Effects of C/N ratio on pollution removal efficiency and cell proliferation during the bioconversion of wastewater by photosynthetic bacteria

Photosynthetic bacteria (PSB) bioconversion is a new technology for wastewater treatment and resource recovery. The C/N ratio is an important factor in biological wastewater treatment. For the first time, the efficient C/N ratio range for PSB bioconversion, and the effects of the C/N ratio on wastewater treatment efficiency and cell proliferation, were studied. The results of this study showed that PSB bioconversion was efficient when the wastewater C/N ratio was within the range of 400-0.1. Chemical oxygen demand (COD) removal was higher than 60% in this C/N range. The change in the NH4⁺ _-N concentration was fitted by the logistic model for each C/N ratio. The V_maxof nitrogen removal was similar to that of other technologies and it decreased as the C/N ratio decreased. This shows that this technology exhibits reliable pollutant removal in the C/N ratio range of 400-0.1. The nitrogen transformation study indicated that the PSB might use a specific mechanism under a low C/N ratio. PSB cell proliferation was fitted by the logistic model in the C/N ratio range of 400-2, and μ_maxwas found to be not correlated with the C/N ratio. The protein content in the cells was 40-60% in the C/N ratio range of 400-0.1. The results showed that PSB bioconversion technology has a very high resource value and the value of the C/N ratio places little restriction on it.