Evaluation of thermophilic anaerobic digestion
The objectives of this study were to examine the effect of temperature on the digestion of a synthetic substrate, alone and with waste activated sludge (WAS), and to determine the effect of nickel, cobalt and molybdenum on thermophilic digestion. Two different types of reactors, batch fed and continuous flow, were operated in four separate phases for over two years. The data indicated that thermophilic digestion could be established from digesting mesophilic domestic sewage sludge by setting the temperature at 50C. An additional acclimation period of about 15 days was required for stimulation of thermophilic bacteria at 60C. Thermophilic digestion at temperatures up to 75C could easily be established in a few days, provided that the digester was well adapted at 60C. The rate of metabolism increased with temperature, reaching an optimum between 60C and 65C. It was possible to shift from 50C to 37C and back to thermophilic temperatures with a minimum of difficulties. Temperature fluctuation of less than 5C did not cause any upset in the performance of the thermophilic digesters operating at 50C to 65C. Addition of Ni, Co and Mo at 1 mg/L appeared to be satisfactory with the suspended solids maintained in the system at long SRT periods. The best substrate removal at 50C was 99.6% reduction at 10 g/L/d COD and 99.6% reduction at 14 g/L/d COD at 55C. The limits for COD loading under a once daily batch fed operations were 24 g/d at 50C and 33 g/d at 55C. The continuous flow fixed-film digester was able to digest WAS with liquid detention times as short as 8 hours. Thirty percent digestion of the volatile solids in WAS was obtained at a 3-day LDT and 16% at an 8-hr LDT.
- Research Organization:
- Kansas Univ., Lawrence, KS (United States)
- OSTI ID:
- 5642013
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
SEWAGE SLUDGE
ANAEROBIC DIGESTION
ACTIVATED SLUDGE PROCESS
BATCH CULTURE
BIOREACTORS
COBALT
CONTINUOUS CULTURE
MOLYBDENUM
NICKEL
SUBSTRATES
TEMPERATURE EFFECTS
BIOCONVERSION
BIOLOGICAL MATERIALS
BIOLOGICAL WASTES
DIGESTION
ELEMENTS
MANAGEMENT
MATERIALS
METALS
PROCESSING
SEWAGE
SLUDGES
TRANSITION ELEMENTS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
090900* - Biomass Fuels- Processing- (1990-)
320604 - Energy Conservation
Consumption
& Utilization- Municipalities & Community Systems- Municipal Waste Management- (1980-)