Total Ammonia Nitrogen Concentrations Research Articles

Effects of Ammonia on Juvenile Sunray Surf Clam (Mactra chinensis Philippi) in Laboratory Tests

The current study aimed to determine the acute and sub-chronic toxicity of ammonia to juvenile surf clams (Mactra chinensis Philippi). Acute toxicity tests were conducted with seven concentrations of ammonium chloride using a 96 h static-renewal approach. Sub-chronic ammonia exposure tests (20 d exposures) were conducted with 6 concentrations at 20 °C. The 96 h median lethal concentration (96 h LC50) was 11.1 (10.0; 12.0) mg/L total ammonia nitrogen (TAN) and 0.56 (0.50; 0.60) mg/L unionized ammonia (NH3). The relative growth rate was significantly reduced at concentrations higher than 1.6 mg/L TAN (0.075 mg/L NH3) in the 20 d tests. The estimated maximum acceptable toxicant concentration (MATC) based on the reduced growth of juvenile M. chinensis was between 0.8 and1.6 mg/L TAN (0.038–0.075 mg/L NH3). Histopathological changes were evaluated in the surviving clams after 20 days of exposure. Exposure to 14.1 mg/L TAN (0.661 mg/L NH3) resulted in changes in the mantle, foot and digestive diverticulum. We also examined the antioxidant enzyme activities of superoxide dismutase (SOD) and catalase (CAT) in 10 d and 20 d at 6 different levels (plus a control) of ammonia from 0.8 mg/L to 14.1 mg/L TAN. Ammonia exposure at 0.8 mg/L TAN (0.038 mg/L NH3) significantly affected SOD and CAT activities. The level of enzymic activity decreased with the increasing concentration of TAN. The results improved our understanding of oxidative damage under ammonia exposure and provided data for the aquaculture of sunray surf clams.

Biofiltration Reactivation Kinetics of a Cyclobio Fluidized Sand Filter in a Warmwater Recirculating Aquaculture System

AbstractThe ability of a commercial‐scale Cyclobio fluidized sand filter was evaluated for ammonia and nitrite removal by dosing with ammonia chloride, NH4Cl, as part of the water treatment unit for the U.S. Department of Agriculture Agricultural Research Service Warmwater Aquaculture Research Unit's (WARU) catfish hatchery in Stoneville, Mississippi, USA. Treatment system water was recirculated through the Cyclobio filter for several months without any feed inputs; thus, our objective was to investigate how quickly a full‐scale Cyclobio fluidized sand filter could be reactivated with NH4Cl substrate dosing in preparation for the upcoming spawning season. A second objective of the study was to examine the decline of the filter's nitrification ability when the supplementary NH4Cl substrate dosings were removed or limited. The effects of daily and weekly substrate additions were evaluated over a 14‐week winter period, with the system water temperature ranging between 20° and 23°C. Total ammonia nitrogen (TAN) concentration decreased within hours of initial dosing. After approximately a 2‐h lag period, the nitrite–nitrogen concentration peaked and then decreased. The rate of TAN nitrification followed a simple first‐order reaction kinetics and increased over time during the 4 weeks of daily NH4Cl substrate dosing. The return to a weekly substrate dosage resulted in a decrease in the kinetic reaction rate, but adequate to maintain the filter during periods of system inactivity. The once‐daily substrate dosage was consumed within hours of the initial dosing and was sufficient for current system loading.

The inhibition of high ammonia to in vitro rumen fermentation is pH dependent.

