Innovative anaerobic upflow sludge blanket filtration combined bioreactor for nitrogen removal from municipal wastewater

In this research, a novel laboratory scale anaerobic/upflow sludge blanket filtration combined bioreactor was designed and operated to improve the efficiency of the upflow sludge blanket filtration process for the simultaneous removal of phosphorus and nitrogen from wastewater. The anaerobic/upflow sludge blanket filtration technique was developed by adding an anaerobic reactor to its influent and operated by varying the main process parameters in order to gain the optimum conditions. The results showed that biological removal efficiency of nitrogen and preservation of sludge blanket strongly depend on wastewater characteristics, hydraulic retention time, sludge age and process controlling parameters. The combined bioreactor performed a total nitrogen removal efficiency of 96.6% with the sludge age of 25 days, total hydraulic retention time of 24 h and optimum "chemical oxygen demand/nitrogen/phosphorus" ratio of 100/5/1. This ratio also improved the compaction quality of sludge blanket in the upflow sludge blanket filtration clarifier. The average specific nitrification and denitrification rates occurred during the process can be expressed as 4.43 mg NOx-N produced/g VSS.d and 5.50 mg NOx-N removed/g VSS.d at the optimum ratio, respectively. To avoid sludge rising due to denitrification process, the optimum total hydraulic retention time of 16 to 24 h was achieved based on the effluent quality. This study suggested that the anaerobic/upflow sludge blanket filtration bioreactor at the optimum operational conditions can be an effective process for removal of nutrients from municipal wastewater

Detection of phenol degrading bacteria and Pseudomonas putida in activated sludge by polymerase chain reaction

Phenol is one of the organic pollutants in various industrial wastewaters especially petrochemical and oil refining. Biological treatment is one of the considerable choices for removing of phenol present in these wastewaters. Identification of effective microbial species is considered as one of the important priorities for production of the biomass in order to achieve desirable kinetic of biological reactions. Basic purpose of this research is identification of phenol-degrading Pseudomonas Putida in activated sludge by polymerase chain reaction [PCR] that has high speed and specificity. In this research, 10 various colonies of phenol-degrading bacteria were isolated from municipal activated sludge and the rate of phenol removal and growth rate of these bacteria were assessed in different concentrations of phenol [200 - 900 mg/L]. Confirmation of the largest subunit of multicomponent phenol hydroxylase [LmPH] gene and gene coding the N fragment in Pseudomonas Putida-derived methyl phenol operon [DmpN gene] through PCR were used for general identification of phenol-degrading bacteria and Pseudomonas Putida, respectively. Presence of a 600 bp [base pairs] bond in all of isolated strains indicated that they contain phenol hydroxylase gene. 6 of 10 isolated bacteria were Pseudomonas Putida because they produced a 199 bp PCR product by DmpN primers. According to PCR results in this study, the best phenol-degrading bacteria that can utilize 500 - 600 mg/L phenol completely after 48 hours incubation, belong to Pseudomonas Putida strains. It is clear that use of isolated bacteria can lead to considerable decrease of treatment time as well as promotion of phenol removal rate

Effects of 4-chlorophenol loadings on acclimation of biomass with optimized fixed time sequencing batch reactor

Chlorinated phenols in many industrial effluents are usually difficult to be removed by conventional biological treatment processes. Performance of the aerobic sequencing batch reactor treating 4-chlorophenol containing wastewater at different loadings rates from 0.0075 to 1.2 g4CP/L.d was evaluated. The sequencing batch reactor was operated with fill, react, settle and decant phases in the order of 10:370:90:10 min, respectively, for a cycle time of 8 h at 10 days solid retention time and 16 h hydraulic retention time in the stable period. The effects of 4-chlorophenol loadings on the 4-chlorophenol and chemical oxygen demand removal percents, yield coefficient [Y], biomass variation and sludge volume index were investigated. High chemical oxygen demand removal efficiencies [95 +/- 3.5%] and approximately complete 4-chlorophenol removal [>99%] were observed even in the absence of growth substrate. The degradation of 4-chlorophenol led to formation of 5-chloro-2-hydroxymuconic semialdehyde, which was more oxidized, indicating complete disappearance of 4-chlorophenol via meta-cleavage pathway. A compact sludge with excellent settleability [sludge volume index=47 +/- 6.1 mL/g] developed during entire acclimation period. High removal efficiencies with sequencing batch reactor may be due to enforced short term unsteady state conditions coupled with periodic exposure of the microorganisms to defined process conditions which facilitate the required metabolic pathways for treating xenobiotics containing wastewater

Performance evaluation of an anaerobic baffled reactor treating wheat flour starch industry wastewater

Feasibility of the anaerobic baffled reactor process was investigated for the treatment of wheat flour starch wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a reactor [with a volume of 13.5 L and five compartments] with diluted feed of approximately 4500 mg/L chemical oxygen demand was accomplished in about 9 weeks using seed sludge from anaerobic digester of municipal wastewater treatment plant. The reactor with hydraulic retention time of 72h at 35°C and initial organic loading rate of 1.2 kgCOD/m3.d showed 61% COD removal efficiency. The best performance of reactor was observed with an organic loading rate of 2.5 kgCOD/m3.d or hydraulic retention time of 2.45 d and the COD conversion of 67% was achieved. The system also showed very high solids retention with effluent suspended solids concentration of about 50 mg/L for most organic and hydraulic loadings studied. Based on these observations, the ABR process has potential to treat food industrial wastewater as a pretreatment and is applicable for extreme environmental conditions