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Ventilation Technology of Dewatered Sewage Sludge and Green Waste Co-Composting

Author: LvDeLong
Tutor: ZhangHua
School: Shandong Institute of Architecture
Course: Environmental Engineering
Keywords: dewatered sludge composting green waste ventilation rate ventilation control mode
CLC: S141.4
Type: Master's thesis
Year: 2011
Downloads: 72
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Abstract

Used as a resource, the dewatered sludge treated by composting is made into a virtuous circle of ecology, which will reduce pollution to the environment and avoid urban ecological environment pollution. Considering the characteristics of green waste, dewatered sludge can be composted with green waste, and the prodect return to green. Hence achieve a real sense of resource utilization for the materials in green, and the zero-discharge for pollutants. This paper studied the key composting parameters of the two materials, and developed the efficient and safe composting technology of green waste and dewatered sludge for their reuse as resource.Raw dewatered sludge from a wastewater treatment plant and the grass, green waste, was selected. They were mixed and composted in the light of static high-temperature aerobic composting in the laboratory. The changes of composting pile temperature, PH, moisture content, TN, TOC, GI and other properties in different ways of the ventilation control or ventilation rates were studied.Sludge and grass were mixed with the mass ratio of 8:1 as raw material, and then composted at the aeration rate of 0.2m3/(min·m3) and ventilation time of 40min with a stop of 20min.The characteristics and their changes with time of sludge indexes under ventilation control mode of time control or joint control of both time and temperature were studied respectively. The results showed that:It is the best that dewatered sludge compost with time+ temperature of controlled ventilation. The maturity time of control of the time+ temperature is 12 days, and 14 days of time control. Joint ventilation control both time and temperature can optimize the ventilation requirements in the composting process effectively; the temperature of sludge compost with time+ temperature of controlled ventilation has down to room on the 12th day, about 2 days earlier than time control, PH value of the two states changed little and remained at between 6 to 8, but the moisture content maintained at 60% as a small dropping. NH4＋-N concentration of the time+ temperature control has down to 0.37 mg/g on the 12th day which was one day less than the time control down to 0.43mg/g. For the poor stability, GI was up to 80% or more which had been considered the requirements of compost maturity. GI of the time+ temperature control was up to 88.02% at the 11th day was two day less than the time control.Sludge and grass composted with mass ratio 8:1 as raw material. Under the time + temperature control and ventilation time was 40min with a stop of 20min. To study the sludge indexes characteristics change with time by the ventilation rate of 0.2m3/ (min·m3),0.25m3/(min·m3) and 0.3m3/(min·m3). The results show that:It is the best that dewatered sludge compost with the ventilation rate of 0.25m3/(min·m3). The maturity time of the ventilation rate of 0.25m3/(min·m3) is 10 days, and 12 or 13 days of the ventilation rate of 0.25m3/(min·m3) and 0.3m3/(min·m3), the results of the ventilation rate of 0.25m3/(min·m3) was the best one which≥50℃of the pile kept about 6 days, and≥60℃for 2 days, PH value of three kinds of ventilation changed little and remained at between 6 to 8. NH4+-N concentrations of 0.25m3/ (min·m3)has been down to 0.37 mg/g at 11th day to meet the decomposition requirements (≤0.43mg/g).0.25m3/(min·m3) of ventilation rate took the least on time-consuming. So the best control conditions of sludge and grass composted with weight ratio 8:1 is that when the ventilation time is 40min with a stop of 20min under the time+ temperature of ventilation control mode ventilation rate is 0.25m3/ (min·m3), and maturity time is 10 days.

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