Enhancing Nitrogen Removal Performance in a Bioreactor Using Immobilized Anaerobic Ammonium Oxidation Sludge by Polyvinyl Alcohol-Sodium Alginate (PVA-SA)

Abstract

Anaerobic ammonium oxidation (anammox) is an efficient and promising pathway for nitrogen removal from wastewater, but its application is usually confined by the low growth rate and susceptibility to surroundings of anammox bacteria. In this study, cultured anammox sludge was immobilized using polyvinyl alcohol (PVA)-sodium alginate (SA) gel and put into a lab-scale column reactor at a packing ratio of 20%, and nitrogen removal performance was evaluated at two hydraulic retention times (HRTs). Anammox was rapidly initiated in the reactor, with ammonium and nitrite removal efficiency reaching 82.3% and 84.7% after an operation period of 10 d. Nitrogen removal efficiency declined greatly after the reduction of HRT from 24 h to 12 h, but then recovered quickly, with an average TN removal rate of 84.5% and 0.43 kg·m -3 ·d -1 achieved under the steady operational state. The immobilized anammox reactor performed significantly better and was more stable in nitrogen removal than that with anammox sludge inoculated directly, indicating the superiority of cell entrapment of anammox biomass in addition to its easy reservation. Nitrogen removal in the reactor increased after stable operation with the HRT. It has potential to apply immobilized anammox sludge entrapped by PVA-SA gel for the convenient establishment of an anammox reactor with stable and high nitrogen removal rates.

Gel immobilization: A strategy to improve the performance of anaerobic ammonium oxidation (anammox) bacteria for nitrogen-rich wastewater treatment

“…Cell immobilization is a new technique that attracted the scientific community as a competitive alternative to avoid cell washout from the reactor (Lu et al, 2018). The immobilization can protect anammox cells from inhibitory effects caused by substrates, organics, and inorganic compounds.…”

“…The immobilization can effectively achieve the rapid start of anammox by alleviating the washout of slow growth anammox bacteria . Anammox bacteria were sheltered from the surrounding, and the loss of anammox cell from the reactor was avoided by immobilizing in the PVA/SA (Hsia et al, 2008;Lu et al, 2018). The rapid start-up of anammox process was achieved by the conditions of immobilization, initial higher concentration of anammox sludge, and retaining of microbial biomass due to entrapment (Quan et al, 2011).…”

Effect of temperature shifts and anammox biomass immobilization on sequencing batch reactor performance and bacterial genes abundance

“…4). Similarly, Lu et al (2018) report that a reactor inoculated with biomass immobilized in PVA-SA was more stable regarding nitrogen removal. In this study, up to day 70 of the experiment, the ratios of the NO 2 − to NH + removed were close to 1.32, and the ratio of NO 3 − produced to NH 4 + was close to 0.26 in the PVA-SA reactor, which are the theoretical values for anammox, and indicates that anammox was responsible for nitrogen removal in the reactor (Magrí et al 2012).…”

Reduction in Hg phytoavailability in soil using Hg‐volatilizing bacteria and biochar and the response of the native bacterial community

“…Homoeostatic mechanisms work to restore the disturbed microbial community to its previous state (Farinati et al ., ). However, further studies should be conducted to maintain the growth and activity of the added bacterial inocula in soils, such as cell immobilization by gel entrapment before addition (Lu et al ., ), to maintain/enhance the Hg remediation efficacy and reduce operation cost.…”