United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory            _- _ ,
Ada OK 74820                 '/i~v
Research and Development
EPA-600/S2-82-076 Sept. 1982
Project Summary
Powdered Carbon-Activated
Sludge—Filtration  Processes
for Petroleum  Refinery
Wastewater

J. S. McBride, A. T. Knecht, S. A. Sevan, D. J. Muhlbaier, and F. M. Pfeffer
  The purpose of this research program
 was to determine the effect of the
 addition of powdered activated carbon
 (PAC) to petroleum refinery activated
 sludge systems. Both bench-scale and
 full-scale tests were performed. A
 wide range of PAC concentrations and
 sludge ages were evaluated.
  Bench-scale  activated  sludge sys-
 tems were designed and constructed.
 The bench-scale  units were initially
 operated to determine the conditions
 for the full-scale test.  Additional
 bench-scale tests were carried out to
 evaluate  conditions impractical to
 meet during the full-scale testing.
  Similar results were obtained during
 the full-scale and bench-scale tests. A
 moderate enhancement of COD re-
 moval was observed. PAC addition
 had little effect  upon the removal
 efficiency of other contaminants or
 the toxicity of undiluted effluents. An
 economic analysis of PAC addition
 was carried out.
  This Project  Summary was devel-
 oped by EPA's Roberts. Kerr Environ-
 mental Research  Laboratory, Ada,
 OK, to announce key findings of the
 research project that is  fully docu-
 mented in a separate report of the
 same title (see Project Report ordering
 information at back).

 Introduction
  The  1974 EPA  effluent limitations
 guidelines for the petroleum refining
 industry proposed  that best available
treatment economically achievable
(BATEA) be secondary treatment fol-
lowed by filtration and granular activated
carbon (GAC) treatment. GAC adsorption
equipment and operations including
regeneration are costly; consequently,
cost-effective  BATEA alternatives to
GAC have been of considerable interest
to both EPA and industry. The addition
of powdered activated carbon (PAC) to
the  activated sludge treatment system
is such an alternative for improving
performance and effluent quality.
  The purpose of this study was to
establish  the effectiveness of adding
commercially available PAC to a full-
scale refinery  activated  sludge treat-
ment system  which was currently
meeting effluent  permit limitations.
Both bench-scale and full-scale studies
were carried out. The main purpose of
the  bench-scale studies was to estab-
lish the conditions to be evaluated
during the full-scale test. In addition,
bench-scale reactors were operated at
conditions that were impractical to meet
during the full-scale testing.

Conclusions

   1. The results from the bench-scale
     units were similar to those
     obtained from the full-scale units
     when operated under similar
     conditions.
  2. PAC addition resulted in the
     moderate enhancement of  COD
     removal. During the bench-scale
                                      » US.OOVERNMENTPRINTINGOfFIOE.1W2-559-017/08Z8

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         testing, the effluent COD from
         the PAC units was 11 -33 percent
         less than from the control units.
         This corresponds to a 2-6 percent
         improvement  in  COD removal
         efficiency in the PAC units based
         upon the overall COD  loading.
         During the refinery  test, the
         effluent COD from the PAC unit
         was 18 percent less than from
         the control which corresponds to
         a 2 percent improvement in the
         overall removal efficiency  of
         COD.
       3. PAC addition resulted in a small,
         but  statistically significant, en-
         hancement of the removal of oil
         and grease. During the bench-
         scale tests, the oil and grease in
         the effluents from the PAC units
         were 0.5 to 2.0 mg/l less than in
         the control effluents. During the
         refinery test, the oil and grease
         concentration was 0.6 mg/l less
         in the PAC  effluent than in the
         control effluent.
       4. PAC addition had little effect
         upon the removal efficiencies of
         TOC, phenol, or phosphorus.
       5. PAC addition resulted in higher
         effluent suspended solids and
         ammonia concentrations during
         the refinery test.
       6. PAC  addition had little effect
         upon the removal of priority
         pollutants or the fish toxicity  of
         the  undiluted effluents during
         the refinery test.
       7. PAC addition  did  result in in-
         creased sludge  compactability
         and sludge settling rates.
       8. PAC  is abrasive  and  its  use
         during the refinery test resulted
         in  increased  wear of  sludge
    i ecycle pumps. It may be neces-
    ;ary  to modify sludge handling
    equipment to prevent the adverse
    (iffects of abrasion when  PAC
    iiddition  programs are  imple-
    mented.
 9. "he mixing requirements of PAC
    iiludge are greater than conven-
    tional sludge.  As was demon-
    i trated during the refinery test, it
    nay  be  necessary to provide
    < dditional mixing to maintain the
    I'AC sludge in suspension.
10. " he mechanism of PAC enhance-
    i tent  appears to be simple ad-
    sorption. Biological regeneration
    (f the PAC surface did not seem
      occur.
11. I the PAC addition program that
    \ vas evaluated during the refinery
    test  were  implemented, the
    c nnual cost  is estimated to be
    * 603,500. This corresponds to a
    cost  of $7/additional Ib COD
    removed and $104.95/additional
    I > oil  and  grease removed.
12. h comparing the results of this
    study to results obtained in other
Official Business
Penalty for Private Use $300
                     0000329
                                               At,
      recent refinery wastewater PAC
      studies, it becomes apparent that
      the effect of PAC addition depends
      upon the circumstances of the
      particular application.  It  should
      not be assumed that PAC addition
      will  have a similar effect at all
      refineries. The suitability of PAC
      treatment should be tested in a
      bench-scale or pilot-scale study
      prior to adoption of a  full-scale
      PAC program.

Recommendations
  1.  Since all refinery systems are not
     equally amenable to PAC treat-
     ment, future work should focus on
     what influent characteristics  or
     operational factors  control  the
     effectiveness of PAC addition.
  2.  No evidence was found for the bio-
     regeneration of the PAC surface.
     Since other workers have claimed
     that bio-regeneration does occur,
     future work should focus on the
     mechanism of PAC enhancement
     to determine under what conditions
     bio-regeneration occurs.
J. S. McBride, A. T. Knecht, S. A. Bevan. and D. J. Muhlbaier are with Atlantic
  /?/ :hfield Company, Harvey. IL 60426; the EPA author F. M. Pfoffer (also the
  EPA Project Officer, see below) is with the Robert S. Kerr Environmental
  Research Laboratory, Ada, OK 74820.
The  '.omplete report,  entitled "Powdered Carbon-Activated Sludge—Filtration
  Processes for Petroleum Refinery Wastewater,"(Order No. PB 82-252 933;
  Co|sf: $10.50, subject to change) will be available only from:
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 22161
The $PA Project Officer can be contacted at:
        Robert S.  Kerr Environmental Research Laboratory
        U.S. Environmental Protection Agency
        Ada. OK 74820
United States
Environmental Protection
Agency


Center for Environr
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Cincinnati OH 452


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