Synthetic Livestock Wastewater Research Articles

Electro-oxidation of ammonia nitrogen using W, Ti-doped IrO2 DSA as a treatment method for mariculture and livestock wastewater.

Animal farming wastewater is one of the most important sources of ammonia nitrogen (NH4+-N) emissions. Electro-oxidation can be a viable solution for removing NH4+-N in wastewater. Compared with other treatment methods, electro-oxidation has the advantages of i) high removal efficiency, ii) smaller size of treatment facilities, and iii) complete removal of contaminant. In this study, a previously prepared DSA (W, Ti-doped IrO2) was used for electro-oxidation of synthetic mariculture and livestock wastewater. The DSA was tested for chlorine evolution reaction (CER) activity, and the reaction kinetics was investigated. CER current efficiency reaches 60-80% in mariculture wastewater and less than 20% in livestock wastewater. In the absence of NH4+-N, the generation of active chlorine follows zero-order kinetics and its consumption follows first-order kinetics, with cathodic reduction being its main consumption pathway, rather than escape or conversion to ClO3-. Cyclic voltammetry experiments show that NH4+-N in the form of NH3 can be oxidized directly on the anode surface. In addition, the generated active chlorine combines with NH4+-N at a fast rate near the anode, rather than in the bulk solution. In electrolysis experiments, the NH4+-N removal rate in synthetic mariculture wastewater (30-40mg/L NH4+-N) and livestock wastewater (~ 450mg/L NH4+-N) is 112.9g NH4+-N/(m2·d) and 186.5g NH4+-N/(m2·d), respectively, which is much more efficient than biological treatment. The specific energy consumption (SEC) in synthetic mariculture wastewater is 31.5 kWh/kg NH4+-N, comparable to other modified electro-catalysts reported in the literature. However, in synthetic livestock wastewater, the SEC is as high as 260 kWh/kg NH4+-N, mainly due to the suppression of active chlorine generation by HCO3- and the generation of NO3- as a by-product. Therefore, we conclude that electro-oxidation is suitable for mariculture wastewater treatment, but is not recommended for livestock wastewater. Electrolysis prior to urea hydrolysis may enhance the treatment efficiency in livestock wastewater.

Achieving simultaneous removal of carbon and nitrogen by an integrated process of anaerobic membrane bioreactor and flow-through biofilm reactor

In this study, a combined system consisting of an anaerobic membrane bioreactor (AnMBR) and flow-through biofilm reactor/CANON (FTBR/CANON) was developed to simultaneously remove carbon and nitrogen from synthetic livestock wastewater. The average removal efficiencies of total nitrogen (TN) were 64.2 and 76.4% with influent ammonium (NH4+-N) concentrations of approximately 200 and 500 mg/L, respectively. The COD removal efficiencies were higher than 98.0% during the entire operation. Mass balance analysis showed that COD and TN were mainly removed by the AnMBR and FTBR/CANON, respectively. The anammox process was the main nitrogen removal pathway in the combined system, with a contribution of over 80%. High functional bacterial activity was observed in the combined system. Particularly, an increase in the NH4+-N concentration considerably improved the anammox activity of the biofilm in the FTBR/CANON. 16S rRNA high-throughput sequencing revealed that Methanosaeta, Candidatus Methanofastidiosum, and Methanobacterium were the dominant methanogens in the AnMBR granular sludge. In the CANON biofilm, Nitrosomonas and Candidatus Kuenenia were identified as aerobic and anaerobic ammonium-oxidizing bacteria, respectively. In summary, this study proposes a combined AnMBR and FTBR/CANON process targeting COD and nitrogen removal, and provides a potential alternative for treating high-strength wastewater.

Electrically charged forward osmosis: Promoting reverse salt flux to enhance water recovery and struvite precipitation

Agricultural wastewater contains high concentrations of nitrogen and phosphorus. There is a growing interest in recovering these nutrients. In this study, an electrically charged forward osmosis (eFO) system was developed to recover struvite and water from synthetic livestock wastewater. By applying a voltage near the surface of the FO membrane, magnesium migrated reversely into the feed chamber and reacted with the ammonium and phosphate in the feed solution to form struvite. As a result of electrical charging, the recovery of struvite and water was enhanced by 77% and 39%, respectively. The enhancement might be because dilutive and concentrative polarization was alleviated on the draw and feed side of the FO membrane during ion migration. High external voltage, high draw concentration, and alkaline/neutral draw pH favored water recovery and struvite precipitation. This study provides insights into harnessing reverse salt flux to improve the recovery of nutrients and water in FO systems.

