Anaerobically Digested Swine Wastewater Research Articles

Growth of Scenedesmus obliquus in anaerobically digested swine wastewater from different cleaning processes for pollutants removal and biomass production

Anaerobically digested swine wastewater (ASW) purification by microalgae provides a promising strategy for nutrients recovery, biomass production and CO2 capture. However, the characteristics of ASW from different cleaning processes vary greatly. At present, the cultivation of microalgae in ASW from different manure cleaning processes is rarely investigated and compared. That may bring uncertainty for microalgae growth using different ASW in large-scale application. Thus, the ASW from three cleaning processes were tested for cultivating microalgae, including manure dry collection (I), water flushing (II) and water submerging processes (III). The characteristics of ASW from three manure cleaning processes varied greatly such as nutrient and heavy metals levels. High concentration of ammonia and copper in ASW significantly inhibited microalgae growth. Fortunately, the supply of high CO2 (10%) effectively alleviated negative influences, ensuring microalgal growth at low dilution ratio. The characteristics of three ASW resulted in significant differences in microalgae growth and biomass components. The maximal biomass production in optimal diluted ASW-I, II and III reached 1.46 g L−1, 2.19 g L−1 and 2.47 g L−1, respectively. The removal of organic compounds, ammonia and phosphorus by optimal microalgae growth in diluted ASW-I, II and III was 50.6%/94.2%/64.7%, 63.7%/82.3%/57.6% and 83.2%/91.7%/59.7%, respectively.The culture in diluted ASW-I, II and III obtained the highest lipids production of 12.1 mg L−1·d−1, 16.5 mg L−1·d−1 and 19.4 mg L−1·d−1, respectively. The analysis of lipids compositions revealed that the proportion of saturated fatty acids accounted for 36.4%, 32.4% and 27.9 % in optimal diluted ASW-I, II and III, as ideal raw materials for biodiesel production.

Modeling growth kinetics and community interactions in microalgal cultures for bioremediation of anaerobically digested swine wastewater

Uncontrolled release of swine wastewater into the environment causes the eutrophication of water bodies, as well as soil and air pollution, among other environmental and health issues. Microalgal-based wastewater treatment (MbWT) is a cost-effective alternative to traditional wastewater treatment methods that offers the opportunity to harvest valuable biomass while simultaneously removing nutrients and organic matter, thus making wastewater treatment a circular bioeconomy process. The aim of this work was to test three microalgal strains, Chlorella vulgaris, Scenedesmus acutus, and Arthrospira maxima, in mono-cultures and co-cultures using raw (undiluted, non-sterilized) anaerobically digested swine wastewater (ADSWW). An overall performance index (OPI) proposed herein showed that the treatments that included C. vulgaris were the most efficient in terms of biomass growth, along with COD and nutrient removal. The co-culture of C. vulgaris and S. acutus achieved the highest OPI of 0.68, displaying a maximum biomass concentration of 2.97 ± 0.36 g/L, as well as 89 %, 56 %, and 67 % removal efficiencies for COD, TN, and TP, respectively. Three mathematical models were used to estimate relevant growth kinetic parameters, including the specific growth rate, lag-phase duration, interspecific interaction, affinity constant, and biomass productivity. The growth curve of the C. vulgaris monoculture was adjusted using a double Gompertz model, showing a growth rate of 0.625 d−1 and a lag phase of 0.71 days in the first growth stage. The Lotka-Volterra model was used to assess interactions between both strains in the co-culture, showing a commensalistic relationship as denoted by the interspecific parameters (βcs = 1.99 ± 0.92 and βsc = −0.007 ± 0.008). Finally, the growth kinetics as a function of the three substrates (COD, TN, and TP) were adjusted to the Monod model, and the resulting parameters were used to simulate a continuous process that evidenced the requirement of P supplementation.

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.

Enhancing nitrogen removal from anaerobically-digested swine wastewater through integration of Myriophyllum aquaticum and free nitrous acid-based technology in a constructed wetland.

