不同底物条件下UASB反应器中碳酸钙的沉淀

以UASB反应器处理含钙的乙酸废水和葡萄糖、可溶性淀粉混合废水,在Ca²⁺浓度800 mg·L^-1,COD容积负荷9 kg·(m³·d)^-1条件下,研究了碳酸钙在反应器中的沉淀规律及其差异.结果表明,碳酸钙在发生大量沉淀前都要经历30 d左右的诱导期,此后反应器中碳酸钙的沉淀率因进水底物不同而出现显著差异.以乙酸为底物时,碳酸钙在污泥中的最大沉淀率可达到65%,然后稳定到25%;而在以葡萄糖和可溶性淀粉为底物的废水中,钙的沉淀率一直维持在7.5%左右.对于这2种废水,钙的沉淀在180 d内可以使污泥的灰分从大约10%分别升高到70%以上和30%左右.但是高的生物污泥灰分含量并没有明显影响废水处理的效果,两反应器的COD去除率始终维持在90%左右.扫描电镜分析发现两反应器内颗粒污泥微观结构存在较大差异,这可能是导致其中碳酸钙沉淀过程和沉淀量存在较大差异的原因.

Calcium Carbonate Precipitation in UASB Reactors with Different Substrates

Two lab scale upflow anaerobic sludge bed (UASB) reactors were operated at an organic loading rate of COD 9 kg·(m³·d)^-1 to treat two kinds of calcium containing wastewaters, one of which took acetic acid as substrate and for the other, glucose and soluble starch were the substrate. Both the wastewaters contained 800 mg·L^-1 Ca²⁺. Precipitation of calcium carbonate in the reactors was observed. The results showed that the kind of substrate had great influence on calcium carbonate precipitation. In the reactor treating acetic acid containing wastewater, a maximum calcium precipitation rate of 65% was achieved and an average rate of about 25% was then maintained. In contrast, the calcium precipitation rate for the glucose and soluble starch containing wastewater was only about 7.5%. It was also found that substantial precipitation only occurred 30 days after the reactor were operated for both of the wastewaters. After 180 days of operation, the ash content of the sludge in the reactors increased from about 10% to 70% for the acetic acid containing wastewater and 30% for the other. However, the increase of ash content had no negative influence on the COD removal efficiency, which was kept at about 90% throughout the experimental period. By the SEM it was inferred that the different substrates caused the differences of the granular sludge microstructure, leading to the diversity of calcium carbonate precipitation in the two reactors.