Gas-diffusion-electrode based direct electro-stripping system for gaseous ammonia recovery from livestock wastewater

Livestock wastewater (LW) typically contains a substantial amount of NH4+ that can potentially be recovered and used in fertilizers or chemicals. In an attempt to recover NH4+ from LW, a novel electrochemical approach using a gas diffusion electrode (GDE) was developed and its efficacy was demonstrated in this study. The GDE-based electrochemical device, when operated at an air-flow rate of 20 mL/min, was free of back-diffusion flux, which is a fatal drawback of any membrane-based NH4+ separation approach. Continuous operation resulted in a nitrogen flux of 890 g N/m2d with synthetic LW and 770 g N/m2d with real LW at a current density of 10 mA/cm2. The electrochemical energy input was 7.42 kWh/kg N with synthetic LW and 9.44 kWh/kg N with real LW. Compared with the traditional stripping method, the GDE-based electrochemical system has a certain potential to be competitive, in terms of energy consumption. For instance, a rough-cost estimate based only on operating costs regarding chemical usage, air blowing, and water pumping revealed that the system consumed 13.44 kWh/kg N, whereas the conventional stripper required 27.6 kWh/kg N. This analysis showed that an electrochemical approach such as our GDE-based method can recover NH3, (particularly in gaseous form) from LW. In addition, with the future development of a smart operation method, as proposed and demonstrated in this study, the cost-effective implementation of a GDE-based method is feasible.

Reactive electrically conducting membranes for phosphorus recovery from livestock wastewater effluents

We present a novel ‘proof-of-concept’ electrochemically based membrane filtration process for the recovery of nitrogen and phosphorus from livestock wastewater following an anaerobic digestion step. Reactive electrically conducting membranes are shown to precipitate and separate struvite, an eco-friendly fertilizer from synthetic livestock wastewater, resulting in the production of a solid fertilizer and a high-quality water stream, fit for irrigation. The recovery process is based on electrochemical hydrolysis and control of local pH in proximity to the surface of the membrane, and therefore, does not require chemical additives for pH adjustment. The system was assessed at varying concentrations of nitrogen and phosphorus corresponding to diluted and concentrated livestock wastewater (up to 1000 mg/L of N and P). Experimental results show up to 65% removal of phosphorus and nitrogen in the first 30 min of electrochemical filtration, and the precipitates were analytically confirmed to be struvite. In addition, the recovery process was shown efficient as it resulted in limited membrane fouling and flux reduction. Fouling and precipitation results were explained by a mathematical model describing the concentration of N, P, Mg ions in the presence of an external electric field. Accordingly, precipitation takes place in proximity to the membrane's surface but not directly on it, thus, limiting surface fouling. The electrochemical filtration system does not require chemical additives for pH adjustment, and the cost associated with electrochemical membrane-based struvite recovery was calculated to be $158 per ton of dry struvite, which is about 1.4 times lower in comparison to conventional recovery approaches. Overall, the electrochemical filtration system may be a promising alternative for nutrient recovery from livestock wastewater in terms of operational costs, recovery efficiency, and fouling mitigation.

Evaluation of wetland substrates for veterinary antibiotics pollution control in lab-scale systems.

The behaviors of typical veterinary antibiotics (oxytetracycline, ciprofloxacin and sulfamethazine) and 75 types of corresponding antibiotic resistant genes (ARGs) in four substrate systems (zeolite, gravel, red brick, and oyster shell) were investigated in this study. The results indicated that during treating synthetic livestock wastewater with individual antibiotic influent concentration of 100μg/L, the effluent contained oxytetracycline and ciprofloxacin concentrations of 0.7-1.5μg/L and 1.0-1.9μg/L, respectively, in the zeolite and red brick systems, which were significantly lower than those of the other substrate systems (4.6-14.5μg/L). Statistical correlation analyses indicated that the difference regarding oxytetracycline and ciprofloxacin removal among the four substrates was determined by their adsorption capacity which was controlled by the chemisorption mechanism. The average removal efficiency of sulfamethazine in the gravel system (48%) was higher than that of the other substrate systems (34-45%), and biodegradation may alter the sulfamethazine performance because of its co-metabolism process. Although tetG, floR, sul1, and qacEΔ1 were the dominant ARGs in all substrate systems (8.74×10-2-6.34×10-1), there was difference in the total ARG enrichment levels among the four substrates. Oyster shell exhibited the lowest total relative abundance (1.56×100) compared to that of the other substrates (1.82×100-2.27×100), and the ARG total relative abundance exhibited significant negative and positive correlations with the substrate pH and system bacterial diversity (P<0.05), respectively. In summary, this study indicated that due to the difference of adsorption capacity and residual abundant nutrient in wastewater, the wetland substrate selection can affect the removal efficiency of veterinary antibiotics, and antibiotics may not be the determining factor of ARG enrichment in the substrate system.

