Wastewater Nutrient Removal Research Articles

Transforming Wastewater into Biofuel: Nutrient Removal and Biomass Generation with Chlorella vulgaris

This study investigates the potential of Chlorella vulgaris for nutrient removal and biomass production in synthetic wastewater. The experiments were conducted in 2 L photobioreactors under controlled aeration, agitation, and lighting conditions for 19 days. Despite a moderate growth rate (0.137 d⁻¹), C. vulgaris achieved efficient pollutant removal, with 97% of nitrate, 90% of nitrite, and 90.6% of COD eliminated. Additionally, the biomass was processed to extract fatty acids, yielding a 20% extraction rate, indicating its potential as a biofuel feedstock. These results demonstrate C. vulgaris’s dual function in wastewater remediation and biofuel production, presenting a sustainable and economically viable approach to addressing environmental challenges.

Process Performance and Nutrient Removal in Fish Processing Wastewater Using a Membrane Bioreactor (MBR) Unit for Reuse for Irrigation

This study investigated the removal of nitrogen and phosphates in fish processing wastewater through process optimization of a membrane bioreactor (MBR) treatment unit. Raw process wastewater was collected from the Makindi fish farm and was pre-filtered through a mesh of 0.8 mm. The experiment was conducted at a lab scale using commercial Polyethersulfone (PES) membranes submerged in the MBR unit. The pre-filtered wastewater sample was added into a denitrification (anoxic) tank. The process was conducted through continuous recirculation between the aeration and the anoxic tank to enhance the removal of nitrogenous compounds. The recirculation flow rate was 10L/h. A hydraulic residence time (HRT) of approximately 22-25h was maintained, and the aeration rate in the aerobic tank was 100L/min. Aluminum sulphate AI2(SO4)318H2O was added continually into the anoxic tank and with constant stirring to enhance the removal of phosphates. A removal rate of 85±2% for NH4+-N, 84±1% for NO3- -N, and 69±3% for PO43--P was obtained. The nutrient concentration in the effluent was successfully reduced to an acceptable level with both nitrogenous compounds and phosphate concentrations obtained within the range of < 30 mg/L and ≤ 5 mg/L as per the WHO guidelines for wastewater reuse for irrigation. The results showed a successful process optimization that can be applied to ensure optimized performance of the MBR unit thus improve its effectiveness for the treatment of fish processing wastewater. The study therefore recommends process optimization as a tool for effective removal of nutrients in the MBR system thus making it a potential recycling approach for treatment of fish processing wastewater for reuse for irrigation purposes.

A hybrid BOA-SVR approach for predicting aerobic organic and nitrogen removal in a gas-liquid-solid circulating fluidized bed bioreactor

This study introduces the hybrid of the Bayesian optimization algorithm and support vector regression (BOA-SVR) models to predict the removal of aerobic organic (total chemical oxygen demand, COD) and nitrogen compounds such as total Kjeldahl Nitrogen (TKN), ammonium nitrogen (NH4-N), and nitrate nitrogen (NO3-N) from municipal wastewater in a gas-liquid-solid circulating fluidized bed (GLSCFB) bioreactor. GLSCFB bioreactors treat wastewater by removing nutrients biologically. The downer of a GLSCFB bioreactor provided experimental data on TKN, NH4-N, NO3-N, and TCOD removal. The hybrid optimal intelligence algorithm (BOA-SVR) has improved model accuracy across multiple domains by combining BOA and SVR. The coefficient of determination (R2), residual, mean absolute error (MAE), root mean square error (RMSE), and fractional bias (FB) were used to analyze BOA-SVR model performance. The models match experimental data from four operational stages well, with R2 or adj R2 values above 0.99 for all responses. The model's accuracy was confirmed by relative deviations and residual plots showing dispersion around the zero-reference line. The BOA-SVR model consistently predicted dependent variables with low RMSE and MAE values (≤ 2.24 and 2.21, respectively) and near-zero FB. Computing efficiency was shown by optimizing TCOD, TKN, NH4-N, and NO3-N models in 70.61, 72.89, 74.37, and 54.07 s. A rigorous test on unseen data with different noise levels confirmed the model's stability. Furthermore, BOA-SVR performs better than traditional multiple linear regression (MLR). Overall, the BOA-SVR model predicts biological nutrient removal in municipal wastewater utilizing a GLSCFB bioreactor quickly, correctly, and efficiently, reducing experimental stress and resource use.

