USING METAZOA TO REDUCE SLUDGE PRODUCTION

Pilot plant experiments have been carried out to study the mineralizat ion of sludge from biological wastewater treatment plants by worms suc h as Tubificidae. Trickling filters filled with lava slags;were contin uously fed with a certain quantity of excess activated sludge of a Dut ch brewery wastewater treatment plant (Bavaria) by recirculation durin g 10 to 14 days. At the starting point of each experiment the tricklin g filters were inoculated with Tubificidae. Recirculation of sludge sh owed that use of Tubificidae resulted in a COD reduction of the sludge (mixed liquor) of 18 - 67%. Without worms this reduction was substant ially lower. The sludge production in a pilot activated sludge system for treating settled domestic wastewater reduced from 0.40 to 0.15 g M LSS/g COD removed when Tubificidae were added to the system. The lower amounts of sludge were always accompanied by an increase of nitrate a nd phosphate concentration in the wastewater. There was no disturbance of the nitrification process. Application of Tubificidae or other wor ms may have interesting potential for practical application. (C) 1997 IAWQ. Published by Elsevier Science Ltd.