Department of Environmental Engineering, Beijing Institute of Petrochemical Technology, Beijing, 102617, China.
SDIC Xinkai Water Environment Investment Co. Ltd, Beijing, 101101, China.
Environ Sci Pollut Res Int. 2022 May;29(21):32161-32170. doi: 10.1007/s11356-021-18453-8. Epub 2022 Jan 11.
The flocs formed during microsand-ballasted flocculation (MBF) have attracted much attention. However, few studies have reported on comprehensive process parameters of MBF and its mechanism is still not well understood. Jar test and pilot-scale continuous experiments were here conducted on two kinds of simulated wastewater, labeled S1 (21.6-25.9 NTU) and S2 (96-105 NTU). Results revealed the hydraulic retention time ratio in the coagulation cell, injection and maturation cell, lamella settler of pilot-scale MBF equipment was 1:3:7.3. The optimum poly aluminum chloride doses for samples S1 and S2 were 0.875 g/L and 1.0 g/L. Besides, the optimum size of microsand was 49-106 μm and the optimum dose was 1.0 g/L. Under aforementioned conditions, the effluent turbidity of S1 was below 0.47 NTU, even lower than the Chinese drinking water standard; that of S2 was below 1.7 NTU, meeting the Chinese recycled water standard. Turbidity removal ranged from 98.0 to 98.8% for S1 and 98.5 to 99.5% for S2 when microsand was added. Therefore, microsand addition enhances MBF performance, where microsand serves as an initial core particle. Some microsand core particles bond together to form a dense core structure of micro-flocs by the adsorption bridging of inorganic polymeric flocculant. Moreover, the size of the largest micro-flocs may be controllable as long as the effective energy dissipation coefficient is adjusted appropriately through specific stirring speeds. This work provides comprehensive pilot-scale process parameters for using MBF to effectively treat wastewater and offers a clearer explanation of the formation mechanism of microsand-ballasted flocs.
微砂强化絮凝（MBF）过程中形成的絮体引起了广泛关注。然而，目前鲜有研究报道关于 MBF 的综合工艺参数，其机理仍不甚清楚。本研究采用烧杯试验和中试连续流试验，对两种模拟废水（S1，浊度为 21.6-25.9 NTU；S2，浊度为 96-105 NTU）进行了研究。结果表明，中试 MBF 设备混凝池、进砂池和熟化池、斜板沉淀池的水力停留时间比为 1:3:7.3。对于水样 S1 和 S2，最佳聚合氯化铝（PAC）投加量分别为 0.875 g/L 和 1.0 g/L。此外，微砂的最佳粒径为 49-106 μm，最佳投加量为 1.0 g/L。在上述条件下，S1 的出水浊度低于 0.47 NTU，甚至低于中国饮用水标准；S2 的出水浊度低于 1.7 NTU，满足中国再生水标准。当投加微砂时，S1 的浊度去除率为 98.0%至 98.8%，S2 的浊度去除率为 98.5%至 99.5%。因此，添加微砂可以增强 MBF 的性能，微砂作为初始核心颗粒。一些微砂核心颗粒通过无机高分子絮凝剂的吸附架桥作用结合在一起，形成致密的微絮体核心结构。此外，只要通过特定的搅拌速度适当调整有效的能量耗散系数，就可以控制最大微絮体的尺寸。这项工作为采用 MBF 有效处理废水提供了全面的中试工艺参数，并对微砂强化絮体的形成机制提供了更清晰的解释。