Influence of hydraulic loading rate on antibiotics removal and antibiotic resistance expression in soil layer of constructed wetlands

Behavior of veterinary antibiotics, the corresponding resistant genes in soil layer of constructed wetlands (red soil), and their response to different hydraulic loading rates (HLR) (2, 5, and 10 cm/d) were investigated. Results indicated that the soil layer had perfect performance for oxytetracycline and ciprofloxacin, yet sulfamethazine removal was unsatisfactory. Detection rates of oxytetracycline, ciprofloxacin and sulfamethazine in the effluent of simulation systems of soil layer were 8.33–36.36%, 8.33–47.83% and 100%, respectively. The model analysis of adsorption and hydrolysis indicated that physical adsorption, which was controlled by exchange reaction process based on diffusion, was the primary adsorption mechanism of target antibiotics in red soil, and the hydrolysis half-life values of antibiotics in the water of soil layer were shorter than them in wastewater. The removal response of oxytetracycline and ciprofloxacin to change of HLR was insignificant, yet the respective effluent concentrations of sulfamethazine at HLR of 2–10 cm/d were 41.90, 61.35 and 73.54 μg/L during treating synthetic livestock wastewater, which revealed significant positive correlation (P < 0.05). The relative abundances of each target resistance genes in soil showed significant increase after treating wastewater (10−5-10−6 to 10−4-10−1), and the total level of those at different HLRs (2, 5, and 10 cm/d) were 3.02 × 10−2, 7.54 × 10−2 and 8.65 × 10−1, respectively. In summary, HLR could affect the removal efficiency of partial antibiotic in soil layer of constructed wetlands, and the expression of antibiotic resistance in the soil gradually increased with increase in the HLR.

Electrochemical ammonia accumulation and recovery from ammonia-rich livestock wastewater

High levels of ammonia inhibit microbial activities and lead to process instability of traditional wastewater treatment. Nitrogen recovery via ammonia stripping is the best developed method, but this approach requires large amounts of alkaline chemicals and substantial energy for stripping. In this study, we designed a simple electrochemical system that allows the facile accumulation of a neutral species of ammonia (NH3), resulting in much lower overall stripping costs. In batch operation treatment of synthetic livestock wastewater (LW), the energy efficiency for total ammonia nitrogen (TAN) migration was found to be the best at a current density of 93.8 mA cm−2. Fed-batch operation, using synthetic or real LW, resulted in very high degrees of TAN accumulation (10,158 mg-N L−1 for synthetic and 17,704 mg-N L−1 for real LW) in catholyte after 400 min. It was found that TAN migration was responsible for 0.221 and 0.492 of total charge migration for synthetic and real LW, respectively. The nitrogen flux across a cation exchange membrane was 5975 g-N m−2 d−1 with an energy input of 28.2 kWh (kg-N)−1 when using real LW. All this supported the conclusion that an electrochemical approach such as this makes it possible to achieve highly desirable ammonia recovery from wastewater in a sustainable manner.

Response of denitrobacteria involved in nitrogen removal for treatment of simulated livestock wastewater using a novel bioreactor

A ceramic filter medium (CFM) and dewatered aluminum sludge (DAS) were used as a small-scale combined biofilter to treat synthetic livestock wastewater. The average removal efficiency of ammonia nitrogen (NH4+-N) and total nitrogen (TN) reached 95.75 and 75.11% respectively. Illumina sequencing indicated that, except for initial media, most beta diversities of napA, narG, nirS, qnorB, and nosZ in the CFM or DAS were in a steady-state condition regardless of space-time variation, while these genes showed discrepancy between the CFM and DAS. In addition, the dominant genera were principally influenced by the synergic environmental factors, namely NH4+-N, TN, chemical oxygen demand (COD), and pH of effluents. This research demonstrated that the elimination of TN for treating synthetic livestock wastewater could be achieved by increasing the relative abundance of Azoarcus, Rhodanobacter, and Burkholderia. Meanwhile, increasing these genera contributes to suppressing the genera disadvantageous to TN attenuation.

Removal of roxarsone from synthetic livestock wastewater by sodium alginate loading with micro-scale zero-valent iron

Removal of roxarsone from synthetic livestock wastewater by sodium alginate loading with micro-scale zero-valent iron

Nitrogen removal performance and ammonia- and nitrite-oxidizing bacterial community analysis of a novel industrial waste-based biofilter

This study employed a newly developed treatment biofilter to remove high nitrogen (N) concentration from synthetic livestock wastewater combined with media containing neutralized used acid (NUA) and dewatered alum sludge (DAS). This biofilter was also utilized to investigate the spatial and temporal distributions of ammonia-oxidizing bacterial (AOB) and nitrite-oxidizing bacterial (NOB) communities and their active responses to effluent characteristics. Data were obtained from 210days of operations. Results showed that N removal was robust, with ammonia N and total N removal efficiencies of 59.8–82.1% and 57.5–74.9%, respectively. Denaturing gradient gel electrophoresis and sequence analyses revealed that the shift of AOB and NOB community structures in DAS was time dependent. These structures did not exhibit distinct differences in both media as depth varied. The retrieved AOB and NOB sequences from both media primarily belonged to Nitrosomonas, Nitrosovibrio, and Nitrobacter. The nitrification rates indicated that the change in AOB activity corresponded to the AOB community structure variation in the system. The peak was observed in DAS at the final time. By contrast, the NOB activity was inconsistent with the trend of its community structure. The AOB rate was positively related to the NOB rate. This finding suggested that AOB and NOB mutually promoted each other. The AOB and NOB activities of DAS rather than those of NUA appeared dependent on available nitrate from the effluent. Overall, these findings on AOB and NOB helped enhance further understanding on the efficient N removal of the NUA–DAS system.