Advances in Water Treatment and Enviromental Management

EUROPEAN DRINKING WATER STANDARDS 21– fungicides,– PCB and PCT.It must be remembered that drafting of the directive 80/778 began in 1974/75 at a timewhen the only compounds investigated were organo-chlorinated and organo-phosporouspesticides, and often for the latter only these that respond to electron capture, which meantthat it was possible to quantify all the compounds present with a single analysis.The maximum admissible concentration level of 0.1µg/l corresponds to the detection limit inthe years 70 to 75 and it must be stated that, in the law makers, pesticides correspond onlyto organo-chlorine and/or phosporous compounds, therefore these thresholds represent thetoxicity of these compounds.The difficulties met to observe the maximum concentration level for the herbicides, speciallyfor the triazines and the lengthy debate on the subject illustrates the part played by politicalfactors in determining standards. It is obvious that the standard adopted for the triazinesand the other pesticides cannot be the result of a strictly scientific approach. We are going tofind ourselves increasingly confronted with decisions made by politicians on matters for whichwe hold no scientific evidence.It is not surprising therefore that difficulties in applying such standards stir up the truedebate, the political one: who can and should take action ? who should pay ? what is thepriority action to be taken ?With a view to protecting the quality of drinking water, regulations have ben drawn up for theprotection of groundwater and surface water catchment sites. They include the installation ofdifferent protective perimeters round the intake areas. However, these measures are notalways easy to implement. The regulation must above all be backed up by a campaign ofinformation and widespread advisory and consultancy services to users of these plant protectiveproducts.There is a question to be answered, however: have we reached contradictory constraints, theprotection of water and agriculture, by imposing such a low level ? We hope that the answeris no and that we can find the solution.2—TREATMENTWater is largely contaminated by atrazine and simazine. Other pesticides appear at the tracelevel, but it is also important to study these that are likely to predominate on the market inthe coming years.Treatments have been tested on atrazine and simazine. Adsorption on granular or powderedactivated carbon and ozonation seems to be the more efficient treatments. The use of ozonationoften explains the high removal rates observed on treatment train. The efficiency achieved atthe outlet of the ozonation step varies between 25 and 50 % depending on the dose rates andthe contact time.Table 3: Extra operating costs required to respect the standard of 0.1µg/1of atrazine in the water