Effects of electric voltage and sodium chloride level on electrolysis of swine wastewater

Enhancing industrial swine slaughterhouse wastewater treatment: Optimization of electrocoagulation technique and operating mode

In this study, industrial swine slaughterhouse effluents were treated by an electrocoagulation process (EC) with aluminum and iron electrodes. Batch and semicontinuous operation were performed. EC tests were carried out in batch operating mode for 2.5 h using fixed current densities (j = 10, 20, and 30 mA cm-2) in sulfate and chloride media. At the laboratory scale, higher TOC removal efficiencies were observed using aluminum electrodes at 20 mA cm-2 without the addition of a supporting electrolyte (82.7%). However, the EC process with Fe electrodes consumed 43.6% less energy. After the best operating parameters were found at the laboratory scale, the process was tested as a semicontinuous prepilot process using a filter-press FM01-LC-type electrochemical reactor equipped with flat plate aluminum electrodes. In this stage, current densities and mean linear flow rates were assessed. The highest TOC removal efficiency of 72.7% (i.e., residual TOC concentration of 85.18 mg L-1) in the semicontinuous process was achieved by the application of j = 25 mA cm-2 and ur = 0.64 cm s-1 with an energy consumption of 19.80 kW h m-3. The residual COD and TP concentrations met the international standard limits. Moreover, complete decoloration and disinfection were accomplished. EDXRF, SEM, EDAX, XRD, and FTIR analyses indicated that pollutants were removed by adsorption on aluminum/iron hydroxides/oxyhydroxides.

La-Ca/Fe-LDH-coupled electrochemical enhancement of organophosphorus removal in water: Organophosphorus oxidation improves removal efficiency

Metal ions or metal (hydrogen) oxides are widely used as active sites in the construction of phosphate-adsorbing materials in water, but the removal of soluble organophosphorus from water remains technically difficult. Herein, synchronous organophosphorus oxidation and adsorption removal were achieved using electrochemically coupled metal-hydroxide nanomaterials. La-Ca/Fe-layered double hydroxide (LDH) composites prepared using the impregnation method removed both phytic acid (inositol hexaphosphate, IHP) and hydroxy ethylidene diphosphonic acid (HEDP) acid under an applied electric field. The solution properties and electrical parameters were optimized under the following conditions: organophosphorus solution pH = 7.0, organophosphorus concentration = 100 mg L-1, material dosage = 0.1 g, voltage = 15 V, and plate spacing = 0.3 cm. The electrochemically coupled LDH accelerates the removal of organophosphorus. The IHP and HEDP removal rates were 74.9% and 47%, respectively in only 20 min, 50% and 30% higher, respectively, than that of La-Ca/Fe-LDH alone. The removal rate in actual wastewater reached 98% in only 5 min. Meanwhile, the good magnetic properties of electrochemically coupled LDH allow easy separation. The LDH adsorbent was characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. It exhibits a stable structure under electric field conditions, and its adsorption mechanism mainly includes ion exchange, electrostatic attraction, and ligand exchange. This new approach for enhancing the adsorption capacity of LDH has broad application prospects in organophosphorus removal from water.

Treatment and utilization of swine wastewater - A review on technologies in full-scale application

The management of swine wastewater has become the focus of attention in the farming industry. The disposal mode of swine wastewater can be classified as field application of treated waste and treatment to meet discharge standards. The status of investigation and application of unit technology in treatment and utilization such as solid-liquid separation, aerobic treatment, anaerobic treatment, digestate utilization, natural treatment, anaerobic-aerobic combined treatment, advanced treatment, are reviewed from the full-scale application perspective. The technologies of anaerobic digestion-land application is most appropriate for small and medium-sized pig farms or large pig farms with enough land around for digestate application. The process of "solid-liquid separation-anaerobic-aerobic-advanced treatment" to meet the discharge standard is most suitable for large and extra-large pig farms without enough land. Poor operation of anaerobic digestion unit in winter, hard to completely utilize liquid digestate and high treatment cost of digested effluent for meeting discharge standard are established as the main difficulties.