Despite of low operation costs and convenient maintenance, the application of natural systems for swine wastewater treatment has been limited by large construction area and unsatisfactory effluent quality. Introducing ammonium high uptake aquatic plants and shifting nitrogen removal pathway from nitrate to nitrite in constructed wetlands (CWs) has been regarded as promising approach to promote their performances. This study aimed to establish nitrite pathway and enhance N removal via free nitrous acid (FNA)-sediment treatment and Myriophyllum aquaticum vegetation in the CWs treating anaerobically digested swine wastewater. Nitrite pathway was successfully and stably achieved in the M. aquaticum CW with FNA-treated sediment. The overall removal efficiencies of ammonium nitrogen and total nitrogen were 42.3±10.2% and 37.7±9.3% in the planted CWs with FNA-treated sediment, which were 76.3% and 65.4% higher than those in the conventional oxidation pond system, respectively. Microbial community analysis (qPCR and metagenomics) suggested that the nitrite pathway established through FNA-sediment treatment was based on the inactivation of nitrite oxidizing bacteria (lower nxrA gene abundance) and the reduction of relative abundances of NOB (especially Nitrobacter and Nitrospira). During the denitrification processes, the integration of M. aquaticum vegetation with FNA-sediment treatment can lower the nitrate reduction by decreasing narG gene abundances and decreasing the relative abundances of napA affiliated bacteria (especially Bradyrhizobium), while strengthening reduction of nitrite and nitrous oxide by increasing nirK and nosZ gene abundances and enriching the corresponding affiliated microbial taxa, Mycobacterium and Bacillus, respectively. Our findings suggest that applying FNA-based technology in CW systems is technically and economically feasible, which holds promise for upgrading current CW systems treating swine wastewater to meet future water quality requirements.

Simultaneous elimination of antibiotics resistance genes and dissolved organic matter in treatment wetlands: Characteristics and associated relationship

Constructed wetlands (CWs) are widely used for treating swine wastewater containing antibiotic resistance genes (ARGs). However, the relation between ARGs removal and dissolved organic matter (DOM) characteristics in CWs remains unknown. This study aimed to assess the removal of ARGs and the dynamitic transformation of DOM from anaerobically-digested swine wastewater in biochar-based CWs with and without forced aeration. Incorporating biochar and aeration into CWs could promote the ARGs (tetA, tetM, tetO, tetW) elimination (0.53–2.14 log) under various influent strengths. Compared with non-aerated CWs, aerated CWs improved the target ARGs removal, while biochar-based CWs without aeration increased the proliferation of ARGs (tetA, tetO, tetW). More accumulation of ARGs was found especially in non-aerated CWs with biochar. Fluorescence excitation-emission spectrophotometry with parallel factor analysis revealed that DOM, mainly including humic-like, protein-like and tryptophan-like components, was significantly reduced with a higher removal efficiency (72.2%) in biochar-based CWs with aeration. Moreover, DOM removal showed an obvious correlation with the elimination of ARGs, except tetW, which might not be influenced by the humification processes. The evolution of microbial communities in different CWs indicated that Actinobacteria, Proteobacteria and Bacteroidetes might play an important role in ARGs and DOM removal. This study could provide new insights on the mechanism of ARGs and DOM elimination by biochar-based CWs with aeration for treating swine wastewater.

Screening of the dominant Chlorella pyrenoidosa for biofilm attached culture and feed production while treating swine wastewater

This research 12 microalgal species were screened for biofilm attached culture in the treatment of anaerobically digested swine wastewater (ADSW). The influence of ADSW on biomass productivity and removal efficiencies were evaluated using biofilm attached culture with the selected Chlorella pyrenoidosa. The variation of nutritional components from algal cells were further analysed to evaluate the potential applications of C. pyrenoidosa. The results showed that C. pyrenoidosa had the highest tolerance to ADSW, and the highest removal efficiencies for wastewater pollutants were reached when cultured in 5 times diluted ADSW. These test conditions resulted in an algal cell biomass composed of 57.30% proteins, 14.87% extracellular polysaccharide, 3.08% crude fibre, 5.57% crude ash, 2.85% moisture. Amino acids in proteins contained 21.73% essential amino acids and the EAA/NEAA value was 0.64. The essential amino acid score indicates that the selected C. pyrenoidosa could be a good protein source for feed addition.

Phytoremediation of anaerobically digested swine wastewater contaminated by oxytetracycline via Lemna aequinoctialis: Nutrient removal, growth characteristics and degradation pathways

The concentration of antibiotics in anaerobically digested swine wastewater (ADSW) usually gradually increases due to the addition of antibiotics in livestock feed. Lemna aequinoctialis was used to treatment synthetic ADSW contaminated by oxytetracycline (OTC) whose concentrations were 0.05, 0.25, 0.50 and 1.00 mg/L, and its influences on NH3-N and TP remove were investigated. The fresh weight, photosynthetic pigment and protein content of duckweed were also investigated. Results have shown that nutrient removal and duckweed growth followed the “dose-response” relationships, and 0.05 mg/L OTC could significantly promote the synthesis of photosynthetic pigments and proteins in duckweed. Meanwhile, the protein content gradually decreased during investigation. More important, the degradation products and possible degradation pathways of OTC were diagrammatized via liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), and twelve intermediates were detected in the duckweed systems. This study can offer a novel view for phytoremediation of ADSW containing antibiotics by aquatic plants.

