Civil Engineering Department, Iowa State University, Ames Iowa, USA.
Water Sci Technol. 2010;62(9):2075-82. doi: 10.2166/wst.2010.538.
Seasonal discharge programs, which take advantage of temporal variation of stream assimilative capacity, are cost effective. However, these seasonal discharge control programs should not increase the risk of water quality violations. A method is presented to estimate the allowable pollutant loads under both seasonal and non-seasonal discharge control programs for a single discharger that maintains the same level of risk of water quality violation. An enhanced in-stream water quality model QUAL2E-UNCAS was applied to a 39-km river reach of the Des Moines River below Des Moines Sewage Treatment Plant (DMSTP) in Iowa. The model was calibrated for dissolved oxygen (DO), biological oxygen demand (BOD), and ammonia as nitrogen with standard errors of 10, 17, and 23% by comparing with the observed water quality data. Monte-Carlo simulation technique was then implemented for seasonal and non-seasonal discharge program to assess the water quality violation risk and the allowable pollutant load. The results indicated that the four-seasonal program offers about 136% increase in BOD loading and 61% increase in ammonia loading when compared with the non-seasonal program without any increase in the violation probabilities, whereas the two-seasonal program only offers 13% decrease in BOD loading and 56% increase in ammonia loading. It is found that the multi-discharge program was beneficial for both water quality indicators, and thus provides a way of reducing the overall cost of waste treatment.
季节性放水方案利用了河流同化能力的时间变化，具有成本效益。然而，这些季节性放水控制方案不应增加水质违规的风险。本文提出了一种方法，用于在季节性和非季节性放水控制方案下，估算单个放水者的允许污染物负荷，同时保持相同的水质违规风险水平。增强型河流水质模型 QUAL2E-UNCAS 被应用于爱荷华州得梅因污水处理厂（DMSTP）下游 39 公里的得梅因河河段。该模型通过与观测水质数据进行比较，对溶解氧（DO）、生物需氧量（BOD）和氨氮进行了校准，标准误差分别为 10%、17%和 23%。然后，采用蒙特卡罗模拟技术对季节性和非季节性放水方案进行了评估，以评估水质违规风险和允许的污染物负荷。结果表明，与非季节性方案相比，四季方案可使 BOD 负荷增加约 136%，氨氮负荷增加 61%，而违规概率没有增加，而两季方案仅使 BOD 负荷减少 13%，氨氮负荷增加 56%。研究发现，多放水方案有利于水质指标的改善，从而为降低污水处理的总成本提供了一种途径。
