Seyed Amin Mirmohammadi, Tatsuya Funabiki, Toshikazu Suenaga, Takehiko Gotoh, Tomonori Kindaichi, S. Nakai
High Resolution Image Download MS PowerPoint Slide As the main challenge in the partial nitrification (PN) process is controlling the nitrate production by nitrite-oxidizing bacteria (NOB), this research aims to propose a pH-adjustable carrier gel to suppress the activities of nitrite-oxidizing bacteria (NOB) but not ammonium-oxidizing bacteria (AOB) in a biological nitrification process, thereby managing the formation of nitrite and nitrate. To this end, the cryopolymerization method was used to synthesize superporous gels based on N, N- dimethylaminopropylacrylamide (DMAPAA) and N, N- dimethylacrylamide (DMAA) monomers. The internal pH values of the gels were adjusted through the change of monomer amounts in the synthesized copolymer, ultimately selecting gels with a pH of 10.8 as the preferred carrier for AOB and NOB to achieve a stable PN. The performance of gels inoculated with the aforementioned bacteria in wastewater treatment was significantly remarkable, as nitrate production was almost completely inhibited for 20, 12, and 16 days while the nitrite concentration was at values of 40.6, 24.5, and 14.8 mg-N/L at initial ammonium concentrations of 100, 50, and 30 mg-N/L, respectively. These findings demonstrate a significant reduction in the growth and activity of NOB, in contrast to the increased ability of AOB. Furthermore, submerging the used gels in a 0.1 M NaOH solution to elevate their internal pH levels extended their usability for at least another 40 days. These findings suggest that poly(DMAPAA- co -DMAA) gel is a suitable support and stabilization medium for nitrifying bacteria, enabling a stable PN process.