Diallo Mamadou B C, Anceno Alfredo J, Tawatsupa Benjawan, Tripathi Nitin K, Wangsuphachart Voranuch, Shipin Oleg V
Environmental Engineering and Management, Asian Institute of Technology, Klong Luang, Pathumthani 12120, Thailand.
J Water Health. 2009 Mar;7(1):133-43. doi: 10.2166/wh.2009.010.
Urban canals play a major socio-economic role in many tropical countries and, particularly, Thailand. One of the overlooked functions that they perform is a significant attenuation of waste-related pathogens posing considerable health risk, as well as pollution attenuation in general. The study dealt with a comparison of three canals receiving: (i) municipal, (ii) mainly industrial and (iii) mainly agricultural wastewater, listed in order of progressively decreasing organic loading. The occurrence and fate of waterborne Cryptosporidium parvum, Giardia lamblia and Escherichia coli were monitored in the canals by both real-time PCR and conventionally for 12 months. The pathogens are etiological agents of an estimated 38% and 47% of diarrhea cases worldwide and in Thailand, respectively. The geographic information system (GIS) was used to evaluate and map point and, particularly, non-point pollution sources which allowed differentiating the canal sections in terms of predominant pathogen sources. The flowthrough canals, which can be viewed as waste stabilization ponds, were found to be efficiently removing the pathogens at the following generalized specific rates: 0.3 (C. parvum), 1.2 (G. lamblia), 1.8 (E. coli) log10/km.d in the dry season. The rates decreased in the rainy season for E. coli and G. lamblia, but increased for C. parvum which indicated different removal mechanisms. Data suggest that E. coli and G. lamblia were mainly removed through sedimentation and sunlight (UV) irradiation, while the likely mechanism for C. parvum was predation. Overall, the specific pathogen removal rates positively correlated with the canal organic loading rates in the rainy season. As an important result, an estimate of the municipal pollution mitigation by over 2280 km canals in the Greater Bangkok suggests that concomitant to the pathogens at least 36-95 tons of BOD5 is being removed daily, thereby saving the receiving Chao Phraya River and Bight of Bangkok, by far exceeding current, from major eutrophication problems.
城市运河在许多热带国家，尤其是泰国，发挥着重要的社会经济作用。它们所履行的一项被忽视的功能是对与废物相关的病原体有显著的衰减作用，这些病原体构成了相当大的健康风险，同时总体上也能减轻污染。该研究对三条接收不同废水的运河进行了比较：（i）城市污水，（ii）主要是工业废水，（iii）主要是农业废水，按有机负荷逐渐降低的顺序列出。通过实时聚合酶链反应（PCR）和传统方法对运河中水源性微小隐孢子虫、蓝氏贾第鞭毛虫和大肠杆菌的存在及去向进行了为期12个月的监测。这些病原体分别是全球和泰国估计38%和47%腹泻病例的病原体。地理信息系统（GIS）用于评估和绘制点源，特别是非点源污染，这使得能够根据主要病原体来源区分运河段。流经运河可被视为废物稳定塘，发现在旱季能以以下广义特定速率有效去除病原体：微小隐孢子虫0.3、蓝氏贾第鞭毛虫1.2、大肠杆菌1.8 log10/千米·天。大肠杆菌和蓝氏贾第鞭毛虫在雨季的去除速率下降，但微小隐孢子虫的去除速率增加，这表明去除机制不同。数据表明，大肠杆菌和蓝氏贾第鞭毛虫主要通过沉淀和阳光（紫外线）照射去除，而微小隐孢子虫的可能去除机制是捕食。总体而言，在雨季，特定病原体去除率与运河有机负荷率呈正相关。一个重要的结果是，对大曼谷地区超过2280千米运河减轻城市污染的估计表明，伴随着病原体的去除，每天至少有36 - 95吨生化需氧量（BOD5）被去除，从而使接纳的湄南河和曼谷湾远超过目前的状况，避免了主要的富营养化问题。
