Role of metal modified water treatment residual on removal of Escherichia coli from stormwater runoff

• Published in: The Science of the total environment 2019-08, Vol.678, p.594-602
• Main Authors: Xu, Dong, Shi, Xueqing, Lee, Lai Yoke, Lyu, Zhiyang, Ong, Say Leong, Hu, Jiangyong
• Format: Article
• Language: English
• Subjects: Adsorption; Bacterial removal; Metal modification; Stormwater runoff treatment; Water treatment residual
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.04.207

Extensive studies have been conducted on bioretention filter media applied in best management practices for stormwater runoff treatment. To date, more reported studies are focused on pollutants elimination such as suspended solids and nutrients. There has been limited research on pathogen removal from stormwater runoff. More focused studies on pathogen removal are therefore required if the intended stormwater is harvested for indirect potable use. In this study, water treatment residuals (WTR), a recycled biofilter media was surface-modified with metals to assess its potential for E. coli removal from stormwater runoff. To achieve this goal, four types of modified WTRs, prepared using iron, copper, platinum, and silver as antibacterial agents, were tested in parallel batch tests. After the cost-effectiveness evaluation among the four modified WTRs for bacterial removal, Fe2O3- and CuO-WTRs were shortlisted for further mechanism and stability studies. Stable antibacterial performances (E. coli log removal of 0.58 ± 0.04 and 0.90 ± 0.04, respectively) were achieved using the Fe2O3- and CuO-WTRs under intermittent synthetic and natural stormwater runoff conditions. No significant metal leaching was observed over prolonged continuous treatment. The experimental results showed the bio-adsorption onto the surface modified Fe2O3- and CuO-WTR was a key mechanism for E. coli removal followed by E. coli inactivation at solid-liquid interface caused by the antibacterial effect of metal coatings (where CuO was reported to have higher biotoxicity than Fe2O3). These findings clearly suggested the potential of CuO-modified WTR for pathogen removal in stormwater treatment practices. [Display omitted] •Water treatment residual (WTR) was surface modified for stormwater treatment.•Modified WTRs were evaluated by antibacterial efficiency and cost-effectiveness.•Fe2O3-/CuO-WTR exhibited robust stability in intermittent-flow test over 18 weeks.•CuO-WTR was recommended with superior bacterial removal and low Cu leaching.•Mechanism studies showed adsorption played a significant role in bacterial removal.