Optimization Of Treatment Process For High-Strength Syrup Wastewater

This research, which has taken from a real engineering project, is focused on the treatment of syrup wastewater with high COD, high SS and low pH.With actual engineering facilities, performances of three kinds of process, such as UASB, coagulation, hydrolytic acidification -biological contact oxidation process, are compared and operation problems are discussed. The objectives of this research are to choose the most effective wastewater treatment process and to optimize the design control parameters.The results show that the hydrolytic acidification -biological contact oxidation process is feasible to treat high-strength syrup wastewater. Even if the wastewater quality and quantity change greatly, the system showed very good stability.The hydrolytic acidification plays an important role to remove SS and reduces energy consumption. The removal rate of SS in the hydrolytic acidification reactor is 44.8%, which is the highest rate of the removal in the all process units. Through the hydrolytic acidification, the biodegradability of wastewater is enhanced.The first biological contact oxidation reactor and the hydrolytic acidification reactor play an important role in the removal of COD, where the total removal rate of COD is 63.3%. But the removal rate of COD in the secondary biological contact oxidation reactor is only 10.5%.The engineering practices shows that, it is important to have a reasonable water distributor for UASB system and not feasible to use a bore pipe as a wastewater distributor.The results get from coagulation experiment shows that FeSO4 and lime milk are able to increase the removal rate of COD, but causes lots of sludge. The removal rate of COD reaches 35% and SS reaches 85%, when adding 250mg/L reagent to thereactor. The result also shows that the larger part of COD in the syrup wastewater is soluble.It is necessary to design and use secondary clarifier in treating the syrup wastewater. The secondary clarifier makes the key function to reduce the losing of biomass in the startup stage. In the steady stage, the secondary clarifier makes a function to increase biomass quantity in contact oxidation reactor, at the same time, it will improve secondary effluent quality.It also shows that, it is necessary to add the nitrogen as nutrient and regulate the pH because the wastewater' s nutrient component is single and pH is low.According to me actual operation results, the optimum volumetric loading of the hydrolytic acidification reactor is 8.273 kgCOD/m3.d, and of the biological contact oxidation reactor is 3.473 kgCOD/m3.d.The screening pretreatment is also important in the treatment of the syrup wastewater. It had better to design mechanical screen with high performance as the last fine screen. As to some high organic strength wastewater, such as flush water (COD>10000mg/L), it is necessary to use separate coagulation reactor as pretreatment process.