • Controlling pH
  • Controlling suspended solids
  • Maintaining a proper rate  of sludge
    removal from thickeners/clarifiers  to
    avoid thickener  upsets  and/or  rake
    change.

Some Effective O&M Practices

Controlling Dissolved Solids
  1)  Using pH control, balanced schedule
      of blowdown and makeup,  and chem-
      ical treatment. Two or sometimes all
      three controls are combined.
  2)  Periodically inspecting the acid system
      and pH sampling/analysis (to back up
      automatic systems).
  3)  Regularly cleaning pH probes.
  4)  Manually adjusting acid  metering
      pump and periodically inspecting to
      see if it is regulated properly.
  5)  Checking the discharge of blowdown
      against the  individual plant's criteria
      and adjusting it if iron and zinc  con-
      centrations  are too high.

Chemical Treatment
  1)  Quick  maintenance action  if the
      polymer system breaks down  and
      becomes plugged.

Controlling Solids/Sludge
  1)  Inspecting cyclones and  classifiers
      each shift and  periodically replacing
      the rubber lining in cyclones.
  2)  Monthly inspection of classifiers  by
      maintenance department  and  work
      performed as needed. A spare is main-
      tained.
  3)  Draining thickeners  yearly   for
      thorough inspection.
  4)  Visually inspecting sludge pumps (by
      operators) each shift.
  5)  Periodic testing polymer additions by
      the manufacturer to ensure optimum
      dosage rate. Polymer representatives
      work closely with operators and peri-
      odically perform bench tests with new
      polymers against which operators can
      compare  their bench tests to see if
      they are in agreement.
  6)  Providing  automatic  rake-lifting
      devices on  thickeners if torque be-
      comes too great.

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  7)  Periodically monitoring and recording
      torque  by operators and  notifying
      supervisors if  readings  are  above
      normal.
  8)  Maintaining on-line spares for all
      sludge pumps.

Hot  Forming—O&M Practices
  Treatment technologies used in hot form-
ing include: primary sedimentation, surface
oil removal, secondary settling or filtration,
and recycle.

Major Areas of O&M Concern
  The major areas of O&M concern for hot
forming (primarily on hot strip mills) waste-
water treatment systems are:
  • Operating scale pits
  • Communicating
  • Handling sludge
  • Treating with chemicals
  • Backwashing filters
  • Operator and maintenance attention/in-
    spection/monitoring of key parameters

Some Effective O&M Practices

Operating  Scale  Pits
  1)  Systematically removing material that
      has settled out in the scale pits once
      a week. This permits maintenance of
      good working volume and reasonably
      constant retention time.
  2)  Clam-shelling of finishing scale pit on
      Sunday (when the  hot strip mill is
      down) to allow the solids adequate
      time to settle before start-up of the mill
      the following day. This was observed
      at one plant.
  3)  Frequently inspecting the scale pit by
     the operator to allow him to detect
     and remove debris (e.g., twigs) on the
     rope skimmers. This is very important;
     several hundred gallons of oil could ac-
     cumulate if a "short-circuited" skim-
     mer  went undetected for several
     hours.
  4)   Maintaining a good supply of spare
     rope skimmers on site.
  5)  Attaching heat lamps near the skim-
     mer's driving gear mechanism to re-
     duce skimmer  stiffness during  cold
     weather.
  6)  Monitoring key parameters; e.g., fre-
     quency of backwashing and the filter
     media level at a plant with deep-bed
     gravity filters.
  7)  Monitoring the following parameters
     at plants with settling ponds:
     a) Pond levels and flows  (once per
        shift)
     b) Oil skimming equipment (once per
        shift)
     c) Periodic checks   (every  several
        months) of solids  depth  in  the
      ponds. (Sometimes determined by
      taking soundings from a boat.)

 Backwashing Filters
   1)  Extended backwashing of sand filters
      to remove accumulated solids that or-
      dinary  backwashes do not remove
      (performed every weekend).
   2)  Periodically steam cleaning filters to
      remove accumulated oil and grease.