Sea Purslane's (Sesuvium portulacastrum) role in nutrient removal and microbial community dynamics of the mariculture wastewater bioremediation systems

The development of intensive mariculture requires effective wastewater treatment solutions, and mariculture wastewater bioremediation systems (MWBSs) are increasingly used for this purpose. One important part of these systems is the macrophyte unit. In this study, we established a MWBS consisting of four sections: sedimentation, biofilm, shellfish, and macrophytes, to investigate the role of sea purslane (Sesuvium portulacastrum) in nutrient removal and microbial community dynamics through controlled experiments (CE) and in situ observations (ISO). Our findings revealed the removal rates of CODMn in the low-density and high-density groups were 45.18 ± 5.42% and 48.25 ± 5.70% in CE, respectively. Furthermore, the removal rate of CODMn in the ISO was 85.28 ± 4.09%. Sea purslane notably enhanced microbial diversity and overall species count in the water. The bacterial community experienced three successional stages in the water and demonstrated more stability in the root system in CE. The stochastic processes were critical in shaping the community assembly. The bacterial dispersal in sea purslane treatment groups was higher than in the control group. Importantly, stochastic processes contributed more to the microbial community in the root system. Furthermore, the influence of stochastic processes was stronger in ISO than in CE. Therefore, it is speculated that the sea purslane demonstrated a substantial impact on microbial community structure and exhibited positive effects on wastewater nutrient removal. This study provided a reference for optimizing treatment areas within comprehensive wastewater treatment systems.

Deactivation of internal recirculation in a full-scale Biological Nutrient Removal (BNR) Wastewater Treatment Plant (WWTP) reveals outstanding microeukaryotic bioindicators

The bioindicator potential of the microeukaryotic community in a full-scale A2O wastewater treatment process was assessed after deactivating the internal recirculation in one of the two parallel treatment lines of the plant. The deactivation of the internal recirculation in one of the lines (NIR-line), led to a strong decrease in nitrogen removal efficiency (53 % ammonia-uptake in the NIR-line versus 97 % in the unaltered line or IR-line), as well as to a lower organic matter removal (95 % BOD5 removal versus 97 % in the IR-line). The microeukaryote community structure changed greatly confirming trends observed in experimental studies and showed a decrease in abundance and richness in the NIR-line. However, this line showed a significant higher abundance of certain ciliate species, such as Epistylis camprubii and Vorticellides infusionum, which are common species in conventional activated sludge. Conversely, the IR-line showed useful indicators of internal recirculation, associated with much higher ammonium and BOD5 removal. These results show that identification to ciliate species level provides a more reliable bioindication in nutrient removal systems, supporting the importance of research on biological parameters, mainly protists, as simple and useful tools for plant operators to manage nutrient removal processes. These observations extend the current boundaries of bioindication.

Sustainable removal of nutrients (n and p) in a wastewater treatment plant, with eggshell (biocalcium)

