钢渣用于多级人工湿地导致出水pH值升高潜能及调控措施

The Use of Steel Slag in Multi-stage Constructed Wetland Leads to the Increase of Effluent pH Value and Control Method

文章建设了白洋淀孝义河河口湿地的等比例缩小系统,在雄安新区容城县开展现场中试及pH调控影响因素小试研究,监测与研究了钢渣砾石基多级人工湿地中的pH值变化规律,分析了多级人工湿地出水pH值的升高与超标的原因,探究了湿地系统对水中高pH值的下行调控作用与原理。考察了原水pH值、运行周期、水流流速、钢渣粒径、植物种植密度对湿地系统中pH值的影响。研究结果表明,当烧杯试验中钢渣与砾石组合填料的体积比为1∶4时,湿地出水pH值由7.91提高至11.24,水质劣Ⅴ类。运行周期(时间)是影响湿地出水中pH值的主要影响因素,运行周期越长,pH值越低;钢渣的粒径是影响pH值的次要影响因素,钢渣粒径越大,pH越低;水流流速对p H有微弱的影响,流速越大,水体pH值越高。高密植种植方式在人工湿地中的使用显著降低了碱性进水的pH值,对于p H值为8.13、8.97、10.00和11.04的进水,pH值分别可降低0.09、0.40、0.75和0.77。钢渣作为填料(占填料总量的20%)应用于水平潜流人工湿地(一级、二级)-表面流人工湿地组合工艺,在原水pH值为(8.38±0.20)的条件下,系统运行42 d后出水pH值降低为9以下;降低水体原始pH值可有效缩短pH值降为9以下的时间,当水体原始pH值为7.89~8.57时,系统在第3天出水pH值降至8.84。表流湿地对pH值具有调控作用,但是在原始水体p H值在(8.38±0.20)条件下,表流湿地在第26天开始成为pH值升高的蓄积池。钢渣作为填料的人工湿地不适用于处理碱性污水。在考虑将钢渣作为填料应用于人工湿地前,应结合水质pH值对系统出水pH值进行评估并做好应急措施。钢渣的合理使用可促进人工湿地净化受污水体的同时推动资源化利用进程的发展。

To investigate the changes in p H of the water caused by steel slag as a filler of artificial wetland and the regulating effect of wetland on pH,this study designed a laboratory-scale experiment,and a combined process of horizontal subsurface flow constructed wetland(HSSFCW)-HSSFCW-surface flow constructed wetland(SFCW).The results show that 20%of the steel slag can increase the pH of water from 7.91 to 11.24.The operating cycle(time)is the main influencing factor of the pH of the water body.The pH gradually decreased with the extension of the working time.The particle size of the steel slag is a secondary influencing factor that affects pH,and pH is inversely proportional to the particle size.Water flow rate has a slight effect on pH,and the low flow rate is beneficial to control pH at a lower level.High-density planting methods in artificial wetlands significantly reduced the pH of alkaline influent water,corresponding to 0.09,0.40,0.75 and 0.77 for influent waters with pH values 8.13,8.97,10.00 and 11.04,respectively.The steel slags were used as a filler(20%)in the HSSFCW-HSSFCW-SFCW combined process.Under the condition that the raw water’s pH is(8.38±0.20),effluent’s pH is reduced to below nine after 42days of operation.Lowering the initial pH can effectively shorten the time for the pH to fall below 9.When the original pH of the water was 7.89~8.57,the pH of the water dropped to 8.84 on the third day.The SFCW has a regulating effect on pH.However,under the condition that the original water p H was(8.38±0.20),the SFCW became a storage pool with an increased pH value after the 26th day.Constructed wetlands with steel slag as filler are not suitable for treating alkaline wastewater.Before considering the use of steel slag as filler in constructed wetlands,the pH of the system’s effluent should be evaluated in conjunction with the pH of the water quality and emergency plan should be taken.The rational use of steel slag can promote the purification of the sewage body in the artificial wetland and promote the development of the resource utilization process.