Zuthi M F R, Khan F, Sajol Md S Z, Kabir M, Kaiser N M E, Rahman M S, Hasan S M F
Department of Civil Engineering, Chittagong University of Engineering and Technology, Chittagong-4349, Bangladesh.
Chemistry Division, Atomic Energy Centre Dhaka (AECD), Dhaka-1000, Bangladesh.
Heliyon. 2023 May 29;9(6):e16615. doi: 10.1016/j.heliyon.2023.e16615. eCollection 2023 Jun.
The study identifies potential carcinogenic health risk-zone of Chattogram city for the occurrence of trihalomethanes (THMs) at its water distribution network. The EPANET-THMs simulation model along with an empirical model have been adopted in the study to predict THMs content of supply water of the distribution network of the city's Karnaphuli service area. The empirical model has estimated THMs level of supply water based on influential water quality parameters, and few of these have been used as pre-set values for subsequent EPANET simulation. The simulation (R= 0.7) shows that THMs' concentrations throughout the network vary from 33 to 486 μg/L. Around 60% of total junctions showed THMs concentrations above 150 μg/L, while that is above 50 μg/L for most (99%) of the junctions. Residual Free chlorine, one of the precursors for the THMs formation in distribution line, has also been simulated by EPANET considering varying applied chlorine dose at the water purification unit and wall (K) and bulk (K) decay constants. The simulated free residual chlorine peaks are found to be closer to the actual values with chlorine dose of 2 mg/L, and decay constants, K = 1 d and K = 1 d. A mean lifetime total risk of cancer due to the presence of THMs has been found to be very high. Spatial distribution of carcinogenic risk shows that the central zone of the service area is the most vulnerable zone, followed by the western and northern zone. The first ever zone wise risk identification could be used as baseline data for operational and regulatory purposes and may raise awareness among the city's inhabitants. Furthermore, the application of EPANET in combination with an empirical model could be an effective tool for predicting THMs' concentration in water distribution networks in developing countries like Bangladesh to minimize the expenses of measuring THMs.
该研究确定了吉大港城市供水网络中三卤甲烷（THMs）出现的潜在致癌健康风险区域。研究采用了EPANET-THMs模拟模型和一个经验模型，来预测该市卡纳富利服务区供水网络的供水THMs含量。经验模型根据有影响的水质参数估算了供水的THMs水平，其中一些参数被用作后续EPANET模拟的预设值。模拟结果（R = 0.7）表明，整个网络中THMs的浓度在33至486μg/L之间变化。约60%的总节点显示THMs浓度高于150μg/L，而大多数（99%）节点的THMs浓度高于50μg/L。考虑到水净化单元不同的加氯剂量以及管壁（K）和水体（K）衰减常数，EPANET还模拟了作为配水管线中THMs形成前体之一的余氯。当加氯剂量为2mg/L，衰减常数K = 1d和K = 1d时，模拟的游离余氯峰值与实际值更接近。由于THMs的存在，发现癌症的终生总风险非常高。致癌风险的空间分布表明，服务区的中心区域是最脆弱的区域，其次是西部和北部区域。首次按区域进行的风险识别可作为运营和监管目的的基线数据，并可能提高该市居民的认识。此外，将EPANET与经验模型结合应用，可能是预测孟加拉国等发展中国家供水网络中THMs浓度的有效工具，以尽量减少THMs测量费用。
