State of water : Cambodia
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2.1.4. Water environment in the Mekong River Systems

The living environment, especially human health, is affected by the discharge of untreated and low quality treated wastewater into receiving waters. The foregoing review has shown that the major urban sanitation problems in Cambodia are technical, financial and institutional in nature. On the technical side, there is no public investment in public infrastructure dedicated solely for sewage. The existing storm drainage system is also used for sewage collection and conveyance. The second technical issue is the inadequacy of existing septic tank systems that are required by law to be installed in all new buildings. As stated above, the waste from these septic tanks flow into the storm drainage system for discharge into receiving waters without any treatment, thereby creating potential environmental pollution problems.

During the rainy season, there is enough dilution water to eliminate or reduce pollution in the receiving bodies of water. During the dry season, the drains mainly convey sewage. Hence, the concentration of pollutants is higher than in the rainy season. Moreover, raw sewage is discharged into the receiving bodies of water at a time when they would have lower amounts of water for dilution. Therefore, the combined sewerage system would tend to lead to water pollution during the dry season. In fact, there are reports that it is already causing growing pollution in the Mekong River and other main water bodies. A second problem with the combined sewerage systems in Cambodia is that they are not designed to prevent the deposition of solids within the storm drains during the dry season when they convey only sewage. Hence, organic solids (such as excreta in the sewage) tend to be deposited in the drains during the dry season. The decomposition of these solids gives rise to widespread odours at street inlets to the drains. It also generates corrosive gases like hydrogen sulfide that attacks concrete storm drains, shortening their design lives because of premature deterioration. Problems are not only limited to the dry season, however. There are reports that during wet seasons, a mixture of sewage and storm water often backs up into houses in low lying areas.

Sector engineers are aware of the limitations of the combined system. But some say they are unaware of alternatives. Thus, a lack of awareness of alternative solutions to urban sanitation problems is another significant issue in urban sanitation in Cambodia, as is also the case in many other countries.

Another technical problem is lack of access by the poor to public storm drainage systems used as combined sewerage for both storm water and sewage. Residents in high-income areas are able to connect their house sewers to storm drainage systems, as described above. However, for the poor, the cost of connecting to storm drains is too high. What this population requires is feeder infrastructure that would serve as a link between them and the storm drainage system. In the absence of such intermediate infrastructure, the poor discharge their waste close to residential environments. Thus in spite of growing needs, access by the poor to sanitation infrastructure is decreasing, resulting in increasing deterioration of environmental conditions.

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Table of contents > 2. River Basins > 2.1. The Mekong River System (Basin)
2.1.1. Introduction
2.1.2. Mekong River tributaries and Rainfall
2.1.3. Detailed survey of rainfall and surface water in the Mekong catchment
2.1.4. Water environment in the Mekong River systems Human activities threatening to water quantity Human activities threatening to water quality Case study on human factors threatening to the water environment Transboundary issues