WHO Drinking Water Quality Research Articles

Development of boron reduction system for sea water desalination

Since boron has been showing to induce male reproductive impediments in laboratory animals, the 1993 WHO guidelines for drinking water quality set the recommended guideline value at 0.3 mg boron/l based on the NOEL (no-observed-adverse-effect level). Since boron is not effectively removed by the conventional water treatment not only for drinking water and domestic wastewater treatment, the concentration in ambient water as well as drinking water is affected by its consumption such as for soaps and detergents in the catchment area. Boron is also affected by leaching from the surrounding geology, drinking water derived water sources affected by a weak alkali spring contains high level of boron. Since the rejection ratio of boron is extremely less than that of salts in RO membrane system applying to drinking water supply in the areas where scarce a fresh water resources, desalinated water contains higher level of boron than that of WHO drinking water quality guidelines. In order to develop of boron treatment system either fresh water or desalinated water, multi stage RO membrane treatment system has studied by using a pilot plant. The boron rejection of RO membrane depends greatly upon pH and driving pressure of RO process. However, the boron rejection does not depends upon its concentration of raw water. Therefore, it is necessary to apply multi stage RO membrane treatment system for producing a finished water that meets the WHO drinking water quality guideline level of boron. Since the secondary and third RO membrane treat less dissolved salt concentration such as observed in fresh water, the driving pressure of RO process for removing boron can operate at low pressure such as about 0.6 to 1.3 MPa. Therefore, multi stage RO membrane sea desalination process and a low pressure RO process can be recommendable for boron management with a reasonable additional cost in drinking water supply.

WHO drinking water quality guidelines for selected herbicides.

Following the successful introduction of its Guidelines for Drinking-Water Quality in 1984, the WHO Regional Office for Europe was approached by the Government of Italy to develop, as a matter of urgency, recommendations for guidelines levels of certain herbicides found in drinking water supplies. Realizing the extent of the problem, the Regional Office for Europe organized two consultations to develop drinking water quality guidelines for the following 11 herbicides most commonly used in Italy: alachlor, metolachlor, pyridate, atrazine, molinate, simazine, bentazon, pendimethalin, trifluralin, MCPA and propanil. The presence of these and other herbicides in ground and surface water has been reported in several countries. Although the main purpose of these guidelines is to provide guidance to the Government of Italy in making risk management decisions, the information given was also intended to assist the other countries of the European Region in setting standards or in developing alternative control procedures where the implementation of standards is not feasible. The purpose of this paper is to review the process of health risk assessment used in the development of the WHO drinking water quality guidelines for selected herbicides. It will also reveal the major dilemmas and concerns expressed by the participating experts during the process of scientific deliberations, in the interests of understanding the complex issues involved in reaching the bare figures of the recommended guidelines.