Electrochemical oxidation of palm oil mill effluent using platinum as anode: Optimization using response surface methodology

This work investigates the electrochemical oxidation of palm oil mill effluent (POME) treatment using platinum (Pt) as anode and graphite as a cathode. The response surface methodology was used to investigate the relationships between different factors conditions (voltage, electrolysis time and chemical support) and responses of the treatment (chemical oxygen demand reduction, colour removal, and total oil removal). A quadratic mathematical model was chosen for all responses using Box-Behnken Design (BBD) with R² 0.9853 for COD reduction, R² 0.9478 for colour removal and R² 0.9185 for total oil removal. According to Derringer's function desirability, under the optimum condition (Voltage 15, electrolysis time 2 h, and 19.95 mg/L NaCl) of POME treatment, 84% of COD reduction, 98% of colour removal and 99% total oil of removal could be achieved. These results indicate that platinum as an anode material is effective for the electrochemical oxidation treatment of POME.

Influence of impressed current cathodic protection systems on chemical characteristics of underground water

Despite well-known corrosion inhibition behavior of cathodic protection (CP) system, this process might be a potential hazard to surrounding ecosystem resulted mostly from continuous electrical current which is applied to the adjacent environment and metallic anode dissolution as well. In this research, deepwater CP wells at different locations of Golestan province, Iran, were taken into consideration to evaluate the impact of these protective systems on underground waters from viewpoint of chemical and physicochemical characteristics resulted from anode dissolution. For this purpose, concentration of metallic constituents of the anode as well as the amount of pH, total dissolved solids (TDS), electrical conductivity (EC), and total hardness were determined. On the basis of obtained results, the concentration of Mn, Cr, and Fe in CP well located nearby an industrial district (i.e., 0.087, 0.475, and 8.5 mg/L, respectively) was higher than both WHO and USEPA standards. This fact can be resulted from the position where the well was dug as well as the CP anode dissolution within the deep CP water wells. PRACTITIONER POINTS: The impact of impressed current cathodic protection (ICCP) system on chemical and physicochemical characteristics of underground water has been evaluated. Anode dissolution of ICCP systems influences the water characteristics nearby the anodes. Despite low dissolution rate of high silicon cast iron anodes, their long-term utilization might be harmful for adjacent ecosystem. The amount of heavy metals in underground waters was demonstrated to be influenced by the employment of ICCP system. Both anode dissolution and the geological properties of the Earth`s crust surrounding the wellbore might be responsible for significant increase of heavy metals concentration.

Simultaneous Removal of Pollutants and Recovery of Nutrients from High-Strength Swine Wastewater Using a Novel Integrated Treatment Process

Simple Summary

Due to the increasing trend of swine consumption in recent decades, swine husbandry practices have become more intensive in Korea. Intensive swine farming practices inevitably result in an increment of wastewater production. Treatment of high strength swine wastewater (SWW) is therefore becoming a matter of concern in Korea. Moreover, with the increasing number of swine heads, swine farms are having issues with malodor, sanitation, and disease control. In this study, a novel integrated treatment process was tested for the simultaneous removal of pollutants and nutrient recovery from high strength swine wastewater. The integrated treatment process used in this study successfully removed the nutrients and other pollutants through biological treatment, recovered the nutrients using struvite crystallization process and decolorized as well as disinfected the effluent before discharge into water bodies by electrochemical treatment. Therefore, using the proposed integrated treatment process, it might be possible to ensure efficient SWW management along with societal and environmental sustainability.

Abstract

In this study, a novel treatment approach combining biological treatment, struvite crystallization, and electrochemical treatment was developed and its efficiency for the simultaneous removal of pollutants and recovery of nutrients from high strength swine wastewater (SWW) was verified. For all the parameters, maximum removal efficiencies in the lab-scale test were obtained in the range of 93.0–98.7% except for total solids (TS) (79.4%). Farm-scale process showed overall removal efficiencies for total nitrogen (TN), total phosphorus (TP), soluble total organic carbon (sTOC), and color as 94.5%, 67.0%, 96.1%, and 98.9%, respectively, while TS, suspended solids (SS), ammonium nitrogen (NH₄-N), and ortho-phosphate (O-P) concentrations were reduced by 91.5%, 99.6%, 98.6%, and 91.9%, respectively. Moreover, the struvite recovered from SWW showed heavy metal concentrations within the range of the Korean standard for fertilizers and feedstocks and thus, suggesting its potential application as fertilizer and in animal feed production. Using the proposed process, the SWW was converted to liquid compost as a quick-acting fertilizer, struvite as a slow-release fertilizer, and the decolorized and disinfected effluent after electrochemical treatment was safe for discharge according to Korean standard. Therefore, the novel integrated treatment process used in this study can be considered as a solution for SWW management and for the simultaneous removal and recycling of nutrients (N and P).

