14010 FBZ 09/71
     Concentrated Mine Drainage
           isposal  Into Sewage
           Treatment  Systems


The Water Pollution Control Research Series
describes the results and progress in the
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Concentrated Mine 0 rain age  Disposal

  Into Sewage Treatment Systems


Environmental Research and Applications, Inc.
              24 Danbury Road
        Wilton, Connecticut  06897
                  for the
            Program #14010 FBZ
              September, 1971

         EPA Review Notice

This report has been reviewed by the Office
of Research & Monitoring, EPA, and approved
for publication.  Approval does not signify
that the contents necessarily reflect the
views and policies of the Environmental
Protection Agency, nor does mention of
trade names or commerical products
consitute endorsement or recommendation
for use.

The effect of artificial iron-rich acid brines on municipal sewage
treatment processes was studied in small scale.  The brines were
devised to simulate concentrates from treatment of acid mine drainage.
The processes included primary settling, activated sludge digestion,
and other unit processes.

The raw brines even at a level of 20% vol/vol or higher do not
interfere with primary settling, but activated sludge digestion is
completely inhibited by the acid.  The brines when neutralized with
lime improve primary settling and the neutralized brines do not inhibit
activated sludge.  Filtration of all sewage fractions is improved by
the lime-acid brine neutral mixture.  At the very high concentrations
used, the neutralized brines give virtually complete removal of
phosphate from primary effluent, activated sludge effluent, or
anaerobic sludge digester decantate.

Cost of reverse osmosis membrane treatment of acid mine drainage to
produce the iron-rich acid brine is estimated to be in the range of
35C/1000 gal, of brine corresponding to original 48,000 gal. of acid
mine water or about 73C per thousand gallons of acid mine water
treated.  Engineering analysis and costs are shown for transporting
the brine from the mine site to the sewage treatment plant by rail,
truck, and pipeline over distances ranging from 10 to 50 miles.
Transportation by pipeline involves per-mile costs on the order of
5C/1000 gal. of brine.


  I      Conclusions                                              ]_

  II     Recommendations                                          3

  III    Introduction                                             5
           Objective of This Study                                5

  IV     Literature Review                                        7
           AMD Treatment Processes                                7
           Phosphate Removal by Iron                             ^2

  V      Scope of This Study                                     19
           Laboratory Investigation                              ^g
           Engineering Analyses                                  ^g

  VI     Methods                                                 21
           Artificial Acid Brine (AAB)                            21
           Experiments on Primary Settling                       22
           Experiments on Activated Sludge (AS)  Digestion        23
           COD-Digestion Experiments                             23
           Dosing Rate for AS Experiments                        24
           Anaerobic Sludge Digestion                            25
           Activated Sludge Digestion of Anaerobic Sludge        25
             Digestion Decantate

  VII    Results & Discussion                                    27
           Experiments on Primary Settling                       27
           Experiments on Activated Sludge Digestion             34
           Experiments on Acid Shocking                          36
           COD Digestion by Activated Sludge                     38
           COD/BOD Relationship                                  38
           Activated Sludge Digestion of Anaerobic Sludge        42
             Digestion Decantate
           Tertiary Treatment                                    42
           Phosphate Removal                                     45
           Biological Nitrification and Denitrification          47
           Anaerobic Sludge Digestion                            50
           Anaerobic Sludge Digester Decantate                   50
           Digested Sludge Disposal                              52
           Sludge Conditioning                                   54
           Oxidation of Ferrous Iron in AAB by Oxygen            54
           Microbiological Status of AAB AS Cultures             57
           Concentration of AMD by Reverse Osmosis               51

                           CONTENTS (Con't)

Section                                                           Page

 VIII             Summary                                          69

 IX               Acknowledgements                                 71

 X                References                                       73

Np_.                                                              Page

I       Excess Sludge Production in Simultaneous and
         Postprecipitation Units for Various Dosage
          of Iron                                                 13

II      Composition of Artificial Acid Brine                      21

III     Recipe for Artificial Acid Brine                          22

IV      Summary of Settleable Solids Volume and Mixed Liquor
         Total Suspended solids for Activated Sludge Cultures     24

V       Composition of Stock Solution of SNP                      24

VI      Preliminary Experiment on AAB and Lime Effects on
         Primary Settling                                         28

VII     Further Preliminary Experiments on Primary Settling       29

VIII    Effect of Ai-lD and Lime on Primary Settling                31

IX      Effect of AAB and Lime on Primary Settling—
         Decantate COB                                            32

X       Effect of 10% AHD-I on Primary Settling The
         pH Effect on the System                                  33

XI      Effect of Concentration of MB on Primary Settling        35

XII     Acid Shocking of Activated Sludge Cultures                37

XIII    Effect of Neutralized AAB on Activated Sludge
         Digestion                                                39

XIV     COD:BOD Relationship of Various Waste-Treatment
         Fractions                                                41

XV      COD-Depletion Experiment on Anaerobic Sludge
         Digestor Decantates                                      43

XVI     Phosphate Removal from Primary Effluent by Lime
         and AAB Treatment                                        45

XVII    Fe, Ca, and Al Contents of Test Samples for
         Phosphate Removal                                        46

TABLES (Con't)
XVIII     Nitrogen Status of Sewage Fractions aac.

XIX       Anaerobic Sludge Digestion in Digesters
           Fed 100 ml Sludge Approximately Daily

XX        Sunraary of Anaerobic Sludge Digestion Data

XXI       Characteristics of Anaerobic Sludge Digester

XXII      Reduction of Dissolved Oxygen by Ferrous Iron

XXIII     Change in Tine of Soluble Iron in AS containing
           20% Neutralized MB

XXIV      Oxygen and Work Requirements for Oxidation of
           Ferrous Iron in Acid Brine

XXV       Pipeline Transport Cost Estinates








1        Flow Diagram of Complete Biochemical Oxidation
          and Limestone. Neutralization Process               10

2        Solubility Diagram for Solid Phosphate Phase        16

3        Precipitation of Phosphate by Fe (III)              17

4        Activated Sludge Digestion of Anaerobic
          Decantate                                          44

5        Disappearance of Soluble Iron in AS Containing
          AAB Neutralized with Lime                          56

6        Theoretical Oxygen Requirements For Oxidation
          of Ferrous Iron                                    58

7        Flow Diagram for Concentrating of AMD - one MGD
          Plant                                              62

8        Flow Diagram for Concentrating of AMD - 10 MGD
          Plant                                              63

                           SECTION I

1.  Many sites where acid mine drainage originates and degrades water
quality will require on-site treatment.

2.  The products of treatment are concentrated acid brines  or brine-
sludge mixtures and relatively pure water.  Depending upon the  method
of treatment, the product water can be suitable for safe discharge to
surface water courses or it can be a high grade water for industrial

3.  The brines produced by treatment are not of sufficient value to
pay for treatment by any known method, but they can be disposed of
through municipal wastewater treatment plants where they will be of
some value especially for sludge conditioning and nutrient removal.

A,  Reverse osmosis offers an attractive method for on-site treatment.

5,  It is economically feasible to transport acid brines from the
mine sites to municipal wastewater treatment plants by pipeline.

6.  Some aspects of the development of an optimum scheme for disposal
of acid brines require further research especially nitrification,
denitrification, hydrolysis, and ultimate sludge disposal.

                           SECTION II

1,  Acid mine drainage sites should be inventoried or existing
inventories should be studied to find a site suitable for installation
of a pilot plant to produce acid brine (and pure water)  for use at an
accessible municipal wastewater treatment plant,

2.  A pilot scale investigation of the disposal of acid  brine at a
municipal secondary wastewater treatment plant should be initiated.
The recommended project could use artificial acid brine  until the
pilot plant brine becomes available,

3.  Laboratory scale investigations of the use of acid brine for
certain advanced wastewater treatment unit processes should be
initiated.  The processes should include biological nitrification and
denitrification, sludge conditioning, alkaline hydrolysis and
adsorption, and ozonation,

                           SECTION III

     Acid mine drainage is a significant water pollution problem in
many mining areas of the United States,  Acid mine waters originate
from the chemical oxidation of pyrites contained in coal and in shales
and other rocks associated with coal deposits and pyritic ore bodies.
In natural hydrographic regimes and especially in the regimes altered
by mining and other excavations, acid water find their way into water
courses.  The acid and heavy metals in the drainage seriously damage
the stream flora and fauna even to the point of local extinction of
the biota.  In the watercourse, acids are eventually neutralized
through reactions with natural alkaline materials and the heavy metals
are precipitated forming deposits of hydrous oxides of iron, aluminum
and manganese.  In the course of this natural self-purification,
however, stretches of streams, miles in extent, can be degraded.

Objective of This Study

     Various schemes for preventing the drainage of acid mine waters
into water courses have been proposed and undertaken, but not all
such problems can be economically solved by sealing the mine,
diverting the flow, or other such approaches (1, 2, 3),  From the
standpoint of economic value, acid mine water are ordinarily too
dilute and too heterogeneous for product recovery (acid, iron,
other heavy metals) to be practical.  Our study examined the feasibility
of concentrating acid mine water by certain processes and transporting
the concentrated brine to municipal waste treatment plants for disposal.
The relatively pure water produced from the treatment process would
be discharged to the local watercourse or used by a local municipality
or industry.  With this broad objective—disposal of concentrated
acid brines via municipal wastewater treatment plants — we undertook
laboratory investigations of the effect of synthetic acid brine on
primary and secondary sewage treatment processes.

                           SECTION IV

                      REVIEW OF LITERATURE

     The term acid mine drainage (AMD)  is applied to drainages  which
have an abnormally low pH value and to drainages which contain  neutral
substances such as ferrous sulfate.  Acid drainage from coal mining
operations usually contains sulfuric acid and ferrous, ferric,
aluminum and manganese salts in fairly high concentrations and  also
calcium, magnesium and sodium salts, carbon dioxide and silicic acid.

     Acid mine drainage is generated when the oxidation products of the
pyrite contaminate the surface drainage and the ground waters drained
from the mine.  The feasibility of controlling the acidic contamination
of coal mine drainage at the source has been studied, discussed and
tried in the U.S.A. (4,5,6).  Most of the suggested methods of  control
have been based on the principle of excluding the mutual contact of the
three components of acid mine drainage: air, water, and pyrite.  Some
of the segregation methods proposed were: diversion of water from acid
producing areas, exclusion of air from abandoned underground mines and
covering the pyritic materials with non-acid forming materials  in
restored strip mine sites and refuse banks.  It is evident from the
physical nature of the sources of acid contamination of coal mine
drainage that segregation will not be possible at some sites, and that
complete segregation will be difficult at many.  It will be particularly
difficult to control the interaction of air, water, and pyrite in active
underground mine workings.  Therefore the acid mine drainage has to be
treated after its formation and the cost of treatment is great.  Thus
there is an increasing demand for cheaper mine drainage treatment

Acid Mine Drainage Treatment Processes

     There are a number of processes reported in the literature for the
treatment of acid mine drainage and these are described in brief as

1.  Precipitation of Iron

    By adding alkaline neutralizing agents such as hydrated lime,
    sodium carbonate, and sodium hydroxide to acid solutions of
    ferrous iron, iron can be precipitated.  Other methods would
    require expensive precipitating agents and are probably not
    economical for high concentrations of iron.

2.  Electrolysis of Iron (II) Solutions

    Direct current hydrolysis of acidified iron  (II) sulfate solutions

    produces a complex set of reactions and the three predominating
    reactions are shown below:

    H20 ------------- ^ 1/2 02  + 2H +    + 2e~
    Fe4"3   + 3H20 --- *• Fe (OH) 3 + 3H+3
    The rate of removal of iron from solutions depends on the current
    density at the electrode surface.  Fe(OH>3 deposits as a brown
    precipitate around the anode.

 3.  Aeration - Filtration

    This is one of the most common methods  used on a commercial scale
    for removing iron from aqueous solutions.   The process consists of
    oxidation of iron (II) to iron (III)  by aeration, followed by
    hydrolysis of iron (III)  and subsequent filtration

       Fe +3    +   3H20 -------- K  Fe (OH)3  (Fe203.  n.H20) + 3H+

    Superficially this process appears  inviting for application to AMD
    but many problems are involved.   The  two major ones are:

      (i)   conversion of Fe (II)  to  Fe  (III) by air oxidation is slow
           in media where the pH is  less  than  seven.

     (ii)   lime or CaCO-j must be added  to increase the pH.   The con-
           version of Fe (II)  to Fe  (III) by aeration is more rapid at
           pH ~?>7 .   However,  for large  volumes of  AMD, neutralization
           would require large amounts  of CaCO-j.

4.  Ultrasonic Methods

    The  use  of  ultrasonic energy in  the oxidation  of  acidified iron
    (II)  sulfate  has  been investigated  to a considerable extent with
    some  promising results.   The rate of  oxidation of iron (II) by
    ultrasonic  energy is  a function  of  the  intensity  of the waves but
    the  relationship  appears  to be non-linear.   Ultrasonic energy may
   be  useful  in  effecting  coagulation  of the  hydrous iron (III)  oxide
    formed by oxidation.

5 . Ozone

   Ozone treatment has  been  considered as  a means  of removing iron
   from aqueous solutions.  A combination  ozone-activated  carbon
   system is presently  in use for the  removal  of  iron and  manganese
   from drinking water.  (7)

6.  Irradiation and Photo-oxidation

    Oxidation ef iron (II)  using alpha,  beta and gama radiation has
    been studied and the mechanism is apparently the same as for
    ultrasonic oxidation.  The reactions appear to be about four
    times faster in aerated water than in oxygen-free water.  The
    problems associated are: yield of the reactions are not partic-
    ularly high and the depth of penetration of the water by the
    irradiating particles is very short.

7.  Lime Processes

    The principle of the lime processes  is that lime (calcium oxide
    or calcium hydroxide) ,  or other strong alkali such as sodium
    hydroxide , is mixed with the acid mine drainage to neutralize
    the acids,
           H2S04     + Ca(OH)2

    and to precipitate the contaminating metal salts

           Fe2(SOA)3 + 3 Ca(OH)2 ------------ + 3 CaS04 + 2 Fe(OH)3

    The sludge formed by sedimentation from lime neutralization has
    a high water content and presents a difficult disposal problem.
    The cost of treatment by lime treatment is estimated at $1.09/
    1000 U.S. gallons (1).  Hanna et^ al (4) , in a review of the acid
    mine drainage problem, concluded that neutralization processes
    were not economically attractive except in specific cases
    involving small well-defined areas.

