Waste stabilisation pond sewage treatment system : its appropriateness to a regional city of Thailand

摘要

An investigation of Khon Kaen WSP revealed that the WSP was more appropriate to theudThai regional cities' situation in both sewage treatment objective and socio-economicudcontext. The WSP was capable of treating raw sewage meeting Thailand's effluentudstandard in BOD, pH, total coliform and faecal coliform counts, except TSS. Sunlight, temperature, pH, phosphate, nitrate, retention time, pond geometry, pondudlocation towards the wind direction and removal of algal mats appeared to be majorudfactors influencing the biological pollutant degradation activities inside the ponds.udOffensive odour, as a main public complaint about the plant, resulted from the abundanceudof floating algal mats.udSome conventional WSP design equations were found to be less effective in effluentudquality prediction compared with the actual pond performance. The result of the analysisudof some of the contemporarily designed BOD loading equations applied to this plantudshowed that such equations were less appropriate to the Khon Kaen city environment.udThe actual BOD loading-removal linear equation investigated from this existing plantudcould be the best method for future WSP development in this region.udThe plant, with low costs of construction, operation and maintenance, was found to beudcost-effective and suited to Khon Kaen city conditions. The plant required moreudoperators and the present workers need additional training and experiences. Supplyingudthe operators with equipment for removing algal mats appeared to reduce offensiveudodours and increased pond performance. Due to TSS level in the final discharge beingudover the country's standard, initiating any measure for decreasing TSS would beudnecessary for this plant.