Impact of water management practice scenarios on wastewater flow and contaminant concentration

Due to frequent droughts and rapid population growth in urban areas, the adoption of practices to reduce the usage of fresh water is on the rise. Reduction in usage of fresh water can be achieved through various local water management practices (WMP) such as Water Demand Management (WDM) and use of alternative water sources such as Greywater Recycling (GR) and Rainwater Harvesting (RH). While the positive effects of WMPs have been widely acknowledged, the implementation of WMPs is also likely to lower the wastewater flow and increase the concentration of contaminants in sewage. These in turn can lead to increases in sewer problems such as odour and corrosion. This paper analyses impacts of various WMP scenarios on wastewater flow and contaminant load. The Urban Volume and Quality (UVQ) model was used to simulate wastewater flow and the associated wastewater contaminants from different WMP scenarios. The wastewater parameters investigated were those which influence odour and corrosion problems in sewerage networks due to the formation of hydrogen sulphide. These parameters are: chemical oxygen demand (COD), nitrate (NO3−), sulphate (SO42−), sulphide (S2−) and iron (Fe) that were contributed by the households (not including the biochemical process in sewer pipe). The results will help to quantify the impact of WMP scenarios on odour and corrosion in sewerage pipe networks. Results show that the implementation of a combination of WDM and GR had highly increased the concentration of all selected contaminant that triggered the formation of hydrogen sulphide, namely COD, sulphate and sulphide. On the other hand, the RH scenario had the least increase in the concentration of the contaminants, except iron concentrations. The increase in iron concentrations is actually beneficial because it inhibits the formation of hydrogen sulphide.