Effect of biosurfactant on ammonia removal from anaerobically digested swine wastewater by multi soil layering treatment bioreactors

ABSTRACT A biosurfactant was harvested from anaerobically digested swine wastewater (ADSW) and employed to enhance ammonia removal in a comparative study using two multiple soil layer bioreactors (MSLs). Results showed that toxicity of the biosurfactant to microorganisms was negligible within the experimental concentration range. Optimal dose of the biosurfactant in MSLs to remove ammonia from ADSW was 0.1 CMC (Critical Micelle Concentration) under different hydraulic loading rate (HLR). For instance, when the HLR was adjusted as 80, 120, 160, and 200 L/(m2·d), the average ammonia removal efficiency in MSL without biosurfactant addition was appeared as 85.6%, 89.2%, 85.2% and 84.1%, respectively, after enhanced by 0.1 CMC of the biosurfactant under the same condition, the average ammonia removal efficiency was improved to 90.1%, 92.6%, 90.3%, and 87.4%, respectively. Inlet ammonia concentration obviously affected ammonia removal, the average ammonia removal efficiency increased rapidly to 93.0% and 89.1% in MSLs (with and without biosurfactant) along with the increasing inlet ammonia concentration from 800 mg/L to 1000 mg/L, and subsequently dropped to 78.9% and 79.7% with a further increase in the inlet ammonia concentration to 1400 mg/L. These results showed that the biosurfactant effectively enhanced ammonia removal by using MSL. Thus, the construction of MSL represented an effective means of reducing ammonia pollution caused by swine wastewater, and the use of biosurfactant was assuredly a promising and feasible option for enhancing the biological activity in MSL bioreactor.

Effects of Hydraulic Loading Rate on Nutrients Removal from Anaerobically Digested Swine Wastewater by Multi Soil Layering Treatment Bioreactor.

A multi soil layering (MSL) treatment bioreactor was developed aiming at nutrients removal from anaerobically digested swine wastewater (ADSW). The start-up of the MSL bioreactor and its performance in nutrients removal at different hydraulic loading rate (HLR) were investigated. Results showed that the MSL bioreactor was successfully started up after operation for 28 days, and at this time, the removal efficiencies of ammonia-N, total nitrogen (TN) and total phosphorus (TP) in the ADSW reached 63.6%, 58.5%, and 46.5%, respectively. The MSL bioreactor showed a stable performance during the whole working process with varying HLR from 80 to 200 L/(m2·day). Maximum removal efficiencies of ammonia-N, TN and TP were obtained at 160 L/(m2·day), and was appeared as 94.2%, 94.4%, and 92.5%, respectively. It was worth noting that iron scraps were the key factor that enhanced the independent capability of the MSL bioreactor in TP removal, because there was only 21.4–25.8% of the TP was removed when the MSL bioreactor run with no iron addition.

Feasibility and Mechanism of Combined Conditioning with Coagulant and Flocculant To Enhance Sludge Dewatering

Coagulation or flocculation is often individually used or in hybrid conditioning with other preconditioning for sludge dewatering. However, combined conditioning with coagulants and flocculants for sludge dewatering is rarely reported. In this study, dewatering performances of sludge with individual use of poly(aluminum chloride) (PACl; as the coagulant) and a biopolymer named “BF-ADSW” (as the flocculant) were investigated, and the feasibility of applying the coagulation–flocculation process using PACl and BF-ADSW for sludge dewatering and the related mechanism were explored. BF-ADSW was harvested from anaerobically digested swine wastewater (ADSW), and its yield was 2.98 g/L, meaning that 2.98 g of BF-ADSW can be harvested from 1 L of ADSW. After conditioning by PACl with a dose of 10% dry solids (DS), the sludge moisture content and settled volume after 30 min were decreased from the raw values of 98.5% and 96.1% to 80.8% and 74.2%, respectively, which were further decreased to 62.3% and 49.2% after fu...

