Swine manure digestate treatment using electrocoagulation

Rúbia Mores Airton Kunz Juliana Steffens Rogério Marcos Dallago Toni Luis Benazzi André Cestonaro do Amaral About the authors

ABSTRACT

Anaerobic biodigestion is an appropriate alternative for the treatment of swine wastewater due to its biogas generation properties and the possibility of its application as a source of energy for heating or electricity. However, digestate can still contain high levels of turbidity, organic carbon and nutrients and must be correctly managed as a biofertilizer, or treated to avoid any impact on the environment. Considering this, electrocoagulation (EC) shows promise as a technology because of its ease of handling and high efficiency in effluent remediation. This study aimed to evaluate the performance of EC in a batch system in the treatment of swine wastewater digestate. The wastewater used in the treatment was sampled from a 10 m3 biodigestor effluent (digestate) located at Concórdia, Santa Catarina, Brazil. A batch-scale experiment was carried out to evaluate the following two variables: electrode distance (ED) and voltage applied (V). The removal efficiency levels (%) for the best operational condition (2 cm, 5 V) after 30 min were: 97 %, 98 %, 77 % and 10 % for color, turbidity, total organic carbon (TOC) and total nitrogen (TN), respectively. The EC batch system produced efficient results, underlining its promise as an alternative to be applied in the treatment of digestate.

electrode distance; voltage; factorial design; batch system

Introduction

Wastewater generated in swine production in Brazil has increased as a result of the expansion of confined animal feeding operations (Broetto et al., 2014Broetto, T.; Tornquist, C.G.; Bayer, C.; Campos, B.C.; Merten, C.G.; Wottrich, B. 2014. Soils and surface waters as affected by long-term swine slurry application in Oxisols of southern Brazil. Pedosphere 24: 585-594.). One of the widespread alternatives for the management and treatment of swine wastewater is anaerobic digestion. This biological process converts organic matter into methane (Kothari et al., 2014Kothari, R.; Pandey, A.K.; Kuma, S.; Tyagi, V.V.; Tyagi, S.K. 2014. Different aspects of dry anaerobic digestion for bio-energy: an overview. Renewable and Sustainable Energy 39: 174-195.; Mari et al., 2014Mari, A.; Secco, D.; Kunz, A.; Edwiges, T.; Maro Junior, A.; Frigo, E.; Alves, H. 2014. Performance of up-flow anaerobic digester in solids removal and biogas production. International Journal of Food Agriculture and Environment 12: 1135-1139.) and generates effluent (digestate) that can be used as a biofertilizer. However, when land application is not possible, due to problems with nutrient balance (high chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) content), digestate treatment alternatives must be used (Amaral et al., 2014aAmaral, A.C.; Kunz, A.; Steinmetz, R.; Cantelli, F.; Scussiato, L.A.; Justi, K.C. 2014a. Swine effluent treatment using anaerobic digestion at different loading rates. Agricultural Engineering 34: 567-576.; Amaral et al., 2014bAmaral, A.C.; Kunz, A.; Steinmetz, R.L.; Justi, K.C. 2014b. Zinc and copper distribution in swine wastewater treated by anaerobic digestion. Journal of Environmental Management 141: 132-137.; Park et al., 2010Park, J.; Jin, H.F.; Lim, B.R.; Park, K.Y.; Lee, K. 2010. Ammonia removal from anaerobic digestion effluent of livestock waste using green alga Scenedesmus sp. Bioresource Technology 101: 8649-8657.).

According to Cho et al. (2010)Cho, J.H.; Lee, J.E.; Ra, C.S. 2010. Effects of electric voltage and sodium chloride level on electrolysis of swine wastewater. Journal of Hazardous Materials 180: 535-541., electrocoagulation (EC) is a modern method to be applied as an alternative to the treatment of swine farming wastewater. EC has its advantages when compared to conventional methods such as: basic equipment, ease of operation, less retention time, reduction or no addition of chemical products as well as fast sedimentation of electrogenerated floc (Gengec et al., 2012Gengec, E.; Kobya, M.; Demirbas, E.; Akyol, A.; Oktor, K. 2012. Optimization of baker's yeast wastewater using response surface methodology by electrocoagulation. Desalination 286: 200-209.; Tezcan Ün et al., 2009Tezcan Ün, Ü.; Koparal, A.S.; Öğütveren, Ü.B. 2009. Hybrid processes for the treatment of cattle-slaughterhouse wastewater using aluminum and iron electrodes. Journal of Hazardous Materials 164: 580-586.).

