添加低比例石灰调质的脱水污泥堆肥试验研究

添加石灰可以快速实现污泥干化,抑制污泥恶臭产生、钝化重金属及杀灭病原微生物,但大量石灰(>5%)的加入不但会增加成本,而且会明显提高产物pH值,极大限制了其后续利用,因此,开展了采用添加低比例(￡5%)石灰调质进行污泥堆肥的研究.试验采用罗迪格(Leodige)高效混合设备制备石灰质量分数分别为1%、5%和5%+熟料的混合污泥作为堆肥原料,与未添加石灰的污泥进行对比堆肥.采用氧温控制系统在线监测氧气和温度,实时反馈并控制系统通风.结果表明:堆肥15d后,添加石灰的3组堆肥pH值分别从9.06、12.17、12.34下降至弱碱性水平(<8.3),挥发分从57.35%、45.97%、44.59%下降至44.20%、39.28%、38.42%;4组堆肥减量比均达到50%以上,除2#减量速率明显较慢外,其他3组堆肥减量速率无显著差异;重金属浸出试验检测发现,重金属浸出浓度受pH值的影响较大,添加5%石灰的堆体,Cu、Ni、Zn的浸出液浓度最低.工程应用中,建议采用添加质量分数5%的石灰与一定的熟料返混,从而提高堆肥效率及产品品质.

Experimental study on composting of dewatered sewage sludge by addition of low ratio lime mixture

With addition of lime, rapid sludge dewatering and sludge stabilization could be achieved. However, high cost and high pH are occurred due to the increase of lime usages (> 5%), and the utilization possibility of the final product is greatly limited due to the high pH values. The effect of co-composting by addition of low ratio lime mixture (￡5%) during the sludge composting process was studied. Four laboratory scale composting trials were set up, in which the lime mass fraction of 1%, 5% and 5% were mixed with sludge as compost raw materials respectively, and in the trial 3some matured compost materials were also added, and the trial CK without lime was used as control. Oxygen-temperature control system was applied to control ventilation with real-time feedback. The results showed that pH values of sludge mixtures significantly decreased from 9.06, 12.17 and 12.34to weak alkaline level (<8.3) and volatile solid of sludge decreased from 57.35%、45.97%、44.59% to 44.20%、39.28%、38.42% respectively after composting processes. The over 50% of weight reduction in three trials could be achieved, while there was no significant difference for reduction rate except trail 2. In addition, heavy metal concentrations in the leachates were strongly influenced by pH. Moreover, Cu, Ni, Zn concentrations in the leachates with 5% lime addition were lowest. For practical application, lime mass fraction of 5% mixing with a certain amount of matured compost materials for sludge composting is recommended in order to improve composting efficiency and product quality.