Assessment of diversity and composition of bacterial community in sludge treatment reed bed systems

Changes of nitrogen and phosphorus removal pattern caused by alternating aerobic/anoxia from the perspective of microbial characteristics

The purpose of this study was to compare the impact of different numbers of alternating aerobic/anoxic (A/O) cycles on pollutant removal. Three sequential batch reactors (SBRs) with varying numbers of alternating A/O cycles were established. Under the tertiary anoxic operating conditions, the removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphorus (TP) were 88.73%, 89.56%, 72.15%, and 77.61%, respectively. Besides, alternating A/O affected the dominant microbial community relative abundance (Proteobacteria and Bacteroidetes) and increased microbial richness and diversity. It also increased the relative abundance of aerobic denitrifying, heterotrophic nitrifying, and denitrifying phosphorus removal bacteria to change N and P removal patterns. Furthermore, the abundance of carbohydrate metabolism and amino acid metabolism was improved by alternating A/O to improve organic matter and TN removal.

Sludge Treatment Reed Bed under different climates: A review using meta-analysis

Sludge Treatment Reed Beds (STRBs) have been used worldwide over the past few decades. This review aims to overarchingly identify and appraise the currently available knowledge of STRB technology and discern climatic patterns through Meta-Analysis (MA). We systematically searched Google Scholar, Scopus, and Web of Science databases (up to Dec 2021) via a combination of keywords to identify English-language studies published in peer-reviewed journals. Of 142 potential articles, 73 studies met the present review objectives and inclusion criteria. Four STRB classifications including typical STRB, earthworm STRB, Sludge Treatment Electro Wetland (STEW), and earthworm STEW were found since 1990. The data and information on STRBs' configuration, operational parameters in terms of location, type of sewage sludge, study scale, Sludge Loading Rate (SLR), Dry Solid (DS), the proportion of Volatile Solid to DS (VS/DS), and their association with the feeding and resting modes were extracted from the selected articles. The analysis was focused on the interconnections between operational parameters and system efficiency for Temperate type 1 (low intensity of solar radiation), Temperate type 2 (high intensity of solar radiation), and Tropical climates. Based on MA, we found the average SLRs of 50, 70, and 101 Kg.DM.m^-2.year^-1 for Temperate type 1, Temperate type 2, and Tropical climates respectively, and DS during the feeding of 33 %, 35 %, and 40 %. A qualitative comparison of Arid and Polar climates was also performed given the reduced number of studies available in these climates. The volume of the sludge reduced was 60 % higher and the height of accumulated sludge was annually 2 cm in the earthworm STRBs, and STEWs compared to typical STRBs, which was 6 cm annually in Tropical climates. Correlation analysis, media characterization, list of plant species, and the removal efficiency of STRBs in the residual sludge and leachate are mentioned as well.

A Review on Microorganisms in Constructed Wetlands for Typical Pollutant Removal: Species, Function, and Diversity

Constructed wetlands (CWs) have been proven as a reliable alternative to traditional wastewater treatment technologies. Microorganisms in CWs, as an important component, play a key role in processes such as pollutant degradation and nutrient transformation. Therefore, an in-depth analysis of the community structure and diversity of microorganisms, especially for functional microorganisms, in CWs is important to understand its performance patterns and explore optimized strategies. With advances in molecular biotechnology, it is now possible to analyze and study microbial communities and species composition in complex environments. This review performed bibliometric analysis of microbial studies in CWs to evaluate research trends and identify the most studied pollutants. On this basis, the main functional microorganisms of CWs involved in the removal of these pollutants are summarized, and the effects of these pollutants on microbial diversity are investigated. The result showed that the main phylum involved in functional microorganisms in CWs include Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. These functional microorganisms can remove pollutants from CWs by catalyzing chemical reactions, biodegradation, biosorption, and supporting plant growth, etc. Regarding microbial alpha diversity, heavy metals and high concentrations of nitrogen and phosphorus significantly reduce microbial richness and diversity, whereas antibiotics can cause large fluctuations in alpha diversity. Overall, this review can provide new ideas and directions for the research of microorganisms in CWs.