Digestion Of Swine Wastewater Research Articles

Anthraquinone-2-sulfonate immobilized on granular activated carbon inhibits methane production during the anaerobic digestion of swine wastewater

Anthraquinone-2-sulfonate immobilized on granular activated carbon inhibits methane production during the anaerobic digestion of swine wastewater

Biochar and modified magnetic biochar enhanced anaerobic digestion of swine wastewater under ammonia stress: Performance and microbial dynamics

This study aimed to investigate the effectiveness and mechanism of biochar and modified magnetic biochar addition in improving the anaerobic digestion (AD) efficiency of swine wastewater under ammonia stress. Two batches of serial experiments were carried out with ammonia levels of 3000, 4500, and 6000 mg/L. The results indicated that a one-time addition of 15 g/L of both types of carbon materials could sustainably optimize the AD performance of swine wastewater at ammonia nitrogen levels of 3000 and 4500 mg/L. In the second batch of experiments, at 4500 mg/L ammonia, groups with C and FeC additions showed 6.5%, 16.2% higher cumulative methane yield and 45.5%, 60.0% greater maximum gas production rates than controls. However, under the ammonia stress condition of 6000 mg/L, the reactor exhibited a mismatch between the carbon material addition and the degree of stress. The maximum methane production rate was intensified only in the first batch, which was 71.8% and 105.1% higher in the C and FeC groups, respectively, than in the control group. The microbiological analysis revealed that biochar optimized the AD performance by enriching the abundance of fermentative bacteria and enhancing the activity of Methanosaeta. In contrast, modified magnetic biochar promoted the enrichment of acetogens and shifted the dominant methanogens from sensitive Methanosaeta to the highly ammonia-tolerant Methanosarcina, thus causing the optimization of AD performance. The findings of this study provided new insights into the mitigation of inhibition and enhancement of efficacy in the anaerobic digestion of swine wastewater.

Coupled In-Situ Fermentation for Enhanced Biological Phosphorus Removal from Digested Swine Wastewater

This study demonstrated the feasibility of enhanced biological phosphorus removal coupled with in-situ fermentation (EBPR-F) to improve phosphorus removal from real digested swine wastewater. We used fermentable substrates (casein hydrolysate and glucose) as the external carbon sources to promote in-situ fermentation and enhance biological phosphorus removal. Compared with conventional EBPR dominated by Candidatus Accumulibacter, EBPR-F had significantly better phosphorus removal with enriched polyphosphate-accumulating organisms (PAOs). Under supplementation with 100 mg/L glucose, total phosphorus (TP) removal was over 95% in EBPR-F, with an average TP concentration in the effluent below 1.0 mg/L, satisfying the discharge standard (8 mg P/L) in China. The PAO activity and relative abundance of Candidatus Accumulibacter (44.7% ± 3.1%) and Tetrasphaera (18.1% ± 6.6%) in EBPR-F were much higher than those in EBPR. The improvement in phosphorus removal of EBPR-F was due to the enrichment of Tetrasphaera through the enhanced in-situ fermentation, as Tetrasphaera can efficiently ferment complex organic matter and provide bioavailable organics for phosphorus removal.

Mechanistic insights into synergistic facilitation of copper/zinc ions and dewatered swine manure-derived biochar on anaerobic digestion of swine wastewater

Biochar-assisted anaerobic digestion (AD) has been proposed an advanced system for swine wastewater (SW) management. However, the effects of metallic nutrients in SW, such as copper/zinc ions (Cu2+/Zn2+), on the biochar-assisted AD of SW are not well understood. This study investigated the influences of individual Cu2+/Zn2+ or dewatered swine manure-derived biochar, as well as their combined additions, on the AD of SW. The results showed that exposure to 50 mg/L Cu2+/Zn2+ temporary inhibited methane production, but the addition of 20 g/L biochar alleviated this inhibition by shortening the methanogenic lag time and increasing methane yield. Following a period of acclimation, both Cu2+/Zn2+ and biochar promoted methane production, although metagenomic analysis revealed distinct mechanisms underlying their promotion. Cu2+/Zn2+ enhanced ATP processing, including electron exchange between NADH/NAD+ and succinate/fumarate transformation, by 26.0–35.8%. Additionally, the gene encoding Coenzyme M methylation was upregulated by 36.2% along with enrichments of Methanocullus and Methanosarcina, contributing to accelerated hydrolysis and methanogenesis rates by 54.7% and 44.8%, respectively. On the other hand, biochar mainly stimulated bacterial F-type ATPase activities by 28.4%, likely facilitating direct interspecies electron transfer between Geobacter and Methanosarcina for syntrophic methanogenesis. The combined addition of Cu2+/Zn2+ and biochar resulted in “win-win” benefits, significantly increasing the maximum methane production rate from 40.3 mL CH4/d to 53.7 mL CH4/d. Moreover, the introduction of biochar into AD of SW facilitated the transformation of more Cu2+/Zn2+ from a reducible Fe–Mn oxides form to a residual form, which potentially reduced the metallic toxicity of the digestate for soil amendment. The findings of this study provide novel insights into understanding the synergistic impacts of heavy metals and biochar in regulating SW during AD, as well as the management of associated digestate.