 Other  Observed Practices
   1)  Periodically inspecting pipes that are
      subject to abrasion to see  if  thick-
      nesses are safe (by sonic testing).
   2)  Stringing floating booms diagonally
      across settling basins to direct floating
      oil and grease to belt skimmers. These
      booms are replaced about every 3 or
      4 months. Catwalks at the end of the
      basins allow access to the final settling
      area to pump off floating oil.
   3)  Periodically sampling filter media by a
      contractor who performs an ash test
      to see  how  much  scale  is accumu-
      lating.  This  information  is  used to
      determine when the media should be
      changed.
   4)  Notifying  the  utilities operator  by
      phone  (by mill rolling foreman)  of
      shutdown and start-up times and oil
      spills.
   5)  Routinely  maintaining wastewater-
      related equipment:  lubricating; vibra-
      tion monitoring/testing  of  major
      pumps, motors, and air blowers; cali-
      brating meters;  checking  software
      weekly; maintaining computer  soft-
      ware;  and  inspecting electrical
      equipment.

Acid Pickling—O&M Practices
  Wastewater is  generated  from  three
sources in the  pickling  operation:  rinse
water, fume scrubber water, and spent acid.

Major Areas of O&M Concern
  Major areas of O&M concern in the acid
pickling wastewater treatment systems are:
  • Sludge accumulation
  • pH  monitors
  • Lime addition
  • Sludge buildup in aeration  tank
  • Exhaust fan
  • Reactor cyclone
  • Waste pickle liquor feed point
  • System pressure drop
  • Preventive maintenance
  • Fines formation

Some Effective  O&M Practices

pH Monitors
  1)  Frequent checking of the readout of
      pH monitors in the system,  using a
      portable pH meter.
  2)  Checking pH hourly, and plotting on
      a  daily chart to illustrate pH control
      and variation in the aerators.

Lime Addition
  1)  Maintaining the  proper  ratio  of
      hydrated lime to limestone.
  2)  Checking lime  shipments to ensure
      that  the  lime  meets  plant quality
      standards.
  3)  Using a single supplier (when possi-
      ble), for a more consistent quality of
      lime.

Clarifiers
  1)  Checking the  height of the water
      above sludge  blanket (i.e., sludge
      depth) every shift.
  2)  Inspecting  the chemical  additive
      system and dosage rate, and visually
      observing  the  formed floe to  note
      anything  unusual  about its  ap-
      pearance.
General  O&M Practices -
Treatment Components
  This discussion  covers  problems con-
cerned with the common treatment com-
ponents in  use at steel mills and current or
suggested  O&M  practices.  Many  of  the
components (e.g., clarifiers, filters) are used
to treat different process wastewaters (e.g.,
blast furnace, basic oxygen furnace).

Clarifier/Thickener
  One  of  the  most  common clarifier
maintenance problems is a plugged  sludge
line. Items such as  hardhats, tools, and
general debris find their way into the clarifier.
At some facilities, a wire mesh or some other
barrier across the top or on the sides of the
clarifier prevents large objects from falling in.
When the  clarifier is emptied for mainte-
nance, the sludge pump should be inspected
thoroughly before the unit is put back on
stream to ensure that nuts, bolts, etc. have
not been  left there  by maintenance per-
sonnel.
  The condition of the clarifier feed  can be
checked with a simple settling  test, con-
sisting of putting a sample of clarifier feed
in a graduated cylinder or Imhoff cone and
noting the sludge level after a specific time.
Although such a test does not give  an  ab-
solute measure of the settling rate, it will
detect an upset in the system. If tested every
few hours, a problem in the clarifier feed can
sometimes  be detected  before it leads to a
major upset.
  Turbidity in the clarifier overflow  should
be checked frequently,  either manually or
with an instrument. If an instrument is used,
turbidity should still occasionally be checked

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manually, to ensure that the instrument is
operating properly.
  A visual inspection of the clarifier will show
the operator if the sludge level is getting near
the overflow weir. The operator should also
check the uniformity of the effluent flow over
the clarifier perimeter weir.
  To be sure the clarifier is not operating at
too high a feed rate, the operator should
check the actual feed rate against the design
feed rate.
  The flocculation and settling performance
of the clarifier feed can be checked, using
a standard jar test apparatus. After the set-
tling rate has been determined, some of the
liquid can be siphoned from the jar for a
suspended solids analysis. The suspended
solids level should approximate the clarifier
overflow, but this test is  most useful  for
comparison  against  a benchmark  test.
Sometimes, settling can be  improved by
switching polymers.

Water Recycling
   Recirculating water in a process treatment
system or as part of an overall plant recir-
culation  strategy involves many different
considerations;  e.g., maintaining  system
tightness,  hydraulic  balance, and  water
chemistry, and providing adequate monitor-
ing and sampling. The report discusses each
in detail.

