Study On The Cause And Control Of Sludge Bulking In Treatment Of Printing And Dyeing Wastewater

Printing and dyeing wastewater is one of the main pollution sources that cause waters polluted in our country. Now, traditional biochemical and physico-chemical methods are used in treatment of printing and dyeing wastewater. Because of characteristics of huge quantity, complex composition, plenty of difficult biodegradable materials and color removal difficulty, traditional methods have bad results or high operating cost, which results in most part of printing and dyeing wastewater can't reach environmental standards when put out. Compared with traditional biochemical and physico-chemical methods, a process combining hydrolysis acidification, UASB and SBR is characterized by low investment, low operating cost and simple operation. The combined process can make printing and dyeing wastewater reach standards stably when it is put out, however, sludge bulking often occurs in the process.It is widely accepted that extensive growth of filamentous bacteria in activated sludge is the main cause of sludge bulking. In order to understand the causes of the sludge bulking, in-spot investigations of the operating conditions and sludge bulking conditions of the hydrolysis acidification-UASB-SBR combined process were taken at wastewater treatment plant of Nanshan Printing and Dyeing Factory of Mianyang. From the investigations, lack of nitrogen and phosphorus, oxygen deficiency in aeration basin of SBR, high concentration of sulfide in the wastewater is found. Filamentous bacteria evolution in activated sludge was monitored using Eikeboom's methods, which were mainly Thiothrix, type 021N and one kind of filamentous bacteria similar to type 1701.In-spot imitation experiments were carried. It is found that sludge bulking control cannot be achieved only by addition of nitrogen and phosphorus, but can be effectively by pre-aeration. In condition of increasing pH of aeration basin at 8.5 or so, sludge bulking can also be controlled without pre-aeration.Organic loading on sludge bulking was studies. The experimental result shows that if low organic loading condition can be maintained, sludge bulking will occur. Proper organic loading scope was also given out when combined process is used. Sludge bulking in different dissolved oxygen concentration conditions was studied,...