Ammonia is an important rumen internal environment indicator. In livestock production, feeding a large amount of non-protein nitrogen to ruminants will create high ammonia stress to the animals, which increases the risk of ammonia toxicity. However, the effects of ammonia toxicity on rumen microbiota and fermentation are still unknown. In this study, an in vitro rumen fermentation technique was used to investigate the effects of different concentrations of ammonia on rumen microbiota and fermentation. To achieve the four final total ammonia nitrogen (TAN) concentrations of 0, 8, 32, and 128 mmol/L, ammonium chloride (NH4Cl) was added at 0, 42.8, 171.2, and 686.8 mg/100 mL, and urea was added at 0, 24, 96, and 384 mg/100 mL. Urea hydrolysis increased, while NH4Cl dissociation slightly reduced the pH. At similar concentrations of TAN, the increased pH of the rumen culture by urea addition resulted in a much higher free ammonia nitrogen (FAN) concentration compared to NH4Cl addition. Pearson correlation analysis revealed a strong negative correlation between FAN and microbial populations (total bacteria, protozoa, fungi, and methanogens) and in vitro rumen fermentation profiles (gas production, dry matter digestibility, total volatile fatty acid, acetate, propionate, etc.), and a much weaker correlation between TAN and the above indicators. Additionally, bacterial community structure changed differently in response to TAN concentrations. High TAN increased Gram-positive Firmicutes and Actinobacteria but reduced Gram-negative Fibrobacteres and Spirochaetes. The current study demonstrated that the inhibition of in vitro rumen fermentation by high ammonia was pH-dependent and was associated with variations of rumen microbial populations and communities.

Optimal Dietary Protein/Energy Ratio and Phosphorus Level on Water Quality and Output for a Hybrid Grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) Recirculating Aquaculture System

In a recirculating aquaculture system (RAS), feed is critical to the growth of fish and is the main source of nutrient pollutants in aquaculture water. An eight-week feeding trial was conducted to investigate the role of feed on the growth efficiency of hybrid grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀) and water quality in a RAS. Five commercial feeds with different respective dietary protein/energy (P/E) ratios and available phosphorus levels were selected (LNLP, 31.97 g/MJ, 0.96%; LNMP, 32.11 g/MJ, 1.54%; MNLP, 36.26 g/MJ, 0.98%; MNMP, 36.53 g/MJ, 1.58%; and HNP, 41.54 g/MJ, 1.97%). The results showed that HNP had the highest growth efficiency and MNLP provided the best economic benefit. The trend in water quality within 6 h after feeding was similar among the five groups. The relative concentrations of ammonia nitrogen, total nitrogen, active phosphate, and total phosphorus reached a maximum 2 h after feeding, and the relative concentration of nitrite reached a maximum 1 h after feeding. The high P/E ratio feed increased the concentrations of total ammonia nitrogen and nitrite nitrogen. The total ammonia nitrogen concentration in HNP was much higher than those in the other treatments. The dietary P/E ratio had no significant effect on total nitrogen concentration. High dietary phosphorus levels increased the total phosphorus concentration in the water, but no significant effect on the active phosphate concentration was observed. Considering the growth efficiency, economic benefit, and water quality, it can be concluded that MNLP is the most suitable feed for RAS breeding hybrid grouper. The results of this study supplement the gap on the effects of feed on RAS water quality and provide data support for the sustainable development of RAS industry.

Ammonia Toxicity in the Bighead Carp (Aristichthys nobilis): Hematology, Antioxidation, Immunity, Inflammation and Stress.

Ammonia is one of the main environmental pollutants that affect the survival and growth of fish. The toxic effects on blood biochemistry, oxidative stress, immunity, and stress response of bighead carp (Aristichthys nobilis) under ammonia exposure were studied. Bighead carp were exposed to total ammonia nitrogen (TAN) concentrations of 0 mg/L, 3.955 mg/L, 7.91 mg/L, 11.865 mg/L, and 15.82 mg/L for 96 h. The results showed that ammonia exposure significantly reduced hemoglobin, hematocrit, red blood cell, white blood cell count, and platelet count and significantly increased the plasma calcium level of carp. Serum total protein, albumin, glucose, aspartate aminotransferase, and alanine aminotransferase changed significantly after ammonia exposure. Ammonia exposure can induce intracellular reactive oxygen species (ROS), and the gene expression of antioxidant enzymes (Mn-SOD, CAT, and GPx) increases at the initial stage of ammonia exposure, while MDA accumulates and antioxidant enzyme activity decreases after ammonia stress. Ammonia poisoning changes the gene expression of inflammatory cytokines; promotes the gene expression of inflammatory cytokines TNF-α, IL-6, IL-12, and IL-1β; and inhibits IL-10. Furthermore, ammonia exposure led to increases in stress indexes such as cortisol, blood glucose, adrenaline, and T3, and increases in heat shock protein 70 and heat shock protein 90 content and gene expression. Ammonia exposure caused oxidative stress, immunosuppression, inflammation, and a stress reaction in bighead carp.