8.  Limestone Processes

    This process used the minerals, limestone and dolomite  (ie CaCO-j,
    and Mg/CaC03) > and tne reaction with the acidic salt would be:
    Fe2 (SOA)3 + 3 CaC03 + 3 H20 ------- > 3 CaSO^ + 2 Fe (OH)3+ 3 C02-
    An upflow expanded bed process using limestone for the treatment
    of acid wastes has been reported (8) .   Sulfuric acid in concentra-
    tions up to 5000 mg/1 could be neutralized without inactivation of
    the limestone.  The process was, however, stated to be unsuitable
    for the neutralization of wastes containing iron salts because
    of inactivation of the limestone.

    There have been a number of cases (9,10,11) where the limestone
    processes have been used.  From a critical review of literature,
    it is found that limestone has found application in the neutraliza-
    tion of acid wastes other than those containing iron and other
    precipitable salts, and that a considerable problem of limestone
    inactivation must be expected when these salts are present.

Acid Mine
— *
Sedimenta- ]
                        Active Sludge
                                                                      Cake to Waste

Figure 1.  Flow Diagram of Complete Biochemical Oxidation and Limestone

                        Neutralization Process

"9.  Biochemical Oxidation Processes

     The simplest procedure to remove ferrous  salts would be  to
     oxidize the ferrous salts to ferric which could be  removed  to-
     gether with the original ferric  salts  by  the  limestone.  Atmospheric
     oxygen is by far the cheapest oxidant  and is  particularly attractive
     since an excess of air could not produce  too  high a redox potential
     in the treated drainage.

     Unfortunately, atmospheric oxygen is not  able to oxidize ferrous
     salts in acidic solution despite the fact that the  free  energy
     change is favorable (12).  A micro organism capable of promoting
     the atmospheric oxidation of ferrous salts in acid  solution has
     been widely reported in acid mine drainages (A,  13, 14). This
     micro organism is an autotrophic bacterium, and  Silverman and
     Lundgren (15) reported the optimum growth temperature  of this
     bacterium to be 28°C, the optimum ferrous concentration  to  be
     9000 mg/1 Fe, and the optimum pH range to be  2.5 to 4.0. The
     bacterium studied by Silverman and Lundgren could not  oxidize
     manganous, nickelous, and cobaltous salts, but several authors
     have reported the tolerance of acidophilic ferrous  oxidizing
     bacteria to metal ions such as manganese, copper, and  zinc. (13)
     A scheme proposed in England (4) for the  control of acid mine
     drainage pollution by biochemical oxidation and  limestone
     neutralization treatment is shown in Figure 1.   The outstanding
     characteristic of the complete process was the ease of control.
     The required supervision was minimal since over-treatment in
     the oxidation and neutralization stages could only  be  beneficial.
     The practicability of the whole  process to the treatment of acid
     mine drainage has been demonstrated by this study.  The  limitations
     of this process are: the dissolved iron content  should be at
     least 10 to 20 mg/1 and a total  acidity of at least 25 mg/1 as
     (CaCO-j) .  The cost of treatment  is estimated  to  range  between
     $0.67 to $1.90 per 1000 gallons.

10.  Foam Fractionation

     A foam fractionation technique (16) has been developed by Garrett
     Research and Development Company, for  removing phosphates and
     suspended solids and lowering chemical oxygen demand.   The
     technique consists of treating the waste stream  with  ferric
     chloride or alum, then dissolving air  in the water  under high
     pressure (about 175 psi).  When  the pressure is  released,
     micro-size bubbles produce a creamlike foam that effectively
     removes not only phosphates but  also particulates  in  general
     and both soluble and insoluble organic matter.

     Tests with wastewater obtained at a Pomona, California,  sewage
     treatment plant showed that when alum  or ferric  chloride were
     used in concentrations of 300 to 400 mg/1, foam fractionation
     removed 90% of the phosphates and 80%  of the suspended solids,


    and lowered the chemical oxygen  demand by  70%.  Preliminary
    estimates for a 10  MGD foam  -  fractionation plant indicate a
    capital cost of $235,000 and an  operating  cost of 6C/1000 gallons.
    The land area requirements are very  low, in the order of half
    acre for a 10 MGD plant. As indicated in  the preceding paragraphs,
    none of these processes  has  yet  been shown to be less expensive
    for general application. In order to bring down the operating
    costs of the sewage treatment  facilities,  attention has been
    given to the use of waste materials, such  as acid mine drainage.
    Iron salts act as flocculating agents in the primary and secondary
    clarification tanks.   Iron salts act as an oxygen carrier in the
    activated sludge process and the effectiveness of the returned
    sludge is increased by the fact  that sludge passing through the
    cycle more than once becomes richer  in iron, aluminum, and other
    hydroxides and thus clarification of sewage and destruction of
    protein are accelerated.  In general it can be assumed that iron
    may be helpful both as an oxygen carrier and as an adsorbent and
    coagulant.  (17)

    The effect of iron  salts on  the  removal of BOD, SS, phosphate are
    discussed in the following sections:

Phosphate Removal by Iron

1.  Elimination of Phosphate from  Sewage

    Phosphorus  removal  processes recently proposed are mostly based on
    precipitation, with  cations  forming  insoluble phosphate salts, or
    on  absorption  by  inorganic hydroxides.  The reactions with Al3+
     •31     l    Or '     "                   01       01
    Fe°  ,  and  Ca  or with combinations  of FeJ  and Ca^  offer some
    economical  possibility for the removal of  phosphorus.

    In  addition to  these inorganic chemical reactions, a biological
    process might be  considered  theoretically, using the well-known
    property  of many microorganisms  to store phosphates as poly-
    phosphates  in  their  cells when phosphorylation substances are
    lacking.  (18)

2.  Iron  (III)  as precipitant

   At pH>7, FePO^ results as a product, whose solubility product
   is Ks = 10~  23 at 25°C (18).   Excess of Fe (III) is required in
   the sewage  treatment for the formation of  a well-flocculating
   hydroxide precipitate which includes the FePO^ particles.  FePO^
   particles act as an efficient absorbent for organic phosphate
   compounds and eventually for polyphosphates.

   Phosphate removal with Fe(III)  has been considered exclusively
   as an absorption process.  This hypothesis contradicts the
   opinion of Galal and Stumm,  who favor a simple chemical precipi-
   tation mechanism.  (19)  However, from a practical point of view,


  both reaction mechanisms  lead  to  the  same  result  and  require  the
  same operating conditions.

  Wben treating an activated  sludge plant effluent,  the stoichio-
  metrical requirement 6f Fe  is  1.8 mg/1 per mg/1 P.  However,  for
  complete phosphate removal  this has to be  supplemented by  at  least
  10 mg/1 for hydroxide formation.   There are two methods of applying
  the precipitants:

  (1)  Simultaneous precipitation
  (2)  Post precipitation

  Simultaneous precipitation  involves addition of the precipitant
  directly to the influent of the  aeration basin, promoting  the
  formation of hydroxide and  binding of phosphates  simultaneously.
  Post precipitation involves the  addition of precipitants to the
  secondary effluents in a conventional manner.  Both the methods
  of applications have been studied on  a laboratory scale (20)  and
  the following are the results:

   A.  Both processes required the  addition  of at least 20 mg/1
  Fe3  for the reduction of phosphate from 7.15 mg/1 to 0.5  mg/1
  or less.

   B.  Fe (OH)., flocculation  in the simultaneous process was
  frequently incomplete, resulting  in an opalescent final effluent
  with considerable carryover of colloidal Fe(OH)3  and  phosphorus.

   C.  The addition of Fe (III)  to  the  activated sludge resulted
  in a striking change of the sludge biocenosis leading to better

   D.  When the dosing was more than 10 mg/1 Fe (III) ,  the protozoan
  fauna disappeared completely within the first two days.

   E.  There was a remarkable increase  of excess sludge volume in
  the simultaneous precipitation units  in comparison to conventional
  treatment.  (See Table 1)

                            TABLE 1

Excess Sludge Production in Simultaneous and Post Precipitation Units
(gallons per gallon of sewage treated)  for Various  Dosage of Iron (20)

  Dosage of Fe3+                10 mg/1     20 mg/1    30 mg/1

  Simultaneous Precipitation    0.5         0.62       0.50

  Post Precipitation            0.41        0.28       0.25


   According to the literature cited the hydroxide sludge  formed  is
   of poor settling and dcwatering characteristics.

3. Removal of Phosphorus with Lime and Iron (III)

   In order to reduce sludge solids production and excess  sludge
   volume in the precipitation unit, a combination of  phosphate
   precipitation with iron (III)  and lime was  tried.   Iron was
   added at 1.8 mg/1 Fe (III) for each mg/1 of phosphate and  lime
   added to raise the pH of the mixture to  8.8.   This  pH was
   selected so that considerable  precipitation of  CaCO^ would take
   place, which might be helpful  as a thickening  aid of the iron
   hydroxide formed; at the same  time the calcium  carbonate was
   thought to act as  an absorbent for colloidal  FePO^ and organic
   phosphate.  The results of an  experiment run for 30 days with
   the final effluent of an activated sludge plant demonstrated
   that phosphorus removal was equivalent to the efficiency achieved
   with lime or iron precipitation alone.   Excess  sludge quantity
   and sludge volume were much smaller but  the settling property  of
   sludge was poor.   Essential factors to be considered for the
   operation of this process  are:  the amount  of orthophosphate to
   be  removed, the alkalinity,  and the Ca hardness of  the  treated
   sewage.   This  combined process  is expected  to be the most  economic
   over a wide range of conditions.   The  quantity  of precipitation
   chemicals are  moderate,  and the sludge produced thickens rapidly
   and can be effectively dewatered to a  highly concentrated  slurry
   or  a filter cake,  which  may  be  dumped without danger of secondary
   leaking of phosphorus.

   Alum and Iron  (III)  precipitation have two  disadvantages:  the
   costs  for the  chemicals  are  relatively high, and the processes
   lead to  a difficult  sludge disposal problem.  In the case  of alum
   precipitation,  the recovery  of  the precipitant  as proposed by  Lea
   et  al  (II) ,  may  lighten  the  cost  burden  to  some degree.

      (a)   Phosphate  Precipitation
                                                          +2    +3
   The  affinity between multivalent  aqueous  metal  ions (Ca , Fe  t
   Al+3)  and  PO^ ~3,  HPO^"2  or  polyphosphate is about  4 -  12K cal per
   mole.  With  simple solutions of orthophosphate, well defined
   reaction  products  such as  FePO^.   21^0 (Strengite)  can  be  formed
   in accordance with the stoichiometry of  the reaction.   Organic
   phosphorus  compounds are  surface-active  and may become  adsorbed
   on precipitates and other  interfaces, but counter-ion adsorption
   alone  cannot account for  the high  removal efficiency because of the
   stoichiometry observed.  A substantial fraction of  the  phosphorus
   in sewage  is contained in  the form of suspended matter; this fraction
   is removed by coagulation  rather  than by precipitation.  Ferric
   salts  are  good coagulants  and can be used to coagulate  the phosphate


 (b)  Solubility Relations

The continuous precipitation of phosphate in treatment of wastes
is a dynamic process; most likely, equilibrium conditions are not
attained.  The formulation of the stoichiometry of the chemical
reaction defines the minimum requisite quantity of chemicals.  The
equilibria (21) that need to be considered are listed below:
1.  Solubility equilibra

                             (log K 25°C)  = -23)
                2H20 (s) ------ >• Fe+3 + PQ-3  +
    2.  Acid - Base Equilibria

        Fe+3 + OH- ------------ fr-FeOH+2
        FeOH+2 + OH~ ----------- -
        Fe(OH)+ + QH~ --------- >>Fe(OH)3 (s)

    3.  Complex Formation Equilibria

        FeHPO,+ -------------- *-Fe+3 + HPO,~2
             4                             4

        FeH2P04+2 ------------- >Fe+3 + H2PO~

        Fe (HP207)2~3 -------- ^Fe+3 -1- 2HP 0?~2

 (c)  Kinetics of Phosphate Precipitation

Equilibrium calculations and experimental verification show, that
FePO^ (s) is a stable solid phase if phosphate is precipitated
in the low pH range of 4 to 6 (See Figure 2).  Precipitation of
phosphate with Fe (III) is very fast.  The rate of removal is
controlled by agglomeration of colloids and by settling.
Precipitation of phosphate by Fe (III) will be more efficient if
the Fe (III) is produced by slow, homogeneous generation of ferric
ion through the oxidation of ferrous ion, than it will be if Fe
(III) as such is added to the wastewater.  In the latter case, ferric
ions, because of relatively high localized concentrations, tend to
react (depending on pH) with OH~ ions rather than with phosphate
species.  If, on the other hand, ferric ion is produced homogeneously,
each ferric ion, as soon as it is being formed, comes into contact
and reacts with phosphate species.  The better scavenging effect
of homogeneously formed Fe (III) when compared to Fe (III) introduced
directly is shown in Figure 3.


M   8
     Figure 2.   Solubility Diagram For Solid Phosphate  Phase

                                           With Fe  (III)
        Fe (III) Homogeneously
Fe (III) Added
    Figure 3.  Precipitation of  Phosphate  By Fe (III)

                           SECTION V

                      SCOPE OF THIS STUDY,
     The subject study consisted of a literature review,  laboratory
experiments, and engineering analyses.  The general literature
review is given separately above and other previous published work
is cited at appropriate places throughout this report.

Laboratory Investigation

     The wastewater treatment processes studied were primary settling,
activated sludge digestion, and anaerobic sludge digestion.  The
general approach was to compare the activity or effectiveness of
acid-brine treated laboratory units with control (untreated) units
with respect to COD removal, suspended solids removal,  and phosphate
removal.  The broad question addressed was whether the  unit process
was degraded or enhanced by acid brine and neutralized  (with lime)

Engineering Analyses

     The general thrust of engineering analyses was economic.  What
are the estimated costs for brine production at the mine site; what
are the costs of transporting brine via pipeline or by tankbarge,
tanktruck, or railway tankcar; what is the value (if any) of acid-
brine at a municipal wastewater treatment plant; what are the costs
for lime or other basic salts for neutralizing acid-brine?

