Nitrification of a High Ammonia Content Sludge
Supernatant by Use of Rotating Discs
CECIL LUE-HING, Director
ALAN W. OBAYASHI, Research Chemist
DAVID R. ZENZ, Research Chemist
BOOKER WASHINGTON, Sanitary Chemist
BERNARD M. SAWYER, Sanitary Chemist
Department of Research and Development
The Metropolitan Sanitary District of Greater Chicago
Chicago, Illinois 60611
INTRODUCTION
As a part of its land reclamation and sludge recycle program, the Metropolitan
Sanitary District of Greater Chicago (MSDGC) has been barging anaerobically digested
sludge to Fulton County, Illinois, a distance of 190 miles, for application to strip-mined
lands (1973 total of 11,000 acres) to promote row crop production and grazing. Before the
digested sludge is applied on the land, it is held in large holding basins or lagoons. Typically,
the sludge remains in the lagoons for a significant period of time, and a substantial layer of
sludge lagoon supernatant (S.L.S.) is formed. The S.L.S. is relatively low in suspended
solids compared to the sludge and has a range of 130 to 160 mg/1. However, the S.L.S.
contains a relatively high concentration of NH3-N (range 740-830 mg/I).
Since a primary consideration in the land application of digested sludge is the
possibility of ground-water contamination by nitrates, the high NH,-N concentration of the
supernatant could significantly restrict the amount of sludge which can be applied without
nitrate leachate becoming a limiting factor (1). Therefore, it was desirable that the MSDGC
develop methods for reducing the NH3-N of S.L.S., in as much as the NH3-N content of the
S.L.S. constitutes up to 50% of the total nitrogen content of the digested sludge.
Basically, there were two alternatives for reducing the NH3-N of the S.L.S. Either the
S.L.S. could be barged back to the West-Southwest Treatment plant in Stickney, Illinois, or
the S.L.S. could be treated on site at Fulton County, with the effluent being discharged to
the local waterways. It was the initial intent of the study to pursue the second alternative and
determine the feasibility of biologically treating S.L.S. for stream discharge.
In order to remove NH3-N biologically from S.L.S., it was apparent that some form of
a biological nitrification-denitrification system would have to be utilized. There have been
few studies reported in the literature concerning sludge supernatant treatment by biological
means. Sorrels and Zeller (2) found that the sludge supernatant was amenable to biological
treatment to some extent on trickling filters. However, at best (the lowest hydraulic
loadings) the NH,-N was reduced from 246 mg/1 to 46 mg/1 with partial nitrification.
The available information concerning nitrification of high ammonia content wastes,
similar in this respect to S.L.S., is somewhat less limited. Adams, et al (3) found that
nitrification of a high ammonia content waste applied over laboratory and plant scale
trickling filters proved to be ineffective. Adams and Eckenfelder (4) considered the
nitrification of three industrial wastewaters which contained relatively high ammonia
content (pulp and paper, refinery and phenolic wastewaters). The treatment process used
was a suspended growth system (activated sludge) and the results were fairly encouraging as
NH,-N removals were 80-90%.
Hutton and LaRocca (5) also used a suspended growth system in nitrifying a high
ammonia content waste which contained very little organic carbon. They found that they
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