Study On The Effect Of Sludge Reduction With Worm Reactor

With the acceleration of socio-economic development and urbanization, the construction of municipal wastewater treatment plant accelerates. The amount of sludge generated from wastewater treatment plant increases. Sludge disposal problem has become increasingly prominent, which has to be solved in wastewater treatment plant, making the sludge reduction become necessary. A new worm reactor with good effect of sludge reduction was developed. The effect of sludge reduction by worm reactor was researched. The selections of worms and packings were investigated.Factors affecting the effect of sludge reduction were studied. The operating parameters of reactor were optimized. The settlement and dehydration performance of sludge after treatment by reactor were researched.The research of worms showed that under the same conditions including mud temperature, aeration rate and worm density, the sludge reduction rate of blood-worm, water-worm, red-worm, lumbricus and Tubifex tubifex were 39.3% to 62%,45% to 67.5%, 40% to 69%,45% to 59% and 85%?93% respectively in different sludge concentration and hydraulic retention time, which were 5% to 7%,7% to 14%,6% to 13%,10% to 14% and 40% to 50% respectively higher than the no worm groups. The Tubifex tubifex had the best sludge reduction effect.Radial material, ornamental fish grass and screen were used as packings of reactor. The experiments of selecting packing showed that in different sludge concentration and hydraulic retention time, the sludge reduction rate of the three packings were 40% to 65%,49% to 75% and 60% to 92%, respectively. The screen was better than the others in sludge reduction.The experiments of factors affecting the sludge reduction with worm reactor were carried. It was found that under the same hydraulic retention time, sludge reduction rate gradually decreased with the increase of sludge concentration. When the sludge concentration was 8g/L or more, sludge reduction rate had a significant reduction with the increase of sludge concentration. With the extension of the hydraulic retention time, the increase of mud temperature, aeration rate and worm density, the rates of sludge reduction were improved. But when the aeration rate reached 3.5L/min, the increase of sludge reduction rate was not obvious with the increase of the aeration amoun. During the sludge reduction the environmental factors changed. The concentration of ammonia nitrogen, total nitrogen, total phosphorus and CODcr in sludge mixture decreased, whose removal efficiencies were 25% to 67%,33% to 54%,48% to 62%,40% to 60%, respectively. The pH fluctuated between 5.5 and 7.6.The process parameters of sludge reduction by the worm reactor were optimized. It was found that in order to reduce the total amount of sludge, the optimal conditions of worm reactor were that sludge concentration was 6g/L, worm density was 40000 per liter mixture of sludge, and hydraulic retention time was 20h. The order of factors affecting sludge reduction was sludge concentration>hydraulic retention time>worm density. Under the best conditions the sludge reduction rate was 87%. The optimal process conditions for the purpose of reducing the organic component in the sludge reduction with worm reactor were that sludge concentration was 8g/L, worm density was 40000 per liter mixture of sludge, and hydraulic retention time was 20h.The order of factors affecting MLVSS reduction was worm density>sludge concentration>hydraulic retention time. Worm was based mainly on predation on organic sludge.The sedimentation and dewatering performance of residual sludge after sludge reduction were tested. It was found that the SV%of residual sludge decreased from between 20% and 40% to between 10% and 30%, the sludge volume index dropped from 75mL/g to between 30mL/g and 55mL/g. So the residual sludge after reduction treatment had a good sedimentation property. SV% decreased with the extension of the hydraulic retention time in the same sludge concentration.When the sludge concentration was more than 6g/L, the SVI value decreased with the extension of the hydraulic retention time. The specific resistance of residual sludge after reduction slightly decreased compared with that before sludge reduction treatment. The dewatering performance of residual sludge after reduction by the worm reactor improved to some extent.