The EC process involves the generation of coagulant “in situ” by dissolving electrically aluminum ions. The generation of metal ions takes place at the anode, and hydrogen gas is released from the cathode. The hydrogen gas also helps float the flocculated particles out of the water (Daneshvar et al., 2012Daneshvar, N.; Oladegaragoze, A.; Djafarzadeh, N. 2012. Decolorization of basic dye solutions by electrocoagulation: an investigation of the effect of operational parameters. Journal of Hazardous Materials 129: 116-122.). According to Chen (2004)Chen, G. 2004. Electrochemical technologies in wastewater treatment. Separation and Purification Technology 38: 11-41., the chemical reactions that occur at the anode and the cathode may be summarized as follows:

According to Kobya et al. (2014)Kobya, M.; Gengec, E.; Sensoy, M.T.; Demirbas, E. 2014. Treatment of textile dyeing wastewater by electrocoagulation using Fe and Al electrodes: optimization of operating parameters using central composite design. Coloration Technology 130: 226-235., the main parameters that control the generation and concentration of aluminum hydroxide coagulant in the EC system are the initial pH, the electrode distance (ED) and the voltage applied. However, it is reported that the optimum pH range for the formation of aluminum hydroxide with the minimum of solubility is between 5.2 - 8.8 (Jiménez et al., 2012Jiménez, C.; Sáez, C.; Martínez, F.; Cañizares, P.; Rodrigo, M.A. 2012. Electrochemical dosing of iron and aluminum in continuous processes: a key step to explain electro-coagulation processes. Separation and Purification Technology 98: 102-108.; Mollah et al., 2001Mollah, M.Y.A.; Schennach, R.; Parga, J.P.; Cocke, D.L. 2001. Electrocoagulation (EC) science and applications. Journal of Hazardous Materials 84: 29-41.).

This study aimed to evaluate the effect of EC operational conditions, applied voltage (V) and electrode distance (ED), the removal of color, turbidity, total organic carbon (TOC) and total nitrogen (TN) in swine manure digestate.

Materials and Methods

Sampling

The swine wastewater (digestate) (Table 1) used in this study was collected in a 10 m3 fiberglass upflow effluent biodigester (Amaral et al., 2014bAmaral, A.C.; Kunz, A.; Steinmetz, R.L.; Justi, K.C. 2014b. Zinc and copper distribution in swine wastewater treated by anaerobic digestion. Journal of Environmental Management 141: 132-137.), located at a swine manure treatment station in Concórdia, Santa Catarina, Brazil (27°18’ S, 51°59’ O). Samples were collected in 5 L polyethylene gallon containers and frozen at -10 °C.

Table 1
− Digestate characterization collected in the fiberglass upflow biodigester used for electrocoagulation studies.

The batch EC reactor (1.7 L) consisted of two pairs of aluminum electrodes (130 mm height and 70 mm width), connected to a direct current power supply. Digestate pH had been previously adjusted to 6.0 using HCl. The system was kept under constant stirring for 30 min. Samples of the experiments were collected at the following times: 0, 10, 20 and 30 min and submitted for analysis.

Experimental Design

To understand the effects of independent variables, the electrode distance (ED) and the applied voltage (V), a factorial design 22 had been elaborated designed for 7 experiments (4 at different combinations and 3 central points). The real and coded variables values are described in Table 2.

Table 2
− Original and coded variables in the factorial design for electrocoagulation experiments using digestate from swine effluent, anaerobically treated.

