Selection of an effective sludge dewatering system for a small wastewater treatment plant

The Jahra Plant was commissioned in 1981 as a secondary treatment plant emp loying the extended aeration process. The plant has been upgraded since tha t time by constructing additional tertiary filtration units to improve effl uent quality. The plant has a design capacity of 66 000 m(3)/d. At present, the daily inflow to the plant is about 47 000 m(3)/d of domestic sewage. T he sludge produced at the Jahra Plant can be classified as excess activated sludge which combines the primary and secondary solids. At present, there are 30 drying beds receiving about 100 m(3) of sludge daily. Sewage-sludge production represents about 0.5% of the total flow treated at the plant and is increasing yearly with increases in population and water consumption. P resent dewatering systems are not adequate to cope with expansion in sewage treatment. Increasing the capacity of the existing plant would require mor e drying beds that could exacerbate existing odor problems. Some dewatering systems, such as the belt filter press and the centrifuge, have been teste d to determine the most effective one under local conditions. Appropriate p olymer doses for thickening have been determined. This paper describes pres ent sludge dewatering units and operating techniques which have been develo ped during the operation of this facility. (C)1999 Elsevier Science Ltd.