Development and experimental validation of the composition and treatability of a new synthetic bathroom greywater (SynGrey)

Abstract

Bathroom greywater, including bathing and handwashing wastewater, can be reused for toilet flushing to reduce 35% of residential water demand. Despite these potential savings, greywater reuse is underutilized and the development of innovative treatment technologies is impeded by a lack of validated synthetic recipes to support laboratory-scale experimentation. The objective of this work was to develop and validate a new, representative synthetic bathroom greywater to enable reproducible and translatable treatment studies. A literature review compiled data from 49 real bathroom greywaters, which was used to set 20 water quality criteria for a synthetic recipe. A new synthetic greywater – SynGrey – was developed to match real bathroom greywater composition across all criteria and was found to be more representative of real greywater than existing recipes. SynGrey's validity was evaluated by comparing its treatability against a real bathroom greywater including via chlorination, aerobic biodegradation, adsorption, and coagulation. Total chlorine residuals were statistically similar between SynGrey and the real bathroom greywater, but doses were an order of magnitude higher than for drinking water. The readily biodegradable fraction of total chemical oxygen demand was about 40% for both greywaters. The dissolved organic carbon percent removal by activated carbon was similar between SynGrey and the real greywater (±14%). Alum coagulation achieved comparable effluent turbidity, but SynGrey had a much more narrow dose curve, and coagulation achieved substantially greater total organic carbon removal from the real greywater. SynGrey represents a superior synthetic recipe for laboratory-scale experimentation to facilitate the evaluation, selection, and optimization of greywater reuse technologies.