EVALUATION DE LA QUALITE PHYSICOCHIMIQUE ET BACTERIOLOGIQUE DES EAUX USEES BRUTES ET EPUREES DE LA VILLE D’OUARGLA. POSSIBILITE DE LEUR VALORISATION EN IRRIGATION

Abstract

Ouargla area had a serious problem of excess water caused in part by a topographically flat receiving environment and hydrogeologically endoreic. In other hand, discharge of wastewater and agricultural drainage water increased the groundwater level. The development of the network of agricultural drainage and implementation of wastewater treatment plants (Treatment plant of Said Otba, Sidi Khouiled and N’gouss) contributed to stitch down the level of the of aquifers valley. Ouargla city has an aerated lagoon treatment plant since 2009 which serves to reduce the pollution of wastewater for possible reuse in irrigation. The objective of this study is to monitor the physicochemical and bacteriological quality of raw and treated wastewater of Said Otba treatment plant to detect anomalies that may exist at the treatment plant and to able to reuse its treated wastewater for irrigation. The physico-chemical and bacteriological results obtained revealed that the raw wastewater has a high enough organic nitrogen and bacteriological pollution. The solids and nitrogen compounds removal appear ineffective due to massive algal blooms in the various stages of biological treatment in particular the finishing basin. The results of microbiological analysis confirmed the presence of various germs such as total bacteria, total and faecal coliforms, faecal streptococci and sulphite-reducing clostridia in number greatly appreciated.