CCWI2017: F63 'Optimal Control for Water Loss from Water Distribution Network: A Case Study of Beijing'

Water loss control is a key issue for most water supply companies all over the world because of freshwater scarcity and ever-rising water demand. Beijing is one of the cities facing severe water scarcity, so water loss control has been emphasized during the past decades. However, due to the huge size of the water distribution network, there is a great need to optimize the water loss control strategies. The water distribution network of Beijing has been planned to be partitioned into over 700 DMAs. Assessment of the DMAs’ water loss conditions and prediction of the achievements of different water loss control measures are critical to manage these DMAs. The goal of this paper is to develop a mathematical model to reveal how low the water loss of a DMA could go, so as to optimize the water loss control strategies. 36 DMAs were selected as study areas and data of the lowest minimal nigh flow (LMNF) and DMA characters (including pipe material, pipe length, number of properties, pipe age, and water pressure) were collected. The relationship between LMNF and DMA characters was established using multi-variant regression method. The model fit the data with R 2 =0.8. The model was then compared to the commonly used water loss indicator UARL and its sensitivity to the input variables was analyzed. Finally, the model was applied by Beijing Waterworks Group to optimize its water loss control strategies

The Presence of Pharmaceuticals and Personal Care Products in Swimming Pools

The introduction of pharmaceuticals and personal care products (PPCPs) into the environment can be partially attributed to discharges of human wastes, which is also relevant in swimming pool settings. Little or no information exists to address this issue in the literature. Therefore, experiments were conducted to examine the presence and behavior of PPCPs in swimming pools. Among 32 PPCPs amenable to analysis by an available method, <i>N</i>,<i>N</i>-diethyl-<i>m</i>-toluamide (DEET), caffeine, and tri­(2-chloroethyl)­phosphate (TCEP) were found to be present in measurable concentrations in pool water samples. Examination of the degradation of selected PPCPs by chlorination illustrated differences in their stability in chlorinated pools. These results, as well as literature information regarding other attributes of PPCPs, indicate characteristics of these compounds that could allow for their accumulation in pools, including slow reaction with chlorine, little potential for liquid → gas transfer, and slow metabolism by humans (among orally ingested PPCPs). The findings of this study also suggest the potential for accumulation of topically applied PPCP compounds in pools. More generally, the results of this study point to the importance of proper hygiene habits of swimmers. The potential for the accumulation of PPCPs in pools raises questions about their fate and the risks to swimming pool patrons

PPCP Degradation by Chlorine–UV Processes in Ammoniacal Water: New Reaction Insights, Kinetic Modeling, and DBP Formation

The combination of chlorine and UV (i.e., chlorine–UV process) has been attracting more attention in recent years due to its ready incorporation into existing water treatment facilities to remove PPCPs. However, limited information is available on the impact of total ammonia nitrogen (TAN). This study investigated two model PPCPs, <i>N,N</i>-diethyl-3-toluamide (DEET) and caffeine (CAF), in the two stages of the chlorine–UV process (i.e., chlorination and UV/chlor­(am)­ine) to elucidate the impact of TAN. During chlorination, the degradation of DEET and CAF was positively correlated with the overall consumption of total chlorine by TAN. Reactive nitrogen intermediates, including HNO/NO^– and ONOOH/ONOO^–, along with ^•OH were identified as major contributors to the removal of DEET and CAF. During UV irradiation, DEET and CAF were degraded under UV/chlorine or UV/NH₂Cl conditions. ^•OH and ^•Cl were the major reactive species to degrade DEET and CAF under UV/NH₂Cl conditions, whereas ^•OCl played a major role for degrading CAF under UV/chlorine conditions. Numerical models were developed to predict the removal of DEET and CAF under chlorination–UV process. Chlorinated disinfection byproducts were detected. Overall, this study presented kinetic features and mechanistic insights on the degradation of PPCPs under the chlorine–UV process in ammoniacal water