Investigation of nutrient removal and associated microorganisms in advanced biological treatment processes

Gradual increase in world?s population has lead to increase in wastewater generationrates, which, in turn, brings the necessity of development of treatment systems thatare more cost-efficient and more environmentally friendly.This study focuses on the use of a pilot-scale biological treatment process of totalvolume 8.6 m3 and capacity 10 m3.d-1 installed within the ISKI Ataköy AdvancedBiological Wastewater Treatment Plant. Two different processes, one being the newlydevelopedModified five-stage Bardenpho process and the other one being two-stagecascade-feed biological nutrient removal process, were evaluated in the aspect theirtreatment performances. Besides, microorganism speciation was done during theoperating period for each process.In the first stage of the study, the treatment of the domestic wastewater with COD =645±115 mg.L-1, TKN = 79±13 mg.L-1, NH4-N = 52±9 mg.L-1, NO2-N = 0.04±0.03 mg.L-1,NO3-N = 0.11±0.10 mg.L-1, TP = 7.9±0.8 mg.L-1, PO4-P = 3.4±0.7 mg.L-1, and SS =321±156 mg.L-1, by newly-developed Modified five-stage Bardenpho process with arecycle ratio of 80% was investigated. The average treatment efficiencies for COD,TKN, NH4-N, TP, PO4-P, and SS by the newly developed process during the whole studyperiod were 76%, 63%, 68%, 80%, 72%, and 80%, respectively. The results showed thatthe system has reached steady-state conditions after 8 weeks of operation. Understeady-state conditions, the treatment efficiencies were calculated as 87%, 86%, 93%,89%, 88%, and 94%, respectively. Microbial speciation was also done during the whole period, the results of which suggested that Nitrosomonas, Nitrosospira,Accumulibacter, Dechloromonas, Firmicutes, and some other uncultured genus wereresponsible for the treatment during the steady-state conditions.In the second stage, the process was converted into a Two-Stage Cascade-FeedBiological Nutrient Removal Process by feeding fifty percent of the inlet wastewater (5m3.d-1) to the bio-P unit, and the rest (5 m3.d-1) to the denitrification2 unit by keepingall other operational parameters constant. Average wastewater characterizationduring this stage of the study COD = 555±60 mg.L-1, TKN = 72±7 mg.L-1, NH4-N = 44±7mg.L-1, NO2-N = 0.03±0.02 mg.L-1, NO3-N = 0.06±0.04 mg.L-1, TP = 8.1±0.4 mg.L-1, PO4-P= 4.0±0.5 mg.L-1, and SS = 316±47 mg.L-1. The treatment efficiencies for COD, TKN, NH4-N, TP, PO4-P, and SS were calculated as 87%, 84%, 93%, 90%, 88%, and 95%,respectively. It was determined that the microorganisms responsible for the treatmentin this Two-Stage Cascade-Feed Biological Nutrient Removal Process wereNitrosomonas, Nitrosospira, Accumulibacter, Dechloromonas, and some otheruncultured genus.Comparing the treatment performances of and operational conditions for bothprocesses, newly-developed Modified five-stage Bardenpho Process would be a betterselection for medium-strength domestic wastewaters. On the other hand, this study isto contribute much to the current literature considering the fact that literature data iscomposed mostly of lab-scale studies.