Responses of microalgae Coelastrella sp. to stress of cupric ions in treatment of anaerobically digested swine wastewater

Microalgae Coelastrella sp. could remove nutrients from anaerobically digested swine wastewater (ADSW) effectively, while its responses to the stress of Cu(II) were not well understood. In this paper, nutrients removal and growth of Coelastrella sp. were investigated at the presence of Cu(II) in ADSW. Results showed ammonium nitrogen concentration in ADSW decreased with culturing duration, while increased with an increased Cu(II) concentration. Total phosphorous concentration decreased with time, while did not drop in 4 days at Cu(II) concentration ≥1.0 mg/L. Microalgal growth was inhibited at all the Cu(II) concentrations, and ceased in about 6–8 days at Cu(II) concentration ≥1.0 mg/L. With an increased Cu(II) concentration, the contents of chlorophyll a and proteins decreased, those of malondialdehyde and superoxide dismutase, and ratios of octadecanoic acid (C18:0), hexadecanoic acid (C16:0) and octadecenoic acid (C18:1) to fatty acids in Coelastrella sp. increased, while octadecatrienoic acid (C18:3) gradually disappeared.

Effect of zinc ions on nutrient removal and growth of Lemna aequinoctialis from anaerobically digested swine wastewater

The effect of Zn2+ on ammonium and phosphorous removal and duckweed growth was evaluated for treatment of anaerobically digested swine wastewater (ADSW) at various initial Zn2+ concentrations ranging from 1.0 to 15mg/L. Lemna aequinoctialis taken from a local pond was selected for the treatment, and its fresh weight and contents of proteins, photosynthetic pigments, and vitamin E were examined. Results showed that the optimal Zn2+ concentration was 5.0mg/L for NH3-N and TP removal, the duckweed growth, and the accumulation of proteins in the duckweed. A maximum content of photosynthetic pigments increased with the increase of initial Zn2+ concentration, and it arrived earlier for a higher concentration of Zn2+. Vitamin E content in the duckweed reached 4.5mg/kg at 15mg/L Zn2+ in 12-day cultivation, which showed the potential for producing and harvesting a high value-added product of vitamin E by culturing duckweed in ADSW.

Enhanced anaerobically digested swine wastewater treatment by the composite of polyaluminum chloride (PAC) and Bacillus megatherium G106 derived EPS

A strain was isolated from biological sludge to produce EPS by using anaerobically digested swine wastewater (ADSW). Potential of the EPS in ADSW treatment were discussed. Results showed that the optimal fermentation medium for EPS production was determined as 4 g K2HPO4, 2 g KH2PO4, and 2 g sucrose dissolved in 1 L ADSW. After fermentation for 60 h, 2.98 g EPS with main backbone of polysaccharides can be extracted from 1 L of fermentation broth. The EPS showed good performances in ADSW treatment, after conditioned by this EPS, removal efficiencies of COD, ammonia, and TP reached 70.2%, 76.5% and 82.8%, respectively, which were higher than that obtained when chemicals were selected as conditioning agents. Removal efficiencies were further improved when the EPS and polyaluminum chloride (PAC) were used simultaneously, and finally reached 91.6%, 90.8%, and 92.5%, respectively, under the optimized conditioning process by the composite of EPS of 16 mg/L, PAC of 12 g/L, pH of 7.5, and agitation speed of 200 r/min.

Nutrient removal and biogas upgrading by integrating fungal–microalgal cultivation with anaerobically digested swine wastewater treatment

This work mainly aimed to compare the growth and tolerance of fungal–algal cultures in various dilutions of anaerobically digested swine wastewater (ASW) and to determine their nutrient removal efficiency and role in biogas upgrading. Three species of microalgae, namely, Chlorella vulgaris, Scenedesmus obliquus, and Pseudokirchneriella subcapitata, were selected for ASW purification and biogas upgrading in photobioreactors with four different concentrations of 1300, 1000, 700, and 300 mg L−1 COD (chemical oxygen demand). Co-cultivation of the fungus Ganoderma lucidum and C. vulgaris in 300 mg L−1 COD was the most efficient for reduction of COD, total nitrogen, and total phosphorus by 79.74 ± 4.87%, 74.28 ± 6.13% and 85.37 ± 6.84%, respectively. With respect to biogas upgrading, co-cultivation of G. lucidum and P. subcapitata in 700 mg L−1 COD showed the maximum CO2 removal efficiency of 84.77 ± 3.04%. These results show the feasibility of simultaneously removing nutrients in ASW and CO2 in biogas using fungi-microalgae pellets.