Proteiniphilum and Methanothrix harundinacea became dominant acetate utilizers in a methanogenic reactor operated under strong ammonia stress.

Microorganisms in anaerobic digestion (AD) are easily affected by ammonia, especially acetoclastic methanogens. Thus, in ammonia-suppressed AD systems, acetate degradation is reported to be carried out mainly by the cooperation of syntrophic acetate oxidizers and hydrogenotrophic methanogens. Previous studies have revealed ammonia inhibition on microbial flora by AD performance, but the effect mechanism of ammonia on microbial metabolism remains poorly understood. In this study, we constructed a mesophilic chemostat fed with acetate as the sole carbon source, gradually increased the total ammonia nitrogen (TAN) concentration from 1 g L-1 to 6 g L-1, and employed the 16S rRNA gene, metagenomics, and metatranscriptomics analysis to characterize the microbial community structure and metabolic behavior. The results showed that even at the TAN of 6 g L-1 (pH 7.5), the methanogenesis kept normal, the biogas production was approximately 92% of that at TAN of 1 g L-1 and the acetate degradation ratio reached 99%, suggesting the strong TAN tolerance of the microbial community enriched. 16S rRNA gene analysis suggested that the microbial community structure changed along with the TAN concentration. Methanothrix predominated in methanogens all the time, in which the dominant species was gradually replaced from M. soehngenii to M. harundinacea with the increased TAN. Dominant bacterial species also changed and Proteiniphilum showed a significant positive correlation with increased TAN. Meta-omics analysis showed that the absolute dominant microorganisms at TAN of 6 g L-1 were M. harundinacea and Proteiniphilum, both of which highly expressed genes for anti-oxidative stress. M. harundinacea and the second dominant methanogen Methanosarcina highly expressed both acetate cleavage and CO2 reduction pathways, suggesting the possibility that these two pathways contributed to methanogenesis together. Proteiniphilum and some other species in Firmicutes and Synergistetes were likely acetate oxidizers in the community as they highly expressed genes for syntrophic acetate oxidization, H2 generation, and electron transfer. These results suggested that Proteiniphilum as well as M. harundinacea have strong ammonia tolerance and played critical roles in acetate degradation under ammonia-suppressed conditions. The achievements of the study would contribute to the regulation and management of the AD process.

Fluctuation Effect of Dissolved of TAN (Total Ammonia Nitrogen) on Diatom Abundance in Intensive Shrimp Culture Ponds

TAN (Total Ammonia Nitrogen) is the accumulation of nutrient elements needed by plankton to grow in intensive shrimp farming ponds. The purpose of this study was to determine the relationship effect of TAN concentration fluctuations on diatom abundance in the intensive shrimp culture cycle. This research was conducted during one intensive shrimp culture cycle at PT. Menjangan Mas Nusantara, Pandeglang, with its research variables is the dominance percentage of plankton abundance and the level of TAN solubility in ponds. The results showed that during the shrimp culture period the abundance of plankton was dominated by predominant diatom, chlorophyceae, and chyanophyceae classes. The percentage of diatom dominance during cultivation has a graph similarity with the level dissolved of TAN fluctuation in the pond. The dissolved of TAN itself is described continue to increase with shrimp farming age. Statically, the relationship between the dissolved effect of TAN concentration on diatom abundance in ponds was modeled by the regression equation y = 2.210 + 32.411 (R2= 0.88; α0.00). The conclusion obtained from the results of this study, the level of dominance by diatom abundance during shrimp culture period is strongly influenced by the fluctuation of TAN concentration as the main nutrient element in ponds with a significance level of 88%.