Analytical Methods

The performance of the EC process was evaluated in terms of the following responses: color, turbidity, total organic carbon (TOC) and total nitrogen (TN). Turbidity was measured by the spectrophotometer method using the colorimeter; TOC was analyzed using Shimadzu (TOC-5000a) equipment (APHA, 2012American Public Health Association [APHA]. 2012. Standard Methods for the Examination of Water and Wastewater. 21ed. APHA, Washington, DC, USA.). TN was analyzed also using Shimadzu (TOC-5000a) equipment; the sample was injected in an oven at 720 ºC with atmospheric oxidant and catalyzed by platinum microspheres, where the TN in the sample thermally decomposes to create nitrogen monoxide. The chemiluminescence detector utilizes the gas-phase chemiluminescence of ozone and nitrogen monoxide, such that the detected nitrogen monoxide analog signal forms a peak. The pH was measured using a pH-meter.

Results and Discussion

Figure 1 shows the removal efficiency of color (A), turbidity (B), TOC (C) and TN (D) obtained at different ED and V, according to the EC operational period.

Figure 1
– Digestate submitted to electrocoagulation color (A), turbidity (B), total organic (TOC) (C) and total nitrogen (TN) (D) removal efficiency.

Color and turbidity reached 98 % removal efficiency after 20 min of treatment, and TOC reached a removal stability level of 68 % after 30 min of treatment (Figure 1). Consequently, the operating time of 30 min is considered optimum for achieving stability in the removal processes, especially in relation to color, turbidity and TOC.

Table 3 shows the factorial design 22 matrix with its respective real and coded values and the responses in removal percentage after a 30 min treatment.

Table 3
− Factorial design 22 matrix with coded values (real) and responses for color, turbidity, total organic total (TOC) and total nitrogen (TN) for 30 min treatment and values of final pH.

The results presented in Table 3 show that runs employing ED of 1 cm and voltage of 4 V and 6 V (runs 1 and 3) had not presented removal efficiency for any of the evaluated responses. Conductivity of 8469.1 μS combined with ED of 1 cm and the voltages of 4 and 6 V applied in the anode and cathode cause short circuits in the EC system. Consequently, under these conditions (runs 1 and 3) no remotions were observed. Mameri et al. (1998)Mameri, N.; Yeddou, A.R.; Lounici, H.; Belhocine, D.; Grib H.; Bariou, B. 1998. Defluoridation of septentrional Sahara water of north Africa by electrocoagulation process using bipolar aluminium electrodes. Water Research 32: 1604-1612. studied the influence of ED on the removal of defluorination and verified that an ED of 0.5 cm combined with conductivity of 40 to 80 μS and current density of 3.12 m−2 caused a short circuit in the EC system.

An increase from 1 cm to 2 and 3 cm in ED, favored removal for runs 2, 4, 5, 6 and 7, with removal levels above 93 % for color, 98 % for turbidity and 68 % for TOC. This is due to electrostatic effects dependent on the ED. Thus, when ED increases, ion displacement occurs allowing for the aggregation and formation of flocs, which, in turn, increase removal efficiency (Daneshvar et al., 2004Daneshvar, N.; Ashassi-Sorkhabi, H.; Kasiri, M.B. 2004. Decolorization of dye solution containing acid red 14 by electrocoagulation with a comparative investigation of different electrode connections. Journal of Hazardous Materials B112: 55-62.; Nanseu-Njiki et al., 2009Nanseu-Njiki, C.P.; Tchamango, S.R.; Ngom, P.C.; Darchen, A.; Ngameni, E. 2009. Mercury (II) removal from water by electrocoagulation using aluminum and iron electrodes. Journal of Hazardous Materials 168: 1430-1436.).

The efficiency in the removal of TN was lower than 11 %, removal stability being reached after 10 min of EC. Akyol et al. (2013)Akyol, A.; Can, O.T.; Demirbas, E.; Kobya, M. 2013. A comparative study of electrocoagulation and electro-Fenton for treatment of wastewater from liquid organic fertilizer plant. Separation and Purification Technology 112: 11-19. and Liu et al. (2015)Liu, Z.; Stromberg, D.; Liu, X.; Liao, W.; Liu, Y. 2015. A new multiple-stage electrocoagulation process on anaerobic digestion effluent to simultaneously reclaim water and clean up biogas. Journal of Hazardous Materials 285: 483-490. observed the same behavior for TN, with removal efficiencies of 18 % and 6 %, respectively.

