EFFECT OF TEMPERATURE SHOCK TO THERMOPHILIC GRANULES

Effects of temperature shock to the activity of thermophilic biogranul es in two upflow anaerobic sludge blanket (UASB) reactors were investi gated. Treating wastewater containing 9450 mg litre(-1) of sucrose, eq uivalent to 10000 mg litre(-1) of COD (chemical oxygen demand) at 55 d egrees C and 24 h of hydraulic retention time (corresponding to a load ing rate of 10 g-COD litre(-1) day(-1), both reactors consistently rem oved 85-90% of GOD. The temperature in Reactor-I was raised to 65 degr ees C for 8 days, while that in Reactor-D was lowered to 37 degrees C for 16 days. The temperature shocks significantly reduced the reactors ' performance: COD removal efficiencies were lowered to 60% for Reacto r-I and to only 40% for Reactor-D. Sludge yields during temperature sh ock were lowered by 25%. In addition, the temperature shock also cause d severe biomass washout, lowering of pH and accumulation of fatty aci ds, in particular propionate. However, both reactors were able to full y recover their efficiencies within 18 days, after the pH was rectifie d by the addition of alkaline and the temperature was re-adjusted to t he normal 55 degrees C. Results of specific methanogenic activity (SMA ) tests show that acetotrophic methanogens were not as sensitive to th e temperature shock as other bacteria. (C) 1997 Elsevier Science Ltd.