Research On Mesophilic And Psychrophilic Anaerobic Treatment Of Domestic Wastewater And Sludge Granulation Process

Rapid urbanization and economic development in China has led to the annual increase of quantity of discharged municipal wastewater. Therefore, it becomes more and more important to develop appropriate wastewater treatment process, which combines high treatment efficiency with low capital investment, maintenance costs and simple operation requirements, especially in most of small cities and towns. Anaerobic treatment technology is an attractive alternative process for small communities wastewater treatment because its advantages including lower energy consumption, lower investment, operation and maintenance costs, little sludge production and energy recovery in the form of biogas and etc. It seems to be an ideal and sustainable solution for water environmental protection.Over the last two decades, researchers all around the world have realized the significance of the high ratio of SRT/HRT by the studying on the dynamics theories, and developed a series of advanced anaerobic reactor systems along with the deep understanding of the biology fixation technologies such as sludge granule and biofilm. Although the anaerobic treatment of domestic sewage has been applied on a large scale in several tropical countries (many as UASB reactors) with great success, the process is so far not applied on a full scale in sub-tropical countries. It's a big challenge to extend the experiences from tropical areas to sub-tropical and moderate climate areas.In this paper, based on the newest relevant research results, we researched the granulation process in UASB reactors which treating very low strength wastewater, inoculated with digested sludge. Then, a feasible municipal wastewater treatment process, the AF+AH system, seeding with the granular sludge we had cultivated, was developed and the process performance was discussed.It shows that the sludge granulation can be realized in about two months even the influent concentration low as 100-200mgCOD/L at ambient temperature(25-9℃) in UASB reactors. The average diameter of the granule is more than 0.5mm. The SVI of the granule is between 23.4 to 27.7 ml/g, means good settlebility. The SMA of the granule is 0.05-0.23gCOD/(gVSS.d), depending on the used temperature and influent concentration. The granule growing in the wastewater of 100-200mgCOD/L and at the temperature of 25-9℃ has the lowest SMA of 0.05 gCOD/(gVSS-d).The AF+AH system was used to treat the real sewage seeded with the mixture of...