According to Mahvi et al. (2011)Mahvi, A.H.; Ebrahimi, S.J.A.; Mesdaghinia, A.; Gharibi, H.; Sowlat, M.H. 2011. Performance evaluation of a continuous bipolar electrocoagulation/electrooxidation-electroflotation (ECEO-EF) reactor designed for simultaneous removal of ammonia and phosphate from wastewater effluent. Journal of Hazardous Materials 192: 1267-1274., the EC does not remove TN (ammonia), and out of the electrochemical processes, electrooxidation is the mechanism responsible for ammonia removal in the effluent. Whereas ammonia is the form of nitrogen present in the digestate (Mezzari et al., 2013Mezzari, M.P.; Silva, M.L.B.; Nicoloso, R.S.; Ibelli, A.M.G.; Bortoli, M.; Viancelli, A.; Soares, H.M. 2013. Assessment of N2O emission from a photobioreactor treating ammonia-rich swine wastewater digestate. Bioresource Technology 149: 327-332.), a modification in the EC reactor configuration is required to increase the removal efficiency of TN (ammonia) by electrochemical process. Mahvi et al. (2011)Mahvi, A.H.; Ebrahimi, S.J.A.; Mesdaghinia, A.; Gharibi, H.; Sowlat, M.H. 2011. Performance evaluation of a continuous bipolar electrocoagulation/electrooxidation-electroflotation (ECEO-EF) reactor designed for simultaneous removal of ammonia and phosphate from wastewater effluent. Journal of Hazardous Materials 192: 1267-1274. proposed that electrodes of Al, RuO2/Ti and stainless steel need to be inserted in an EC reactor, to form a configuration of electrocoagulation/electro-oxidation.

Recently, the anaerobic oxidation process (anaerobic ammonium oxidation - Anammox) has attracted attention because of its advantages compared to conventional nitrification-denitrification processes (Casagrande et al., 2013Casagrande, C.G.; Kunz, A.; De Prá, M.C.; Bressan, C.R.; Soares, H.M. 2013. High nitrogen removal rate using anammox process at short hydraulic retention time. Water Science and Technology 67: 968-975.; Du et al., 2015Du, R.; Peng, Y.; Cao, S.; Wang, S.; Wu, C. 2015. Advanced nitrogen removal from wastewater by combining anammox with partial denitrification. Bioresource Technology 179: 497-504.). During the anammox process, ammonia nitrogen is converted into gaseous nitrogen. Because of its low C:N ratios the anammox process is suitable for wastewater. At C:N ratios above 1, the anammox bacteria cannot compete with heterotrophic denitrifying bacteria (Molinuevo et al., 2009Molinuevo, B.; García, M.C.; Karakashev, D.; Angelidaki, I. 2009. Anammox for ammonia removal from pig manure effluents: effect of organic matter content on process performance. Bioresource Technology 100: 2171-2175.). In this sense, the effluent from EC can provide adequate and stable conditions for Anammox.

As regards final pH (Table 3), independent of the variables of the processes (ED and voltage), there was an increase to between 6.4 and 8.5. The EC has the property of increasing the wastewater's pH after its treatment, due to OH- production in the cathode (Eq. 02) (Tezcan Ün and Ozel, 2013)Tezcan Ün, Ü.; Ozel, E. 2013. Electrocoagulation of yogurt industry wastewater and the production of ceramic pigments from the sludge. Separation and Purification Technology 120: 386-391..

To better evaluate the influence of ED and the tension (V) applied to the EC process, an estimates analysis of independent variable effects over the dependent ones are presented in the Pareto diagrams (Figure 2A (color), B (turbidity), C (TOC) and D(TN)).

Figure 2
− Pareto diagrams showing the importance of the effects of electrode distance (ED) and applied voltage (V) on removal percentage of responses color (A), turbidity (B) total organic carbon (TOC) (C) total nitrogen (TN) and (D).

The results achieved demonstrate that the independent variable ED presented significant positive effects (p < 0.05) in terms of dependent variables on color, turbidity and TOC. The dependent variable TN did not present any significant effect on the independent variables ED and V.