Combined effects of oxytetracycline concentration and organic loading rate on semi-continuous anaerobic digestion of swine wastewater

High concentrations of antibiotics in swine wastewater raises concerns about the potential adverse effects of anaerobic digestion (AD). Current studies mainly focused on the effects of various antibiotic concentrations. However, these studies didn’t take into account the fluctuation of swine wastewater quality and the change of reactor operating conditions in practical engineering applications. In this study, it was found that in the operating systems with COD of 3300 mg/L and hydraulic retention time (HRT) of 4.4 days, the continuous addition of oxytetracycline for 30 days had no effect on the AD performance. Nevertheless, when COD and HRT were changed to 4950 mg/L and 1.5 days respectively, oxytetracycline at 2 and 8 mg/L increased the cumulative methane yield by 27% and 38% at the cost of destroying cell membrane, respectively, while oxytetracycline at 0.3 mg/L improved the performance and stability of AD. These results could be referred for practical engineering applications.

Co-precipitation of heavy metals with struvite from digested swine wastewater: Role of suspended solids

Struvite production can recover ammonia and phosphorous from digested wastewater as fertilizer. During struvite generation, most of the heavy metals was co-precipitated with ammonia and phosphorous into struvite. Understanding the precipitation behavior of heavy metals with suspended solids (SS) might provide the possible strategy for the control of co-precipitation. In this study, the distribution of heavy metals in SS and their role on the co-precipitation during struvite recovery from digested swine wastewater were investigated. The results showed that the concentration of heavy metal (including Mn, Zn, Cu, Ni, Cr, Pb and As) ranged from 0.05 to 17.05 mg/L in the digested swine wastewater. The distribution analysis showed that SS with particles > 50 μm harbored most of individual heavy metal (41.3–55.6%), followed by particles 0.45–50 μm (20.9–43.3%), and SS-removed filtrate (5.2–32.9%). During struvite generation, 56.9–80.3% of individual heavy metal was co-precipitated into struvite. The contributions of SS with particles > 50 μm, 0.45–50 μm, and SS-removed filtrate on the individual heavy metal co-precipitation were 40.9–64.3%, 25.3–48.3% and 1.9–22.9%, respectively. These finding provides potential way for controlling the co-precipitation of heavy metals in struvite.

Fertilizer Performance of a Digestate from Swine Wastewater as Synthetic Nitrogen Substitute in Maize Cultivation: Physiological Growth and Yield Responses

Nitrogen (N) is the primary nutrient required for plant growth. During the last few decades, there has been extensive use of synthetic N-containing fertilizers in agriculture, resulting in increased environmental pollution. In this study, the feasibility of replacing synthetic N with biofertilizer in maize cultivation was investigated. A liquid biofertilizer (digestate obtained from the anaerobic digestion of swine wastewater) was obtained and applied to large plots as a total (100%) or partial (50%) substitute for synthetic N fertilizer. Moreover, the most efficient fertilization mode, i.e., basal versus foliar application, was studied. Physiological growth indices, leaf nutritional status, and grain yield were assessed for each biofertilization treatment and compared with the conventional treatment with synthetic minerals. Compared with the conventional treatment, the total substitution of synthetic N by the biofertilizer (basal application) did not affect the growth parameters and grain yield of maize; the other treatments usually resulted in lower growth rates and yields, although not statistically significant (p ≥ 0.05). No difference was observed among the treatments for the contents of N, P, K, or Mg in the leaves. Generally, the highest means for Fe, Ca, Cu, Zn, and Mn contents in leaves were observed after in-row broadcast of synthetic fertilizers or basal application of the digestate as a total substitute for synthetic N, with a significant effect for Fe (p < 0.05). The mode of the biofertilizer application did not have any significant effect on either growth parameters or leaf nutrients. The data show that under the specific conditions of the study, the total substitution of mineral N with basal application of biofertilizer is the best strategy for minimizing the use of synthetic chemicals in maize cultivation without yield penalties.