                           SECTION VI


     For analyses of pH, acidity,  alkalinity,  iron,  dissolved
oxygen, BOD, COD, etc., Standard Methods (22)  or simple modifications
of standard methods were used.   Raw sewage,  primary  sludge,  digestor
sludge, and primary effluent were obtained from the  City of  Norwich,
Conn, sewage treatment plant,  The Norwich sewer system is virtually
completely combined stormwater  and sanitary wastewater with  some
industrial wastewater including those from textile dying and finishing
and food manufacturing.  There  is considerable day-to-day variation
in the raw wastewater and in the quality of the primary effluent.   The
sewage is ordinarily faintly acid pH 5.5-6.5 with a  total alkalinity
of about 100 mg/L (as CaC03>.

Artificial Acid Brine

     The recipe for artificial  acid brine (AAB) was  devised  to mimic
a typical natural acid mine water concentrated about fifty-fold by
a membrane process or any other suitable process (see Tables II, &

     In order to simulate more  ideally the composition of acid
brines produced from natural acid mine drainage, all salts used should
be the sulfates, because acid mine water is very low in other anions
including chloride.  The use of the magnesium and ferric chlorides,
however, does not obviate the validity of any results obtained and
reported here.  The processes investigated are not sensitive anions
over the range used in the present work,

                            Table II

              Composition of Artificial Acid Brine

     pH                                2.0

     acidity                           5000 mg/L as  CaC03

     ferrous iron                      1000 mg/L

     ferric iron                       1000 mg/L

     magnesium                         250 mg/L

     aluminum                          250 mg/L

     manganese                         100 mg/L

     calcium sulfate                   saturated


 The receipe used to achieve that composition is given in Table  3.
 The stock solution is labeled AAB-I.

                            Table III

                Recipe for Artificial  Acid Brine

      Ferrous sulfate          FeSO^-7H20       5,0  gm

      Manganous sulfate        MnSO,-H^O        0.3  gm
                                   *r   •&

      Potassium alum           A1K(SO^)2'12H_0  4.4  gm

      Ferric chloride          FeCl3«6H20       4.8  gm

      Magnesium chloride        TIgCl «6H 0       2.1  gm

Make up  to  1.0 liter with water  saturated with  calcium sulfate  and
adjust to pH 2.0 with sulfuric acid.   The solubility  of calcium
sulfate  dihydrate at room temperature is on  the order of 3  grams per
liter; a saturated solution has  a  pH  of 6.3.  Adding  sulfuric acid
to  make  the solution pH  2.0 does not  increase the solubility because
the sulfate added decreases the  dissociation of the salt.   The  recipe
above with  sulfuric  acid added to  bring the  pll  to 2.0 has a titrated
acidity  of  7800 mg/L (as CaCO-j) .

      A second  recipe (AAB-II)  was  used  with  ferrous iron (as the
sulfate) added to make the  total iron 10,000  mg/L.  The second  AAB
formulation had a titration acidity of  23,000 mg/L  (as CaC03).  AAB
stock solutions were stored under  ambient conditions  and no appreciable
oxidation of ferrous iron occurs from contact with  air because  of the
low pH.  (2.0).

Experiments  on Primary Settling

     Using  Standard  Methods, total suspended  matter was  determined on
various sewage  treatment fractions by settling  in an  Imhoff cone and
by membrane  (0.45 microns porosity) filtration.  For  some purposes
gravity filtration through  coarse paper was used to obtain  filtrates,
a procedure which removes somewhat more suspended matter than primary
settling.  For  obtaining decantate from laboratory  anaerobic sludge
digesters,  centrifugation at 1800 rpm for  five minutes was  used.  That
speed corresponds to a relative acceleration  value  of  about 600g.  The
centrifugation  procedure produces a decant about equal  in quality
to gravity filtration through  coarse  paper.   We have  noted  the  type of
separation procedure used in specific instances in  the Discussion section.


 Experiments on Activated Sludge Digestion

     Laboratory units for activated sludge  digestion  (AS)  were
polyethlene battery jars of twenty-liters capacity containing about
ten liters of mixed liquor.  AS cultures  were  stirred with a one-
inch disc impeller at about 1000 rpm and  were  aerated with a single
tube with a capillary tip at the bottom of  the culture.   The aerators
were set to deliver about 750 ml/min of air across a  column depth  of
nineteen centimeters.  The surface area of  the cultures  is 150  cm2.
These parameters combine to give an aeration rate of  50  L/m2.min or
0.17 ft3/ft*.min.  Dissolved oxygen measurements with a  Yellow  Springs
Instrument Co. Model 54 dissolved oxygen  meter indicated that dissolved
oxygen in the AS cultures would fall to 40-60% of saturation  following
batch feeding and would rise to virtual saturation within one hour.

     AS cultures were not thermostated; ambient temperatures  varied
between 60 and 85°F  (16-29.5°C).

     Suspended (settleable) solids levels in control AS cultures were
maintained at about 40 ml/L, and in the AAB-fed cultures, at  190 ml/L,
The average ratio of settleable solids volume by Imhoff cone (ml/L)
to total suspended solids by membrane filter (mg dry/L)  was 12.3 for
control cultures and 10.8  for AAB-fed cultures.  For 53 samples of
control AS mixed liquor, the average total suspended solids was
492.5 mg dry/L and for seventeen samples of AAB-fed cultures the
average was 2094.0 mg dry/L.  -These data are summarized in Table IV.
The ratio of  total suspended solids to settleable solids  is not a
valid measure of the dry weight per unit settled volume of the sludge
because the total suspended solids also  contains some so-called residual
suspended solids or  non-settleable suspended solids.  Typical values
of residual suspended solids—the  total  suspended solids  by membrane
filter of the Imhoff cone  decantate—are 70 mg dry/L for  control AS
cultures and  190 mg  dry/L  for AAB-fed.

COD-Digestion Experiments

      In a typical  COD-digestion experiment, one  or more  control AS
cultures would be  fed a  dose  of primary  effluent and the  AAB-AS
culture would be  fed the same  dose with  twenty  percent by volume
of AAB.   Samples  of  mixed  liquor would be  withdrawn periodically
and  settled  in  Imhoff  cones,  and the COD of the decantates would  be
determined.   This  was done day after day.  A  single  experiment would
involve  taking  the decantate  COD before  feeding, the decantate COD
immediately  after feeding, called the  zero-time COD, and the decantate
COD  after two,  four, six hours and 20-24 hours—the  following  day.
In many  experiments, only the 20-24  hour decantate COD  was taken
because  of  the  difficulty in handling  many COD analyses in a few  hours
 time.   In our experience,  COD-digestion  is virtually complete  in
four to  ten hours.  Corresponding BOD^'s were also taken in  some
 instances.   The BOD/COD relationship is  discussed below.   It was


 promptly learned that raw AAB completely inhibited  AS  digestion, and
 from that time on all COD digestion experiments  were done with AAB
 neutralized with lime (Pfizer-Nelco High Calcium lime  containing
 73.0% CaO and 0.5% MgO).

                             Table IV

       Summary of Settleable Solids Volume and Mixed Liquor
       Total Suspended Solids for Activated Sludge Cultures

                53 samples                   17 samples

              Control Cultures           AAB-fed  Cultures

         Settleable   Total Suspended    Settleable  Total Suspended
           Solids         Solids            Solids       Solids

            (ml/L)      (mg dry/L)          (ml/L)      (mg dry/L)

         Range   Ave.    Range    Ave,      Range  Ave.   Range     Ave.

         20-70   40.1   200-900  492.5      150-260 193  1500-2400 2094.0

         492.5/40.1 = 12.3 mg dry/ml       2094.0/193 = 10.85 mg dry/ml

 Correcting for non-settleable solids (see text)

         492.5-60/40.1 = 10.8 mg  dry /ml,'  2094-190/193 = 9.8 mg dry/ml

J)osing  Rate for AS Experiments

      As has been mentioned,  the  Norwich  sewer system is combined storm
 and  sanitary.   Thus during periods of heavy  rains,  the sewage becomes
 very dilute and at those  times the primary effluent used as feed for
 AS cultures was augmented with a synthetic mixture  of  sucrose, potassium
 phosphate,  and ammonium carbonate  formulated to  give a ratio of C:N:P
 of approximately 7:1:0.05 or 140:20:1.   The  recipe  for SNP is given
 in Table V.

                             Table  V

              Composition  of  Stock  Solution of SNP

         Sucrose                           250 gm/L

         (NH4)2  C03.H,0                     50 gm/L

         KH2P04                             3.0 gm/L

         SNP  solution  has  a COD of  about  250  mg/ml.


     In a typical COD-digestion experiment four liters  of mixed liquor
would be drawn off and settled for sludge recovery and  return (if
necessary to maintain the design level),  and for determination of the
decantate COD before feeding.  A four-liter batch of feedstock was
prepared by mixing water, primary effluent of known COD,  and SNP
(if necessary) to bring the zero-time (after feeding) COD to about
400 mg/L.  A typical calculation for the  feed mixture is  shown below.

     CODzero - t ^ 400 - 400 = 4 x C°Dfeed + C°Dbefore


        before was typically about 60 for control AS and  120 for
AAB-fed.  Thus for a nominal value of 100,    feed would  be 850 mg/L.
If primary effluent were higher than that, it would be  diluted with
water; if lower, SNP would be added,

Anaerobic Sludge Digestion

     Two anaerobic sludge digesters for four-liters capacity were
charged with 400 ml heavy primary sludge  plus 2500 ml water.  Thereafter
one was maintained on control activated sludge and the  other on AAB-fed
activated sludge.  The digesters were kept closed and stirred with a
magnetic stirring bar.  The digesters were not heated;  the ambient
temperature varied between 65 and 75°F (18.5 and 24°C).  The head-space
in the digestors was 900 ml.  Every morning the anaerobic cultures
were removed from the stirring motor and  permitted to settle.  A 100-ml
portion of decant was removed for analyses and 100 ml of settled
activated sludge was added to restore the original volume.  Decant
samples were analyzed for pH, iron, COD,  occasionally BOD, and total
phosphorus.  Occasionally small samples of mixed liquor were withdrawn
for total suspended solids determinations to follow the course of
sludge accumulation and/or digestion.  Toward the end of the period of
experiment, it was deemed expedient to obtain decantate by centrifugation.

Activated Sludge Digestion of Anaerobic Sludge Digestion Decantate

     Conventionally, digested sludge is either drawn off and dried on
sand beds for land-fill disposal or it is dewatered on a vacuum drum
filter.!.  In the latter case the filtrate, which is very high in BOD
and COD is recycled through the plant.  In order to determine  the
treatability of anaerobic sludge digestion decantate, we centrifuged
the contents of our two digestors.  The decantate from the control
digestor had a COD of more than 4000; the decant from the sludge
digester fed iron-rich activated sludge had a very low COD—on the
order of 100.  The former (control) decantate was passed through  the
AAB-fed AS digestor without added AAB, and the latter  (iron-rich)
decantate was passed through a control AS digestor augmented with SNP
synthetic feed-stock to a COD level equal to our conventional  batch

feed.  The purpose of the latter test was merely to determine whether
the iron-rich anaerobic decantate was toxic to AS.   As discussed
latfer, the decantate proved to be nontoxic.

                           SECTION VII

                     RESULTS AND DISCUSSION
Experiments on Primary Settling

     Experiments on sludge settling were carried out in Imhoff cones.
The results of a preliminary experiment on the effects of AAB, lime,
and AAB plus lime are shown in Table VI.

     On the occasion of the preliminary experiment raw Norwich sewage
contained only a small amount of settleable solids (this is frequently
the case).  Lime alone improves settleability markedly, if sufficient
lime is added to bring the pH to 10.5.  That effect may be due in
part to precipitation of sesquioxides.  It is not shown in the Table
(VI) but the quantity of acid required to neutralize the lime treated
sewage from pH 10.5 to pH 8.4 (as if for stream discharge from primary
sewage treatment only) is equivalent to 50 mg/1 (as CaCO^).  Coincident
tally, that is equal to 50 mg H^SO^/L.  AAB alone enhances solids
settling appreciably, albeit this response is much more variable than
with lime alone.  AAB alone causes some coagulation of suspended matter
but the clots are bulky and sludge volume shown in Table VI is some-
what misleading.  Neutralizing the AAB-sewage mixture is equivalent
to adding AAB plus lime, in which case a hydrous iron oxide floe forms,
which scavenges colloid and other particles as it settles.  The
addition of AAB plus lime produces a copious sludge, which settles very
rapidly (a few minutes), and produces a clear effluent, albeit a pale
yellow-colored one.

     Another preliminary experiment is shown in Table VII.