Nitrogen loads in urban surface runoff from a major, cold-region North American city in 1991–2021

Long-term monitoring of pollutant loads in urban surface runoff is important but uncommon. In this study, we examined nitrogen loads in stormwater and snowmelt runoff from four urban catchments of a major, cold-region North American city over the past 31 years (1991–2021). Temporal variability of total organic nitrogen (TON), nitrate and nitrite nitrogen (NOx-N), total ammonia nitrogen (TAN), and total nitrogen (TN) were similar in the four catchments, which had an increasing trend from 1992 (TN: 1.3–3.4 kg/ha/year) to 2006–2011 (TN: 5.5–19.3 kg/ha/year) and a decreasing trend afterward. Trends and change points in the four urban catchments were influenced by storm/snowmelt events, land use, urban drainage infrastructure issues, and stormwater management facilities. The maximum monthly fluctuation occurred in March/April and July due to high variations of snowmelt and storm events. The ratios of monthly loads during the storm season (April to October) to the snow season (November to March) for TON, NOx-N, and TN were 1.31, 1.12, and 1.15, respectively; whereas it was 0.95 for TAN. TKN, TAN, and TN event mean concentrations (EMCs) in snowmelt were higher (18.0%, 94.0%, and 10.8%, respectively) than those in stormwater. However, the NOx-N EMC in snowmelt was lower (9.3%) than in stormwater.

Evaluation of digestate-derived biochar to alleviate ammonia inhibition during long-term anaerobic digestion of food waste

The feasibility of using food waste anaerobic digestate-derived biochar (FWDB) to mitigate ammonia toxicity in an anaerobic digester was evaluated. The optimal conditions for preparing and adding the activated FWDB were explored using response surface experiments, and the long-term effects of adding activated FWDB on digester performance under optimum conditions were verified in semi-continuous experiments. The results showed that the optimal preparation and addition conditions for activated FWDB were pyrolysis temperature of 565 °C, particle size of 0–0.30 mm, and dosage of 15.52 g·L−1. During the long-term operation of the digesters, when the total ammonia nitrogen (TAN) concentration was higher than 2000 mg·L−1, the control and experimental digesters showed deteriorated reactor performance. Volatile fatty acids in the control digester accumulated to 20,306 mg·L−1 after the TAN concentration increased to 3391 mg·L−1, the methane yield decreased to 31 mL·g VS−1, and the digester experienced process failure. In contrast, the experimental digester with added activated FWDB only suffered a slight short-term accumulation of acetate and a slight decline in methane yield. This may be attributed to the adsorption of NH4+/NH3 by activated FWDB, which reduced the TAN concentration in the anaerobic digestion (AD) system and mitigated ammonia toxicity. Microbial analysis and metagenome predictions demonstrated that the community richness, diversity, and evenness, as well as the abundance of acetogens and related key genes (ACSM1, paaF, and acdA) were higher in the experimental digester than in the control digester. This study provides a closed-loop AD enhancement strategy by pyrolysis of digestate and in-situ supplementation into the digester.

Food waste digestate composting enhancement by sodium polyacrylate addition: Effects on nitrogen transformation processes and bacterial community dynamics

The influences of sodium polyacrylate (PAAS) at the ratios of 0% (CK), 0.5% (F1), 1.0% (F2), 1.5% (F3), 2.0% (F4) and 2.5% (F5) on nitrogen transformation and bacterial community composition were investigated in the composting of food waste digestate (FWD) and corn straw (CS). PAAS addition increased the thermophilic temperature but had no significant effect on pH values. PAAS exerted significantly effects on the concentration of total nitrogen (TN), ammonia nitrogen (NH4+-N), nitrite-nitrogen (NO2−-N) and nitrate-nitrogen (NO3−-N). The compost product in 1.0% PAAS treatment was more active in absorbing nutrients. Firmicutes (9.40–83.54%), Actinobacteriota (9.98–51.50%), Proteobacteria (0.20–27.87%) and Bacteroidota (0.11–34.69%) were the dominant phyla in FWD composting. Moreover, relative to CK, PAAS promoted the propagation of dominant bacterial phyla Firmicutes with increment of 30.05–102.06% in the thermophilic phase. Kroppenstedtia, Thermobifida and Saccharomonospora were observed to be dominant at the maturing phase and correlated with NH4+-N, NO2−-N, TN and NO3−-N. Therefore, they might be regarded as probable biomarkers symbolic for the maturing phase during FWD composting. The compost product had the highest maturity degree in 1.0% PAAS treatment. These results indicated that PAAS addition improved the maturity and nutrient contents of the compost product as well as altered compost bacterial community dynamics.