Scale Pits/Sedimentation Basins
  Although scale pits are among the least
sophisticated and most low-profile treatment
technologies, they play a key role in the per-
formance of water treatment plants at hot
strip mills. If properly operated, systemati-
cally cleaned, and equipped with oil-skim-
ming equipment, they provide an effective
pretreatment   step  prior  to secondary
treatment.
   The solids removal efficiency of any scale
pit is a function of the effective detention
time. It is not uncommon for plants to ex-
perience increased solids loadings out of the
pit during scale removal activities; therefore,
it is advisable to dredge the pits during mill
operation downtimes or to have additional
cells or spare pits. Good housekeeping and
well-maintained oil skimmers are the most
effective controls for scale pits. If used, these
controls can intercept much of the free oil
resulting from oil spills and line breaks.

Filtration
   In the iron and steel industry, filtration is
used to  remove suspended  solids from
wastewater (polishing filters) and to dewater
sludge (dewatering filters).

Polishing  Filters
   One of the mills visited was trying to im-
prove the operation of its multimedia filters:
                                      6
it was experimenting with declining  rate
filtration. This operation begins the filtration
cycle at a high flow rate and then reduces
the rate for the rest of the run, which reduces
the suspended solids in the filter effluent.
  Another plant reported oil buildup in the
filter media. One way to wash out this ex-
cess oil is to use steam (in addition to air and
water) when backwashing the filter.
  At one plant, with a horizontal multimedia
filter, the media was being washed out on
the backwash cycle. This filter had slotted
distributor plates, and the bottom distributor
plates were covered with gravel. To solve the
problem, the plant put screens on the  slot-
ted plates at the top of the filter and bubble-
cap  strainers on the  bottom  distributor
plates.
  This plant also had rectangular sand filters,
and (during backwash) the air scour created
so much turbulence that the media washed
into the troughs and out with the backwash
water. This problem was solved by screens
on the rims  of the discharge troughs.

Dewatering Filters
  Most plants consider dewatering filters to
be a high-maintenance item  because the
filter cloths are easily torn and the belt on
a drum filter can stretch and get out of align-
ment,  ft is necessary to keep an adequate
inventory of spare cloths for each filter.

pH  Control Systems
  The pH electrode assemblies are a fre-
quent  cause of malfunction of pH control
systems. The proper maintenance of these
electrodes is important to the precision and
the accuracy of pH control and monitoring.
The three types of maintenance required are
calibration, cleaning, and replacement. Many
plants calibrate daily, and daily cleaning is
not unusual. One plant piped service water
to the line containing the pH electrodes; the
process flow is  turned off periodically, and
the service water valve is opened to flush the
electrodes with clean water.
  Because of its low cost, lime is frequently
used for pH control. The amount of calcium
oxide in the lime must be controlled for con-
sistent operation. Sometimes a temperature
test  is used  to quickly evaluate the quality
of lime shipments.  Measured amounts of
water and lime are mixed, and the tempera-
ture  is recorded to  determine the calcium
oxide content.  Plants should  be especially
cautious  of  lime  quality with  changing
vendors.
  A  common problem that occurs when lime
slurry is used to adjust pH is plugged equip-
ment.  A control valve in lime slurry service
should be checked regularly for signs of
pluggage or erosion. Maintaining a historical
record of electrode failures, control valve
failures, line pluggage, etc., will allow a plant
to set up a preventive maintenance schedule
to avoid these problems. Good preventive
maintenance is the key to successful  pH
control.

Chemical Addition Systems
  Because the flow rate of chemical  ad-
ditives (e.g., polymers) is low,  it is some-
times difficult  to  determine if they  are
flowing. Ideally, these chemicals should be
introduced above the level of the liquid to
which they are being added so the operator
can see them falling from the end of the pipe
into the tank and thereby verify the flow.
  Care should be taken that the vendor's in-
structions regarding the use and mixing of
a specific polymer are followed closely.  Ex-
cessive  mixing  can shear the polymer and
damage its effectiveness. Also, to achieve
maximum efficiency, many polymers must
be aged for 12 to 24 hours after they  are
mixed.
  Care should be taken not to use a polymer
that is so old it has lost  its effectiveness.
Also, polymers should be stored where they
are protected from freezing, which is damag-
ing  to them.
  Some vendors provide jar test apparatus
to evaluate their polymers for application in
a particular plant. An evaluation by plant per-
sonnel may be more objective, however, and
certainly would provide  results for  com-
parison  against those of the vendors.

