| Biofilm processes bear the advantages of stable removal efficiency, good resistance toshock loads, no sludge swelling or no need for backwashing or drawbacks, making it one ofthe most important methods to decontaminate wastewater. Heretofore, the moving bed biofilmreactor (MBBR) and the biological aerated filter (BAF), two of the novel biofilm technologies,have both become significantly effective treatments of wastewater due to their respectivecharacteristics. MBBR is now being applied wildly abroad, while with few reportsdomestically, among which are the ones on the phase of lab scale still. BAF is successfullydeveloped internally and put into practice in all kinds of projects at present. However, studyon the multistep MBBR-BAF reactors in tandem for wastewater treatment has never beenpresented before, thus making it a promising field to investigate.Proper disposing of paint wastewater is undoubtedly of great significance nowadays. Inthis paper, it presents the basic principles of MBBR and BAF and the reasons for putting thesetwo technologies in series. Moreover, it investigated the factors affecting the function of thetreatment system as well as its capacity to remove organic compound, suspended solids (SS)and turbidity.Firstly, the adsorption capacity of lava as the media of BAF reactors was monitored. Theresults showed that the system was able to remove 66.67% of the chemical oxygen demand(COD) when two reactors were used in tandem, the ratio of carriers filled into the reactorswas 70%, the temperature was set at 25oC and the hydraulic retention time (HRT) of singleBAF was more than 8h. This indicated that lava has an excellent adsorption capacity, thusbringing an approach for the integration of biological removal and adsorption possible.Secondly, the performances of two kinds of carriers supporting MBBR and BAF reactorsrespectively were compared in the process of pre-inoculation. It presented that pre-inoculationbiofilm benefited both treatment systems for a quick start-up. It took only one week to getthese two biofilm systems matured, allowing the effluent COD removal up to 80%,respectively.Then, a biofilm treatment system for a paint industry wastewater (mixed with someartificial sewage water) was designed, using two MBBRs followed by two BAFs in series. Nosolids separation and sludge handling was installed. The system performed well during thewhole experiment. With a very high specific biofilm surface area, MBBRs followed by BAFsoffer a compact process combination for complete biological treatment of paint wastewater.The experimental data presented that the average COD removal efficiency of the effluent wasas high as 93%. Finally, the paper reports the effects of removing SS and turbidity in this treatmentsystem. The average removal efficiency of SS in the effluent reached to 95.38% and theturbidity level had descended below the detection limit (lower than 3 NTU). Therefore, thetreated water was clear and transparent. Additionally, the investigated parameters reached thenational standard requirements. Meanwhile, the experiment data presented an interestingincrement in pH values of the outlet of MBBR1, with small changes in the other threereactors.
|
PDF Full Text Request