Stocking Density Effects on Pacific White Shrimp Litopenaeus vannamei Hatchery Performance in Algal‐Bacterial Biofloc Systems

AbstractThe effects of stocking density of Pacific white shrimp Litopenaeus vannamei from hatchery stages nauplius 5 (N5) through postlarval 5 (PL5) were evaluated in algal–bacterial biofloc systems. Triplicate stocking densities of 200 (D200), 300 (D300), and 400 (D400) shrimp larvae/L were used. No water exchange or additional carbon source was conducted during the 14‐d experiment. Compared with other groups, the D400 stocking density had significantly higher concentrations of total ammonia nitrogen and nitrite‐nitrogen (0.55 and 0.66 mg/L, respectively). Nitrate‐nitrogen and total nitrogen continuously accumulated throughout the experiment, with no significant difference among the three groups. The chlorophyll‐a concentration, alkalinity, and pH of all three groups showed a downward trend in the later stage of the experiment. Shrimp larvae at the lowest stocking density had a higher survival during the rearing. Total Vibrio spp. count in the D200 group was lower than that of the other two but was not significantly different. In conclusion, we found that a stocking density of 200 shrimp larvae/L resulted in better survival and water quality conditions in the rearing systems tested.

Design methodologies to determine optimal staging of membrane-aerated biofilm reactors for mainstream treatment with anammox.

Partial nitritation anammox (PNA) membrane-aerated biofilm reactors (MABRs) can be used in mainstream nitrogen removal to help facilities reduce their energy consumption. Previous PNA MABR research has not investigated the impacts of staging, i.e. arraying MABRs in series, on their nitrogen removal performance, operation, and ability to suppress nitrite oxidizing bacteria. In this paper, a mathematical model simulated PNA MABR performance at different influent total ammonia concentrations and loadings. A design methodology for staging PNA MABRs was created and found that the amount of membrane surface area is dependent upon the total ammonia-nitrogen concentration and loading, and the air loading to the membrane must be proportional to the total ammonia-nitrogen loading to maximize the total inorganic nitrogen (TIN) removal rate. This led to approximately equal-sized stages that each had a TIN removal percentage of 71% of the influent total ammonia nitrogen. Staging a treatment train resulted in 9.8% larger total ammonia and 9.3% larger total nitrogen removal rates when compared with an un-staged reactor. The un-staged reactor also was not able to produce an effluent total ammonia concentration below 5 mg N/L which would be necessary for many facilities' permits.

The Effect of Substrate on Water Quality in Ornamental Fish Tanks.

Simple SummaryFish kept as pets are almost always held in tanks with substrate such as gravel or sand on the bottom of the tank. This may be added as a form of enrichment to encourage natural fish behaviours, or for aesthetic reasons. However, substrate can also harbour elevated levels of waste products and unwanted bacteria; therefore, whether the use of substrate in home aquaria is advantageous or disadvantageous has not been fully considered. Here, we investigated whether there was a difference in water quality in home aquaria that contained either no substrate (bare tanks), plastic plants as enrichment but no substrate, sand or gravel substrate. Water quality (e.g., temperature, oxygen, pH and ammonia) and the presence of bacteria were measured over a 7-week period. As water quality can also vary with the season, the study was repeated at different times of the year. Addition of both gravel and sand substrate resulted in increased pH and the waste products ammonia and nitrate. Substrate was also associated with a greater presence of bacteria. In conclusion, the use of substrate affected water quality, with further research needed on the use of substrate in home aquaria.Almost all home aquaria contain substrate, either as intentional enrichment or for aesthetic purposes. For fishes, benefits of structural enrichment have been well considered, particularly in research and aquaculture settings. However, our understanding of the impacts of tank substrate as enrichment is limited. While substrate can induce foraging in some species, a major drawback is the potential of substrate to harbour elevated levels of waste and pathogenic bacteria. Here, we considered whether substrate as a form of environmental enrichment significantly altered water quality and bacterial presence in home aquaria. Water quality (temperature, oxygen, pH, TAN, unionised ammonia, nitrate, Ca2+, Na+, Mg2+ and K+) and bacterial presence (Pseudomonas spp.) were measured over two seven-week periods in stand-alone, tropical, freshwater tanks that simulated home aquaria. The following four enrichment conditions were considered: bare tanks, plastic plants, gravel substrate or sand substrate. The addition of both gravel and sand resulted in increased pH, concentrations of total ammonia nitrogen and nitrate. Substrate was also associated with a greater Pseudomonas presence. Decreased pH alongside an increased concentration of ions were also observed depending on the time of year. In conclusion, enrichment type affected the water quality of home aquaria, with further research needed on the role of the tank biome in fish welfare.