Effects of ciprofloxacin on biogas production and microbial community composition in anaerobic digestion of swine wastewater in ASBR type reactor

ABSTRACT In swine farming, antibiotics are often used to reduce disease and promote animal growth. Part of these compounds is not absorbed by the swine body, being excreted and later reaching the treatment systems, soil, and nearby waterbodies. This research sought to investigate the influence of adding ciprofloxacin (CIP) on the anaerobic digestion of swine wastewater. For that, a bench-scale anaerobic sequential batch reactor (ASBR) was used, with 5 L of working volume in six different phases, with volumetric organic loading rate (VOLR) and CIP dosage variation. According to the results, the optimal VOLR for the reactor was 0.60 ± 0.11 gSV L−1 d−1, resulting in biogas productivity of 0.51 ± 0.03 Lbiogas L−1 d−1. After initial stability, adding substrate with 0.5 mgCIP L−1 resulted in an abrupt drop of 82% in the productivity from the 7th to 11th day of addition, coinciding with volatile acids accumulation. Afterward, the reactor recovered and reached apparent stability, with productivity similar to the previous step without the drug. For 2.5 mgCIP L−1 in the substrate, the biogas productivity at equilibrium was 11.8% lower than in the phases with the same VOLR and 0.0 and 0.5 mgCIP L−1. Organic matter removals near 80% were achieved for both dosages. The 16S rRNA metagenomic analyses showed an increase in the relative abundance of most of the phyla found, indicating that the dosages used allowed the acclimatization of microorganisms and possibly the compound biodegradation.

Mechanism of action of single and mixed antibiotics during anaerobic digestion of swine wastewater: Microbial functional diversity and gene expression analysis

The mechanism by which antibiotics in swine wastewater affect anaerobic digestion (AD) remains unclear. Herein, we investigated how single and mixed antibiotics affect AD in swine wastewater. Both single and mixed antibiotics stimulated methane production at actual concentrations of 0.5–2 mg/L. Low-dose antibiotics (0.5 mg/L) exerted the most significant stimulatory effect on methane production, which increased by 211.63% (single) and 60.93% (mixed), respectively. However, an increased dose decreased the stimulatory effect on methane production. Overall, single antibiotics were more beneficial for methane production than mixed antibiotics since single antibiotics could promote the conversion of propionic and butyric acid, while mixed antibiotics inhibited the process. Microbial community analysis showed that single and mixed antibiotics could also lead to large changes in functional acidogens, ultimately leading to changes in methanogenic pathways.

Effects of Sulfamethazine and Cupric Ion on Treatment of Anaerobically Digested Swine Wastewater with Growing Duckweed.

Duckweed (Spirodela polyrrhiza) has the potential to treat anaerobically digested swine wastewater (ADSW), but the effects of antibiotics and heavy metals in ADSW on the treatment performance and mechanism of Spirodela polyrrhiza are not clear. Herein, an experiment was conducted to investigate the effects of sulfamethazine (SMZ) and cupric ion on NH4+-N and total phosphorus (TP) removal from synthetic ADSW. The activity of superoxide dismutase (SOD) and the contents of photosynthetic pigments, vitamin E, and proteins in duckweed were also evaluated. Under the stress of SMZ, duckweed showed excellent removal efficiency of nutrients, and the results of SOD activity and photosynthetic pigments content indicated that duckweed had good tolerance to SMZ. Interestingly, a combined application of SMZ and cupric ion would inhibit the nutrient removal by duckweed, but significantly increased the contents of photosynthetic pigments, proteins, and vitamin E. In addition, the consequence indicated that high value-added protein and vitamin E products could be produced and harvested by cultivating duckweed in ADSW. Furthermore, possible degradation pathways of SMZ in the duckweed system were proposed based on the analysis with LC-MS/MS. This research proposed a novel view for using duckweed system to remove nutrients from ADSW and produce value-added products under the stress of SMZ and cupric ion.

