Cotman M, Zagorc-Koncan J, Droic A
National Institute of Chemistry, Ljubljana, Slovenia.
Water Sci Technol. 2001;44(6):47-54.
Surface waters are used for disposal of treated effluents from wastewater treatment plants. These effluents usually contain only small amounts of various contaminants but these harmful components accumulate over time in the river, especially in sediments. An integrated approach for the evaluation of the impact of treated effluents was used to predict an ecological risk assessment to the Krka river beside Novo Mesto. The effluents from pharmaceutical and municipal wastewater treatment plants were discharged too closely into the receiving stream, so that separate impacts could not be distinguished. Biologically treated industrial effluents contained great amounts of barely biodegradable organic pollution, organic nitrogen, ammonia and phosphorus, and sometimes zinc. The toxicity of effluents was mostly dependent on their chemical composition. The municipal discharge contained greater amounts of organic pollution that was completely biodegraded but still had a great nutrient pollution load. The effluents were nontoxic. The harmful substances from the effluents were traced in the river. In the downstream site slightly higher concentration of organic pollutants, organic nitrogen, phosphorus, and zinc were detected due to discharges. The river water was over-saturated with oxygen, especially in the summer. In toxicity tests, samples of the river water were nontoxic. Sediments at the downstream site accumulated from discharged organic nitrogen, phosphorus, or zinc. The results of our study show that the main problem is eutrophication of the river Krka, so it is obvious we must reduce the quantity of nutrients in the effluents from wastewater treatment plants. In both effluents it will be necessary to reduce the polluting load of phosphorus, the limiting element for growth of algae and macrophytes in the receiving stream. In the industrial effluent it will be necessary to reduce substances which cause toxicity, such as zinc and nonbiodegradable organic compounds that may be accumulatec the water ecosystem over time.
地表水被用于处理来自污水处理厂的经过处理的废水。这些废水通常只含有少量的各种污染物，但随着时间的推移，这些有害成分会在河流中积累，尤其是在沉积物中。采用一种综合方法来评估经过处理的废水的影响，以预测对新梅斯托附近的克尔卡河的生态风险评估。制药和城市污水处理厂的废水排放过于靠近接收溪流，以至于无法区分各自的影响。经过生物处理的工业废水含有大量几乎不可生物降解的有机污染物、有机氮、氨和磷，有时还含有锌。废水的毒性主要取决于其化学成分。城市排放物含有大量可完全生物降解的有机污染物，但仍有很大的营养污染负荷。这些废水无毒。在河流中追踪到了废水中的有害物质。由于排放，在下游站点检测到有机污染物、有机氮、磷和锌的浓度略高。河水的氧气过饱和，尤其是在夏季。在毒性测试中，河水样本无毒。下游站点的沉积物积累了排放的有机氮、磷或锌。我们的研究结果表明，主要问题是克尔卡河的富营养化，所以很明显我们必须减少污水处理厂废水中的营养物质数量。在这两种废水中，都有必要减少磷的污染负荷，磷是接收溪流中藻类和大型植物生长的限制元素。在工业废水中，有必要减少导致毒性的物质，如锌和随着时间推移可能在水生态系统中积累的不可生物降解的有机化合物。