Biological treatments have become insufficient to treat municipal wastewater with greater toxicity and excess nitrogen and phosphate species, thus affecting the organisms that consume the water. In this work, a process was implemented for the removal of nutrients through three stages: stage A, complete aeration (24 h, 43 months); stage B, decreased aeration (12 h, 17 months); and stage C, decreased aeration with biocalcium (12 h, 19 months). The addition of biocalcium from eggshell promoted the formation of flocks, which resulted in the removal of nitrites (61 %), nitrates (84 %), total nitrogen (57 %), total phosphorus (8.3 %), sedimentable solids (50 %), total suspended solids (69 %), BOD5 (76 %), helminth eggs (50 %) and fecal coliforms (54 %). The statistical analyses in the three stages indicated that there is a strong correlation between the concentration of fats and oils and the removal of sedimentable solids and total suspended solids, since these parameters were correlated by 97 and 89 %, respectively. Sedimentable solids were correlated with total suspended solids by 94 %, while nitrates and total nitrogen were correlated 92 %, which favors the removal of nutrients in wastewater. The increase in the concentration of nitrogen in the sludge in stage C generated a C:N ratio of 7.98. This ratio shows that the sludge is feasible for use as a mediator of soils and a biofertilizer because of the high contents of calcium, phosphorus and nitrogen. In addition, biocalcium promoted the precipitation of hydroxyapatite, struvite, calcite and quartz. In general, the three stages of the treatment contributed to the stabilization of the wastewater treatment plant (WWTP) in an efficient, economical, and safe way.

Hydrothermal but Not Mechanical Pretreatment of Wastewater Algae Enhanced Anaerobic Digestion Energy Balance due to Improved Biomass Disintegration and Methane Production Kinetics

This study used pilot-scale high-rate algae ponds to assess algal–bacteria biomass productivity and wastewater nutrient removal as well as the impact of mechanical and hydrothermal pretreatments on biomass disintegration, methane production kinetics, and anaerobic digestion (AD) energy balance. Mechanical pretreatment had a minor effect on biomass disintegration and methane production. By contrast, hydrothermal pretreatment significantly reduced particle size and increased the solubilized organic matter content by 3.5 times. The methane yield and production rate increased by 20–55% and 20–85%, respectively, with the highest values achieved after pretreatment at 121 °C for 60 min. While the 1st-order and pseudo-1st-order reaction equation models fitted methane production from untreated biomass best (R2 > 0.993), the modified Gompertz sigmoidal-type model provided a superior fit for hydrothermally pretreated algae (R2 ≥ 0.99). The AD energy balance revealed that hydrothermal pretreatment improved the total energy output by 25–40%, with the highest values for volume-specific and mass-specific total energy outputs reaching 0.23 kW per digester m3 and 2.3 MW per ton of biomass volatile solids. Additionally, net energy recovery (energy output per biomass HHV) increased from 20% for untreated algae to 32–34% for hydrothermally pretreated algae, resulting in net energy ratio and net energy efficiency of 2.14 and 68%, respectively.

Nitrite accumulation in activated sludge through cyclic anaerobic exposure with acetate

Achieving nitrite accumulation still remains challenging for efficient short-cut biological nitrogen removal in municipal wastewater treatment. To tackle the problem of insufficient carbon in incoming wastewater for biological nutrient removal, a return activated sludge (RAS) fermentation method has been proposed and demonstrated to enable producing supplemental volatile fatty acids (VFAs) and enhance biological phosphorus removal via sludge cycling between mainstream and a sidestream anaerobic reactor. However, the impacts of long anaerobic exposure with acetate on nitrifying bacteria, known as the aerobic chemoautotrophic microorganisms, remains unexplored. In this study, the activated sludge underwent a cyclic anaerobic treatment with the addition of acetate (Ac), the effects on nitrification rate, abundance and microdiversity of nitrifying communities were comprehensively assessed. Firstly, batch activity tests proved the direct addition of high acetate (above 1000 mg/L) could cause inhibition on the nitrification rate, moreover, the inhibitory effect was stronger on nitrite-oxidizing bacteria (NOB) activity than that of ammonia-oxidizing bacteria (AOB). Then, a sequencing batch reactor (SBR) was applied to test the nitrogen conversion performance for low-strength ammonium wastewater. Nitrite accumulation could be achieved via the cyclic anaerobic exposure with 1000–5000 mg Ac/L. The maximum effluent concentration of nitrite was 40.8 ± 3.5 mg N/L with nitrite accumulation ratio (NAR) of 67.6 ± 3.5%. The decrease in NOB activity (72.7%) was greater than AOB of 42.4%, promoting nitrite accumulation via nitritation process. Furthermore, the cyclic anaerobic exposure with acetate can largely reshape the nitrifying communities. As the dominant AOB and NOB, the abundance of Nitrosomonas and Nitrospira were both decreased with species-level microdiversity in the nitrifying communities. However, the heterotrophic microorganism, Thauera, were found to be highly enriched (from 0 to 17.3%), which may act as the potential nitrite producer as proved by the increased nitrate reduction gene abundance. This study can provide new insights into achieving mainstream nitrite accumulation by involving sidestream RAS fermentation towards efficient wastewater treatment management.