Exploration of Microalgal Species for Nutrient Removal from Anaerobically Digested Swine Wastewater and Potential Lipids Production.

Bio-treatment of anaerobically treated swine wastewater (ADSW) mediated by microalgae has been deemed as a promising strategy. In the present study, six microalgal strains were used to conduct batch experiments in 0~100% ADSW in order to evaluate their potentials for nutrient removal and biodiesel production. Two strains, Chlorella vulgaris FACHB-8 and Chlorella sp. FACHB-31, were selected based on their better growth performances, higher tolerance to wastewater (up to 100%), and better nutrient removal abilities. The capacity of each strain to remove TN, TP, NH4+-N, as well as lipid production and biomass composition in 100% ADSW were further examined. After 15 days of culture, 87.68~89.85%, 92.61~93.68%, and 97.02~97.86% of the nitrogen, phosphorus, and ammonia nitrogen were removed by Chlorella sp. FACHB-31 and C. vulgaris FACHB-8. Their lipid content and lipid productivities were 29.63~33.33% and 18.91~23.10 mg L−1 d−1, respectively. Proteins were both the major biomass fraction followed by lipids and then carbohydrates. Their fatty acid profiles both mainly consisted of C-16:0, C-18:1, C-18:0, and C-18:2. Taken together, our results suggest that C. vulgaris FACHB-8 and Chlorella sp. FACHB-31 are potential candidates for biodiesel production by using ADSW as a good feedstock.

Improved mesophilic anaerobic digestion of swine wastewater by ammonia stripping with microwave irradiation

ABSTRACT Ammonia (NH3) stripping by microwave irradiation was used to increase the efficiency of anaerobic digestion. The effects of final temperature (FT) (80 ≤ FT ≤ 100°C) and microwave irradiation time (MIT) (2.5 ≤ MIT ≤ 5.5 min) of NH3 stripping, and hydraulic retention time (HRT) (7 ≤ HRT ≤ 20 d) in anaerobic digester were quantified. NH3 concentration decreased from 2794 to 140 mg/L within 5.5 min at FT = 100°C. The highest cumulative biogas production (>1800 mL/L) and efficiency of volatile solid removal (> 68%) were achieved at FT = 100°C and MIT = 5.5 min. The removal efficiency of volatile solid in digesters fed with untreated swine wastewater (control) and swine wastewater treated by NH3 stripping decreased as HRT decreased. The highest relative improvement of properties compared to the control occurred at 10 or 15 d HRT. Increases in biogas production compared to the control increased with the NH3 stripping as HRT was reduced to 10 d (243% higher at 10 d). The methane content of the produced biogas was 64–69% for control and 68–75% with NH3 stripping in the range of 10–20 d HRT. NH3 stripping using microwave irradiation is an effective pretreatment to improve the anaerobic digestion of swine wastewater.

Intermittent air mixing system for anaerobic digestion of animal wastewater: Operating conditions and full-scale validation

An air mixing system for anaerobic digestion has been proved to be beneficial for methane production. The aim of the present study was to further investigate the appropriate conditions for air mixing. The effective methane production time (EMPT) was defined to determine the air mixing time in the article. The results indicated that the appropriate aeration intensity was 66.7 mL air per volume of reactor per min and mixing time was 1.5 min. When air mixing time exceeded 3 min on each occasion, total CH4 production was less than that achieved under the no mixing condition due to a decrease in the EMPT. In addition, the possibility of air mixing was evaluated in an anaerobic full-scale plant comprising a continuous stirred tank reactor. One year of operating data validated the feasibility of air mixing during the anaerobic digestion of swine wastewater.

