Huisman Jacco L, Gasser Thomas, Gienal Claudio, Kühni Matthias, Krebs Peter, Gujer Willi
Swiss Federal Institute of Environmental Science and Technology (EAWAG), P.O. Box 611, CH-8600 Dübendorf, Switzerland.
Water Res. 2004 Mar;38(5):1237-47. doi: 10.1016/j.watres.2003.11.012.
Quantification of the oxygen fluxes in the sewer system is at present the optimal methodology to obtain information about the influence of sewers on transformations and mass balances in the urban drainage system. However, the relative and absolute values of these fluxes are practically unknown. In this work, the oxygen fluxes were quantified experimentally in a full-scale aerobic main sewer. The sewer biofilm respiration was determined with an in situ flow cell, a method that has not been used before in the sewer. The surface reaeration was determined with a gas tracer method based on the inert, non-radio-active and non-toxic gas tracer sulphur hexafluoride. In addition, the wastewater biomass respiration rate was measured. The validity of the applied methods was verified with redundant oxygen balances over a 2-km-long section. Measurement campaigns under different hydrodynamic conditions showed that the relative contribution of the biofilm, the wastewater, the reaeration and the in- and outflow with the water, all contributed significantly. However, the absolute contributions varied extensively and depended especially on the discharge. The COD conversion in the sewer could be estimated from the aerobic activity. The aerobic total degradation in the study reach was 3%. However, when extrapolated to the entire sewer net of the catchment area with 5000 PE, the COD conversion was estimated as high as 30% of the dissolved COD during the night. This indicates that the wastewater composition at the treatment plant will be strongly affected by the sewer system.
目前，量化下水道系统中的氧通量是获取有关下水道对城市排水系统中转化和质量平衡影响信息的最佳方法。然而，这些通量的相对值和绝对值实际上是未知的。在这项工作中，在一个全尺寸的好氧主下水道中对氧通量进行了实验量化。采用原位流动池测定下水道生物膜呼吸作用，该方法此前未在下水道中使用过。采用基于惰性、非放射性且无毒的气体示踪剂六氟化硫的气体示踪法测定表面复氧。此外，还测量了废水生物量呼吸速率。通过对一段2公里长的区域进行多余氧平衡验证了所应用方法的有效性。在不同水力条件下的测量活动表明，生物膜、废水、复氧以及与水的流入和流出的相对贡献都很大。然而，绝对贡献差异很大，尤其取决于流量。下水道中的化学需氧量（COD）转化可通过好氧活性进行估算。研究区域内的好氧总降解率为3%。然而，外推到集水区拥有5000人口当量（PE）的整个下水道网络时，夜间COD转化估计高达溶解COD的30%。这表明污水处理厂的废水成分将受到下水道系统的强烈影响。
