Simulation and mitigation of water conservation consequences in a domestic UK wastewater collection system

Abstract

Domestic water conservation strategies have already resulted in water use reduction. Water use is considered energy-intensive, which means that a reduction in water use will also reduce carbon emissions and therefore contribute to climate change mitigation strategies. However, a reduction in water use will automatically reduce wastewater flow and negatively impact solid transportation and therefore wastewater system performance thereby making the system more susceptible to blockages. Furthermore, it may also deliver wastewater to the treatment plant that is outside of required plant operational parameters. These two concerns could result in greater carbon emissions than carbon savings. This highlights the necessity to determine the optimal water reduction level of water conservation strategies, as opposed to simply ‘the maximum reduction possible’. The UK Building Codes control the dimensional layout of building wastewater systems and would need to be updated to make use of optimal water reduction guidance advice. This dissertation fills this gap by postulating a general optimum water conservation level of between 20%-40% before adverse performance manifests, by using verified computer simulations primed with verified site data, derived in collaboration with a national-level Steering Panel comprised of UK Water Industry Research members. Guidance and recommendations include allowing 75mm discharge pipes and tipping tanks to facilitate aggressive water conservation tactics while maintaining adequate wastewater system performance and still conserving water.