Starting up anammox system with high efficiency nitrogen removal at low temperatures: Performance optimization, sludge characterization and microbial community analysis.

Anaerobic ammonia oxidation (anammox) has potential advantages for nitrogen removal when operating at medium temperatures, but the increased operation costs of heating limit its application. It would be advantageous to start and operate anammox at low temperatures, the feasibility of which was studied here on a lab scale. Two identical expanded granular sludge bed (EGSB) reactors were inoculated at 35 ± 1 °C (Amed) and 15 ± 3 °C (Alow). Results showed that anammox was successful after 138 d for Alow, only 7 d longer than Amed. Stable operation to 194 d in Alow, the nitrogen loading rate (NLR) increased to 1.01 kg m-3·d-1, giving a high nitrogen removal efficiency (NRE) of 85%, which was only slightly lower than that of Amed (90%). More extracellular polymeric substance (EPS) was produced by the microbes of Alow compared to Amed, which prevented anaerobic ammonia oxidizing bacteria (AnAOB) against low temperature stress. Microbial community revealed presence of Candidatus Jettenia in Amed with relative abundance 7.4%, while the "cold-tolerant" Candidatus Kuenenia with 4% was the dominant anammox bacteria in Alow. The anammox granules adapted well to low temperatures and demonstrated high efficiency in anammox process without heating. Therefore, constructing an energy-saving and cost-effective anammox system in high latitudes or high altitudes can be considered.

Treatment of high-concentration phosphorus wastewater based on foamed concrete.

Phosphorus is a nonrenewable resource, and the recovery of phosphorus from wastewater containing high concentrations of phosphorus is of great importance. In this work, a novel method for highly efficient treatment of high-concentration phosphorus-containing wastewater (50 mg/L, 100 mg/L and 150 mg/L) with low energy consumption was developed by using the block waste foam concrete (FC) as a potential phosphorus recovery material. The results showed that acid leaching significantly improved the accumulation efficiency of phosphorus in calcium hydroxyphosphate (HAP) via accelerating the release of calcium in wastewater. The recovery rate of phosphorus could reach 99.0% under the pH value of 9.0 at 25 °C, using 2.0 g FC. It was also found that the microporous structure of the surface of FC provided the adsorption sites for phosphorus, resulting in the adsorption rate in different concentrations of phosphorus-containing wastewater up to 14.5%. It indicated that FC achieved the recovery of phosphorus from high-concentration phosphorus-containing wastewater by coupling HAP crystallization and physical adsorption to polyphosphorus.

Removal of microorganisms and antibiotic resistance genes from swine wastewater: a comparison between polyaluminum chloride (PAC), polyaluminum sulfate (LST), and aluminum hydroxide iron (LT).

The presence of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) in swine wastewater may present a threat to the environment and public health. Conventional swine wastewater treatment processes generally fail to effectively reduce the content of ARGs. Therefore, it is necessary to develop a highly efficient and low-cost treatment method to solve this environmental problem. In doing so, we evaluated the application of three common coagulants in the treatment of swine wastewater. Using metagenomics, we evaluated the removal efficiency of ARG loads, as well as the effect of coagulation on the structure and diversity of swine wastewater, and on the bacterial community. The results showed that the three coagulants could effectively reduce the physicochemical pollution indexes of swine wastewater (e.g., TP, NTU, COD). After treatment, the loads of a variety of antibiotics in the swine wastewater were significantly reduced, with the exception of NFX and SMD, which were all close to 100%. At the same time, in evaluating the total number of microbial colonies and the total number of fecal Escherichia coli bacteria under the three conditions, Polyaluminum Chloride (PAC) ranked first among the three coagulants with 89.18%, 93.07%, 89.92%, 98.76%, 99.60%, and 98.68%. Metagenomic analysis revealed that the abundance of cfcC, tetX, mphE, msrE, tet36, and other ARGs in the water sample after the LST treatment was significantly lower than that of the original swine wastewater sample. These findings demonstrate the feasibility of using coagulants to treat swine wastewater, which is of great significance for improving water quality and reducing the potential impacts of ARGs.

Rapid start-up of autotrophic shortcut nitrification system in SBR and microbial community analysis.

Shortcut nitrification is crucial for application of autotrophic nitrogen removal which is beneficial for treating carbon-limited wastewater. In this experiment, rapid start-up of autotrophic shortcut nitrification system was studied in a small sequencing batch reactor (SBR) built in laboratory with intermittent aeration operation mode. The influent was artificially simulated inorganic domestic wastewater (the ammonium nitrogen concentration was 35.19-57.54 mg/L), the pH value was 7.6-7.8, the hydraulic loading was 1L, the operating temperature was 24.3-28.3 °C, and the dissolved oxygen (DO) was 2-4 mg/L and 0.5-0.9 mg/L at the stage of complete nitrification sludge domestication and shortcut nitrification sludge domestication. High-throughput sequencing technology was used to analyse the composition and changes of microbial populations in sludge. The experimental results showed that on the 24th day of the experiment, shortcut nitrification was started successfully, the accumulation rate of nitrite was 81.63% and the removal efficiency of ammonium nitrogen was 99.25%; the richness of the main denitrifying bacteria phylum Proteobacteria increased from 30.21% to 42.85%; the richness of Nitrosomonas (ammonia oxidizing bacteria, AOB) increased from 0.37% to 22.43%, and at the species level, AOB was the salt-tolerant bacteria Nitrosomonas. europaea; the richness of Nitrospira (nitrite oxidizing bacteria, NOB) decreased from 2.59% to 0.47%.