Abstract
The technical feasibility of treatment of low strength wastewater by upflow anaerobic sludge blanket (UASB) reactor was experimentally investigated using an actual domestic wastewater at a HRT of 4.7 hrs in the temperature range of 25 to 13°C. The result obtained from a continuous flow experiment indicated a fairly promising system performance, i.e., the removal efficiencies of total CODcr, solid CODcr and BOD (based on influent total-BOD and effluent soluble-BOD) achieved to be 60-85%(70% in average), 73-83%(80%) and 66-92%(85%), respectively.
The removal rates of total COD and soluble COD depend on the influent strength, but not on the temperature. On the other hand the particulate organic matters in the influent were effectively removed by entrapment into the sludge bed. The hydrolysing rate of the entrapped organics within bed was significantly affected by temperature, that is, 58% of the entrapped particulate organics was liquefied at 25°C, whereas only 33% at 13°C.
The methanogenic activity of the sludge cultivated on the domestic wastewater at low loading rate (1.6 KgC0Dcr·m-3·d-1) decreased to 4%(for sucrose as a vial test substrate) and 10%(for acetate) of the seeded granular sludge which had been formed on carbohydrate at high loading rate (11 KgC0Dcr·m-3·d-1).
Similary, the contents of ATP and coenzyme F42O of the sludge decreased to 1/2-1/4 and 1/4 - 1/7, respectively, of the seeded granular sludge.
Furthermore, observation of morphological structure of the sludge fed on the domestic wastewater by scanning electrOn microscopy revealed that the granules had a tendency to be partly cracked and to be in a state of autolysis, even though remaining granular forms as a whole.
