ANAEROBIC TREATMENT OF THERMAL SLUDGE
CONDITIONING LIQUOR WITH FIXED-FILM
AND SUSPENDED-GROWTH PROCESSES
Eric R. Hall, Process Development Engineer
Michael Jovanovic, Contract Engineer
Wastewater Technology Centre
Environment Canada
Burlington, Ontario L7R 4A6
One aspect of the search for cost-effective wastewater treatment systems involves the
development of processes which are energy-efficient. Anaerobic methane fermentation
has been identified as an example of innovative technology which can provide low-cost
treatment of medium- to high-strength organic wastewaters [1]. Although several reactor
designs have been proposed to facilitate high-rate methane fermentation, the common
aspect among these systems is an elevated biomass concentration which allows operation
with a relatively short hydraulic residence time.
The development of high-rate methane fermentation has produced a variety of process
configurations, several of which have been demonstrated at full scale [2-5]. For a potential user of anaerobic technology, an assessment of the relative performance of the available
systems would be beneficial. However, comparison of the processes is difficult given the
wide variety of industrial applications for which performance data are available.
This chapter summarizes initial results from a pilot-scale study undertaken at the Wastewater Technology Centre to evaluate the performance of alternative anaerobic reactors
with a variety of general wastewater types. Four high-rate methane fermentation systems
were constructed for examination during parallel operation with a common feed. Thermal
sludge conditioning supernatant or heat-treat liquor was chosen as the substrate for startup of the pilot plant.
Heat-treat liquor is particularly suitable for anaerobic methane fermentation as it is
produced at an elevated temperature and therefore requires no heat input during processing.
Since several authors have reported results from single reactor studies with heat treat liquor
[6-10], previous data were available for evaluation of the overall pilot plant performance.
In addition, the operating data were of interest for the selection and design of a full-scale
plant to treat 1400 m3/day of thermal conditioning liquor. The pilot-scale studies carried
out with this wastewater included a lengthy start-up phase and a relatively short-term
steady-state run during which three of the reactors were maintained under similar operating
conditions. The results revealed trends in reactor performance during start-up and indicated
potential difficulties in the application of specific high-rate anaerobic technologies to complex soluble wastewater.
FACILITIES AND METHODS
Pilot-Plant Facilities
The high-rate anaerobic pilot facilities used in this study (Figure 1) included a down-
flow biofilm or stationary fixed-film system (DSFF), an anaerobic fluidized-bed (Anitron),
an upflow anaerobic sludge blanket system (UASB) and an upflow anaerobic filter (Anfil).
The Anfil, DSFF and UASB systems all utilized a common basic reactor configuration.
This was a cylindrical steel tank of diameter 0.76 m and height 2.5 m. A conical section of
0.3 m depth formed the bottom of each tank. The anaerobic fluidized-bed was a skid-
mounted treatability unit provided by Dorr-Oliver Incorporated.
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