     The data of Table VII confirm in a general way the results of
earlier preliminary experiments.  The improvement in clarity of the
supernatant from AAB plus lime is especially noteworthy.  The addition
of AAB at a level higher than 10% AAB-I vol/vol as shown in sample #6
does not improve decantate clarity; AAB-II at 5% vol/vol is equivalent
in its iron content to 25% AAB-I.  In these experiments turbidity was
measured with a Klett-Summerson industrial model colorimeter using a
#42 blue filter.  The decantate from AAB/Lime treated samples is very
clear but it does have some yellow color; except for highly colored
solutions, however, the error is not significant.  In order to check
the sludge volume due to iron precipitates themselves and to determine
the apparent turbidity of the decantate due to AAB itself, a sample of
AAB 10% vol/vol in water was neutralized with lime to pH 7.6 and the
sample was settled in an Imhoff cone in the usual way.  That sample
is shown as sample #7 in Table VII.  The sludge volume of 250 ml, higher
than that of sample #5 (180 ml), indicates either that precipitation
of iron hydrous oxide is inhibited somewhat by substances in sewage or
that the solids in AAB/lime treated sewage settle more densely than


                                                 TABLE VI

                   Preliminary Experiment on AAB and  Lime  Effects  on  Primary  Settling
mple It
(200 mg/L)
AAB-I + Lime
(10% vol/vol)*
(10% vol/vol)
(10% vol/vol)
(250 mg/L)
Volume of Sludge
Settled (ml)
Clarity of
  *   AAB-I  + Lime (10% vol/vol) means the part lime neutralized AAB-I to nine parts sewage,

                                                TABLE VII

                                  Further Preliminary Experiments on
                                           Primary Settling
     Sample //
Volume of Sludge
  Settled (ml)
Relative Turbidity
 of Supernatant
(100 mg/L)
(10% vol/vol)
(5% vol/vol)
AAB-I + Lime
(10% vol/vol, lime
                             to pH 6.0)

                          AAB-II + Lime
                      (5% vol/vol, lime       6.0
                             to pH 6.0)

                          AAB-I + Lime
                      (10% vol/vol in water)  7.6

 the hydrous iron oxide in lime-neutralized  AAB.  Judging  from the
 appearance of the settled hydrous  iron  oxide  in  the latter case, we
 prefer the interpretation that  the sewage-solids/hydrous-iron-oxide
 mixed solids are denser.   The turbidity of  the decantate  from sample
 #7 was 8 units;  thus,  the turbidity from suspended solids of samples
 #5 and #6 can be considered to  be  slightly  lower than the measured
 turbidities shown in Table VII. For comparative purposes, a kaolin
 suspension prepared according to Standard Methods gives a Klett
 turbidity of 4.5 units per mg kaolin/L.

      The results of a  third preliminary experiment on primary settling
 are shown in Table VIII.

      The results confirm  earlier experiments.  Especially noteworthy are
 samples  #5 and #6 which show that  amounts of  lime-neutralized AAB in
 excess of 10% AAB-I do not give any further improved clarification of
 sewage,  and also sample #4,  which  shows that  lime in a quantity of
 sufficient to raise the pH of the  Norwich sewage to pH 9.0 significantly
 improves primary settling.   In  other trials with lime alone, we observed
 that settled sludge volume was  approximately  doubled by lime treatment
 to pH 10  or slightly  higher.

      The results of a  definitive experiment,  in  which COD analyses of
 primary  settling decantate were carried out,  are given in Table IX.

      Unlike earlier experiments, this experiment showed good clarification
 from the highest level of lime-neutralized  AAB tested (50% AAB-I
 equivalent to a  total  iron concentration of 1000 mg/1 in the AAB/sewage
 mixture).   Of course,  something less  than half of the clarification
 is  due to  the simple dilution effect.   It should be noted that the
 turbidity  units  are given in terms  of the kaolin equivalent in mg/1;
 for comparison with earlier  reported  turbidities in Klett optical
 density  units  multiply by 4.5.  Thus  the sewage used in this  experiment
 had a Klett  turbidity  of  330 units  in comparison to 160 and 225
 units in earlier experiments.   On the other hand the sewage had
 virtually  no  settleable solids  as shown by sample #1.

     The  COD  removal by 10%  neutralized AAB-I (sample #4) was 23%, and
 for 50%  neutralized AAB-I (sample  #6), nil.   At  the lower concentration,
 neutralized acid  brine  can remove some suspended and soluble COD not
 removed by ordinary primary  settling.

     In order  to  determine the effect of pH on the decantate clarity
 and  COD-removal  in  AAB-treated  sewage, an experiment using 10% vol/
 vol AAB-I was  run.  The results of  the experiment are given in Table X.

     From  the  data  it  is  clear  that the optimum  lies between 6 and 8.
 That conclusion  agrees with  Packham's (23) results on water clarifica-
 tion using alum.   Packham determined the amount  of alum needed to remove
50% of various colloidal  suspensions  (kaolin, other clays, calcite, and
quartz) as a function of  pH.  The minimum quantity of alum for 50% removal


                                        TABLE VIII

                      Effect of AMD and Lime on Primary Settling

Sample #        Treatment           pH          Sludge Volume            Turbidity of
                                                      (ml)                 Decantate

  8                none             6.0               7.5                    160

  1               AMD-I
              (10% vol/vol)         2.8             12                       90

  2               AMD-I
              (50% vol/vol)         2.0               1                      135

  3               AMD-II
              (10% vol/vol)         2.6               7.5                    160

  4               Lime              9.0               8                       90

  5           AMD-I + Lime
       (10% vol/vol; Lime to pH 7)  7.0            200                       65

  6           AMD-I + Lime
       (50% vol/vol; Lime to pH 7)  7.0            350                       95

  7           AMD-II -f Lime
       (10% vol/vol; Lime to pH 7)  7,0            400                      175

                                               TABLE IX

                                  Effect of AAB and Lime on Primary
                                       Settling—Decantate COD
e # Treatment pH
none 7 . 1
Lime alone 10.0
(250 mg/L)
AAB-I alone 3.0
(10% vol/vol)
AAB-I + Lime 7.0
(10% vol/vol; 1100 rag Lime/L)
AAB-I alone 2.4
(50% vol/vol)
AAB-I + Lime 6.8
Settled Sludge
Volume (ml)
< 1.0
              (50% vol/vol;  5650 mg  Lime/L)
        Corrected  for  dilution and  COD of  ferrous iron added

                                               TABLE X

                               Effect of 10% AMD-I on Primary Settling  &
                                      The pH Effect on the System
   pH of decant

   Lime requirement

   Settled volume
£      (ml)

   Turbidity (mg/L)

   Decantate COD





   COD removal (%)

 of all the colloids fell between 6.5 and 7.5.  Morgan and Stumm (24)
 suggested that hydrous iron oxide suspended particles bind anions
 and colloids optimally at a pH range of 5.0 to 8.0.

      To determine more precisely the effect of concentration of
 neutralized AAB on primary settling, an experiment was conducted
 using AAB-I at 5, 10, and 25% levels, and AAB-II at  5 and 10%.   To
 obviate the necessity for making corrections on COD  analyses, COD
 measurements were made on the gross mixtures (before settling)  and
 on the decantates after settling.  The results of the experiment are
 given in Table XI.

      On the  assumption that  acid brines would only be disposed  of  in
 municipal wastewater treatment  plants with  secondary  or higher  grade
 treatment, the turbidity  data is only of  interest as  a very  rough
 measure of removal of suspended solids.   Based on corrected  turbidity
 measurements,  the optimum level of AAB is AAB-I 10%;  the  corresponding
 level of AAB-II is 2%. In terms of COD removal,  the  highest AAB
 levels  tested  gave the best  results.   It  should be stressed, however,
 that  higher  levels of AAB require larger  amounts  of lime  for
 neutralization.  Furthermore, the sludge  volume to be disposed  of,
 mostly  hydrous iron oxides,  is  considerably greater at the higher
 AAB levels.  For example, for 25% AAB-I or  50% AAB-I,  the settled
 sludge  volumes are 50% and 45%  of the volume of raw sewage treated,

      The  general conclusions  drawn from the above experiments are  that
 primary settling is improved  by the addition of AAB at a  level  as
 high  as  10%  vol/vol neutralized with  lime to a pH in  the  range  of  6.0
 to 8.0, that the lower end of the pH  range  calls  for  less lime, and
 that  primary settling  is  not  impaired by AAB in the range 10-15%
 even without neutralization.  As  will be shown  later  in this  report,
 neutralization of  acid in added AAB is necessary  for  proper  functioning
 of activated sludge.   The option  of neutralizing  before or after
 primary settling is  however open  to the operator.  If  primary sludge
 is combined with settled  activated  sludge for  disposal, however, the
 option  is  academic.

 Experiments on  Activated  Sludge  Digestion

     Activated  sludge  cultures  (AS) were operated on  a daily batch
basis on weekdays  during  October, November,  and December.  A series of
experiments on  acid  (AAB)   shocking  of AS cultures  was carried out to
determine  the safe interval between adding AAB  and neutralizing to the
physiological  range of pH.  It should be noted  that the alkalinity of
the primary effluents we  used was only about 100 mg/1  as CaCOn which
is equivalent  to only  13  ml of AAB-I  stock  solution.    If more than that
quantity of AAB is added  to primary effluent, the pH  drops below the
physiological range.  Other experiments were carried out to  compare
AS digestion in control cultures with that of a culture fed  lime-
neutralized AAB.  A third series of experiments was done to  determine
the AS digestibility of decantate from anaerobic sludge digesters.

                                                   TABLE XI

                             Effect of Concentration of AAB on Primary  Settling
// Treatment pH Lime Turbidity Kaolin
Required Equivalent
(rag/L) (mg/L)
COD Settled
Before Decantate % Sludge
Settling (mg/L) Removal Vol. (ml)
Uncorr. Corr,
for Color
None 6.5 	 90 90
AAB-I 7.2 300 325 44
(5% vol/vol)
AAB-I 7.2 1000 89 27
(10% vol/vol)
AAB-I 7.6 2000 74 59
(25% vol/vol)
AAB-II 7.2 1000 205 163
(5% vol/vol)
AAB-II 7.2 2500 280 214
1550 1440 7 4
1550 1135 27 40
1550 1025 34 170
1760 950 54 380
1480 1010 32 280
1580 920 42 400
            (10%  vol/vol)

 Experiments on Acid Shocking

      The results of acid shocking experiments  are  given in Table XII.
 The experiment shown was done  at  low  loading;  but  it  is obvious that
 exposure to acid for only one-half hour does not seriously impair
 digestion.   Exposures for one  hour or longer does  inhibit digestion.
 In a second experiment a culture  was  exposed to acid  for 24 hours
 and then neutralized and fed a portion of  strong waste sufficient
 to bring the initial COD to  1000  mg/1.   Both the control and the
 acid-exposed AS culture gave a 24-hour^ COD of about 250 mg/1 or
 about 25% COD removal in 24  hours.  A third experiment at low loading
 was carried out on  a culture exposed  to acid for 24 hours (pH 3.2).
 After the exposure,  the culture was neutralized and fed along with a
 control.   The results are given below.   Although digestion is obviously
 slowed down for 16  hours, after 24  hours a comparable amount of digestion
 is obtained.

            Control                               Acid-Exposed

         COD    % removal                      COD       % removal

 initial 185                                   148

 15 hrs.   73      60                           129           13

 18 hrs.   92                                   111

 24 hrs.   75      60                            75           50

      In a fourth  experiment, COD  digestion was followed for the first
 two hours after neutralizing and  feeding an AS culture exposed to acid
 for 24  hours.   The  results are  given  below:

            Control                               Acid-Exposed

        COD    %  removal                       COD        % removal

 initial 310                                    292

 20 min. 256                                    292

 60 min. 220                                    256

 120 min.183       40                           256           12

 Thus, COD digestion begins within an hour  of neutralizing and feeding
but the inhibition is quite marked.

     The general conclusions to be drawn from the  above experiments are
that AS cultures can be exposed to AAB  at  concentrations sufficient to
reduce pH to below 3  for one-half hour without significantly affecting


                                             TABLE XII

                            Acid Shocking of Activated Sludge Cultures

                                        Exposed to AAB             Control

                                Time exposed before neutralizing

2 hr.
4 hr.
6 hr.
24 hr.
1/2 hour
1 hour
4 hours


 the COD digestion capability.   Longer exposures  damage  the digestion
 capability, but activity recovers  after neutralization.   The time
 required for recovery depends  upon the time  of exposure  and on the
 loading, which introduces new  active  microbes along with digestible
 organic matter.  Even with an  exposure to  acid of  24 hours and with a
 low loading following neutralization, recovery is  virtually complete
 in 24 hours.  Even before recovery, a reasonably clear  effluent with
 some COD removed can be produced in the damaged  culture  because of
 the improvement in suspended solids removal  due  to hydrous iron oxide.

 COD Digestion by Activated Sludge

      A comparison between the  day-to-day performance of  control AS
 cultures and a culture fed neutralized AAB is given in Table XIII.
 Table XIII  shows the initial COD's, the COD  after  24 hours aeration,
 and the % removal of COD in the two types  of AS  cultures.  Some
 typical COD-depletion curves are given in  a  later  section (COD digestion
 by AS on anaerobic sludge digestion decantate),  but for  present purposes
 it is sufficient to say that 85-90% of the 24-hour digestion occurs in
 the first ten hours.   From the  data it is  clear  that the performance of
 the AAB-fed culture is about the same as that of the control in terms
 of daily COD removal.   The lower COD  removal (average 64.3%) in the
 AAB-fed culture in comparison  to the  control (average 70.8%) may be due
 in part to  the fact that the AAB-fed  culture was loaded  in the average
 at a rate about 6% lower than  the  controls,  without regard to the
 solids  levels in the  cultures.  The settleable solids level in the AAB-
 fed culture was maintained at  about 190 ml/L as  compared to about 40 ml/L
 in the  controls,  but  the greatest  part of  the solids in  the AAB-fed
 culture was hydrous  iron oxide  (and other  hydrous  sesquioxides).  Judging
 from mixed-liquor COD  and BOD analyses the organic solids contents of
 both  types  of AS  cultures  were  about  equal,  at around 500 mg dry solids/L.
     We note a rough trend in the data on COD removal in which the
performance in the second half of the period is poorer than in the first
half while just the opposite seems to be  the case in controls.  In the
latter case, one can attribute the trend to adaptation to the substrate;
in the former case we would attribute it to an increased turbidity in
the one-hour decantates.  The turbidity seemed to be due to very small
coccoid bacteria with a thin rind of iron oxide, but we would not press
that point too far.  With longer settling times, e.g. four hours, the
AAB-fed AS cultures produces a remarkably clear decantate.  Another
important characteristic of the AAB-fed activated sludge is its filter-
ability.  Ordinary activated sludge clogs a laboratory vacuum filter
(paper or membrane) in a matter of seconds, whereas the AAB-fed AS
filters rapidly through a thick pad of sludge.  The same can be said of
the anaerobically digested sludges.

COD/ uiQD Rela tion ship

     In order to translate treatment effectiveness measured by COD


              TABLE XIII

Effect of Neutralized AAB on Activated
          Sludge Digestion

               Control             AAB

Nov .





