K. J. Kennedy

Stability and performance of anaerobic fixed film reactors during hydraulic overloading at 10–35°C

Abstract Anaerobic fixed film reactors could be hydraulically loaded to 94 kg COD m −3 day −1 for a 24 h period and regain normal performance 12–48 h after overloading. COD conversion decreased with increased overloading and was dependent on operating temperature and type of waste. The quality and amount of digester gas was also affected but returned to normal steady values once overloading was stopped.

Support materials for stationary fixed film reactors for high-rate methanogenic fermentations

SummaryNeedle punched polyester material and red drain tile clay were most effective in developing an active biomass film. Maximum methane production rates (0.045–0.055 m3/m2/day, or 4.5–5.5 m3/m3/day for a reactor with 100 m2 film support area per m3) were achieved in 40–50 days.

Anaerobic digestion of piggery waste using a stationary fixed film reactor

Abstract A fixed film digester with a 35 litre support void volume, treating piggery waste at 35°C, was capable of handling high organic loading rates and short hydraulic retention times without process failure. The digester had a film support made of fired potters clay and a surface-to-volume ratio of 157 m 2 m −3 . It could be loaded to 18·7 kg Volatile Solids (VS) m −3 day −1 without substantial increases in volatile acid levels or a reduction in the quality of the digester gas. Maximum methane gas production was 3·8 m 3 (STP) m −3 day −1 and the conversion of Volatile Solids into methane decreased with decreasing hydraulic retention time.

Role of resin acids in the anaerobic toxicity of chemithermomechanical pulp wastewater

Abstract Chemithermomechanical pulp (CTMP) wastewaters are being treated anaerobically, in full scale operations, in spite of the presence of inhibitory compounds. These compounds are neither well identified nor are they placed in an order of priority in terms of inhibition to anaerobic bacteria. In this study anaerobic toxicity assays were used to quantify the relative toxicity of resin acids to the total toxicity in bleached CTMP (BCTMP) wastewater. Resin acids are partitioned between the soluble wastewater and the fiber fractions. Therefore fiber toxicity was also compared to raw BCTMP wastewater toxicity. Resin acids were found to be toxic to anaerobic bacteria but were not found to be responsible for all the toxicity in BCTMP effluents. Toxicity associated with the fiber is soluble in methanol. The bulk of the fiber which is not methanol soluble exhibited no toxicity to the anaerobic cultures used.

A generally applicable technique for the extraction of restrictable DNA from methanogenic bacteria

Abstract We present a method, which is generally applicable to a wide variety of methanogenic bacteria, for the extraction of restrictable genomic DNA. Lysis involves treatment of frozen-thawed cells with pronase, dithiothreitol and sodium dodecyl sulphate, followed by recovery of the DNA by ethanol precipitation.

Anaerobic fixed-film reactors treating carbohydrate wastewater

Abstract Anaerobic downflow stationary fixed-film reactors operated at 35°C, successfully treated synthetic (sucrose-based) wastewater of different concentrations at high organic loading rates and short hydraulic residence times. Waste stabilization was due to the high concentration of active biomass retained in the biofilm. Biofilm biomass concentration increased with organic loading rate reaching a maximum of 8.7 kg VFS m −3 of reactor volume (0.112 kg VFS m −2 support surface). The biofilm was found to be completely active and unaffected by diffusional limitations up to an average thickness of 2.6 mm.

Thermophilic downflow stationary fixed film reactors for methane production from bean blanching waste

SummaryActive thermophilic (55°C) biofilms developed in downflow stationary fixed film (DSFF) reactors (needle punched polyester or red draintile clay support material) within 8 weeks. Maximum steady state methane production rates were similar to those for mesophilic reactors.

Media effects on performance of anaerobic hybrid reactors

Abstract Effects of cross-flow media angle and depth on hybrid anaerobic upflow-sludge-blanket-filter (UBF) reactors treating a medium strength wastewater were investigated. Results showed that media angle, media depth and sludge bed height had a relatively minor effect on sludge retention and COD removal while hydraulic retention time (HRT) and concomitant volumetric organic loading rate (OLR) had the largest impact. Variations in sludge granulation were noted, with the proliferation of more settleable granules in the reactor containing random media and UBF reactor with the shallow packing slope. Although the settleability of the sludge in each UBF varied the sludge activity in all reactors was relatively constant.

Effect of hydraulic and organic overloading on thermophilic downflow stationary fixed film (DSFF) reactor

SummaryTests to determine the stability of thermophilic DSFF reactors using bean blanching waste as substrate, showed them to become unstable at 30 to 40 kg/m3/day whether hydraulically or organically overloaded. This level is significantly less than mesophilic reactors could handle (90 kg/m3/day).

Continuous vs slug loading of downflow stationary fixed film reactors digesting piggery waste

Downflow stationary fixed film reactors successfully digested piggery waste at retention times down to 2.6 days either loaded continuously or once-a-day. Daily methane production rates of up to 2.6 m3/m3 were recorded for both loading methods. The rate for the slug loaded reactor peaked within 2–6 hours after being loaded.