English abstract
ABSTRACT
Shortage of water in arid and semi arid regions leads to a search for other sources such as reuse of domestic wastewater. Greywater is a component of domestic wastewater, which is defined as all the wastewater that drains from the household except the toilet water. In this study a sequencing batch reactor is used to treat greywater which is an activated sludge process that operates in time rather than in space and consists of five different phases: fill, react, settle, draw and idle. Samples of greywater were collected from an Omani household.
All the experiments were conducted in a 25 bench scale plexiglass single tank reactor with one discharging port placed at the bottom of the reactor. The reactor was of cylindrical shape, 37 cm in height and 29 cm in diameter and the volume prior to fill was 20 liters.The experiment showed the capability of the sequencing batch reactor in treating greywater with reduction of chemical oxygen demand (COD) ranging from 75% to 94%, and percent Tenn removal of suspended solids (SS) ranging from 65% to 100%. The obtained results are very satisfactory and meet the Omani standards where the maximum value of COD allowed is 150
mg/L and the highest value obtained for post treated water is 124 mg/L. In term of SS, the maximum value allowed by Omani standard is 15 mg/L and about 80% of SS values obtained are below this limit. The biomass seeding of the system ranged from 30% to 35%. The 11 operational modes that were investigated in this study were 0.5 hr fill and 4.5 hrs react, Ihr fill and 4 hrs react, 1.5 hrs fill and 3.5 hrs react, 2hrs fill and 3 hrs react, and 2.5 hr fill and 2.5 hrs react. A higher loading of organic matter gave better results than using low loadings. As organic loadings increased the substrate removal efficiency, also increased. The excellent performance of SBR was achieved when the fill time was 40% of the track time at operational mode of 2 hrs fill: 3 hrs react. An excellent settlement characteristic of sludge was obtained through use of SBR and the problem of sludge bulking or foaming was absent.
