Research on an emergency treatment technology for black-odor water caused by macrophytes decaying

Abstract

水草腐烂加速水体耗氧和水体还原性物质的溶出进程,在夏、秋季高温条件下极易引发局部水体黑臭.以太湖沉水植物优势种马来眼子菜(Potamogeton malaianus)、苦草(Vallisneria natans)及浮叶植物优势种莕菜(Nymphoides peltatum)为受试材料,利用太湖原位底泥培养模拟水草腐烂形成的黑臭水体,考察不同的环境材料处置方式(壳聚糖(CTS)、聚合氯化铝(PAC)、聚丙烯酰胺(PAM)、CTS+PAC和PAC+PAM)对黑臭水体浊度、溶解氧浓度、挥发性硫化物等黑臭水体特征污染物的絮凝沉降规律及去除机理.结果表明:(1)絮凝处理24 h后,CTS+PAC组合对黑臭水体的浊度去除效果最佳,浊度去除率达70.3%,上覆水溶解氧浓度明显提高,增加率为261.5%;(2)加石英砂悬浊液加速絮体沉淀,形成絮体之后加石英砂使水体浊度稳步下降,4 h之后,浊度去除率达74.9%,显著高于与絮凝剂一起加入的处理组(29.8%);(3)植物腐烂释放的含硫特征嗅味物质主要为硫化氢(H₂S)、甲硫醚和二甲基三硫醚.不同植物体腐烂释放的含硫挥发性有机物浓度差异显著,马来眼子菜释放的4种含硫有机物总和分别为莕菜和苦草释放的319.8%和252.2%;(4)CTS+PAC处理后苦草及马来眼子菜腐烂水体中挥发性有机硫化物浓度较对照组分别降低了18.6%和44.5%.PAC+PAM组合絮凝处理组对莕菜腐烂水体中H₂S有较好的去除效果,去除率达到52.4%.CTS+PAC絮凝剂组合处理的H₂S浓度均低于对照组,苦草、马来眼子菜和莕菜腐烂后黑臭水体中H₂S浓度分别降低了27.4%、41.0%和28.6%.CTS+PAC组合对H₂S和二甲基硫醚类物质等致臭物释放的抑制效果优于PAC+PAM组合絮凝处理.;Aquatic plants decaying will accelerate the process of dissolved oxygen depletion and promote the dissolution of reducing substance, which can easily lead to partial water black-odor in a hot summer. In this study, dominant species of submerged plants Potamogeton malaianus, Vallisneria natans and floating-leaved dominant species Nymphoides peltatum in Lake Taihu were selected as test material. Then the macrophytes decayed in cylindrical sediment in the culture system in which simulated conditions in situ. The black-odor waters were formed to study the flocculation and sedimentation kinetics, removal mechanism of water turbidity, volatile sulfide, dissolved oxygen and other water and soil interface characteristics which were treated with different environmental material disposals(chitosan(CTS), poly aluminum chloride(PAC), polyacrylamide(PAM), CTS+PAC and PAC+PAM). The results suggest that:(1) After 24 h, the turbidity removal of black smelly water treated by CTS+PAC was optimal, when turbidity removal rate was 70.3%. The CTS+PAC combination can increase the dissolved oxygen in overlying water more significantly than other environmental material disposals, and the increase rate is 261.5%.(2) Taking flocculation experiments by joining flocculants in the black smelly water with different flocculants, the suspension of quartz sand was added at different timing. Quartz sand suspension can accelerate flocculant precipitation, adding quartz sand before flocculant is significantly better than after it with turbidity removal rate 74.9% compared to 29.8%.(3) Sulfur characteristic odor compounds released by decay aquatic plants are mainly hydrogen sulfide(H₂S), dimethyl sulfide and dimethyl trisulfide. volatile organic sulfur compounds(VOSCs) released by difference decayed plants was significantly different. The sum of the four forms of organic sulfur released from Potamogeton malaianus were 319.8% of Nymphoides peltatum and 252.2% of biter grass.(4) Volatile organic sulfur compounds contents of Vallisneria natans and Potamogeton malaianus decaying water treated by CTS+PAC was reduced by 18.6% and 44.5%. Treatment PAC+PAM has a good deodorizing effect on Nymphoides peltatum for the removal rate of H₂S reached 52.4% when treatment CTS+PAC affected both three kind of plants. The content of H₂S reduced by 27.4%, 41.0% and 28.6% in Vallisneria natans, Potamogeton malaianus and Nymphoides peltatum, respectively. The inhibitory effect of odorant(such as H₂S and dimethyl sulfide) in treatment CTS+PAC was higher than that in treatment PAC+PAM.