Treatment of Low C/N Ratio Wastewater by a Carbon Cloth Bipolar Plate Multicompartment Electroenhanced Bioreactor (CBM-EEB)

Abstract

The traditional biological denitrification process has the problems of low removal rates and lack of a carbon source when treating wastewater with high ammonia nitrogen concentration and a low carbon–nitrogen ratio. Based on a bio-electrochemical system (BES), a novel carbon cloth bipolar plate multicompartment electroenhanced bioreactor (CBM-EEB) system was constructed. In this study, nitrogen removal efficiency and enrichment of functional bacteria using CBM-EEB under different voltage conditions were investigated. The results from next-generation sequencing indicated that the CBM-EEB included heterotrophic nitrification and aerobic denitrification (HNAD) and was dominated by heterotrophic nitrification aerobic denitrifying bacteria (HNADB). The applied voltage was confirmed as having the ability to regulate the microbial community structure and abundance of functional genes, thereby further enhancing the nitrogen removal efficiency of the system. The total nitrogen removal efficiency was 77.70 ± 1.14, 87.10 ± 0.56, 86.40 ± 0.59, and 89.30 ± 0.53% under applied voltages of 0.4, 0.7, 1.0, and 1.3 V, respectively. All values were significantly higher than the control group (62.86 ± 2.06%). HNADB had the highest abundance among the 17 detected genera related to nitrogen metabolism. Facultative denitrifying bacteria, Pseudoxanthomonas, along with key bacteria of HNADB, such as Flavobacterium, constructed a shortcut simultaneous nitrification–denitrification (SND) process. Poisson analysis and redundancy analysis (RDA) showed that the applied voltage improved the denitrification efficiency by changing the microbial community structure, reducing the abundance of heterotrophic bacteria, and increasing the unit abundance of key functional genes so that less organics were required for the denitrification process. The increased nitrogen removal efficiency in the experimental group was mainly related to simultaneous nitrification–denitrification process and cooperation of microbial communities in the anode and the cathode. This study highlighted the feasibility of CBM-EEB to enhance the HNAD reaction and the response of wastewater with a low C/N ratio to enhance the abundance of microbial bacteria and their functional gene abundance.

Preliminary Study on the Preparation of Conductive Nanosized Calcium Carbonate Utilizing Biogas Slurry by a Synchronous Double Decomposition Coating Method

“…Biogas slurry is rich in ammonium ions (NH 4 + ), bicarbonate ions (HCO 3 − ), and soluble organic matter such as humic acid (HA) [ 30 , 31 , 33 ]. The content of HA in biogas slurry was measured based on COD concentration.…”

“…effectively control the growth of inorganic nanoparticles and prevent the agglomeration of nanoparticles. Biogas slurry is rich in ammonium ions (NH4 + ), bicarbonate ions (HCO3 − ), and soluble organic matter such as humic acid (HA) [30,31,33]. The content of HA in biogas slurry was measured based on COD concentration.…”

“…The characteristics of the CNCC were further examined and analyzed. Biogas slurry is the product of anaerobic fermentation of organic waste [ 30 , 31 ]. Due to the use of anaerobic fermentation to achieve the hydrolytic transformation of organic matter, biogas slurry contains high concentrations of ammonia nitrogen, bicarbonate ions, and soluble humic acid.…”

A Highly Packed Biofilm Reactor with Cycle Cleaning for the Efficient Treatment of Rural Wastewater

“…For the microorganisms capable of heterotrophic nitrification and aerobic denitrification, the total relative abundance increased significantly from 8.13% to 12.93%. Heterotrophic nitrification and aerobic denitrification via different enzymes also contributed to the SND process in HPBR, especially when traditional nitrification was slightly compromised by the cycle cleaning process [27][28][29]. The stable presence of these microbes could be due to the anoxic zone in the inner layer of the biofilm caused by the thick biofilm.…”

Macroscale preparation of nanosized calcium carbonate by exploiting biogas slurry synchronous metathesis encapsulation method

“…Biogas slurries, which belong to anaerobic fermentation products, with affluent nitrogen, phosphorus, potassium, and other essential nutrients for crop growth are used to irrigate farmlands as a liquid organic fertilizer. 39,40 However, a large amount of biogas slurry has exceeded the load of farmland and the excessive biogas slurry storage is urgently to be solved reasonably. Traditional methods only dispose of biogas slurry from the perspective of sewage governance, whereas it is difficult to satisfy the discharge standard using solitary biochemical technology because of the biogas slurry with refractory organic matter and high concentration of ammonia nitrogen.…”