Study On Organic Wastewater Treatment By Pressurized Biological Contact Oxidation Technology

The conventional aerobic wastewater treatment technology is a fundamental and constantly used technology. At the same time, several disadvantages exist in the technique, such as high aeration energy consumption, high land occupancy and low volume load. Moreover, high sludge yield and large sludge disposition expense bring on a great operation payout. The pressurized biological contact oxidation reactor as a new aerobic wastewater treatment technology was comprehensively studied. Several combined technologies based on actual wastewater and treating needs were also researched, concluding simultaneous nitrogen and phosphorus removal of anaerobic phosphorus release-pressurized biological contact oxidation process, pesticide wastewater treatment by hydrolysis acidification- pressurized biological contact oxidation process. The following results were obtained:The operating capability and treating effect of pressurized biological contact oxidation process were generally studied. Compared with conventional biological contact oxidation process, as the jet aeration-pressurized biological contact oxidation process adopted pressure and self-priming jet aerator as aeration devices, the aeration capability was remarkably advanced, and the air-water ratio reduced obviously. Jet aeration can enhance the activity of dissociative microorganism effectively. The best hydraulic residence time(HRT) of domestic sewage treated by pressurized biological contact oxidation process was about 1.0 hour. When the volume load was less than 15 kgCOD/(m3·d), the dissolved oxygen(DO) could maintained in 4~5mg/L while the air-water ratio was only 1~4. The technology could get a high COD removal ratio as 80~95%, and COD of the treated water could keep lower than 100mg/L.The salt and pressure resistant ability of microbe in pressurized biological contact oxidation reactor was studied. The studies showed that even the biofilm was not domesticated and the salt concentration of the wastewater was as high as 20g/L, The microorganism in pressurized reactor could endure a higher salt concentration impact than which in a conventional activated sludge or biofilm process. Salt-tolerant microorganism could exist in pressurized condition after a period of domestication, which ensured the effect of organic wastewater with high salt concentration treatment by pressurized biological contact oxidation process. Low pressure (0.1~0.4MPa) had little impact on microorganism metabolism, and higher pressure made no difference to oxygen uptake rate of biofilm and COD removal ratio. The oxygen uptake rate under the same volume load lied only on the dissolved oxygen concentration.Two aspects of excess sludge reduction mechanism was included in pressurized biological contact oxidation process, including uncoupling metabolism (substrate-sufficient conditions and high concentration of dissolved oxygen) and cryptic growth (biofilm and presence of anoxic layer). The pressurized bio-contact oxidation process was an effective excess sludge reduction technology. The sludge yield was about 0.07~0.14 kgSS/kgCOD when the volume load changed within 16.8 kgCOD/(m3·d), which showed that the technology had a remarkable superiority of excess sludge reduction compared with conventional technologies.