Model-based comparison of biological wastewater and sludge treatment combinations for nutrient removal, sludge and biogas production

One of the strategies for reducing the potential environmental and health-related risks associated with wastewater treatment sludge is to select treatment options that would minimize its production while using its beneficial products and meeting effluent discharge standards. In this regard, simulation models can aid in estimating treatment performance, sludge production, and biogas formation. This study evaluates effluent concentrations focusing on nutrients, sludge production, and biogas generation rates for various combinations of wastewater and sludge treatment alternatives for varying strengths of domestic wastewater. Overall, 105 scenarios were simulated for three different wastewater strengths for 35 treatment schemes. Bardenpho-5 (B5) was superior over A2O (A2) in removing nitrogen and phosphorous. Adding primary sedimentation to A2 and B5 models improved sludge and in turn biogas production. Effluent total phosphorus (TP) was usually higher in scenarios with anaerobic sludge digestion. However, struvite precipitation following anaerobic digestion helped reduce total nitrogen (TN) and TP effluent concentrations for all wastewater treatment technologies. Sludge production amounts ranged between 2865 kg/day to 38,709 kg/day (total solids) for an influent flow rate of 100,000 m3/day. Sludge production rates were relatively insensitive to sludge treatment alternatives for extended aeration (EA) compared to conventional activated sludge (AS), A2, A/O (AO), and B5. Generally, the impact of a sludge treatment option was significant for wastewater treatment technologies with higher waste sludge production. Thermal hydrolysis followed by anaerobic digestion provided the lowest sludge production and significantly improved the biogas production.

Impact of Naproxen on Wastewater Biological Treatment: Focus on Reactor Performance and Mechanisms

Pharmaceutical contamination has emerged as a significant environmental concern; yet, the impact and underlying mechanisms of widely detected naproxen (NPX) on wastewater biological treatment remain poorly understood. To address this knowledge gap, this study investigates the influence of NPX on biological nutrient removal in wastewater treatment under mesophilic conditions, and elucidates the associated mechanisms. The results demonstrate that NPX concentrations below 0.05 mg/L have no significant effect on the removal of pollutants and nutrients in wastewater, whereas the concentrations exceeding 0.5 mg/L hinder the removal of both chemical oxygen demand (COD) and nutrients, with a more pronounced inhibitory effect observed at higher NPX doses. When the concentration of NPX was 2.0 mg/L, the removal efficiency of COD, NH4+-N and phosphate decreased to 81.2~83.6%, 82.5~84.2% and 80.2~82.6%, respectively, which was much lower than that of the blank. Furthermore, NPX leads to a decrease in activated sludge concentration and organic matter content within the sludge. Additionally, NPX promotes the secretion of extracellular polymeric substances (EPS). Periodic investigations reveal that NPX inhibits the biosynthesis of intracellular polymer polyhydroxyalkanoate (PHA), thereby reducing energy production during later stages of degradation. Enzyme activity analysis indicates that high NPX concentrations suppress the activity of key enzymes associated with biological nitrogen and phosphorus removal. These findings provide theoretical insights for the treatment of NPX-containing wastewater using activated sludge processes.