Efficacy of quick-start nitrifying products in controlled fresh-water aquaria

Quick-start nitrifying products (QSNP) are sold to aquarium hobbyists with the claim that the nitrogen cycle is rapidly initiated allowing for instant addition of fish. Despite these claims, none of these products have been the subject of peer-reviewed evaluation. Six 10-gallon aquaria were used to simulate a naïve fresh water system. Water temperature, pH and dissolved oxygen were measured to ensure stability between aquaria. On Day 0, 1.0-ppm ammonium hydroxide was added to each of the aquaria. Five aquaria received a different QSNP on Day 1 of the study. One aquarium acted as a control, receiving no QSNP. Total ammonia nitrogen (TAN), nitrite and nitrate levels were monitored every 48-hours for 14 days. Total ammonia nitrogen concentrations were significantly lower in the Tetra® samples compared to all other samples and controls (all p<0.001). Additionally, TAN concentrations were significantly lower on days 4-14 compared to baseline (all p<0.001). There were no significant differences in nitrite concentrations by treatment (F=1.3, p=0.263) or time (F=1.0, p=0.416). Nitrate concentrations were significantly higher in the Cycle® (p<0.001) and Tetra® (p=0.001) samples compared to the control samples. Nitrate concentrations were also found to be significantly higher on days 4 (p=0.027), 10 (p=0.041), 12 (p=0.011), and 14 (p=0.007) compared to baseline. Four out of five QSNP failed to reduce TAN concentrations from baseline levels over the 14-day test period. One of the QSNP appears to significantly be able to reduce TAN concentrations in controlled freshwater aquaria. Quick-start nitrifying products should not be recommended as a sole method when initiating the nitrogen cycle in fresh water aquaria until further studies have evaluated these products.

Reducing Carbon Input Improved the Diversity of Bacterial Community in Large-Scale Biofloc Shrimp Culture Facilities

In this study, a group of large-scale biofloc shrimp culturing facilities were designed. The bioflocs were domesticated by continuously reducing the ratio of carbon to feed. The bacterial community diversity on the 20th, 40th, 60th, and 80th days was analyzed by high-throughput sequencing technology. The results showed that the biofloc content (0~16.8 ± 4.3) mL/L, TSS concentration (0~247.46 ± 27.3) mL/L, total ammonia nitrogen concentration (0~0.28 ± 0.052) mg/L, nitrite nitrogen concentration (0~4.13 ± 1.42) mg/L, nitrate nitrogen concentration (108.57 ± 19.6) mg/L were all within the safe concentration range of Litopenaeus vannamei. With the progress of reducing carbon input, the Chao1 index, the number of operational taxonomic units, and the Shannon index increased significantly. The number of OTUs of B80 (572.36 ± 13.26) was significantly higher than that of B60 (489.69 ± 12.97), B40 (423.35 ± 18.46) and B20 (407.67 ± 15.65) (p &lt; 0.05). The Chao1 index of B80 (768.58 ± 36.96) was significantly higher than that of B60 (646.8 ± 52.53), B40 (569.7 ± 46.53) and B20 (516.3 ± 21.35) (p &lt; 0.05). The Shannon index of B80 (5.63 ± 0.16) was higher than that of B60 (4.85 ± 0.13), B40 (4.68 ± 0.21) and B20 (3.65 ± 0.22), with significant difference (p &lt; 0.05). At the end of the experiment, the domestication formed a micro-ecosystem with Proteobacteria as the carrier (46.98 ± 15.82%), Chloroflexi as the skeleton (2.2 ± 0.36%), Nitrospirae (1.35 ± 0.26%) as the main water treatment functional bacteria, and other bacteria as auxiliary nitrogen and phosphorus removal; At the genus level, unclassified_f_Rhodobacteracea (22.97 ± 3.82%), Ruegeria (10.35 ± 1.26%), Muricauda (5.73 ± 0.61%), Algoriphagus (3.75% ± 0.85%) and Nitrospira (1.56 ± 0.56%) are the dominant bacteria. Under the synergistic effect of the above bacteria, the biofloc system remains relatively stable. The survival rate and unit yield of shrimp were (65.32 ± 6.85)% and (4.15 ± 1.58) kg/m3, respectively.

