Sludge Reduction Of Worm Reactor And The Growth Rule Of Worm

With social and economic development, the quantity of municipal sewage has been increasing, and large amount of sludge is created in the traditional activated sludge process. The acute problem of handling sludge makes it necessary to reduce sludge quantity. Tubifex, a kind of microfauna, has been used to reduce sludge quantity. This method, reducing sludge quantity from the source, is becoming a research hotspot as it processes the advantages of low energy consumption, low cost and no secondary pollution.This paper mainly studies on the stability of sludge reduction of worm reactor and sludge worm’s growth regularity. Various factors that influence stability of sludge reduction of worm reactor are studied including sludge density of inflow, settling ratio, volatile component, total phosphorus and temperature. The growth law of the worm at different temperatures and sludge concentrations is researched experimentally. Fitting curve of the law, which qualifies relationship between growth and time, was drawn and analyzed. Kinetic parameters of the growth and the relationship between growth cycle time and sludge reduction is discussed too.During the operation time of a half year, It shows that factors like sludge density of inflow, settling ratio, volatile component, total phosphorus and temperature make a greater impact on reducing sludge quantity. Sludge reduction works best when the mixed liquor suspended solids (MLSS) of sludge is about 6 g/L, while the rate of sludge reduction decreases when MLSS is higher than 6 g/L. The improvement of the value of MLVSS/MLSS is beneficial to sludge reduction, while the increase of TP decreases the rate of sludge reduction. The rate of sludge reduction increases with the increasing of temperature, and it’s higer in summer than that in winter. It significantly decreases as the temperature decreases in winter.Study shows worm density is not the same in different space of the reactor. The distribution of worm density is low to high along sludge flow direction. The reactor has the capacity of self adjusting and keeps the amount of worms steady. The density is of between 30000 to 40000 worms per liter in reactor.Through the research of growth law of the worm, it can be found that the complete growth cycle is about 100 to 110 days. Experiment shows that afer 100 days’cultivation the relationships between wet weight of worm and time can be very good in GuassAmp function at temperature 15℃ and 25℃ under different sludge concentration (300mg/L, 600mg/L,900mg/L 、1800mg/L and 2700mg/L). At certain sludge concentration (300mg/L、600mg/L、900mg/L、1800mg/L、2700mg/L) and at 15℃, the worm can reach steady period in advance with increasing concentration. When the concentration is 300mg/L, the worm can reach steady period on the 65th day. While the concentration is 600,900,1800 and 2700 mg/L, the worm can reach steady period on the 60th,60th,50th, 55th day respectively. Under the same sludge concentration, the specific growth rate of worm in both young stage and rapid growth stage at 25℃ is greater than that in 15℃. The rise of temperature promotes the growth and reproduction of the worm, and increases the yield coefficient obviously. At the same temperature, the time required to reach the maximum specific growth rate of worm is reduced gradually as the concentration increases at 15℃.While the time change little for the worm is cultivated in 25℃. At low temperature, the increase of concentration is beneficial for the worm to reach the maximum specific growth rate.The relationships between specific growth rate and sludge concentration satisfies the Monod equation at 15℃ and 25℃.At 15℃ or 25℃, the half-saturated coefficients in Monod equation satifies KTSS death period＜ KTSS young period＜KTSSrapic growth period＜KTSS mature period. The worm needs higher sludge concentration in young period than in death period since they need more substrate to grow and reproduce when they are young.