Inhibition of tetracycline on anaerobic digestion of swine wastewater

The inhibition of tetracycline on anaerobic digestion of synthetic swine wastewater was examined with a semi-continuous operation for 103 days at a dosage ranging 2–8 mg/L. COD concentrations, VFA compositions in effluents and methane production were measured. The negative effects of tetracycline on the four individual steps of anaerobic digestion and its toxicity on anaerobic microorganisms were also evaluated. Results showed that continuous addition of 8 mg/L tetracycline in the bioreactor resulted in 73.28% reduction of daily methane production and made anaerobic digestion upset. Besides, methanogenesis was particularly inhibited compared to other three steps and the corresponding enzyme activities decreased by 66%. Furthermore, the polysaccharide contents in EPS increased after exposure to tetracycline, which could inhibit direct connections among microorganism. At last, long-term exposure to tetracycline inhibit anaerobic microbial activities and caused liberation of lactate dehydrogenase. The results would provide novel insights for anaerobic digestion of swine wastewater.

Performances of simultaneous enhanced removal of nitrogen and phosphorus via biological aerated filter with biochar as fillers under low dissolved oxygen for digested swine wastewater treatment.

This study aims to explore the feasibility of biochar as a carrier to improve the simultaneous removal of nitrogen and phosphorus in biological aerated filters (BAFs) for treating low C/N digested swine wastewater (DSW). Two similar BAFs (BAF-A with hydrophobic polypropylene resin as fillers and BAF-B with bamboo biochar as carrier) were developed for DSW treatment. Results showed that the NH4+-N, TN, and TP removal performances in BAF-B were higher than those in BAF-A. Carrier type had an obvious influence on the structures and diversity of the microbial population. The biochar carrier in BAF-B was conducive to the enrichment of the functional microorganisms and the increase of microbial diversity under high NH4+-N conditions. Microbial analysis showed that the genera Rhodanobacter (10.64%), JGI_0001001-h003 (14.24%), RBG-13-54-9 (8.87%), Chujaibacter (11.27%), and Ottowia were the predominant populations involved in nitrogen and phosphorus removal in the later stage of phase III in BAF-B. BAF with biochar as carrier was highly promising for TN and TP removal in low C/N and high NH4+-N DSW treatment.

Removal of Nutrients From Anaerobically Digested Swine Wastewater Using an Intermittent Cycle Extended Aeration System.

Swine wastewater contains high concentrations of organic compounds, nutrients (nitrogen and phosphorus), heavy metals, and residual antibiotics, amongst others, that have negative impacts on the water environment. The main aim of this work was to remove nutrients from anaerobically digested swine wastewater using an intermittent cycle extended aeration system (ICEAS). The effects of operational parameters such as cycle time, organic loading rate, C/N ratio, and aeration/mixing ratio on the pollutant removal efficiencies of ICEAS were studied and compared with the performance of a conventional sequencing batch reactor (SBR). The following optimal conditions were obtained: cycle time, 6 h; organic loading rate, 0.86 kg COD m−3 day−1; C/N ratio, 2.49–2.82; and aeration/mixing ratio, 1.57. The pH was maintained in the range of 6.0–8.0. The total organic carbon (TOC), total nitrogen (TN), ammonium (NH4+), total phosphorus (TP), and color removal efficiencies of ICEAS were higher than those of the conventional SBR, with removal efficiencies of 95.22, 88.29, 97.69, 85.81, and 97.84%, respectively, compared to 94.34, 81.16, 94.15, 77.94, and 96.95%, respectively, observed in the SBR. TOC, TN, NH4+, TP, and the color removal efficiencies of ICEAS were higher by 0.88, 7.13, 3.54, 7.87, and 0.95%, respectively, than the conventional SBR. The good results from this study show that ICEAS is a promising technology for the removal of organic contaminants and nutrients from anaerobically digested swine wastewater and that the effluent water quality meets the Vietnamese discharge standard (QCVN 62-MT:2016/BTNMT) for swine wastewater effluents.

Effects of Ammonia Stripping and Other Physico-Chemical Pretreatments on Anaerobic Digestion of Swine Wastewater