Study on Soil Leaching Risk of Reuse of Reclaimed Fertilizer from Micro-Flush Sanitary Wastewater

In view of the potential soil leaching risk of the reuse of fertilizer reclaimed from micro-flush sanitary wastewater, the batch tests of soil adsorption and degradation, soil column percolation test and multi-stage soil box percolation test were adopted. The characteristics of leachate after the interaction between reclaimed fertilizer and soil, as well as the changes of soil attributes in the soil box system, were analyzed. After obtaining the correlation coefficients of solute transport in soil through the above experiments, the HYDRUS-1D model was constructed to simulate the solute migration and transformation in the soil with a duration of 1 year and a soil thickness of 5 m. The impacts of leachate on groundwater and soil were analyzed. The results showed that the adsorption intensity of total ammonia nitrogen (TAN) (1n=0.8009) in the tested soil was lower than that of chemical oxygen demand (COD) (1n=1.1830). The HYDRUS prediction showed that concentrations of TAN and COD at the soil depth of 5 m were 0, while total nitrogen (TN) still had a concentration of 0.11 mg/L. However, the TN leaching into the deep soil mainly came from the soil itself. The TAN at 3.4 m soil showed an upward trend in the prediction period. In addition, the reuse of reclaimed fertilizer can expand the soil nutrient inventory, which is conducive to the improvement of soil fertility. It can be concluded that the soil leaching risk of reuse of reclaimed fertilizer is not significant in the short term (one year). However, the risk of fertilization on soil with high-nitrogen background value should be paid attention to in the long term.

Positive effects of replacing commercial feeds by fresh black soldier fly (Hermetia illucens) larvae in the diets of Pacific white shrimp (Litopenaeus vannamei): Immune enzyme, water quality, and intestinal microbiota

This study investigated the effects of replacing commercial feeds with fresh black soldier fly larvae (BSFL) on the immune enzyme activities, water quality in the culturing environment, and intestinal microbiota of Pacific white shrimp (Litopenaeus vannamei). Five different feeding regimes were designed, in which 0% (control group), 25%, 50%, 75%, and 100% commercial feeds were replaced with equal wet weight of fresh BSFL, respectively. The experiment lasted for 45 days, and the results showed that the serum T-NOS (total nitric oxide synthase), AKP (alkaline phosphatase), and ACP (acid phosphatase) activity were significantly increased in the BSFL25% group. However, the immune enzymes of the hepatopancreas decreased significantly in all the BSFL-containing groups compared to the control group. Total ammonia nitrogen concentrations throughout the experimental phase and nitrate concentrations in the middle and later phases of the experiment were negatively correlated with the replacement rate of fresh BSFL in the diet, whereas pH was positively correlated with the replacement rate of fresh BSFL in the diet. Proteobacteria and Bacteroidetes were dominant phyla in the intestines of shrimps, but the relative abundances of Proteobacteria and Firmicutes decreased, with those of Bacteroidetes and Planctomycetes increased in the BSFL-containing groups. Among them, higher relative abundances of potential probiotics such as Motilimonas, Shimia, Pseudoalteromonas, and Shewanella and lower relative abundance of genus Vibrio were observed in the fresh BSFL-containing groups. Furthermore, shrimps fed with BSFL-containing diets had higher bacterial richness and diversity in the intestines. In conclusion, a proper replacement of commercial feed with fresh BSFL had a positive effects on the immune-related enzyme activities, water quality, and intestinal health in the L. vannamei.

