钢渣微粉与混凝剂复合对城市污水处理厂尾水深度除磷的试验研究

Research on deep phosphorus removal of municipal secondary effluent by combination of coagulation and steel slag powders

针对北方严寒地区低温时生物单元处理效能低下,污水处理厂二级出水TP浓度较高且不稳定的问题,将钢渣微粉与混凝剂复合处理城市污水处理厂尾水,以提高TP的处理效能。研究结果表明,钢渣微粉投加量为4g/L时,其对50mg/L含磷溶液处理效果最佳,处理2h后TP去除率可达75.16%;溶液初始pH对除磷效果有一定影响,最佳初始pH为7～8;小试试验表明,与单独聚合硫酸铁(PFS)混凝沉淀除磷相比,投加4g/L钢渣微粉使PFS最佳投加量由10mg/L降至6mg/L,且TP去除率显著提高,絮体沉降时间缩短,钢渣微粉-PFS絮体沉降2min时絮体体积分数降至10%,远低于PFS絮体。在连续30d的中试运行中,进水TP为1.40～1.98mg/L时,出水TP质量浓度可稳定维持在0.35～0.46mg/L,运行后期pH可降至9以下,满足《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级A排放标准,运行期间药剂成本仅为0.06元/m3,具有一定经济性。

Since the performance of biological treatment was not good at low temperature,the TP concentration in the secondary effluent of wastewater treatment plant was always high and unstable in the north area of China.In this paper,the steel slag powders(SSP)and polymeric ferric sulfate(PFS)were applied for the deep dephosphorization of secondary effluent.Results showed that after2h of treatment,75.16%of TP could be removed from50mg/L phosphorus containing solution by4g/L SSP.The initial pH could also influence the TP removal effects and the optimal initial pH was between7and8.Lab-scale test showed that compared with single PFS dephosphorization,adding4g/L SSP could decrease the optimum PFS dosage from10mg/L to6mg/L.At the same time the TP removal rate was improved and the precipitation time was shortened.The PFS-SSP flocs could reduce to10%of the initial volume in2min which was shorter than that of PFS flocs.During30d of pilot scale test,the influent TP was fluctuated in1.40-1.98mg/L,while the effluent concentration remained stable at0.35-0.46mg/L,and the pH could be under9in the later running,which could meet the first A standard of“Discharge standard of pollutants for municipal wastewater treatment plant discharge standard”(GB18918-2002).According to the commercial analysis,the cost of medicament was0.06yuan per cubic meter,which had certain economic and feasible value.