Electrochemical Removal of Ammonium Nitrogen and COD of Domestic Wastewater using Platinum Coated Titanium as an Anode Electrode

Biological treatment systems face many challenges in winter to reduce the level of nitrogen due to low temperatures. The present work aimed to study an electrochemical treatment to investigate the effect of applying an electric voltage to wastewater to reduce the ammonium nitrogen and COD (chemical oxygen demand) in domestic wastewater. This was done by using an electrochemical process in which a platinum-coated titanium material was used as an anode and stainless steel was used as a cathode (25 cm2 electrode area/500 mL). Our results indicated that the removal of ammonium nitrogen (NH4+–N) and the lowering of COD was directly proportional to the amount of electric voltage applied between the electrodes. Our seven hour experiment showed that 97.6% of NH4+–N was removed at an electric voltage of 5 V, whereas only 68% was removed with 3 V, 20% with 1.2 V, and 10% with 0.6 V. Similarly, at 5 V, the removal of COD was around 97.5%. Over the seven hours of the experiment, the pH of wastewater increased from pH 7.12 to pH 8.15 when 5 V was applied to the wastewater. Therefore, electric voltage is effective in the oxidation of ammonium nitrogen and the reduction in COD in wastewater.

Electrochemically-assisted ammonia recovery from wastewater using a floating electrode

This work presents and explores a novel methodology for the removal and recovery of ammonia from wastewater based upon two mechanisms: electrochemical oxidation and a previously unreported electrochemically-assisted surface transfer mechanism. Recovery of ammonia is enabled by placing a porous cathodic electrode at the wastewater-air interface. In this configuration, the cathode creates local alkalinity and an electric field that draws ammonium ions towards the wastewater-air interface, resulting in near-linear reductions of dissolved ammonium irrespective of concentration. This approach leads to significant ammonia recovery without the need for ion-exchange membranes. In addition, anodic reactions that simultaneously occur at depth in the wastewater induce ammonia oxidation in accordance with proven mechanisms. The floating electrode approach offers improved ammonia removal efficiency in comparison to electrooxidation. Trials conducted on synthetic wastewater (900 mg NH₄⁺-N l^-1) and filtered anaerobic centrate (560 mg NH₄⁺-N l^-1) demonstrated ammonia concentration decreases up to 216 mg l^-1 hr^-1 and 110 mg l^-1 hr^-1, respectively, under the application of 5 mA cm^-2 current density. The technology would be best used to treat municipal and industrial wastewaters possessing high ammonia concentration, including anaerobic digester centrate and urine, and offers potential to assist in removing ammonia from environmental waters.

Optimization of electrochemical reaction for nitrogen removal from biological secondary-treated milking centre wastewater

In order to remove the residual nitrogen from the secondary-treated milking centre wastewater, the electrochemical reaction including NH4-N oxidation and NOx-N reduction has been known as a relatively simple technique. Through the present study, the electrochemical reactor using the Ti-coated IrO2 anode and stainless steel cathode was optimized for practical use on farm. The key operational parameters [electrode area (EA) (cm(2)/L), current density (CD) (A/cm(2)), electrolyte concentration (EC) (mg/L as NaCl), and reaction time (RT) (min)] were selected and their effects were evaluated using response surface methodology for the responses of nitrogen and colour removal efficiencies, and power consumption. The experimental design was followed for the central composite design as a fractional factorial design. As a result of the analysis of variance, the p-values of the second-order polynomial models for three responses were significantly fit to the empirical values. The nitrogen removal was significantly influenced by CD, EC, and RT (p < .05), whereas colour removal was significantly governed by EA, CD, RT, the interaction of EA and EC (p < .05). For higher efficiency of nitrogen removal over 90%, the combination of [EA, 20 cm(2)/L; CD, 0.044 A/cm(2); EC, 3.87 g/L as NaCl; RT, 240 min] was revealed as an optimal operational condition. The investigation on cathodic reduction of NOx-N may be required with respect to nitrite and nitrate separately as a future work.