Knowledge Mapping of High-Rate Algal Ponds Research

High-rate algal ponds (HRAPs) are a highly promoted wastewater treatment system that uses sunlight as an energy source to provide the oxygen needed in the system through photosynthesis and has a high nutrient and organic matter removal capacity. In addition, the microalgae in the system can use wastewater as a growth substrate to produce valuable bioproducts, biomaterials, and bioenergy, so it is receiving more and more attention. This review uses bibliometric analysis to explore current research hotspots and future research trends in this emerging technology. By analyzing research papers related to HRAPs published in the Web of Science (WOS) from 1987 to 2021 based on the co-occurrence and clustering of keywords, it shows that the research hotspots of HRAPs are mainly focused on wastewater treatment, nutrient removal, microalgal biomass, biofuel, and biogas upgrading. In the future, in-depth research will continue to be added on the contribution of HRAPs to environmental sustainability, including E. coli removal, biogas upgrading and oxygen removal, treatment of aquaculture wastewater, purple phototrophic bacteria, aqueous biorefineries, and biorefineries. The results assist scholars in systematically understanding the current research status, research frontiers, and future trends of HRAPs from a macro perspective.

Selective removal of ammonium ions with transition metal hexacyanoferrate (MHCF) electrodes

This study investigated the potential of using transition metal hexacyanoferrates (MHCF) to selectively capture NH4+ over Na+ in brine for nutrient recovery from wastewater. The electrochemical characteristics of five different MHCF (M is Ni, Cu, Fe, Co or Zn), known as Prussian blue analogues (PBA), was investigated using a hybrid capacitive deionization device, and their desalting capacity, stability and energy consumption were evaluated. By adjusting the mass ratio of electrodes, applied voltage, and ion concentration, the relationship between NH4+ removal and selectivity was explored. Results showed that all five MHCF electrodes exhibited high selectivity (> 4) for NH4+ over Na+, but the selectivity is not stable due to comprehensive factors (such as the structural stability of electrode, solution composition, and current density, etc.). Among them, the NiHCF electrode showing the best performance in terms of specific desalination capacity (∼1.23 mmol/g), charge efficiency (>80%), and stability (82.5% capacity retention after 50 cycles). This study demonstrates that PBA has promising potential as NH4+ selective electrodes for nutrient removal and recovery in wastewater.

Development of economical and sustainable cultivation system for biomass production and simultaneous treatment of municipal wastewater using Tetraselmis indica BDUG001

ABSTRACT Microalgal-based bioprocess offers several advantages including wastewater reclamations, therefore present study assessed the usability of the combination of untreated municipal sewage wastewater (UTMSWW) and secondary treated municipal sewage wastewater (STSWW) for nutrient removal and recovery by Tetraselmis indica (T. indica) BDUG001. The present study optimized the additional nutrient supplementations (e.g. ASN-III) percentage and day-night cycle, pH and pH with aeration for monitoring high-rate biomass production and nutrient recovery. The study results showed that the combination of 75% UTMSWW + 25% ASN-III supported maximum biomass production (2.65 ± 0.07 g/L). In the optimized day-night cycle (12:12 h), T. indica BDUG001 showed improved biomass production (2.75 ± 0.07 g/L), biomass productivity (165.63 ± 4.42 mg/L/d), and photosynthetic pigments production. Under optimized pH∼ 7.0 with aeration, maximum total nitrate (TN) removal efficiency (87.67 ± 3.08–91.55 ± 1.92%) was observed, while COD and TP removal was maximum at pH ∼ 9.0. The maximum biomass production (2.35 ± 0.07–2.77 ± 0.04 g/L) with biomass productivity (93.75 ± 167.19 ± 2.21 mg/L/d) and lipid content (42.98 ± 1.86–47.85 ± 0.21% DCW) were also at pH 7.0. with aeration. The present study verified the utilization of UTMSWW with the combination of conventional medium, optimized day-night cycle, pH with aeration along with designing low-cost PBR. It was the ideal system for the cultivation of T. indica BDUG001 for the recovery of nutrients from wastewater, production of biofuels and value-added feedstock.