In order to overcome anaerobic digestion (AD) inhibition due to the large nitrogen content of swine wastewater (SW), air stripping (AS) and other chemical and physical pretreatments were applied on raw SW before AD. The efficiency of these pretreatments on both ammonia removal—recovering ammonia salts to be used as fertilizers in agriculture—and the increase of methane production were assessed in batch tests. Since the pH, temperature, and air flow rate heavily influence AS efficiency and the composition of treated SW, these parameters were set individually or in combination. In more detail, the pH was increased from the natural value of SW to 8 or 10, temperature was increased from the room value to 40 °C, and the air flow rate was increased from zero to 5 Lair LSW−1 min−1. AS was generally more efficient at removing ammonia (up to 97%) from raw (non-treated) SW compared to the other treatments. However, the tested pretreatments were not as efficient as expected in increasing the biogas production, because the methane yields of all pretreated substrates were lower (by about 10–50%) to compared raw SW. The inhibitory effect on AD could have been due to the lack of nutrients and organic matter in the substrate (due to the excessive removal of the pretreatments), the concentration of toxic compounds (such as metal ions or furfural due to water evaporation), and an excess of alkali ions (used to increase the pH in AS). Overall, AS can be considered a sustainable process for the recovery of ammonium sulphate and the removal of other polluting compounds (e.g., organic matter) from SW. Conversely, the use of AS and other chemical and/or thermal processes tested in this study as pretreatments of SW before AD is not advised because these processes appear to reduce methane yields.

Recent advances on anaerobic digestion of swine wastewater

Anaerobic digestion is a valuable technology for the elimination of biodegradable pollutants and stabilization of agro-industrial wastes. This review focuses on the AD of wastewaters derived from swine production within the scope of wastewater treatment and bioenergy production. Fundamental principles of AD as a biochemical and microbiological process are described. The effect of essential parameters is also examined in the context of swine wastewater, especially the relation between chemical and operational factors, process stability and performance. The review continues with a discussion of current trends and future achievements in AD research of swine wastes, namely co-digestion with carbon-rich substrates, integration with pretreatment methods, process enhancement via the use of additives, and digestate management. Finally, a brief outlook on the economy of biogas utilization is provided to better understanding the future of AD as biotechnology for on-farm treatment of swine wastewater.

Auto-flocculation microalgae species Tribonema sp. and Synechocystis sp. with T-IPL pretreatment to improve swine wastewater nutrient removal

It is recognized coupling microalgae, which is rich in lipids or protein with wastewater treatment offers extra economic benefits that can potentially make microalgal production feasible by reducing production costs and providing environmental benefits. However, the pretreatment of high concentration nutrients such as ammonia nitrogen (NH3-N), total phosphorus (TP) and chemical oxygen demand (COD) in swine wastewater is the premise of application for microalgae in wastewater treatment. This study two auto-flocculation microalgae Tribonema sp. and Synechocystis sp. were selected for evaluation; they were cultivated in diluted swine wastewater together after it was pretreated with titanium dioxide (TiO2) plus intense pulsed light (T-IPL). The results showed that the growth of the two strains in the wastewater pretreated with T-IPL grew better than when grown without the pretreatment. The content of lipid in the two algae, cultured in the pretreated wastewater, was also higher than the lipid content from the un-pretreated wastewater; but protein content was lower. Overall, the removal efficiencies of pollutants NH3-N, TP, and COD by the two microalgae in anaerobic digestion of swine wastewater (ADSW) with T-IPL pretreatment, were higher than the removal efficiencies without pretreatment. This research also indicates that these two auto-flocculation microalgae have the potential to reduce harvesting costs. And, using T-IPL to pretreat wastewater could provide a promising method for the pretreatment of wastewater.

High rate anaerobic digestion of swine wastewater in an anaerobic membrane bioreactor

Efficient treatment of swine wastewater at a high rate would facilitate the development of a sustainable pig industry. In this study, to investigate methane fermentation and membrane filtration performance, an anaerobic membrane bioreactor was operated under mesophilic conditions for 207 days during four stages, with a hydraulic retention time (HRT) decreasing from 5 to 3, 2, and 1 day, and a changing of solid retention time/hydraulic retention time (SRT/HRT) ratio from 18,18 to 8 and 3.2. The results showed that a higher volumetric methane production of 1.63 L/(L·d) and a lower VFAs concentration (<200 mg/L at stable stage) could achieved when the HRT was 1 day and SRT/HRT ratio was only 3.2. The specific methanogenic activity slightly decreased under the shorter HRT, and with SRT/HRT shortening, hydrogenotrophic Methanocorpusculum tended to dominate in bulk sludge while acetoclastic Methanosaeta dominated in the biofilm. Membrane fouling was observed after 4 months with a flux decline and a significant increase in trans-membrane pressure. A serial cleaning test indicated that organic pollutants contributed highly to the membrane fouling.