复合人工湿地中低浓度有机物的去除及Monod模型模拟

以复合人工湿地工程实例为研究对象,研究了其在连续5个月内对低浓度有机污染物的深度处理效果,采用简化的Monod动力学模型对研究湿地进行模拟并验证,讨论了污染负荷与去除率的相关性以及BOD/COD比值对有机污染物降解系数的影响。研究湿地总面积为5 000 m2,进水水量为860～1 560 m3/d,水力停留时间为1.48～2.69 d,水力负荷为0.17～0.31 m/d,进水中有机污染物浓度较低(BOD53.0～25.6 mg/L;COD 22.9～89.8 mg/L)。结果表明,复合湿地组合形式对BOD5和COD的去除率分别介于37.9%～79.0%和41.0%～68.7%之间,简化的Monod模型对湿地中BOD5和COD去除的预测值与实验观测值吻合程度较好;BOD5、COD的去除率分别随着进水BOD5和COD浓度的增加而增大,而增长趋势逐渐变缓,当有机污染负荷低时,模型的K值较小;低浓度有机污染物在VSF、FWS和HSF湿地中的去除效率与有机物是否容易或者缓慢被微生物降解的性质相关性较差,这可能与人工湿地中存在的其他因素促进了有机污染物的去除有关。

Removal effect of low-concentration organic pollutants and simulating with Monod model in hybrid constructed wetland

The removal effect of low-concentration organic pollutants in a hybrid constructed wetland(HCW) engineering was monitored and studied from May to October. Monod kinetic model was introduced to analyze the treatment effect of low-concentration organic pollutants and verified through three statistical parameters. Correlation of input organics loading vs. removal rates, kinetic coefficients from Monod kinetics against BOD/COD ratio in influent were discussed. The total area of HCW was 5 000 m², and the influent flow rate was 860~1 560 m³/d, hydraulic retention time was 1.48~2.69 d, hydraulic loading was 0.17~0.31 m/d. The input organics concentrations were low(BOD₅ 3.0~25.6 mg/L, COD 22.9~89.8 mg/L). Results showed that the removal efficiencies of BOD₅ and COD reached 37.9%~79.0% and 41.0%~68.7% respectively in hybrid constructed wetland. Regressions of Monod kinetics for correlating inlet and outlet organics values in wetland system indicated the difference between actual and predicted value was very slight. The removal efficiencies of BOD₅ and COD increased in accord with BOD₅ and COD concentrations of the influent, but the increasing tendency became slow. K values derived from Monod model were smaller when organic pollution loads were lower. The efficiencies of organics removal in wetland system appeared to be insensitive to the nature of organic matter when organics pollutants concentrations were low in the influent, whether the organic matter was easily or slowly degradable. This might be related to other factors that promoted removal of organics pollutants in HCW.