Removal of organic matter and nitrogen in swine wastewater using an integrated ion exchange and bioelectrochemical system

Swine wastewater was treated using an integrated ion exchange and bioelectrochemical system. This system contains three chambers separated by a cation exchange membrane (CEM) and an anion exchange membrane (AEM). Each chamber acted as a bioanode chamber, an aerated biocathode chamber, and a denitrification chamber. To accelerate the ammonium transportation through CEM, a bioelectrochemical system was installed between bioanode and aerated biocathode. The current was provided by a programmable DC power supply. The average chemical oxygen demand (COD) removal efficiencies at applied voltages of 0, 1 and 3 V were 65.6%, 75.4% and 80.6%, respectively. Unlike the COD removal, the total nitrogen removal was proportional to the ammonium flux through the CEM. The average total nitrogen removal efficiencies at the applied voltages of 0, 1 and 3 V were 37.0%, 63.1% and 70.5%, respectively.

Pretreatment of poultry manure anaerobic-digested effluents by electrolysis, centrifugation and autoclaving process for Chlorella vulgaris growth and pollutants removal

Different pretreatments (electrolysis, centrifugation and autoclaving) coupled with Chlorella vulgaris biological system was used for the treatment of poultry manure anaerobic-digested effluents. The pretreated effluents were used as the growth medium for algal cultivation. The pollutant removal efficiencies of the combined treatments were determined. Electrochemical pretreatment can efficiently remove the ammonia (NH4+), total phosphorus (TP), total organic carbon (TOC), total carbon (TC), turbidity and bacteria in the digested effluents. About 100.0% NH4+, turbidity and bacteria, 97.6% TP, 81.5% TOC and 96.6% inorganic carbon were removed by 5-h electrochemical treatment. The maximal algal biomass accumulation (0.53 g L(-1)) was obtained from culture in the effluents pretreated with 2-h electrolysis. The pollutants removal amounts by the combination of electrolysis and biological treatment were much higher than the other combinations.

Novel integrated carbon particle based three dimensional anodes for the electrochemical degradation of reactive dyes

Granular activated carbon (GAC) particles can be shaped into an integrated 3D-anode using PVDF binder and electro oxidation of reactive dyes in a three-dimensional flow-through carbon anode reactor (TDFCR) delivers a clean effluent free from carbon dust.

Assessment of the formation of inorganic oxidation by-products during the electrocatalytic treatment of ammonium from landfill leachates

This work investigates the formation of oxidation by-products during the electrochemical removal of ammonium using BDD electrodes from wastewaters containing chlorides. The influence of the initial chloride concentration has been experimentally analyzed first, working with model solutions with variable ammonium concentration and second, with municipal landfill leachates. Two different levels of chloride concentration were studied, i) low chloride concentrations ranging between 0 and 2000 mg/L and, ii) high chloride concentrations ranging between 5000 and 20,000 mg/L. Ammonium removal took place mainly via indirect oxidation leading to the formation of nitrogen gas and nitrate as the main oxidation products; at high chloride concentration the formation of nitrogen gas and the rate of ammonium removal were both favored. However, chloride was also oxidized during the electrochemical treatment leading to the formation of free chlorine responsible of the ammonium oxidation, together with undesirable products such as chloramines, chlorate and perchlorate. Chloramines appeared during the treatment but they reached a maximum and then started decreasing, being totally removed when high chloride concentrations were used. With regard to the formation of chlorate and perchlorate once again the concentration of chloride exerted a strong influence on the formation kinetics of the oxidation by-products and whereas at low chloride concentrations, chlorate appeared like an intermediate compound leading to the formation of perchlorate, at high chloride concentrations chlorate formation was delayed significantly and perchlorate was not detected during the experimental time. Thus this work contributes first to the knowledge of the potential hazards of applying the electro-oxidation technology as an environmental technology to deal with ammonium oxidation under the presence of chloride and second it reports efficient conditions that minimize or even avoid the formation of undesirable by-products.