Recent studies show increases in the ED results and a decrease in removal efficiency due to the fall in ohmic tension between the cathode and the anode (Anand et al., 2014Anand, M.V.; Srivastava, V.C.; Singh, S.; Bhatnagar, R.; Mall, I.D. 2014. Electrochemical treatment of alkali decrement wastewater containing terephthalic acid using iron electrodes. Journal of the Taiwan Institute of Chemical Engineers 45: 908-913.; Attour et al., 2014Attour, A.; Touati, M.; Tlili, M.; Ben Amor, M.; Lapicque, F.; Leclerc, J.P. 2014. Influence of operating parameters on phosphate removal from water by electrocoagulation using aluminum electrodes. Separation and Purification Technology 123: 124-129.; Merzouk et al., 2010Merzouk, B.; Madani, K.; Sekki, A. 2010. Using electrocoagulation-electroflotation technology to treat synthetic solution and textile wastewater, two case studies. Desalination 250: 573-577.; Zhang et al., 2013Zhang, S.; Zhang, J.; Wang, W.; Li, F.; Cheng, X. 2013. Removal of phosphate from landscape water using an electrocoagulation process powered directly by photovoltaic solar modules. Solar Energy Materials & Solar Cells 117: 73-80.). However, in our study an inverse effect was observed, where an increase in 1 cm ED of 2 and 3 cm favored the removal of color, turbidity and TOC. This difference is due to the electrical conductivity of digestate (8469.1 μS), because the electrical conductivity significantly affects the removal efficiency of the pollutants (Al-Shannag et al., 2015Al-Shannag, M.; Al-Qodah, Z.; Bani-Melhem, K.; Qtaishat, M.R.; Alkasrawi, 2015. M. Heavy metal ions removal from metal plating wastewater using electrocoagulation: kinetic study and process performance. Chemical Engineering Journal 260: 749-756.). It is inversely proportional to the ED (Akbal and Camci, 2011Akbal, F.; Camci, S. 2011. Copper, chromium and nickel removal from metal plating wastewater by electrocoagulation. Desalination 269: 214-222.) and determines the effect of the mobility of ions in relation to the applied electric field (Vasudevan et al., 2013Vasudevan, S.; Lakshmi, J.; Kamaraj, R.; Sozhan, G. 2013. A critical study on the removal of copper by an electrochemically assisted coagulation: equilibrium, kinetics, and thermodynamics. Asia-Pacific Journal of Chemical Engineering 8: 162-171.). Thus, it is recommended to use 2 and 3 cm of ED for the treatment of digestate using EC.

Conclusion

For the digestate treatment, the following two parameters were evaluated by electrocoagulation: distance between the electrodes and the voltage applied. The electrode distance was the variable that presented an effect on the treatment process. The increase in electrode distance from 1 cm to 2 and 3 cm, favored removal of color, turbidity and total organic carbon with values above 93 %, 98 % and 68 %, respectively, and an operating time of 30 min. The removal of total nitrogen was below 11 %, because the electrocoagulation did not promote ammonia oxidation in the digestate. Thus, the effluent from EC can provide adequate and stable conditions for Anammox.

Electrocoagulation batch technology offers as an alternative stage to be incorporated into the wastewater treatment system in swine farming due to its elevated efficiency levels on the removal of color, turbidity and TOC.

Acknowledgements

URI - Erechim, CAPES, CNPq, Embrapa Swine and Poultry and Eletrosul.