Oil Skimming System
  The simplicity  of oil skimmer systems
makes them very reliable, and maintenance
relatively easy. Nevertheless, they should be
checked daily. The skimming mechanism re-
quires periodic lubrication, adjustment, and
replacement of worn parts. Heating is sug-
gested  during winter months to keep  the
skimmer from freezing. If this is not possi-
ble,  a  backup removal  system (e.g.,  a
vacuum truck)  should be provided.
  The paddle skimmer should be checked to
ensure that each blade touches the water for
the full length of the blade. Rope skimmers
should be checked to ensure that the rope
is not rubbing against an object that could
scrape off collected oil or abrade the rope.
The inspector should observe the rope for
one full revolution to be sure it is not abrad-
ed at some point. The operator at one plant
said rope skimmers could be more effective
if the tubes penetrated the water surface  bet-
ter. The plant was going to experiment by
injecting some lightweight antifreeze fluid
into the plastic tubes to provide additional
weight for better immersion. (This might  also
make the skimmer operate better in subfreez-
ing weather.) Belt skimmers also should be
observed for one full revolution to check for
rips, holes, or other problems with the belt.
The operator also should check the scraper

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blade on the belt to be sure it is removing
 he oil from the  belt.
  The skimmed oil usually falls into a trough
that drains into  a collection tank. These
troughs must be kept clean so that the oil
does not build up and overflow. The level of
oil in the tank itself also should be checked
periodically.

Cooling Towers
  Cooling towers remove heat from water
by  evaporating the water.  The ones dis-
cussed here involve contact water systems
(such as those used in blast furnace recycle
systems and, to a lesser extent, in coke plant
and rolling mill treatment operations).
  It is important that the makeup and blow-
down rates be checked and that the cycles
be  calculated  (to minimize corrosion, de-
posits, and slime). Factors that affect cor-
rosion, deposits,  and slime are controlled by
a bleed stream or blowdown, by coagulation
and filtering,  or by adding inhibitors and
chemicals that attack the specific problems.
The latter include dispersants, fungicides,
and slimicides. Adding chemicals properly is
important, not only for performance, but also
because fungicides and slimicides are toxic.

Ammonia Stills
  Ammonia stills reduce the ammonia con-
centration in the weak ammonia solution that
"> produced in the collecting mains of coke
jvens when water is sprayed  on the hot
gases leaving the ovens.
  Most problems with ammonia-stripping
systems involve the handling of lime. It is im-
portant  for incoming shipments  to  be
checked to ensure the calcium oxide content
and particle size.  Because lime tends to foul
and plug lines, control valves, instrumenta-
tion,  and the stripping column itself,  a
preventive maintenance schedule should be
set up to break apart and clean the equip-
ment before it becomes inoperable. Such a
schedule was developed by an operation's
supervisor at one plant. He plotted the am-
monia still effluent concentrations over a
period of time  (Figure  4)  and  reviewed
maintenance logs to see if the times of equip-
ment pluggage and/or breakdown correlated
with the excursion dates. When a definite
correlation was  evident,  he developed  a
schedule incorporating the finding.
  Pressure drop across the column is a good
indicator of tray  fouling, and the operator
should keep frequent watch to note when
the trays need to be cleaned. Operators
should also monitor the pressure in the bot-
tom of the ammonia still. When the pressure
reaches an established upper limit, the col-
umn should be taken off line and cleaned.
  Since pH control is important, cleaning the
  1  probe should be included as preventive
  .500
 1*00
S 300

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      R.  T. Price. W.  F. Kemner, W. E. Gallagher, and Gopal Annamraju are with
        PEDCo Environmental, Inc., Cincinnati. OH 45246.
      Jeff Chappell is the EPA Project Officer (see below).
      The complete report, entitled "Characterization of Operating and Maintenance
        Practices for Wastewater Treatment Systems in the Iron and Steel Industry,"
        (Order No. PB 84-182 666; Cost: $29.50. subject to change) will be available
        only from:
              National Technical Information Service
              5285 Port Royal Road
              Springfield, VA 22161
              Telephone: 703-487-4650
      The EPA Project Officer can be contacted at:
              Industrial Environmental Research Laboratory
              U.S. Environmental Protection Agency
              Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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            CHiCAGU  1L
                                                                                    U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/967'

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