Carbon sequestration pathway of inorganic carbon in partial nitrification sludge

High-rate partial nitritation as a pretreatment of anammox process

In this study, a laboratory-scale partial nitrification reactor (PN reactor) was used to treat high-ammonia-nitrogen wastewater, by changing the influent NH4+-N conversion rate as the main operating strategy, to investigate the upper limit of its NH4+-N conversion rate (ACR) and explore its feasibility as an anammox pre-process. During the experiment, PN reactor was successfully activated in only 10 days. The PN reactor reached the highest ACR value of approximately 10.24 kg N/(m3 · day) when the influent ACR was 16.57 kg N/(m3 · day), and the ammonia conversion efficiency (ACE) was 61.78% at this time. The ratio of [NO2--N]Eff/[NH4+-N]Eff was approximately 1.37 which was close to the theoretical ratio of 1.32. And feasibility exploration experiment proved that it was feasible to use this PN reactor as a pre-process of anammox. The PCR-DGGE results showed that the dominant phylum and genus in the reactor during the ACR experiment were Proteobacteria and Nitrosomonas, respectively. With the increase in the ACR, the relative concentration of Nitrosomonas sp. G1 increased from 15 to 40%. This indicates that its abundance is directly correlated with the increase in the ACR. High-throughput sequencing showed that increasing the ACR of the PN reactor greatly reduced the diversity and abundance of the system microbial community structure and changed the dominant phylum and genus; however, the stability of the system was not disrupted. High-throughput sequencing experiments showed that the abundance value of nitrosation enzymes accounted for 91.62%, which was positively correlated with the expression of nitrification genes in the genus Nitrosomonas.

Full-Scale Application of One-Stage Simultaneous Nitrification and Denitrification Coupled with Anammox Process for Treating Collagen Casing Wastewater

The ammonia nitrogen (NH₄⁺-N) concentration in the effluent released from the secondary sedimentation tank of the original collagen enteric coating wastewater treatment process considerably exceeded the Chinese effluent discharge standard. Therefore, a one-stage simultaneous nitrification and denitrification coupled with the anaerobic ammonia oxidation (SNDA) process was designed to terminally treat collagen enteric coating wastewater containing low COD/NH₄⁺-N (C/N). The entire process start-up and NH₄⁺-N loading (NLR) domestication phase was completed within two months. During the NLR domestication, the NH₄⁺-N removal rate was more than 90% and its effluent concentration was less than 15 mg/L, guaranteeing that the NH₄⁺-N in the subsequent effluent was within the standard value. The results of microbial diversity show that Acinetobacter, Bacillus, and other heterotrophic nitrification–aerobic denitrification bacteria, and anammox ammonia oxidation bacteria were the main functional bacteria at the genus level, exhibiting high denitrification performance. The one-stage SNDA process effectively and stably removed nitrogen; the treated sewage satisfied the national comprehensive wastewater discharge standard (GB8978-1996), effectively saving 30–40% of the floor area and reducing 67.6% of the additionally added alkali, wherein the system’s denitrifying bacteria compensated for some alkali consumed during the nitrification reaction.

Relationship between nitrifying microorganisms and other microorganisms residing in the maize rhizosphere

The microbial network of rhizosphere is unique as a result of root exudate. Insights into the relationship that exists with the energy metabolic functional groups will help in biofertilizer production. We hypothesize that there exists a relationship between nitrifying microorganisms and other energy metabolic functional microbial groups in the maize rhizosphere across different growth stages. Nucleospin soil DNA extraction kit was used to extract DNA from soil samples collected from maize rhizosphere. The 16S metagenomics sequencing was carried out on Illumina Miseq. The sequence obtained was analyzed on MG-RAST. Nitrospira genera were the most abundant in the nitrifying community. Nitrifying microorganisms were more than each of the studied functional groups except for nitrogen-fixing bacteria. Also, majority of the microorganisms were noticed at the fruiting stage and there was variation in the microbial structure across different growth stages. The result showed that there exists a substantial amount of both negative and positive correlation within the nitrifying microorganisms, and between them and other energy metabolic functional groups. The knowledge obtained from this study will help improve the growth and development of maize through modification of the rhizosphere microbial community structure.

Application of the Anammox Process for Treatment of Liquid Phase Digestate

The liquid phase of the digestate (LPD) contains a relatively high concentration of nitrogen, with total ammonium nitrogen being the dominant form of nitrogen, as well as other essential nutrients such as phosphorus and potassium. Consequently, it must be treated before it is released into the environment. However, there are no reports of co-purification of LPD in the anammox process in sequencing batch reactor with granular sludge, which is a novelty for the presented research. The main objective of this paper is to assess the possibility of nitrogen removal in the anammox process with LPD from biogas plants conducting the co-fermentation process along with the participation of agricultural products (cattle slurry). This publication presents the research results of the efficiency of the anammox process, accounting for the effect of dissolved organic matter. The conducted experiments revealed the potential of LPD purification, which co-ferments waste activated sludge and bovine slurry for the anammox process. In the reactor ammonium utilization rate (AUR) process with LPD addition increased from 2.3 mg N/(g VSS∙h) with 0.5% LPD addition to 8.5 mg N/(g VSS∙h) with 7.5% LPD addition. SAA in the reactor with LPD addition increased from 5.3 mg N/(g VSS∙h) with 0.5% LPD addition to 18.5 mg N/(g VSS∙h) with 4 and 5% LPD addition. With the addition of 7.5% LPD, SAA dropped to a value of 18.1 mg N/(g VSS∙h) in the LPD reactor.

Domestic Sewage Treatment Using a One-Stage ANAMMOX Process

A one-stage anaerobic ammonium oxidation (ANAMMOX) reactor can be quickly started within 40 days by mixing partial nitrifying sludge with ANAMMOX granular sludge with an average temperature of 30 °C. After 70 days of nitrogen load acclimation, Acinetobacter, including Candidatus Kuenenia, became the dominant strain of the system within the reactor, which exhibited high efficiency and a stable nitrogen removal performance. At an influent chemical oxygen demand (COD), NH₄⁺-N content, total nitrogen (TN) content, hydraulic retention time (HRT), temperature, and reactor dissolved oxygen (DO) content of 100, 60, and 70 mg/L, 6 h, 30 ± 1 °C, and below 0.6 mg/L, respectively, the one-stage ANAMMOX reactor could effectively treat domestic sewage on campus. The removal rates of COD, NH₄⁺-N, and TN were approximately 89%, 96.7%, and 70%, respectively.

Application of the Anammox in China-A Review

Anaerobic ammonia oxidation (anammox) has been one of the most innovative discoveries for the treatment of wastewater with high ammonia nitrogen concentrations. The process has significant advantages for energy saving and sludge reduction, also capital costs and greenhouse gases emissions are reduced. Recently, the use of anammox has rapidly become mainstream in China. This study reviews the engineering applications of the anammox process in China, including various anammox-based technologies, selection of anammox reactors and attempts to apply them to different wastewater treatment plants. This review discusses the control and implementation of stable reactor operation and analyzes challenges facing mainstream anammox applications. Finally, a unique and novel perspective on the development and application of anammox in China is presented.