Removal of veterinary antibiotics from anaerobically digested swine wastewater using an intermittently aerated sequencing batch reactor

A lab-scale intermittently aerated sequencing batch reactor (IASBR) was applied to treat anaerobically digested swine wastewater (ADSW) to explore the removal characteristics of veterinary antibiotics. The removal rates of 11 veterinary antibiotics in the reactor were investigated under different chemical organic demand (COD) volumetric loadings, solid retention times (SRT) and ratios of COD to total nitrogen (TN) or COD/TN. Both sludge sorption and biodegradation were found to be the major contributors to the removal of veterinary antibiotics. Mass balance analysis revealed that greater than 60% of antibiotics in the influent were biodegraded in the IASBR, whereas averagely 24% were adsorbed by sludge under the condition that sludge sorption gradually reached its equilibrium. Results showed that the removal of antibiotics was greatly influenced by chemical oxygen demand (COD) volumetric loadings, which could achieve up to 85.1%±1.4% at 0.17±0.041kgCOD/m-3/day, while dropped to 75.9%±1.3% and 49.3%±12.1% when COD volumetric loading increased to 0.65±0.032 and 1.07±0.073kgCOD/m-3/day, respectively. Tetracyclines, the dominant antibiotics in ADSW, were removed by 87.9% in total at the lowest COD loading, of which 30.4% were contributed by sludge sorption and 57.5% by biodegradation, respectively. In contrast, sulfonamides were removed about 96.2%, almost by biodegradation. Long SRT seemed to have little obvious impact on antibiotics removal, while a shorter SRT of 30–40day could reduce the accumulated amount of antibiotics and the balanced antibiotics sorption capacity of sludge. Influent COD/TN ratio was found not a key impact factor for veterinary antibiotics removal in this work.

Enhanced nutrient sequestration from swine wastewater using zeolite synthesized from fly ash integrated with surface amendment technique

Nutrient removal during treatment of anaerobically digested swine wastewater (ADSW) is problematic due to high nutrient concentrations. In this study, nutrient sequestration from ADSW was investigated using zeolite fly ash (ZFA) that was synthesized using an alkaline hydrothermal technology. Two surface amendment techniques, i.e., bivalent alkali metals (Ca2+/Mg2+) synthesis-doping technique and impregnation-doping technique, were used to improve the nutrient removal properties of ZFA. Both amendment techniques increased the specific surface area and phosphorus (P) immobilization capacity of the ZFAs; however, Mg2+-amendments failed to increase nitrogen (N) removal efficiency due to enhanced ion competition effects. Enhanced N and P removal efficiencies were achieved with Ca2+-amended ZFAs due to a combination of ion exchange, adsorption and chemical precipitation. Phosphorus removal (mg) per unit of Ca2+-amended ZFAs (g) increased 1.4–41.3 times relative to that of the un-amended ZFA. Non-linear correlations between N and P removal efficiencies with ZFAs dose were described using power and natural logarithm equations, due to the multiple mechanisms behind nutrient removal. Using these relationships, a dose of 2.65g of Ca2+-amended ZFA (impregnation-doping technique) per 100mL of ADSW is recommended to achieve 74% N and 96% P sequestration from ADSW.

Synthesis of nano-zeolite from coal fly ash and its potential for nutrient sequestration from anaerobically digested swine wastewater

The treatment of anaerobically digested swine wastewater (ADSW) is problematic due to its high nutrient concentration. This study investigated the simultaneous sequestration of ammonium (N) and phosphate (P) from ADSW using nano-zeolites synthesized from fly ash (ZFA). The nanometer-scale crystalline structures plentiful of zeolite-NaP1 coating on ZFA particle increased the levels of specific surface area and cation exchange capacity at times of 40 and 104, compared to raw fly ash. Kinetic N and P sorption experiments with ZFA were well described by both the Langmuir and Freundlich models, suggesting the co-existence of homogeneous and heterogeneous sorption mechanisms. N and P removal efficiencies ranged from 41% to 95% and 75% to 98%, respectively, across a range of ZFA doses (from 0.25 to 8g/100ml). Collectively, application of the laboratory-synthesized ZFA can alleviate the nutrient loads in ADSW and therefore modify the ratio of N:P in wastewater beneficial for subsequent biological treatment.