Reading guidance：With the popularity of the urban sewage treatment plants, treatment of sewage sludge is urgent. The investment of waterworks construction also has been greatly increased. The sludge is one of the final

     With the popularity of the urban sewage treatment plants, treatment of sewage sludge is urgent. The investment of waterworks construction also has been greatly increased. The sludge is one of the final product of the biological waste water treatment process. The treatment sludge of the investment and operation cost is huge, accounting for 25% to 65% of the entire waste water treatment plant investment and operating cost, which has become heavy burden in waste water treatment plant.
      In foreign sludge disposal methods, sludge in Britain and America is mainly used in agriculture while is mainly used for incineration in Japan. At present, over 90% sludge is disposed by using sanitary landfill, agricultural application and incineration. Research on sludge reduction mainly focuses on following three points: 1. Reduce production amount of microbe; improve traditional disposal methods for biological treatment of waste water (such as adopting oxygen aeration and decoupled metabolism); 2. Improve sludge disposal process; 3. Research sludge disposal.
     If you use micro animals, there is no need to use additional investment. The running cost is very low and there is no by products. Compared with other technologies, it holds strong superiority. At present, worms are greatest metazoan observed in activated sludge. Because sludge earthworm feeding amount is considerable. It has great potential for sludge reduction. It is widely applied.
     Water earthworm situ digestion sludge technology depends on ecological principle and second law of thermodynamics. Simulate aquatic ecosystem, in the sewage treatment system into higher trophic level metazoan and tubificidae to extend the sewage treatment system in the food chain, promote material cycle and energy flow, construct an artificial enhancement of the ecological system, cooperative role in situ digestion sludge with water earthworms and microorganisms. Finally, realize process of sludge reduction.
     Water earthworms used in sewage treatment plants often present in red color, camp omnivorous aquatic earthworm using the cooperate with microbial action and the main feeding sludge organic debris and bacteria, in the pre processing system with water, in order to ensure the water quality standards, the investment and added to the pool in situ digestion sludge, reduce excess sludge production, reduce subsequent artificial rapid infiltration system sludge load.
     It is demonstrated in relevant survey that sludge presents a more compact structure after disposal of water earthworms. Reduction effect of sludge will be more obvious with the increase of temperature. The best effect can be got at each July, which Mainly due to the summer water earthworm metabolism active, large amount of sludge degradation, secondly because of more rain in summer. Inlet cod is low, the COD processing effect is good; low winter temperatures, water earthworm reduced metabolism, reproduction speed slows down, the sludge degradation effect weakened.
     Under the microscope observation, it is found that the sludge after water earthworm digest the structure is more compact, MLVSS/MLSS value by 48. 6% drop was 35. 3% and repeatedly after the degradation of the organic content is more and more low sludge aging slowed. Microorganism and water earthworm has good synergistic effect: water earthworm in the system can promote microbial growth and reproduction, maintain the balance of the population, inhibit the growth of filamentous bacteria, prevent sludge aging; at the same time water earthworm's body and metabolites to microbial decomposition of the formed a benign circulation system.
  Adding water earthworm can significantly sludge produced. The reason is that tubificidae and pollutants and activated sludge microorganisms together constitute the a simple, small ecosystem, water earthworm is introduced in the system to extend pool in the biological chain and promote material cycle and energy flow of the system.
   Although water earthworms holds low cost and cause no secondary pollution, cultivating water earthworms needs to adjust proper environment for sludge, which brings great difficulties for wide application and promotion. Therefore, more researchers and common efforts are needed in order to explore a new way to dispose sludge.
 

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