, 357




 changes into BOD terms,  both waste-strength parameters  were  measured
 on various waste treatment fractions—primary effluent, AS mixed  liquor,
 AS decantate, and anaerobic sludge digestor decantate.   The  results of
 the analyses are given in Table XIV.   As  can be seen in the  data,  the
 Norwich primary effluent has a lower  COD  than BOD,  the  average  COD:BOD
 ratio being 0.72.  In oxidation of organic matter by acid chromate,
 the oxidation proceeds only to the stage  of low molecular weight  organic
 acids; in other words, low molecular  weight organic acids are  refractory
 in the COD analysis.   The Norwich sewage  is almost  always slightly acid
 and has a sour or ester-like odor. Control AS mixed liquor  shows  an
 average COD:BOD ratio of 1.46, which  is typical of  a general mixture of
 biological materials.  Cell walls and cellulosic matter are  nearly
 completely oxidized by acid chromate, but only incompletely  in  a  5-day
 BOD incubation.   The  CODrBOD ratio is higher in the AAB-fed  mixed
 liquor (1.93)  indicating more biorefractory materials in the sludge.
 The decantates from AS cultures have  even higher CODrBOD ratios,  a
 reflection of the fact that biological sorption and oxidation of  sub-
 strate has taken place in the AS cultures.  Decantate from the  anaerobic
 sludge digestor fed control sludge has a  COD:BOD ratio  of about 1  and
 even more noteworthy  a very high COD  and  BOD.   The  anaerobic sludge
 digestor fed iron-rich sludge (from the AAB-fed AS  culture)  had'very
 low COD and BOD in comparison.  The ratio in this last  case  is  of  no
 particular significance.

      We have discussed AS digestion in terms of COD thus far.   Because
 of  the COD:BOD ratios, the performance of AS cultures in BOD terms
 can be shown to  be markedly better, as follows.

                  % COD removal = CODp - COD24  * 100 ?
 in  a typical case:

                  757  = 400 - 100 x 100
                  1  /0       400
With  our  typical batch feeding regime where four liters of primary
effluent  is  fed  to  a  starved AS  culture with a final  volume  of  ten

                  „,_    AS decantate  COD  x 6 + Primary  Effluent COD x 4
                  COD0	—

in  a  typical case:

                  400 = 100  x  6 + 850  x 4

Using the average COD:BOU  ratios  from Table  XIII  to convert  COD to BOD,
one gets:

                  BOD0= (100/1.9)  6 +  (850/0.72)4  =315 + 4700 =  502
                                  10                   10
                 % BOD removal =   502  - 100/1.9 = 90%


                           TABLE XIV
                COD:BOD Relationship of Various
                   Waste-Treatment Fractions
Primary effluent
Activated Sludge
Mixed liquor


Activated Sludge
Anaerobic Sludge
Digestor Decantate





 In the case of AAB-fed AS,  with a typical effectiveness  of 65% COD
 removal and with an AS-decantate COD:BOD ratio  of  2.4, the same
 calculation shows removal to be also  90%.

 Activated Sludge Digestion  of Anaerobic  Sludge  Digestion Decantate

      After anaerobic sludge digestors (SD) had  operated  for about a
 month, the whole volumes  of the decantates were collected and passed
 through activated sludge  to determine toxicity  (if any)  and digestibility.
 As is discussed in a later  section, and  as is shown in Table XIV, the
 decantate from the SD fed iron-rich sludge had  a low COD (175) whereas
 the SD fed control sludge had a decantate with  about 4000 mg/1 of COD.
 The iron-rich SD decantate  was augmented with SNP  and fed to a control
 AS culture.  The decantate  from the SD fed control sludge was suitably
 diluted and fed to the AAB  AS culture.   The  results are  given in Table
 XV and Figure 4.

      From the results shown,  it is obvious that iron-rich anaerobic
 decantate is not toxic to ordinary activated sludge, and AAB-fed
 AS can handle control anaerobic decantate about as well  as it digests
 ordinary primary effluent.   Other qualities  of  the anaerobic decantates
 are discussed later.

 Tertiary Treatment

      Activated charcoal adsorption has   become  a major tertiary treat-
 ment  method.   Zuckerman and  Molof (25) recently discussed alkaline
 hydrolysis  (with lime at  pH  11.5) as  a preliminary step  to adsorption
 and they concluded that activated sludge secondary treatment adds
 nothing to  the over-all effectiveness of treatment when  hydrolysis/
 adsorption  is  used for tertiary treatment.   In  alkaline  hydrolysis
 treatment it  is  necessary to  readjust  pH to the neutral range with
 carbon dioxide or  strong mineral acid.   Although hydrolysis/adsorption
 treatment is  still in the pilot plant stage  of  development, it is of
 interest  to consider  how  acid  brine disposal could affect the method.
 Obviously acid brine  could be  used to adjust pH following alkaline
 hydrolysis,  and  the acid would itself be neutralized in  the process.
 The hydrous  iron oxide  precipitate would also no doubt assist in the
 flocculation  of  unhydrolyzed  colloidal organic  particles and molecules.
 On  the  other hand,  the  unsettleable hydrous  iron oxide might have an
 adverse effect on  adsorbtion or regeneration of activated charcoal.

     Ozone has also been promoted for destruction of refractory organic
matter  and  for disinfection.   Precise pH control and adequate buffering
are very  important to the effectiveness  of ozonation (26).   For the
integrity of activated sludge,  it is necessary  to neutralize acid brine,
as has been discussed.  The neutralization process can be carried to any
pH between 2.0 and 11.5 and the  resultant mixture is well buffered.
Copper oxide has been shown to be an important  heterogeneous catalyst
in ozonation, but the role of other metal oxide particles (including iron)
is problematical.  The impact of lime-neutralized brine  on ozonation
is a prime subject for future  research.


                    TABLE XV

      COD-Depletion Experiment on Anaerobic
            Sludge Digester Decantates

Fed Control Decantate

Time   COD       %
(hrs) (mg/L)  removal










                       Fed Iron-Rich Decantate

                       Time    COD        %
                       (hrs)  (mg/L)   removal










                          SNF + Fe - rich SD decant
                                                    Control  SD.  decant
                                            12          16

                                               Time,  hrs.
                  Figure  A.   Activated  Sludge  Digestion of  Anaerobic Decantate

                    TABLE XVI

     Phosphate Removal from Primary Effluent
            by Lime and AAB Treatment
Portion           Treatment
                  pH = 5.8

              Membrane filter
                (0.45 aicron)

             Add lime to pH 8.5

             Add lime to pH 9.7

             Add AAB-I 20% vol/vol
               Add lime to pH 7.7
                Membrane filter

                As portion 5, but

                As portion 5, but
          aerate 15 min. before decant
Total Phosphorus
    (mg P/L)







   *  In our method of analysis, zero P means much less
   than 0.020 mg P/L; trace means approximately 0,015 mg P/L,

 Phosphate Removal

      Phosphate removal from primary  effluent by  lime and by AAB plus
 lime  was  studies  on a batch of  effluent  containing  8.5 mg total P/L
 and 5.83  mg soluble P/L.   Several  portions  of  the effluent were
 treated in various  ways and the membrane filtrates  or decantates
 were  acid digested  and analyzed for  P by the standard molybdate-blue
 method with the following resul-ts  (Table XVI) .   From the results it
 is  apparent that  treatment with AAB  plus lime  gives virtually 100%
 removal of phosphate in the filtrate or  decantate.  In actual plant
 practice, where alum, lime, iron salts,  or  combinations of them are
 used  for  phosphate  removal, only slightly more than stoichiometric
 quantities are used because of  cost, and typically  only about 90%
 (or less) removal of phosphate  is  accomplished.  For efficient phos-
 phorus removal,  according to Wuhrmann (20) , the  stoichiometric amount
 of  iron (Fe:P  equal to 1.8)  has to be supplemented  with at least 10 mg
 Fe/1  for  hydroxide  floe formation.   Wuhrmann showed the lime sufficient
 to  raise  the pH to  8.8 can be substituted for  the excess iron, in which
 case  sludge quantity and  volume will be  much reduced and the sludge
 produced  has better handling properties.  If the emphasis is on acid
 brine disposal, those points are mott.

      The  actual amounts of Ca and  Fe contained in tests 5, 6, and 7
 are shown in Table  XVII along with the stoichiometric amounts in
 relation  to phosphorus based on the  empirical  formula of the simplest
 iron  phosphate and  calcium phosphate salts.  In  addition to the iron
 and calcium, test protions  5,6, and 7 contained 25 mg Al/1.

                            TABLE XVII

             Fe,  Ca,  and  Al Contents of  Test Samples
                       for Phosphate  Removal

             Actual  Amount         Stoichiometric   Factor
                (mg/L)               Amount          of
                                     (mg/L)         Excess

      P            8.5                 	          	

      Fe         200                   15.2          13.3x

      Ca         325                   16.6          19.6x

     Al           25                    7.4           3.4x

     Analyses  for nitrogen  fractions were not  included in the protocol
 for phosphate  removal  test,  but  some information is available from
the literature.   Neil  (27)  used  a  combination  of alum (94 ppm = 8.5 mg
Al/L)  and activated  silica  (3.4  ppm) for  raw sewage treatment and he
reported  removal  of  98% soluble  phosphate; Kjeldahl nitrogen was reduced


 by  35%.  Rohlich  (28) observed that 200 ppm of alum  (18 rag Al/L)
 added  to the  effluent of the Madison, Wis. Nine Springs Sewage Treatment
 Plant  reduced phosphate to 0.06 mg P/L (from an initial value in range
 5-10 mg  P/L), and  the treatment effected  a 68% removal or organic
 nitrogen compounds.  Rohlich found no removal or inorganic nitrogen
 compounds.  There  is no reason to expect  sorption and/or precipitation
 of  ammonia  or nitrate by lime, alum, or iron salts.  Rohlich and
 colleagues  (29)  later reported 60% removal or organic nitrogen (from
 secondary effluent) by  flocculation with  250 mg alum/L.  In the same
 tests  25% removal  of nitrate and nitrite  was found  but no removal of
 ammonia  nitrogen.   The possibility of nitrate reduction and/or denitri-
 fication by ferrous iron is discussed later.  Rand  and Nemerow (30)
 reported preliminary results of chemical  flocculation studies at the
 Metropolitan  Syracuse Treatment Plant using 5 ppm Fe2(SO,)3 and 30 ppm
 lime.  For  three runs, they observed 48,  64, and 80% phosphate removal.
 Kjeldahl nitrogen  increased in two of the three runs, which was
 attributed  to "sampling procedures".  On  the single run in which
 Kjeldahl nitrogen  was reduced, 22% removal was found.  Thus it is
 reasonable  to conclude  that chemical coagulation of sewage  fractions
 can remove  a  significant amount of nitrogen.

 Biological  Nitrification and Denitrification

      It  was hoped  in  the present  project  to study  the  effect  of  AAB
 on biological nitrification and denitrification, but we were  unable
 to produce  an adapted  sludge  culture until  the  last few days  of  the
 period devoted to  experimental work.  A  description of the manage-
' ment  and behavior  of  the nitrifying  sludge  culture  follows.

      —Recipe for  feed  stock solution  (SGP)  for  nitrifying

 Sludge cultures —

      Sucrose                            15.0  g/L

      Gelatin                            11.7  g/L (<-o7% N)

      KH2P04                              0.8 g/L

      The mixture has a pH of 6.2

      — Ammonium sulfate stock solution  (to contain 10 mg


       (NH4)2S04                      47 g/L

       —Soil  extract is made from rough turf growing on a fertile
 sandy loam low  in calcium.  Ten grams of air-dried soil is treated
 with  100 ml  hot water and the mixture is filtered  through  coarse paper.


      A typical daily routine would be to feed 15 ml SGP,  10 ml
 soil extract (for trace elements)  and 2 ml ammonium sulfate (20  mg
 N).  Sludge solids in the culture were maintained at 1400-1600 mg/l
 by wasting or returning settled sludge.

             Data on a typical run are given below.

              Time            Nitrate in decantate
                                  N03 . N (mg/L)

       Before feeding                 18                pH 5.7

       20 min. after feeding          16

       40 min, after feeding           4,5

       60 min. after feeding           4,0

      150 min. after feeding          19

       24 hrs. after feeding          20                pH 5,5

       On this regime,  the nitrate  nitrogen content  before feeding
 will remain in the neighborhood of 20 mg N/L,  The  diminution of
 nitrate  after feeding  is  problematical but we  would attribute it
 to binding or sorption of nitrate  to gelatin and sorption of gelatin
 by sludge cells.   Metabolic uptake of nitrate  is a  simpler explana-
 tion,  but we do not believe that would occur in  the presence of  20
 mg NH-j.N/L,  and under  a high rate  of aeration.   Biological nitrogen
 removal  has  been comprehensively reviewed by Wuhrmann  (20)  and also
 by Balakrishnan and Eckenfelder (31) .   According to Wuhrmann the
 nitrogen status of sewage fractions  is typically as shown in Table

                          TABLE  XVIII

              Nitrogen  Status  of Sewage Fractions (20)

                             Organic  N     NH3-N    N03/N02-N

      Primary effluent        40-45%        50-60%    0-5%

      After  biological        <20%         10-60%   20-80%

Over-a.1.1  proper biological  treatment  removes about  50%  of  total
nitrogen  from primary effluent.  The proportions of  ammonia-N and
nitrate/nitrite-N  in the  effluent  from biological treatment  varies
over wide limits depending  upon  operating  conditions in the  plant.
The peneral  scheme  for biological nitrogen removal  involves  digestion
of nitrogenous organic matter by a variety of aerobic heterotrophic

microbes, conversion of ammonia to nitrate by Nitrosomonas spp.  and
Nitrobacter spp.  (nitrification) and conversion of nitrate to
molecular nitrogen (or to N20 according to Wuhrmann) under anaerobic
conditions by a variety of "nitrate-respiring" bacteria-  Nitrate can
also be feduced to ammonia by a variety of microbes, and culture
conditions with regard to detention time and loading rate in the
aeration stage must be controlled in order to favor denitrification
over mere nitrate/nitrite reduction (to ammonia) under anaerobiosis.

      Nitrification (the oxidation of ammonia to nitrate ) is a
two-step process effected by two raicrobial groups:

                      Nitrosomonas spp.

             1)  NH3+ 3/2 02	>  N02~+ H20 4- H+


                      Nitrobacter spp.