A Model-Based Comparison of Biological Wastewater and Sludge Treatment Combinations for Nutrient Removal and Sludge Production Performances

A Model-Based Comparison of Biological Wastewater and Sludge Treatment Combinations for Nutrient Removal and Sludge Production Performances

Enhanced growth and lipid productivity by living Chlorella sorokiniana immobilized in Ca-alginate beads

The bottleneck for the production of biofuels from microalgae consists on costly harvesting processes and low lipid production, immobilization technology could play a part on making the production of biofuels more feasible. The aim of this study was to evaluate the effect of alginate immobilization on the growth and lipid productivity of the microalgae Chlorella sorokiniana, so far, the main focus of immobilization technology has been its use for wastewater treatment and nutrient removal from effluents. The microalgae Chlorella sorokiniana was cultured in both free and immobilized forms under optimal autotrophic growth conditions. Microalgae were immobilized in calcium alginate beads generated by mixing algal cells with a sodium alginate solution, followed by extrusion into a CaCl2 solution. The results obtained in this study showed that the growth of the microalgae immobilized in alginate beads, was enhanced and achieved a dry cell weight 1.4-fold higher than that of a free cell culture, a higher light transmittance was also achieved in the alginate immobilized culture, and the lipid productivity was increased from 54.21 ± 2.48 mg l−1 d in the free cell culture to 82.22 ± 8.48 mg l−1 d in the immobilized culture. These results demonstrate the effectiveness of immobilization technology for promoting growth and lipid productivity in the microalgae Chlorella sorokiniana.

Glycerol conversion by aerobic granular sludge

Glycerol is abundantly present in wastewater from industries such as biodiesel production facilities. Glycerol is also a potential carbon source for microbes that are involved in wastewater nutrient removal processes. The conversion of glycerol in biological phosphorus removal of aerobic granular sludge processes has not been explored to date. The current study describes glycerol utilization by aerobic granular sludge and enhanced biological phosphorus removal (EBPR). Robust granules with good phosphorus removal capabilities were formed in an aerobic granular sludge sequencing batch reactor fed with glycerol. The interaction between the fermentative conversion of glycerol and product uptake by polyphosphate accumulating organisms (PAO) was studied using stoichiometric and microbial community analysis. Metagenomic, metaproteomic and microscopic analysis identified a community dominated by Actinobacteria (Tessaracoccus and Micropruina) and a typical PAO known as Ca. Accumulibacter. Glycerol uptake facilitator (glpF) and glycerol kinase (glpK), two proteins involved in the transport of glycerol into the cellular metabolism, were only observed in the genome of the Actinobacteria. The anaerobic conversion appeared to be a combination of a substrate fermentation and product uptake-type reaction. Initially, glycerol fermentation led mainly to the production of 1,3-propanediol (1,3-PDO) which was not taken up under anaerobic conditions. Despite the aerobic conversion of 1,3-PDO stable granulation was observed. Over time, 1,3-PDO production decreased and complete anaerobic COD uptake was observed. The results demonstrate that glycerol-containing wastewater can effectively be treated by the aerobic granular sludge process and that fermentative and polyphosphate accumulating organisms can form a food chain in glycerol-based EBPR processes.

Simultaneous Promotion of Microalgal CO2 Assimilation, Biomass Accumulation, Lipid Production, and Wastewater Nutrient Removal by Adding 5-Aminolevulinic Acid

Microalgae-based wastewater management has the potential to serve dual purposes, including biofuel production and wastewater bioremediation. The current study investigates the role of 5-aminolevulinic acid (5-ALA) in the regulation of photosynthesis, biomass accumulation, lipid production, and nutrient removal from wastewater by Chlorella pyrenoidosa. In wastewaters, a 3 μM concentration of 5-ALA was considered optimal, as it increased the photosynthetic light reaction and CO2 assimilation of C. pyrenoidosa cells, thereby facilitating cellular growth, metabolism, and biomass accumulation. The acceleration of algal cellular metabolism increased the substrate pool and enhanced the expression of lipogenic genes, thereby promoting lipid production. Meanwhile, the removal of nutrients from wastewater was accelerated after the addition of 5-ALA. The accelerated nutrient removal from wastewaters following 5-ALA treatment was related to C. pyrenoidosa cell growth. C. pyrenoidosa is capable of utilizing nitrogen and phosphorus from wastewater and accumulating biomass. The biomass from microalgae can be used as a feedstock to produce biofuels. Therefore, the current study provided a novel strategy for simultaneously promoting CO2 assimilation, biomass accumulation, lipid production, and wastewater nutrient removal with microalgae. It is possible to use microalgae for the management of wastewater if research and development on commercializing technologies based on microalgae, both upstream and downstream, are carried out continuously.

