Enviromental impact of point pollution sources

[摘要] English: Due to the importance of groundwater as an alternative for supplementing existingsources of this precious fluid, any study that may help in understanding thecomplexity of the groundwater environment is an asset. Therefore this dissertationwas written with the sincerest hope that the people and organisations involved withgroundwater will gain a better understanding of it.The need to protect our groundwater sources has become very important and thereforea different, more practical approach to delineate borehole protection zones wasconsidered based on the existing standards set by Germany and other Europeannations.As part of the study, emphasis was placed on the effect of the unsaturated (vadose)zone on the migration of pollutants before it reaches the groundwater environment.Field tests on the saturated as well as unsaturated zones were conducted with aconservative tracer (Fluorecein) as well as microbial tracers (bacteriophages), to assistin the delineation process. Thereafter it was decided to propose that three protectionzones should be assigned depending on i) the size of the population and ii) thevulnerability and importance of the aquifer. The effect of a pollutant on human healthand the possibility of fatalities were the criteria for deciding which protection zone isapplicable under given circumstances.Protection zone I involves fencing off the immediate area around the borehole (aradius of 5 m is proposed) as well as the necessity of a well-constructed sanitary seal.Where a borehole supplies water to less than 20 people, a sanitary seal will besufficient.To determine the extent of protection zone II, the idea was to protect the drinkingwater from microbial (bacteria and viruses) and nitrate pollution. Emphasis wasplaced on these two parameters because of their association with pitlatrines and septictanks. Methods to estimate the fracture extent are proposed and, depending on theestimation of the nitrate and bacterial travel times and loads, a guideline to use i) halfthe fracture extent, ii) the whole extent of the fracture or iii) double the fractureextent, is proposed.Only if there is the possibility of a hazardous substance that may pollute thegroundwater, it is proposed that protection zone III be assigned. The use of the wordhazardous could make the decision more complex and therefore the issue of riskassessment and management is also addressed very generally in this dissertation. Theproposed extent for protection zone III is the whole catchment area of the borehole.A programme called Borehole Protection Zone (BPZONE) was developed bymaking use of Microsoft Excel to assist the person(s) responsible in the decisionmaking processes of delineating borehole protection zones.Information gathered during the field tests conducted at the Campus Test Site of theUniversity of the Free State as well as the Meadhurst Test Site outside Bloemfontein,yielded very positive results, in terms of delineating protection zones.

[发布机构] University of the Free State