             2)  N02~+ 1/202	*•  N03~


      The growth rate of both those groups of organisms is low
in comparison to ordinary heterotrophic bacteria and their growth is
more diminished by low temperatures.  Thus in continuous AS culture,
in which both decantate and excess sludge are continuously being
harvested, the nitrifying microbes can easily be washed out of the
culture.  In batch culture, the experimentor has more freedom to
alter compositon of the feed, feed dosing, return sludge, etc. but
in the in the long run, the problem is the same, maintaining enough
of the active species to handle the dosing of ammonia.  Over-all,
nitrification is dependent upon conditions of operation which
minimize excess sludge production.  The critical oxygen tension for
nitrification is lower than formerly thought.  A concentration as
low as 1.0-1.5 mg 02/L is adequate.

      As we mentioned, denitrification requires anaerobic conditions;
this condition can be achieved simply by holding sludge without air
for a time.  After a period of aeration and limited feeding sufficient
to induce nitrification, exogenous substrate has been used up but
sufficient endogenous substrate remains to maintain the nitrate
respiration of the sludge until all the nitrate is used up.  It is
not necessary to add raw sewage or other exogenous sources of hydrogen
donor substances if endogenous reserves are present in amounts
equal to the nitrate/nitrite.  In fact one gets the impression that
exogenous substrate may promote nitrate reduction as opposed to

       Biological nitrogen removal can thus be  seen  to depend upon
 a number of parameters,  some  hydraulic and some biological or chemical.
 In the disposal of acid  brines  through municipal waste  treatment plants,
 nitrogen removal could be profoundly  affected; for  example, high
 ferric iron concentrations may  favor  nitrifying species over ordinary
 heterotrophs,  ferrous iron can  reduce the time needed for nitrifying
 sludge to pass into anaerobiosis  in the denitrification vessel. These
 questions are  amenable to experimental inquiry and  they should be
 given prompt attemtion in the future.

 Anaerobic Sludge Digestion

       The digesters were operated for two months, during which time
 they received  about thirty-five 100-ml portions of  settled sludge.
 Volume was maintained constant  by dedecanting  off liquor after settling
 the sludge in  the digesters.  Table XIX gives  the time  course of
 build-up of solids in the digesters.

       Over the two-month period,  the  mixed liquor suspended solids
 built up from  8.2 to 9.3 gm/L in  the  control digestor.  In the digester
 fed iron-rich  sludge,  the solids  built up from 14.8 to  20,1 gm/L.
 Both digesters were originally  charged a month previous to the period
 reported with  400 ml of  heavy digestor sludge  plus  2500 ml of water,
 the solids level in both digesters being initially  about 7,0 gm/L.
 During the period reported in Table XIX, the control digestor received
 about 36 grams dry weight of  sludge,  and the iron-rich digestor
 received about 40 grams.   Table XX summarized  the sludge digestion

       The specific digestion  rate is  of special interest; it should
 be  noted that  it is independent of volume and  sludge concentration,
 The specific digestion rate designates the fraction of resident
 sludge that can be digested in  a  day.   In other words, about 2% a
 day in the control and slightly less  than 1% in the iron-rich digestor.

 Anaerobic Sludge Digestor Decantate

       We have  already  discussed the COD and BOD quality of the
 decantates.  The phosphate and  iron contents of the decantates are
 given  in Table  XXI.

       The difference in  phosphorus content between  the control and
 the  iron-rich  digestor decantates  is  quite striking, while the
 relatively small difference in  iron content is surprising.  We
hasten  to point   out that  even  though  analyses were run on decantates
 and  filtrates,   it  would  be incorrect  to conclude that the contents
 shown  represent  iron and  phosphate in  solution.  Decantates (actually
 coarse-paper filtrates in  some  cases)  are quite turbid and the analytical
methods  used release iron  and phosphate into solution from particles
 in  the  sample.    The control liquor filters extremely poorly; in fact,


                           TABLE  XIX

            Anaerobic Sludge Digestion in Digesters
             Fed 100 ml Sludge Approximately Daily
     Elapsed Time          Mixed Liquor Suspended Solids
        (days)                        (gm/L)
























                               9.3                        20.1
The table shows day-by-day values and averages over 10-day periods.


                             TABLE XX

             Summary  of Anaerobic  Sludge Digestion Data

                                         Control      Iron-Rich

   I   Range  of dry suspended solids      0.5-2,1      0.4-2,2
      fed  (gm/100 ml)

   II  Average of dry suspended solids      1.04         1.15
      fed  (gm/100 ml)

 III  Total  for 35 100 ml portions        36.4         40,2

   IV  Average daily  feed (111/60)          0.60         0.67

   V   Initial total  resident dry  sludge   23.8         42.0
  VI  Final total resident dry sludge     27.0         58,3

 VII  Sludge increase in 60 days (gn)      3,2         16.3

VIII  Average daily increase in dry        0,05         0.27
        sludge (VII/60) (gm/day)

  IX  Average daily sludge digestion       0,55         0,40
           (IV-VIII) (gm/day)
  X   Specific digestion rate (gm/day.     0,022        0.008
      gm  (IX/ (VI + V) /2)
 it doesn't centrifuge very well:.   The iron-rich liquor both filters
 and centrifuges remarkably well*      "  .iwer phosphorus content of
 iron-rich decantate can thus be       uted partly to higher iron and
 partly to improved filterability. 'Another extremely striking difference
 between the two digesters is odor.  The control digester odor is about
 as foul as can be imagined, typical of an anaerobic sludge digester.
 The iron-rich digester has a mild odor reminiscent of crude petroleum.

 Digested Sludge Disposal

      Time did not permit any experiments on sludge drying or
 incineration, but samples of both control and iron-rich sludge have
 been frozen and saved for future  work.  Certain things can be said,


however, even without experimental evidence.   First,  the iron-rich
digested sludge is no doubt largely a mixture of ferrous oxides and
ferrous sulfide probably amorphous in form rather than crystalline,

                          TABLE XXI

             Characteristics of.Anaerobic Sludge
                     Digestor Decantate

                                         Range         Average

     Phosphorus (mg/L)                    8-92          57.6

     Iron       (mg/L)                   22-69          47.8

     COD        (mg/L)                     -          4150


                                         Range         Average

     Phosphorus (mg/L)                    2^15          6.0

     Iron       (mg/L)                   31-222       118.0

     COD        (mg/L)                     -          181
     In the course of anaerobic digestion sulfates become reduced
to sulfides and the sulfhydryl compounds of digested microbial
tissue also suffer the same fate.

     The land disposal of sludges rich in iron sulfide could pose
a problem unless full assurance against oxidation could be provided.
Oxidation and leaching of such a sludge dump would produce a leach
water similar to acid mine drainage.  Incineration of the sludge
would produce a quantity of sulfur dioxide, and stack scrubbings
would also resemble acid mine drainage.  The iron-rich sludge is
much higher in iron relative to sulfur than are pyrites, the
minerals which produce acid mine water in weathering.  In the
disposal of acid brine in municipal waste treatment plants, the iron
will pass very largely into sludge while the sulfate will move
through the plant in decant fractions,  The ratio of iron to sulfur
in digested sludge should be determined in future work.  In any case,
digested iron-rich sludge probably has about the same composition
as limonite iron ores and as such should be of some, albeit limited,

 Sludge Conditioning

      All methods  of sludge  disposal  are  benefited by  conditioning
 or dewatering.  Chemical  conditioning  of sludge by  sulfuric acid,
 aluminum sulfate,  ferric  sulfate,  ferric chloride,  and  lime was
 reviewed by Balakrishnan  et al  (32).   Relative dewatering rates
 more  than 100  times the untreated  rate have been achieved through
 the use of the  chemicals  listed  above.   We have alluded to the improved
 filterability by  primary  sludge, activated sludge,  and  digested
 mixed sludge from sewage  treatment using lime-neutralized acid brine.
 Masselli et al  (33)  have  reported  that 2000-5000 gal. primary sludge
 is produced per million gallons  of raw sewage and 5000-15,000 gal.
 activated sludge  are produced from the same quantity  of primary
 effluent.   Chemical conditioning of  sludge uses chemicals in the
 range of a few  hundred parts per million, and thus  only a small part
 of the quantity of acid brine available  for use at  a  municipal waste-
 water treatment plant would be used  in sludge conditioning, but there
 is no doubt about  the potential value  of acid brine in  sludge
 conditioning.   If  acid brine were introduced at the primary stage of
 sewage treatment,  there might not be any need for the sludge condition-
 ing step,  as we have mentioned,

 Oxidation  of Ferrous Iron in AAB by Oxygen

      In  order to determine  the additional aeration  capacity needed
 for the  oxidation  of ferrous iron in acid brines added  to sewage
 and to determine the rate of the reaction under typical conditions
 two simple  experiments were carried out.  In the first, samples of
 AAB neutralized with lime to pH 5.25 were added to  tap  water samples
 saturated with  dissovled oxygen.  Dissolved oxygen  was  measured with
 a YSI model  54  oxygen meter at the beginning of the tests, after 10
minutes, and after  15 minutes.  The test jars were  left open to the
 air but were not shaken or stirred.  The results are  given in Table

                          TABLE XXII

         Reduction of Dissolved Oxygen by Ferrous Iron

Test #                  Ratio of Fe-H-  to 02         % of 02 used up in
                         present (equivalents)        10 Min.   15 Min.

 1                              0.9                     22        22

 2                              1.9                     —        43

 3                              3.0                     53        57

 4                              4.2                     —        73

 5                              5.6                     70        83


     The data in Table XXII can be interpolated to conclude that even
under quiescent conditions the dissolved oxygen will be 50% reacted
in 5-10 minutes at high oxygen demand levels due to ferrous iron.
The actual reaction rate depends upon the concentrations of the
reactants and the amount of mixing.  At a feed rate of 20% AAB
(1000 rag Fe-H-/liter), the zero-time ferrous iron concentration is
200 Fe-H- per liter; for oxidation to be complete in a ten-hour
period, 20 mg Fe++/L/hr must be oxidized requiring theoretically
20/7 = 3.0 mg 02/L/hr.  For a four-hour detention time, the oxygen
rate requirement would be 7.0 mg 02/L/hr.  With typical activated
sludge plants the oxygen supply rate from aeration is more than 100
mg 02/L/hr.

     In a second type of experiment, a two-liter sample of AAB-I
was neutralized with lime and added to an eight-liter batch of
freshly fed activated sludge.  The mixture had a pH of 6.8,  The
mixture was then aerated in our standard AS set-up.  Small samples
of the culture were taken at intervals, filtered through a membrane,
and the filtrate was analyzed for iron.  At pH 6,8, it can be
assumed that only ferrous iron would remain in solution.  The change
"in soluble iron content with time is shown in Table XXIII and
Figure 5.

                         TABLE XXIII

        Change in Time of Soluble Iron in AS containing
                      20% Neutralized AAB

Time (after neutralizing)                  Fe in Filtrate
         (hours)                              (mg/L)

            0                                  50

            2                                   6,3

            4                                   3.8

            6                                   1.0

It should be noted that the ferrous iron content of the mixture was
initially 200 mg/L; thus, three-fourths of the ferrous iron was
oxidized and precipitated or was scavenged by the precipitated
ferric hydroxide floe in the few minutes required for neutralizing
the MB, sampling the AS mixture, and  filtering the sample.   From
the color change in the AS mixture  from greenish brown to orange
brown almost all of the ferrous iron added was oxidized  (and
precipitated) in the first few minutes of aeration.

     The aeration requirements in engineering terms are  given in Table
XXIV and Figure 6.


Ui   £
O   4J


      40 .
    - 30 .
                                                     1.   Initial Concentration  400 mg/1  (200 rag/1
                                                               and  200 mg/1  Fe+3)

                                                     2.   3/4  of Ferrous  iron was  precipitated  in a
                                                          few  minutes
             1234            56
                                       Time, hrs.
Figure 5.  Disappearance of Soluble Iron in AS Containing AAB Neutralized with Lime

                          TABLE XXIV

          Oxygen and Work Requirements for Oxidation
                 of Ferrous Iron in Acid Brine

     Fe-H-               Increased D.O.            Increased Work
     (mg/L)           Requirement (mg/L)        Requirement H,P. Hr,

       5                    0.7                      0.125

      10                    1.4                      0.25

      25                    3.5                      0.625

      50                    7.0                      1.25

     100                   14.0                      2.5

     200                   28.0                      5.0

     500                   70.0                     12.5


     1.  Stoichiometric relation is one equivalent oxygen per
equivalent iron.  In English units: one pound of oxygen oxidizes
seven pounds of ferrous iron.

     2.  Aeration efficiency is 2//02/H,P.Hr.

     3.  1.0 mgd capacity.

Actual aeration requirements would be slightly, but only slightly,
higher because of the speed of the oxidation reaction in relation
to detention times in actual practice.

Microbiological Status of AAB AS Cultures
     The term iron bacteria has been used variously to describe
microbes associated with iron oxide crusts or deposits in water,
soils, and in man-made systems.  In the general sense in which the
term, iron bacteria, is used in Standard Methods, both autotrophic
and heterotrophic forms are included.  In the former instance
carbon dioxide is fixed with energy derived from oxidation of ferrous
iron, and in the latter instance, some form of organic carbon is
assimilated.  Heterotrophic bacteria can also bring about the precipi-
tation of hydrous iron oxide by digesting the organic ligand from
soluble ferric chelates, or the surfact of bacterial colonies can
simply serve as a nucleus for the precipitation of ferric hydroxide


                            Stoichiometric relation is one equivalent

                            oxygen  per  equivalent iron;

                            ie  0,14  mg/1  02 is needed to convert
                            1 mg/I  Fe+2 to Fe+3
                            Aeration  Transfer = 2 Ib.