Nutrient and organic pollutants removal in synthetic wastewater by Pseudomonas aeruginosa and Chryseobacterium sp./biofilter systems.

Nutrient and organic pollution raise serious problems for aquatic ecosystems through the accumulation of organic carbon, the reduction of light penetration, and the loss of submerged aquatic vegetation. The over-enrichment of water with nitrogen and phosphorus leads to an imbalance in nutrient ratios, creating favorable conditions for toxic algal blooms, formation of oxygen-depleted water, etc. Thus, developing new technological solutions to reduce their amount is imperative. The present study investigates the capacity of Pseudomonas aeruginosa and Chryseobacterium sp. bacterial strains to form biofilm on solid support (biofilter), both individually and in tandem, using various analytical techniques. Also, the biofilm/biofilter systems' efficiency in removing nutrients such as nitrate, nitrite, ammonium, and phosphate ions from municipal wastewaters is assessed. The results showed a reduction of nutrient pollution of up to 91%, 98%, 55%, and 71% for nitrite, nitrate, ammonium, and phosphate ions. A reduction of about 78% of COD was also observed. The results were obtained in the absence of an additional aeration process, thus having a great potential for reducing total costs of wastewater treatment and developing ecological systems for wastewater management.

Synchronous removal of ammonia nitrogen, phosphate, and calcium by heterotrophic nitrifying strain Pseudomonas sp. Y1 based on microbial induced calcium precipitation

Pseudomonas sp. Y1, a strain with superior synchronous removal ability of ammonia nitrogen (NH4+-N), phosphate (PO43−-P), and calcium (Ca2+) was isolated, with the removal efficiencies of 92.04, 99.98, and 83.40 %, respectively. Meanwhile, the chemical oxygen demand (COD) was degraded by 90.33 %. Through kinetic analysis, the optimal cultivated conditions for heterotrophic nitrification-aerobic denitrification (HNAD) and biomineralization were determined. The growth curves experimental results of different nitrogen sources indicated that strain Y1 could remove NH4+-N through HNAD. The results of excitation-emission matrix (EEM) proved that the appearance of extracellular polymeric substances (EPS) promoted the precipitation of phosphate minerals. Finally, the characterization results of the bioprecipitates showed that the HNAD process produced the alkalinity required for microbial induced calcium precipitation (MICP), resulting in the removal of PO43− via adsorption and co-precipitation. This study provides a theoretical basis for the application of microorganisms to achieve synchronous nutrient removal and phosphorus recovery in wastewater.

Rhizopus oryzae fermentation wastewater nutrient removal coupling protein fodder production by employing Chlorella pyrenoidosa

The scenario was to investigate feasibilities of employing Chlorella pyrenoidosa for Rhizopus oryzae fermentation wastewater nutrient removal coupling protein fodder production. Results stated that TN, TP, NH3-N, COD, BOD removal reached 99.79%, 94.70%, 98.80%, 97.60%, 99.60% to acquire discharge permit under fed-batch manipulation, whilst the peaked protein yield (19.94 g/L) was 6.04-fold more than batch manipulation. Rhizopus oryzae fermentation wastewater feeding C. pyrenoidosa was praised as high-quality protein not only with 26.78% essential amino acids and essential amino acids/nonessential amino acids value of 0.84 but also pathogenic bacteria and heavy metal loads complying with fodder standards. In vitro digestibility of dry matter, protein, lipid, and starch achieving 80.07%, 92.13%, 95.93%, 91.9% and bioavailability of polypeptides, triglycerides, free fatty acids, and oligosaccharides displaying 98.67%, 87.12%, 93.86%, 30.21%, which were roughly-equivalent to corn/soybean fodder. The findings formed exemplifications in utilizing other microalgal systems for wastewater nutrient removal coupling chemicals production.