Improving the efficiency of involved bacteria in aeration tanks of waste water stations

Abstract

Advanced bioremediation in waste water and sewage treatments currently represents one of the important aspects of biotechnology. The removal of pathogenic microorganisms, complex hydrocarbons, heavy metals and nutrients were intensively investigated. The present work aims to improve the efficiency of involved bacteria in aeration tanks for maximizing mineralization process of organic substances and consequently reduce the time of the treatment process. Other target is the elimination of nutrients (N & P) to avoid their environmental and hazardous effects. In order to achieve these goals, isolation and identification of dominant microflora in aeration tanks were carried out and highly active strains were selected. Trails are newly done for hybridization or cloning one or more of dominant strains to increase their oxidizing efficiency. A pilot experiment was established in a green house to stimulate biological stage of municipal plant and to test the achieved genetically modified strains (Modell experiment). Also, monthly data were recorded of 20 parameters to highlight and controlling input and output of wastewater station of Taif city. Biological oxygen demand (BOD 5) and chemical oxygen demand (COD) clearly decreased in out fluent indicating lower organic load. The decrease of total organic carbon (TOC), total dissolved solids (TDS) and total suspended solids (TSS) assured the previous obtained data. Presence of large amount of dissolved oxygen (DO) in the out fluent means the efficiency of aeration pumping process. Nitrate content (NO 3 -) and nitrite content (NO 2 -) were sharply decreased in the out fluent indicating the higher requirement of H-acceptors. NH 3 (ammonia content) decrease, however total Kjeldahl Nitrogen (TKN) increase were due to intensive microbial bodies load. Total hardness (TH) decrease, which means lower conc. of Ca ++ and Mg ++ and better quality of output water. pH values were slightly decreased because of microbial acidic products. Turbidity was dramatically reduced because of different precipitation process. Phosphorous (P) content and Sulfate (SO 4 =) content decreased indicating consumption or fixion in microflora bodies. Otherwise, chloride (Cl -) content were increased in outfluent because of chlorination process. Oil and grease were quite reduced in the outfluent. Finally, different heavy metals and hydrocarbons were found in the limit or lower than the permit levels globally. Total microbial count increased considerably in outfluent, especially in summer months; however, fermentative bacteria were very low because of enough O 2 present in outfluent. Only 15 strains of 280 isolates (about 5.4%) were found to be highly active in mineralizing organic substances which were completely identified. The most active one was used to modify the dominant strains by cloning technology and reinoculated in the pilot experiment