                               200    250    300     350

                           Fe+2 Concentration,  mg/1

Figure 6.  Theoretical Oxygen Requirements  For Oxidation of Ferrous Iron
        .  15.0
                                                                                          .. 2.5


formed by chemical oxidation of ferrous iron in solution.   Metallic
iron and pyrites (FeS2) are attacked by natural waters,  especially if
the water contain dissolved oxygen.   Iron bacteria are often if  not
always associated with the dissolution or corrosion process in nature.
The special role of iron (and sulfur) bacteria in the formation  of
acid mine waters from pyrite was very recently elucidated  by Baker
and Wilshire (34).  Those authors pointed out that Ferrobacillus
ferrooxidans oxidizes only ferrous iron, Ferrobacillus sulfooxidans
oxidizes S= and ferrous iron, and Thiobacillus thiooxidans oxidizes
only S= (and thiosulfate). All three of these autotrophic  bacteria
are capable of growing in media with a pH as low as 2.0, but that
capability has not been shown for the some dozen of other  species
described as "iron bacteria",

     Pringsheim (35,36,37) demonstrated that the "sewage fungus"
Spaerotilus natans can grow as autotrophically as an iron  bacterium,
and Skerman et_al_ (38) demonstrated that species' ability  to grow
as a "sulfur bacterium"} thus it seems to have the same range of
chemoautotrophic capability as Ferrobacillus sulfooxidans.  The
taxonomic status of many microbial entities, described as  iron
bacteria, is problematical as witnessed by Lundgren's (39,40,41)
reference to Thiobacillus ferrooxidans as a participant in acid  mine
water genesis.

     Baker and Wilshire in their studies on pyrite dissolution and
oxidation found a variety of ordinary aerobic heterotrophs in
their reactors, and they concluded that these microbes, (Penicillium,
Pseudomonas, Aerobacter) growing on organic moieties contained in the
coal particles associated with the pyrites, play a significant role
in the genesis'of acid mine water by supplying carbon dioxide to the
autotrophic iron bacteria; at low pH carbon dioxide is far less
soluble than it is near neutrality.

     In summary, chemoautotrophy in iron bacteria, postulated by
Winogradsky in 1922, was unproven in 1949;  a large number  of
filamentous iron bacteria are referrable to Sphaerotilus natans,
an obligate aerobic variable species which grows perfectly well
heterotrophically but does not tolerate low pH.  At pH close to
neutral, ferrous iron is oxidized so fast chemically by dissolved
oxygen that it is doubtful that microbes can avail themselves of the
energy.  Pringsheim did not rule out the possibility, however, and
he pointed out especially that Sphaerotilus in nature grows where
ferrous iron, often complexed with humates, is to be found  in oxygenated
water.  At pH 2-3 ferrous iron is oxidized very slowly by  dissolved  oxygen
except in the presence of a bacterial catalyst.  Chemoautotrophy in
Ferrobacillus sp., which grows at pH 2-3, was convincingly  demonstrated
by Lundgren and colleagues in the fifties, and the point was further
amplified by them in several papers  in  the sixties  (14,15,42,43).


      Our own work on the role of iron bacteria in activated sludge
 fed AAB consisted of attempts to isolate Ferrobacillus from the AS
 cultures using Silverman & Lundgren's medium (15) and following
 procedures outlined by them.  Both control AS cultures and AAB-AS
 cultures yielded a mixture of heterotrophs, including pleomorphic
 molds, and iron bacteria in Silverman & Lundgren's medium.  The
 granular and crusty deposits formed in the iron bacteria cultures
 was in every way reminiscent of the material called "yellow-boy"
 in acid mine waters.  Our experience with small iron-bacteria cultures
 using an acid medium containing ferrous iron correspond very well
 with those of Baker & Wilshire (34), who used a continuously flowing
 pilot plant with pyrite as the reduced iron source.  In their case,
 the growth of heterotrophic microbes was supported by coal substances
 and in our case we are forced to conclude that the substrates were
 substances leached from new polyethlene stock solution bottles—the
 medium we used contained no organic substrates in its recipe.

      As far as the identification or enumeration of Ferrobacillus
 S£p_ is concerned,  we have not  succeeded in obtaining growth  on
 the solid medium recommended for that  purpose by Lundgren &  Schnaitman
 (42)  from AS cultures or  from  the inorganic liquid  enrichment  cultures
 derived from them.   It is quite  clear,  however,  that inoculated
 liquid cultures  form yellow-boy  in a few days and uninoculated flasks
 do  not.  In any  case, this discussion  of the physiology and  ecology
 of  iron bacteria is  academic in  the present context; activated sludge
 at  neutral pH does not provide the environment for  the  growth  of
 chemoautotrophic iron bacteria,  even though they obviously survive
 in  the environment.   Since that  group  of microorganisms grows
 autotrophically  by the oxidation of ferrous iron, sulfur or  siilfide,
 there  is no reason to believe  that they should be important  in the
 economy of AS.

     Wuhram (20) pointed  out another, more important, microbiological
 consequence of high  iron  in activated  sludge.  He observed that iron
 in  excess  of 10  mg/L caused the  complete disappearance  of the
 protozoan  fauna  within two days.   In his work, technical grade iron
 salts  were  used; thus,  toxicity  from contaminating  heavy metals
 cannot  be  ruled  out  as  the cause  of the disappearance.  Our control  AS
 cultures characteristically contained  three types of protozoa, small
 fast-moving flagellates,  small and medium-sized  notile  ciliates, and
 large  flash-shaped stalked ciliates (vorticellids).   AAB-fed AS
 cultures contained no  protozoa except  for  a problematical large
 subspherical  "amoeba" x^ith a very dense granular protoplasm, blunt
 pseudopodia,  and a conspicuous rind or  plasmalemma.   These "amoeba"
 change  shape  very slowly  (if at all); these objects  may be immature
mold sporangia, but  no mycelial strands were evident in the  culture.

     Protozoa in AS  play  a manifold role.   Through  predation they
remove bacterial strains  that might otherwise build  up  to the
detriment of  the system.   In addition they  are responsible for the
digestion o£  a part  of the  organic load and the  assist  in flocculation,


The latter function is probably exercised by small,  dense excretory
particles from the protozoa acting as "cement bridges" between
larger, less-dense particles,  mostly clumps of bacteria.   The loss
of protozoa in AAB-fed AS need not be particularly detrimental,
however, because of the physico-chemical flocculative action of  the
iron hydroxide particles, but  the absence of protozoa could have a
long-term detrimental effect because of the lack of cropping of
undesirable bacterial strains.

Concentration of AMD by Reverse Osmosis

     Reverse osmosis has been  chosen as the process of concentrating
acid mine drainage effluent to acid mine drainage effluent to acid
brine because of the following reasons:

     1,  Process is feasible at reasonably economic levels,

     2.  The potential for considerable reduction in the cost of
         of concentration is high due to the anticipated  improve-
         ment in the membrane  science and technology.

     The flow chart for the concentration process is shown in Figures
7 and 8.  The total dissolved  solids (TDS) level of the acid mine
drainage effluent is assumed at 50 mg/1.  The TDS level of concentrated
acid brine at the end of two stages is 675 mg/1 and concentration
factor is about 13.  With the  addition of third stage reverse osmosis
unit, the TDS of concentrated acid mine will be about 2400 mg/1
resulting in a concentration factor of close to 50,

     The unit cost figures were taken from the information published
by Channabasappa and Harris in Industrial Water Engineering  (44),
These cost figures were adjusted for second and third stage reverse
osmosis units to allow for the type of membranes to be used, pH
adjustment etc.  The costs of concentrating acid mine drainage
effluent to 675 mg/1 TDS and 2400 mg/1 TDS are calculated for plant
sizes 1 and 10 MGD as follows:

1 .MGL Feed

     Cost for the first stage is assumed at 55C/1000  gallons product
water.  Allowing 10% and 50%  increase  for the second  and  third  stage
respectively over the first state the unit costs  for  the  second stage
is 61^/1000 gallons product water and 83C/1000 gallons product  water
for third stage.

     (1)  To achieve a concentration of 675 mg/1, two stages of
          R.O. units have to be employed.  The cost  for  the  two

   1 MGD @ 50 ing/I
   500 psi
 0.25  MGD  @  188 mg/1
 0.75 MGD
 @ 7 mg/1

 First Stase
                                           0.0625 MGD @ 675 mg/1
                           0.1875 MGD
                           @ 25 ng/1

                           Second Stage
                                                  0.0156 MGD <§
                                                     ,430 tng/1
                                                    0.0469 MGD
                                                    @ 90 mg/1

                                                    Third Stage
rlgure 7.  Flow Diagram for Concentrating of AMD - one MGD Plant

    10 MGD @ 50 rag/I IDS
     500 psi
2.5 MGD @ 188 mg/1
   7.5 MGD
   @ 7 mg/1

   First Stage
                                500 psi
                            0.625 MGD (3 675 mg/1
                                                                  0.156 MGD
             1.875 MGD
            =  $0.55	  (750.000) + $0.61      (187,500)
              1000 gal             1000 gal

            =  413 + 114

            =  $527 / 62,500 gallon of concentrated AMD.
            Cost of producing 1000 gallons
            of concentrated AMD @ 675 mg/1  = $527     (1000)

                                           = $8.45

       (2)  For the concentration of acid brine to 2400 rag/1, three
            stages have to be employed.  The total cost for all the

            -  $0.55     (750,000) + $0.61     (187,500) +
              1000 gal              1000 gal

            $0.83     (46,900)
            1000 gal

            = 413 + 114 + 39

           = $566/15,600 gallon of concentrated AMD
           Cost of producing 1000 gallons of
           concentrated AMD @ 2400 mg/1 = $566     (1000 )

                                        = $36.4

Cost of Transporting by Tank Truck

     Source:  1.   McCormack T.I, Trucking Co., Inc.
                  Bulk Liquid Transporters
                  U.S.  Highway No.  9
                  Woodbridge, New Jersey

              2.   MatLac  Pennsylvania - 215-CL9-9800
                  Trucking Charges  up to 100 miles
                  23.5  cents/100 Ib  on a minimun of 40,000 Ib.
                  27  cents/100 Ib for 40,000 Ib.
                  Cost  of transporting by tank trucks
                  1000  gallons = 23.5_    1    (8340)
                                100   '   100
                               = $19.60

Transporting by Rail

     Source:  Reading Pennsylvania Railways
              For distances less than 10 miles,
              $0.58   (8340 Ib) = $48.5/1000 gallons
              100 Ib
              For distances more than 10 miles
              $0.49    (8340 Ib) = $41,00/100 gallons
              100 Ib
              For bulk transportation and an extended period,
              special reduced rates could be obtained by writing
              to the railways.

Cost of Transporting Brine via Pipeline

     The volume of concentrated brine considered for transporting
is in the range of 10,000 gpd to 250,000 gpd.  The distance to be
transported is in the range of 10 to 50 miles.  The cost figures for
the four cases are determined as below:

Case 1

     10,000 gpd - 50 miles                         ,
     From a preliminary engineering analysis, a 4"(7)  reinforced
plastic pipe and 8 hours pumping are selected,

     A.  50 miles, 4"G> reinforced plastic pipe
         (? $1.40/ft, = (5280)   (50)  (1.40) =        $268,000

     B.  Cost of pumphouse                              5,000

     C,  Cost of pumps and motors                       2,000

     D.  Excavation and filling 3' x 3'
         section assumed.  Volume =
         (5280)  (50) (3 x 3) /27 = 88,000 cu, yd.
         @ 55 cu. yd/hr., hrs,  of backhoe operation
         = 38?000    =  1600 hrs. or 200 days

Backhoe and operator 0 $320/day 200 x 320 = 64,000
2 laborers @ $50/day x 200 days  =          20.000

                Total Capital Cost                     359.000

            Contingencies (? 15%                        54.000

            Engineering 9 10%                           41^300
                                                      il4,300  or 455,000


      Amortizing the capital cost for 20 yr life and 5%
      interest, annuity cost = 455,000 x (8,024) (10~2)
                             =  36,500
                  Daily cost =  36f500 =                 $100.00

                  Power:  5HP @ 1 p 24 hr/day =              0.50
                              HP hr,

                  Maintenance @ 2 hrs.  operators    )
                                time/day at $100/day)    =  25-°°

                         Total operating Cost             125.50

Case 3
     250,000 gpd - 50 miles  ,
     Pipe size selected = 8"Q  reinforced plastic pipe

        Pumping hours    = 24 hrs.

        HP               =25

     A,  50 miles, 8"© reinforced plastic pipe
                                          Subtotal         309,800
                                    Contingencies @15%      46,200
                                    Engineering @ 10%       35,600
                                         Total Capital  $  391,600
     Amortizing for 20 yrs 5% interest
      annuity cost = 391 600 (8.024 x 10~2) = 86.00
                Power                          2.00
                Maintenance as is Case 3     100,00
                   Total operating Cost     $188.00

Cost of pumping 1000 gallons )  _
 of acid brine - 10 miles    )  = i§§	 (100°)
                                = $0.75

     The costs of pipelining are shown in Table XXV.  In that table
the numerator figures are the costs per thousand gallons for the
distances shown, and the denominator figures are the cost per thousand
gallons per mile for the plant sizes shown,

                          TABLE XXV

              Pipeline Transport Cost Estimates

            Plant Size                    Distance
                                     10 miles    50 miles

            10,000 gpd                $4.71       12.55
                                      T574T       "TT.TT

           250,000 gpd                 0.75        2.15

                          SECTION VIII

     This report examines the feasibility of concentrating acid mine
waters by certain processes and transporting the concentrated brine
to municipal wastewater treatment plants for disposal.   Relatively
pure water is a by-product of the acid mine water treatment,  and the
iron-rich acid brine is of some value in sewage treatment. The
artificial brine used in the laboratory research was devised  to
simulate a fifty-fold concentration of acid mine water  with respect
to iron and acidity, (2000-10,000 mg Fe/L and acidity 7,800-23,000
ing/L as
     In experiments on primary settling acid brine was added at levels
up to 50% vol/vol with no significant effect on the process.  With
acid brine neutralized with lime, a marked improvement in primary
settling was found.  In addition, virtually 100% removal of phosphate
is achieved,

     Activated sludge digestion was found to be completely inhibited
by acid brine at the levels included in this study, but lime-
neutralized brine was not particularly inhibitory.  Over a two-month
period the control activated sludge culture achieved as high as 89%
removal of COD and averaged 71% removal.  The activated sludge culture
fed 20% vol/vol lime-neutralized acid brine achieved as high as 90%
COD removal and average 64%.  The corresponding averages for BOD
removal were 90% in both the control and the acid brine activated sludge

     Anaerobic sludge digestion was studied using the daily harvests
from control and acid brine-fed activated sludge units over a two-
month period.  The specific digestion rate in the control digester was
2% per day and 1% per day in the digestor fed iron-rich sludge.  Both
digesters produced a decantate that was readily digested by activated
sludge.  In contrast to the control anaerobic digestor, the iron-rich
digestor produced a decantate that was low in phosphate, low in COD,
and virtually odor-free.

