Study On Horizontal Spiral Device For Aerobic Dynamic Composting

The sewage sludge with a high volume and complicated characteristics is the necessary product of wastewater treatment and should be treated and disposed to protect from secondary pollution and to ensure the treatment effect, because of many toxic and harmful substances present in. However, it also contains some kinds of useful matters that can be reused. In this paper international and domestic sewage sludge treatment and disposal technologies and development trend were reviewed systematically, and composting techniques were particularly introduced. On this basis, the problem of aerobic dynamic composting techniques of sewage sludge were put forward. A horizontal spiral device for aerobic composting was developed. By using this device, a pilot-scale test on treating anaerobic digested sewage sludge, from Chongqing Tangjiaqiao Sewage Sludge Treatment Plant, was carried out, employing the technique of batch-dynamic composting with wood dust as amendment at a moderate temperature. The pile temperature, organic matter, pH value, total nitrogen and organic carbon was mainly investigated in various conditions when the moisture contents, the ratio of sewage sludge to wood dust and the aeration rate were controlled in a certain range. The main results are as follows.1. The composting of sewage sludge can be successfully carried out when the moisture contents, the ratio of sewage sludge to wood dust and the aeration rate are appropriate. The composting cycle are eight days ,and the ratio of organic substance wiped off is 18%~20%.2. Moisture contents can obviously influence the process of composting, the appropriate moisture contents are 50%~60% for this dynamic device. The higher the moisture contents in a certain range, the lower the temperature of the composting pile, the lower the ratio of organic matters decomposed when the ratio of sewage sludge to wood dust and the aeration rate are same.3. The ratio of sewage sludge to wood dust can obviously influence the process of composting, when it is 10:1.0~1.5, the ratio of organic matters decomposed to total organic matters is relatively high. the appropriate ratio of sewage sludge to wood dust is 10:1.0~1.5 for this dynamic device in view of the energy consumed when the mixed matters go forward along the helix axis.The higher the ratio of wood dust in a certain range, the more the moisture contents wiped off, the faster the speed of composting pile temperature rise, the higher the temperature and the more organic matters decomposed when the aeration rate and moisture contents are same.4. Aeration rate can obviously influence the process of composting, the appropriate aeration rate is 6.7~8.3m3/h.t for this dynamic device to achieve a high composting pile temperature and ratio of organic matters decomposed. Superfluous and scanty aeration rate will slower the speed of rising of composting pile, reduce the temperature and reduce the ratio of organic matters decomposed.