混凝对附着生物膜的微塑料的去除效能

Effect of Coagulation on the Removal of Microplastics Attached to Biofilm

作为一种新污染物,微塑料进入水体后其表面会逐渐形成生物膜。微塑料携带的污染物及生物膜中潜在的致病菌加重了微塑料的环境危害,且微塑料可能随原水进入水厂影响水质安全,因此对水中附着生物膜的微塑料的去除显得尤为重要。以聚合氯化铝(PAC)为混凝剂,以微塑料去除率作为评价指标,考察了混凝法对在自然水体中滞留一段时间的聚苯乙烯(PS)微塑料的去除效能。结果表明,当PAC投加量为60 mg/L、pH为7时,对滞留9 d的PS微塑料达到58.4%的最佳去除率。此外,生物量在一定程度上影响微塑料的去除效率。微生物表面所带的负电荷有利于微塑料与混凝剂水解的金属离子结合形成团聚体,从而促进沉淀。Zeta电位表明混凝过程中发生了电荷中和,傅里叶红外光谱表明PS微塑料与混凝剂在混凝过程中形成了新的化学键。研究混凝去除附着生物膜的微塑料的效果及机理对保证供水安全、保障人体健康具有重要的现实意义。

As a kind of emerging contaminants,microplastics are widely distributed in water.The pollutants carried by microplastics and the potential pathogenic bacteria in biofilm aggravate the environmental hazards of microplastics,and microplastics may enter the water treatment plant with raw water to affect the safety of water quality.Therefore,the removal of microplastics attached to biofilm in water is particularly important.The coagulation was used to remove polystyrene(PS)microplastics that had stayed in natural water for a period of time,polyaluminum chloride(PAC)was used as the coagulant,and the removal rate of microplastics was used as an index to evaluate the coagulation performance.The results showed that when the dosage of PAC was 60 mg/L and pH was 7,the best removal rate of 58.4%was achieved for PS microplastics retained for 9 days.In addition,it was also found that biomass affected the removal efficiency of microplastics to a certain extent.The negative charge on the surface of microorganisms was conducive to the combination of microplastics and metal ions hydrolyzed by the coagulant to form aggregates,thereby promoting precipitation.Zeta potential indicated that charge neutralization occurred during coagulation,and Fourier transform infrared spectroscopy indicated that new chemical bonds were formed between PS microplastics and coagulant during coagulation.It is of great practical significance to study the removal effect and mechanism of microplastics attached to biofilm by coagulation to ensure the safety of water supply and human health.