     Oxygen and work requirements for oxidation of ferrous  iron in
acid brine were determined to be 0.14 mg oxygen per milligram ferrous
iron and 0.025 horse power hour per milligram ferrous iron  in a one-
mgd plant.  Thus in a one-mgd plant handling acid brine and having 500
mg/L ferrous iron in the plant flow, the work requirement^ for pumping
air to oxidize the ferrous iron is 12.5 horse power hour.

     The microbiological status of the acid brine activated sludge
unit was monitored along with the control,  Activated sludge at
neutral pH does not provide a suitable environment for  the  growth of
chemoautotrophic iron bacteria, but they can be isolated from  such


 cultures.  As had been previously observed in Switzerland where iron
 salts are used  for nutrient removal in sewage treatment, protozoa
 were absent  from our acid brine-fed activated sludge unit.  Their
 absence, however, did not cause any impairment of flocculation in the

     Reverse osmosis offers an attractive method for concentrating
 acid mine water.  The process produces a concentrated brine and a
 relatively pure water as a by-product,  A three-stage system could
 produce a brine of 24000 mg TDS/L from acid mine water containing 50
 mg TDS/L - a concentration of about fifty-fold.  The cost of brine
 production in a 1-mgd plant is estimated to be $36,40/1000 gal, brine
 or 76C/1000 gal. acid mine water treated.  The process will produce
 47,000 gal.  pure water for every 1000 gal. of brine produced.

     Pipeline transport of the brine from the mine site to municipal
 sewage treatment plants is estimated to be cheaper than truck or
 rail, but the pipeline method  requires a capital outlay, right-of-
way purchase, and construction,  Tanktruck transportation costs would
be on the order of $20,00 per 1000 gal. for up to 100 miles.  Standard
rail rates would be roughly twice that amount, but bulk rates and an
extended contract would permit a reduction of the rate.  The pipeline
transport costs, not including costs for right-of-way but including
amortization of other capital outlay,  are estimated to be in the
range of $4.30 per thousand gallons for a one-hundred mile pipeline
of 250,000 gpd capacity.

                           SECTION IX

     This report was written by R.J.  Benoit,  Ph.D and S,  Balakrishnan,
Ph.D.  It describes work under Contract No.  14-12-847 between the
Federal Water Pollution Control Administration and Environmental
Research & Applications, Inc. of Wilton, Connecticut.  Dr. J.M. Shackelford
was project officer for FWPCA,  The author gratefully acknowledge the
assistance of Dr. M. H, Naimie and Mr. A. G.  Attwater in the laboratory.

                           SECTION X

 1.   Glover, H. G., "The Control of Acid Mine Drainage Pollution by
     Biochemical Oxidation  and Limestone Neutralization Treatment,"
     Proc.  22nd Ind. Waste Conf., p. 823, Purdue Univ., (May, 1967).

 2.   Dillon, K, E., "Waste Disposal Made Profitable," Chem. Eng., 75:
     (5)  146-148,  (1967).

 3.   Gerard, L., and Kaplan, R, A,, "Design and Economics of Acid
     Mine Drainage Treatment Plant—Operation Yellowboy," Amer. Chem.
     Soc. Div. of  Fuel  Chem.. 10: ;07-116, (1966).

 4.   Hanna, G. P., Lucas, J. R., Randies, C. I., Smith, E. E., and Brant,
     R. A., "Acid  Mine  Drainage Research Potentialities", J. Wat.
     Pollut. Contr. Fed.  35, 275 - 296,  (1963).

 5.   Porges, R., Berg,  L. A., V.d. and Ballinger, D. G., "Renewed
     Evaluations of an  Old Problem, Acid Mine Drainage Control",
     National  Symposium on Sanitary Engineering Research Development
     and  Design.   Pennsylvania  State University,  (July 1965).

 6,   Biesecker, J.  E.,  and George, J. R., "Stream Quality  in Appalachia
     as Related  to Coal Mine Drainage", U.S. Geological Survey Circular
     526, p. 27,  (1965).

 7.   Simpson,  D. G.,  and Rozelle, R.B.,  "Studies  on  the Removal  of
     Iron From Acid Mine Drainage", Mellon  Institute, May  20th-21st,
     pages  64  - 82,  (1965).

 8.   Gehro,  H.W.,  "Neutralization  of Acid Waste Waters with Upflow
     Expanded  Limestone Bed",  Sewage Works  Journal,  16, pp 104-120,  (1944)

 9.   Jacobs,  II.L,, "Acid Neutralization",  Chem,  Eng. Progr.  43,  pp.
     247  - 254,  (1947).

10.   Lulcas, V. d.p.,  "Treatment of  Acidic  Wastes and Calcite",  Sewage
     and  Industrial Wastes,  27, pp.  1253 - 1258, (1955).

11.   Ohyama,  T.,  Shimoizaka,  J.,  and Usui,  S.,  "The Sedimentation
     Characteristics  of Calcium Carbonate Neutralization Method in
     Mine Water Disposal",  Tohoku Kozan, 4,pp.  21 - 26, (1957).

12.   Stumm, W.,  and Lee, G.  F., "The Chemistry of Queous Iron", Rev,
     Suisse.  d'Hydrologie,  22, pp.  295-319, (1960).

13.   Kusnetsov, S.I., Ivanov,  M.V., and Lyalilova, N.N., "Introduction
     to Geological Microbiology", McGraw-Hill, p. 252, (1963).


 14.  Lundgren, D. G.,  and Schnaitraan,  C.A.,  "The  Iron  Oxidizing
      Bacteria Culture  and Iron Oxidation",  Symposium on Acid Mine
      Drainage Research, Mellon Institute, May 20th-21st, pp. 14-22,

 15.  Silverman, M.P.,  and Lundgren,  D.  G.,  "Studies on the Chemoautotrophic
      Iron Bacterium Ferrobacillus  Ferrooxidans, I.  An Improved Medium
      and a Harvesting  Procedure for  Securing High Cell Yields", J. Bact.
      77, pp.  642-647, "II.   Manometric Studies", ibid. 78, pp. 326-331,

 16.  Anon,, Chementator,  Chemical  Engineering, September 21, (1970),

 17.  Wolman, A,,  "Notes on the Role  of  Iron  in the Activated - Sludge
      Process".  Engineering  News Record, Vol.  98. No.  5 pp. 202-204,

 18.  Kaltwasser,  H, G.  Vogt,  and H.  G.  Schlegel.  "Polyphosphatsynthese
      WHhrend der  Nitratatmung von  Micrococcus denitrifleans Stamm 11".
      Arch.  Mikrobiol..  44, pp.  259-265  (1962).

 19.  Galal-Gorchev, H., and  W,  Stumm.   "The  Reaction of Ferric Iron
      with Orthophosphate", J.  Inorg, Nucl, Chem., 25,  pp. 576-584.

 20.  Wuhrmann, K.  "Objectives,  Technology, and Results of Nitrogen
      and Phosphorus Removal  Processes", Advances  in Water Quality
      Improvement,  Water Resources  Symposium  No, 1., pp. 21-48, (1968),

 21.   Leckie,  J,,  and Stumm, W.,  "Phosphate Precipitation", Water Quality
      Improvement  by Physical  and Chemical Processes, Water Resources
      Symposium No. 3,  pp.  237-249, (1970).

 22.   "Standard Methods  for the  Examination of Water and Wastewater,"
      Twelfth Edition,  Aner. Public Health Assoc.. Inc., New York, p1.
      768,  (1965).

 23.   Packham,  R.F., "Polyelectrolytes in Water Clarification, "Proc.
      Society  for Water  Treatment & Examination, Folkeston, England,

24.  Morgan, J.J., and  Stumm, W,, Proc. Intern, Conf.  Water Pollution Res.
      2nd, pp.  103-131,   Tokyo,  (1964).

25.  Zuckerman, M.M. and A.H. Molof "High Quality Reuse Water by
     Chemical-Physical  Wastewater Treatment".  JWPCF 43 (3) Part 1:
     438-456.  (1970).

26.  Dalton-Dalton-Little, and Resource Engineering Associates.,
     "Advanced Waste Treatment Facilities and Plan for Modernization
     of Existing Southerly Wastewater Pollution Control Center." City
     of Cleveland, Department of Public Utilities, August (1970),


27.  Neil, J.H., "Problems and Control  of Unnatural  Fertilization of
     Lake Waters," Proc.  12th Purdue Ind. Waste  Conf . ,  Ser,  94:  310,

28.  Rohlich, G. A,, "Chemical Methods  for  the Removal  of  Nitrogen  and
     Phosphorus from Sewage Plant Effluents." Algae  & Metropolitan
     Wastes, Trans, of the 1960 Seminar, SEC. TR.  W61-3 USDHEW,  Robt.
     A. Taft Sanitary Eng. Ctr., Cincinnati, Ohio, 1961, p.  130-135

29.  Malhotra, S.K., Lee, G.F. , and Rohlich, G.A., "Nutrient Removal
     from Secondary Effluent by Alum Flocculation  and Lime Precipitation,"
     Intl. J. Hater Poll. 8: 487-500, (1964).

30.  Rand, M.G., and Nemerow, N.L., "Removal of  Algal Nutrients  from
     Domestic Eastewater," Research Report  No.  11, Part 1  -  Literature
     Survey, New York State Dept. of Health, Albany, N.Y. , p. 76.  (1964).

31.  Balakrishnan, S., and Eckenf elder, W;.W. ,  "Nitrogen Relationships
     in Biological Treatment"

          I. "Nitrification in  the Activated  Sludge Process"
              Water Research 3:73-81.

         II. "Denitrification in the Modified  Activated Sludge Process"
              ibid. 3:177-188,

32.  Balakrishnan, S., D. E. Williamson and R.  W.  Okey.  "State of the
     Art Review on Sludge Incineration Practice."    (17070 DIVO 4/70).
     Advanced FWQA-USDI Waste Treatment Laboratory Cinn,,  0, April.

33.  Masselli, J.W. , N.W. Masselli and M.  G.  Burford.,   "Controlling
     the Effects of Industrial Wastes on Sewage Treatment."  (TR-15),
     New England Interstate Water Pollution Control Commission Boston
     June.  (1970).

34.  Baker,  R.A.,  and Wilshire, A.G. , "Microbiological  Factor in Acid
     Mine Drainage Formation:  A Pilot Plant Study" Env.  Sci. & Tech.
     4:  (5)  401-407,  (1970).

35.  Pringsheim, E.G., "Iron  Bacteria," Biol. Rev.  (Cambridge)  24:
     200-245 (1949).

36.  ibid.   "The Filamentous  Bacteria Sphaerotilus . Leptothrix.
                and Their Relationship to  Iron  and  Manganese,"  Phil. Trans.
     Roy.  Soc. London.  Ser. B. 233;453-465. (1944) .

 37.  ibid.   "Iron Organisms," End£amn 11"208-214.  (1949).

 38.  Skerman, V.B.D., Dement jeva,  G.,  and  Carey,  B.J.,  "Intracellular
     Deposition  of  Sulfur by Sphaerobilus  natans,"  J. Bact.  73:509-512,


39.  Agate, A.D., Lundgren, D. G., and Vishniac, W., "Control of
     Thiobacillus ferrooxidans  from Acid Mine Water," Abstract of
     paper presented at the 3rd Int'l. Conf. on Global Impacts of Appl.
     Microbiol., Bombay., (Dec. 1969).

40.  Silverman, M.P., and Ehrlich, H.L., "Microbial Formation and
     Degradation of Minerals," Adv. in Appl. Microb. 6:153-206, (1964).

41.  "Sulfide to Sulfate Reaction Mechanism," USDI FWPCA Report 14010
     FPS 02/70 USGPO, Research Fdn, Wash. D.C., Ohio State,, (1970).

42.  Maclay, W.G., and Lundgren, D.G., "Carbon Dioxide Fixation in the
     Chemoautotroph, Ferrobacillus ferrooxidans," Biochem. and Biophys.
     Res. Comm. 17;603-607, (1964).

43.  Dugen, P.R., and Lundgren, D.G., "Energy Supply for the Chemoauto-
     trophic, Ferrobacillus ferrooxidans." J.Bact. 89:825-834, (1965).

44.  Channabasappa,  K.C., and Harris, F. L., "Economics of Large-Scale
     Reverse Osmosis Plants," Ind. Water Engrng, 20-24 (Oct., 1970).

                            Stibjeft Field & Group
                                               SELECTED WATER RESOURCES  ABSTRACTS
                                                     INPUT TRANSACTION FORM
      Environmental Research & Applications, Inc.
      24 Danbury Road
      Wilton.  Connecticut   06897
      Concentrated Mine Drainage Disposal Into  Sewage  Treatment Systems

Benoit, R.J.
Balakrishnan , S .
Attwafrer, A.J.
l,t Project Designation
" Program # 14010 FBZ,
21 Note

Contract # 14-12-897

 Descriptors (Starred First)

* Effects of Soluble  Iron Waste, ^Municipal Waste Treatment Facilities,  Primary
  Settling, Activated Sludge Process, Sludge Digestion, *Sludge Conditioning,
  Biological Nitrification,  *Biological Denitrification, * Phosphate  Removal,
  Concentration of Acid Mine Drainage,
 Identifiers*(Starred First)
   *Effects of  Soluble Iron,  Municipal Waste Treatment

Laboratory scale  studies were carried out to evaluate the disposal methods for
concentrated  acid mine drainage in the municipal waste treatment.   The studies
indicate 'that the concentrated acid mine drainage produced,  are  not of sufficient
value to pay  for  treatment by any known method, but they can be  disposed of through
municipal wastewater treatment plants, where they will be of some  value especially
in sludge conditioning and nutrient removal.
 WR:I02 (REV. JUt-Y 19S9)
                                            SEND TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
                                                   U.S. DEPARTMENT OF THE INTERIOR
                                                   WASHINGTON. D. C. 20240