SLUDGE ACCUMULATION IN AN ANAEROBIC LAGOON-ANAEROBIC
FILTER SYSTEM TREATING POTATO PROCESSING WASTEWATER
G. J. Brown, Environmental Engineer
A. A. Cocci, Environmental Engineer
R. C. Landine, Senior Environmental Engineer
T. Viraraghavan, Environmental Engineer
ADI Limited, Consulting Engineers
Fredericton, New Brunswick
Canada E3B 472
K. C. Lin, Associate Professor
Department of Civil Engineering
University of New Brunswick
Fredericton, New Brunswick
Canada E3B 472
The advantages of anaerobic treatment have become well known such as economy of
construction and operation, no aeration requirement, production of methane, low sludge
yield and digestion of volatile waste solids. The digestion of volatile solids is particularly
important in treating wastewaters with high volatile suspended solids (VSS) concentrations.
Treatment of these wastewaters by more conventional means often results in primary
and secondary sludge disposal problems. Depending upon waste characteristics anaerobic
systems may reduce or even eliminate solids disposal problems.
This laboratory study was initially undertaken to determine the efficiency of an anaerobic
lagoon-anaerobic filter system for the treatment of potato processing wastewater. The
objective of this investigation was to determine the rates of sludge accumulation and volatile
solids digestion in the anaerobic lagoon portion of the system studied. Since the anaerobic
filter received very little solids its sludge accumulation is of great interest to the designer
who must consider the possibility of lagoon desludging. The non-volatile content of the
lagoon solids input and the rate of volatile solids digestion are, of course, firmly linked
with the rate of sludge accumulation. Armed with some knowledge of digestion rates,
the engineer may decide to design lagoons for some types of wastes on a volatile solids
loading basis rather than an organics loading, or a detention-time basis.
ANAEROBIC SLUDGE ACCUMULATION
Parker and Skerry [ 1 ] have outlined the role of solids in anaerobic lagoons. They noted
that anaerobic sludge is capable of rapid gas production. They found that sludge
accumulation in lagoons treating domestic waste (suspended solids (SS) load of 0.1 2 kg/m /
d) was more rapid than the buildup in a lagoon treating tomato cannery waste (SS load
of 0.02 kg/m3/d) which had 80% volatile solids destruction per year. They also noted that
the mixing of solids and supernatant caused by gas generation substantially increased biochemical oxygen demand (BOD) removal. The same authors, in another study [2], found
that sludge accumulation in an anaerobic lagoon treating a combination of cannery and
municipal wastes was not significant after seven years of operation.
Oswald [3] reported that when lagoon temperature was less than 19 C that volatile
solids accumulated more rapidly than they could be degraded. When the temperature was
greater than  19 C equilibrium  between degradation and deposition occurred. Sollo [4]
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