An Oxic–Hydrolytic–Oxic Process at the Nexus of Sludge Spatial Segmentation, Microbial Functionality, and Pollutants Removal in the Treatment of Coking Wastewater

Abstract

Toxic inhibition and wash-out of nitrifying bacteria in traditional single-activated sludge processes frequently cause instability of nitrification in industrial wastewater treatment and limit the total nitrogen (TN) removal efficiency. A novel oxic–hydrolytic–oxic (O/H/O) process based on a three-sludge regime was developed to treat coking wastewater with a high C/N ratio and biological toxicity. The results demonstrated that high COD removal (89.6%, 91.3%, 90.4%, and 87.1% in four different modes) was achieved with the complete elimination of phenol, sulfide, total cyanide, and thiocyanate. TN removal varied from 14.0% to 88.7% at an influent flow of 1.6–2.0 kg of COD m–3 day–1, depending on prenitrification, internal recycling, and the presence of a sufficient carbon source for denitrification. The first oxic (O1) and hydrolytic (H) reactors made predominant contributions to the removal of organic and toxic pollutants. The removal of these pollutants guaranteed a stable and favorable environment for nitrification in the second oxic (O2) reactor, in which high ammonium removal was observed because of the predominance of Nitrosomonas and Nitrospira. The O/H/O process has the potential to become a promising industrial wastewater treatment process because it promotes functions that are independent of microbial and process stability with respect to the removal of pollutants, especially nitrogen.

Evaluation of Carbon and Nitrogen Removal Performance of the Oxic-Hydrolytic and Denitrification-Oxic Process in Coking Wastewater Treatment

“…Our group has studied coking wastewater treatment technology for over 20 years, and we have designed and operated many coking wastewater treatment projects. Our team has been investigating coking wastewater from 26 projects and found that the COD of coking raw wastewater is 3000–5000 mg/L. − ,, The raw wastewater enters the regulation reservoir, and then, the effluent from the regulation reservoir (biological inflow) enters the biological treatment process. The biological influent wastewater quality used for the calibration of TCW-ASM3 model parameters is shown in Table .…”

“…Direct anaerobic/anoxic treatment was shown to be inefficient for the treatment of coking wastewater with toxic pollutants. , For toxic wastewater, the aerobic reactor should be placed forward due to the strong resistance of aerobic sludge to OLR and toxicity. Wei et al have showed that the O/H/O process is the most cost-effective process for coking wastewater treatment and has the potential to be extended to the treatment of other wastewaters with similar characteristics . The O/H/O process used biological fluidized bed reactors to form a three-sludge system, which ensures the stability of microbial population structure and process operation.…”

“…4 Among them, CAS has been widely applied in WWTPs due to its efficiency and economic features. The CAS emerges in various process configurations according to the unit reactor layout, such as anaerobic-anoxic-oxic (A/A/O), 5 oxic-anoxic-oxic (O/A/O), 6 anoxic-oxic (A/O), 7 anoxic-oxic-oxic (A/O/O), 8,9 oxic-hydrolytic and denitrification-oxic (O/H/O), 10,11 anoxic-oxicanoxic-oxic (A/O/A/O), 9 and anoxic-oxic-hydrolytic and denitrification-oxic (A/O/H/O) 12 processes. Although the A/A/O process has been widely applied in municipal wastewater treatment plants, it has obvious disadvantages for industrial wastewater (such as coking wastewater) treatment.…”

“…Direct anaerobic/anoxic treatment was shown to be inefficient for the treatment of coking wastewater with toxic pollutants. 11,16 For toxic wastewater, the aerobic reactor should be placed forward due to the strong resistance of aerobic sludge to OLR and toxicity. Wei wastewater treatment and has the potential to be extended to the treatment of other wastewaters with similar characteristics.…”

“…Wei wastewater treatment and has the potential to be extended to the treatment of other wastewaters with similar characteristics. 11 The O/H/O process used biological fluidized bed reactors to form a three-sludge system, which ensures the stability of microbial population structure and process operation. The O/H/O process makes it possible to manage the carbon source in the wastewater and achieve near-zero total nitrogen discharge, which cannot be achieved in the A/A/ O process.…”