Low-strength influence on nitrogen removal performance and bacterial community structure of the anammox process

Rapid start-up strategy and microbial population evolution of anaerobic ammonia oxidation biofilm process for low-strength wastewater treatment

The implementation of the anaerobic ammonium oxidation (anammox) process in treating low-strength wastewater is limited by the difficulty in enriching anammox bacteria (AnAOB). Here, the first enrichment of AnAOB at a high nitrogen (N) loading rate (NLR) as a strategy was proposed to achieve the rapid start-up of the anammox biofilm process treating low-strength wastewater. The long-term stability of the anammox biofilm process after start-up operating at a low NLR of 0.2-0.4 kg N/(m3⋅d) was evaluated. Results showed that the N removal efficiency was up to 75 % under a low NLR of 0.2 kg N/(m3⋅d) condition. Low-strength organic matter promoted the metabolic coupling between partial denitrifying bacteria (PDB) and AnAOB. The genus Candidatus Brocadia as AnAOB (18 %-27 %) can coexist with Limnobacter (PDB, 9 %-12 %) for efficient N removal. This study offers a rapid start-up strategy of anammox biofilm process in treating low-strength wastewater.

Homogeneously and heterogeneously structured biofilm models for wastewater treatment

Biofilm, a layer comprising extracellular polymeric substances, is the platform where the embedded living cells degrade the substances in the wastewaters. Biofilm models have been developed as part of the comprehensive models for the wastewater treatment process. This review summarizes the biofilm models applied in contemporary literature based on the spatial dimensions adopted for model build-up. The most commonly applied biofilm models are null-dimensional, considering the biofilm active biomass for the substrate sink's biological reaction. The one-dimensional, multi-species models are the second standard models for contemporary studies, providing transport and reaction resistances of substrates in the biofilm matrix and the interactions of competing or collaborating strains in the biofilm. The structural homogeneity of the biofilm challenges the validity of the uniformly structured models, highlighting the need to re-examine the validity of the uniformly structured models. The challenges and prospects of biofilm model developments and applications are outlined.