Long-term evaluation of the anaerobic co-digestion of food waste and landfill leachate to alleviate ammonia inhibition

To evaluate the feasibility of the co-digestion of food waste (FW) and landfill leachate (LL) to alleviate ammonia inhibition, a series of batch co-digestion experiments were conducted to explore the optimal substrate mixing ratio, and semi-continuous experiments were conducted to evaluate the long-tern effects of LL addition on methane generation and digestate characteristics of the anaerobic co-digestion system under ammonia stress. The optimum methane generation and digestate properties were observed when the concentration of LL in the dilution liquid in the co-digestion reactor was 40 % (v/v). Significant volatile fatty acid accumulation and lower methane yields were both observed during the long-term FW mono-digestion when the total ammonia nitrogen (TAN) concentration reached 3391.27 mg·L–1. However, stable methane generation was observed in the co-digestion system, even when the TAN was 3721.59 mg·L–1, confirming that the LL alleviated the ammonia inhibition of the FW-based anaerobic digestion (AD) system. Microbial analysis of the AD reactors demonstrated that the relative abundance of Pelotomaculum was higher in the co-digestion system than in the mono-digestion system. Analysis of the phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) confirmed the enrichment of genes involved in butyrate, propionate, and methane metabolism in the co-digestion system. In addition, analysis of the digestate characteristics (i.e., dewaterability, germination index, and heavy metals concentrations) indicated that there was no ecological risk for utilization of the digestate after long-term co-digestion operation. These results aim to provide guidance for using LL to promote the processing of FW in the future.

Organic matter removal performance, pathway and microbial community succession during the construction of high-ammonia anaerobic biosystems treating anaerobic digestate food waste effluent.

This study aimed to establish anaerobic biosystems which could tolerate high ammonia, and investigate the microbial community structure in these reactors. High-ammonia anaerobic biosystems that could tolerate 3600mgL-1 total ammonia nitrogen (TAN) and 1000mgL-1 free ammonia nitrogen (FAN) were successfully established. The removal efficiencies of COD and total volatile fatty acids (TVFAs) in R1 with dewatered sludge as inoculum were 68.8% and 69.2%, respectively. The maximum methane production rate reached 71.7±1.0mL CH4 L-1 d-1 at a TAN concentration of 3600mgL-1. The three-dimension excitation-emission matrix analysis indicated that both easily degradable organics and refractory organics were removed from ADFE in R1 and R2. Functional microorganisms which could bear high ammonia were gradually enriched as TAN stress was elevated. Lysinibacillus, Coprothermobacter and Sporosarcina dominated the final bacterial community. Archaeal community transformed to hydrogenotrophic methanogen. The synergy of Coprothermobacter and Methanothermobacter undertook the organic matter degradation, and was enhanced by increasing TAN stress. This study offers new insights into anaerobic bioremediation of ammonia-rich wastewater.

Water spray reactor for ammonia removal via air stripping: An evaluation on mass transfer and process efficiency

This paper offers a technical assessment of a developed reactor for ammonia removal via air stripping method. Optimum operational conditions were determined by experimenting numerous major parameters such as water flow, air flow, initial TAN (Total Ammonia Nitrogen) concentrations, pH, and orifice diameter of nozzles. It was found that water flow of 10 L/min, air flow rate at 120 L/min, and pH 11 were of significant parameters that facilitated higher ammonia removal efficiency up to 99 % after 7 h of experimental run with KLa = 0.0114 min-1. Empirical mathematical expression generated by employing Buckingham’s π theorem was shown to be a good fit (R2 = 0.992) to identify the relationship among Reynolds number, Weber number, and mass transfer coefficient KLa. Our newly developed reactor demonstrated satisfying performance with relatively lower air consumption (2016 L air/L liquid) compared to that of jet loop reactor (2266 L air/L liquid) and water-sparged aerocyclone (2394 L air/L liquid). The future development of this air stripping device is propitious since our reactor also enables advantages e.g., adjustable input volume and simple maintenance from scaling and fouling.