Study on Aerobic Digestion of Sludge in a Sewage Treatment Plant in France

Since early 2008,the Cagnes-sur-Mer water treatment plant has been operated with high loading rate to improve the effluent quality.While this operation increased the effluent sludge quantity correspondingly increased the costs of sludge disposal and transportation.Therefore the sludge was stabled adopting aerobic process using pure oxygen made in site.The influent and effluent sludge of the aerobic digester were sampled and test daily for testing items of MLSS,MLVSS,pH,COD,dryness and so on.The results showed that by aerobic digestion,the organic materials of the sludge reduced by more than 60%.It means 40 tons of sludge was reduced per month.Furthermore,the sludge of the digester could be pumped out even in Sunday due to the operation of the digester.So it alleviated the problems of over high concentration of sludge in the aeration tank on Monday due to no discharging sludge on Sunday.Thereby the effluent water quality was improved.The digester temperature was maintained at about 40°C without any heating device due to the exothermic reaction within the digester.The data collected by this project are helpful for development of this process.And it provides a novel method for the sewage treatment plants who want to reduce the sludge.Because it has advantages of low cost,getting quick returns and simple operation