References

  • Akbal, F.; Camci, S. 2011. Copper, chromium and nickel removal from metal plating wastewater by electrocoagulation. Desalination 269: 214-222.
  • Akyol, A.; Can, O.T.; Demirbas, E.; Kobya, M. 2013. A comparative study of electrocoagulation and electro-Fenton for treatment of wastewater from liquid organic fertilizer plant. Separation and Purification Technology 112: 11-19.
  • Al-Shannag, M.; Al-Qodah, Z.; Bani-Melhem, K.; Qtaishat, M.R.; Alkasrawi, 2015. M. Heavy metal ions removal from metal plating wastewater using electrocoagulation: kinetic study and process performance. Chemical Engineering Journal 260: 749-756.
  • Amaral, A.C.; Kunz, A.; Steinmetz, R.; Cantelli, F.; Scussiato, L.A.; Justi, K.C. 2014a. Swine effluent treatment using anaerobic digestion at different loading rates. Agricultural Engineering 34: 567-576.
  • Amaral, A.C.; Kunz, A.; Steinmetz, R.L.; Justi, K.C. 2014b. Zinc and copper distribution in swine wastewater treated by anaerobic digestion. Journal of Environmental Management 141: 132-137.
  • American Public Health Association [APHA]. 2012. Standard Methods for the Examination of Water and Wastewater. 21ed. APHA, Washington, DC, USA.
  • Anand, M.V.; Srivastava, V.C.; Singh, S.; Bhatnagar, R.; Mall, I.D. 2014. Electrochemical treatment of alkali decrement wastewater containing terephthalic acid using iron electrodes. Journal of the Taiwan Institute of Chemical Engineers 45: 908-913.
  • Attour, A.; Touati, M.; Tlili, M.; Ben Amor, M.; Lapicque, F.; Leclerc, J.P. 2014. Influence of operating parameters on phosphate removal from water by electrocoagulation using aluminum electrodes. Separation and Purification Technology 123: 124-129.
  • Broetto, T.; Tornquist, C.G.; Bayer, C.; Campos, B.C.; Merten, C.G.; Wottrich, B. 2014. Soils and surface waters as affected by long-term swine slurry application in Oxisols of southern Brazil. Pedosphere 24: 585-594.
  • Casagrande, C.G.; Kunz, A.; De Prá, M.C.; Bressan, C.R.; Soares, H.M. 2013. High nitrogen removal rate using anammox process at short hydraulic retention time. Water Science and Technology 67: 968-975.
  • Chen, G. 2004. Electrochemical technologies in wastewater treatment. Separation and Purification Technology 38: 11-41.
  • Cho, J.H.; Lee, J.E.; Ra, C.S. 2010. Effects of electric voltage and sodium chloride level on electrolysis of swine wastewater. Journal of Hazardous Materials 180: 535-541.
  • Jiménez, C.; Sáez, C.; Martínez, F.; Cañizares, P.; Rodrigo, M.A. 2012. Electrochemical dosing of iron and aluminum in continuous processes: a key step to explain electro-coagulation processes. Separation and Purification Technology 98: 102-108.
  • Daneshvar, N.; Ashassi-Sorkhabi, H.; Kasiri, M.B. 2004. Decolorization of dye solution containing acid red 14 by electrocoagulation with a comparative investigation of different electrode connections. Journal of Hazardous Materials B112: 55-62.
  • Daneshvar, N.; Oladegaragoze, A.; Djafarzadeh, N. 2012. Decolorization of basic dye solutions by electrocoagulation: an investigation of the effect of operational parameters. Journal of Hazardous Materials 129: 116-122.
  • Du, R.; Peng, Y.; Cao, S.; Wang, S.; Wu, C. 2015. Advanced nitrogen removal from wastewater by combining anammox with partial denitrification. Bioresource Technology 179: 497-504.
  • Gengec, E.; Kobya, M.; Demirbas, E.; Akyol, A.; Oktor, K. 2012. Optimization of baker's yeast wastewater using response surface methodology by electrocoagulation. Desalination 286: 200-209.
  • Kobya, M.; Gengec, E.; Sensoy, M.T.; Demirbas, E. 2014. Treatment of textile dyeing wastewater by electrocoagulation using Fe and Al electrodes: optimization of operating parameters using central composite design. Coloration Technology 130: 226-235.
  • Kothari, R.; Pandey, A.K.; Kuma, S.; Tyagi, V.V.; Tyagi, S.K. 2014. Different aspects of dry anaerobic digestion for bio-energy: an overview. Renewable and Sustainable Energy 39: 174-195.
  • Liu, Z.; Stromberg, D.; Liu, X.; Liao, W.; Liu, Y. 2015. A new multiple-stage electrocoagulation process on anaerobic digestion effluent to simultaneously reclaim water and clean up biogas. Journal of Hazardous Materials 285: 483-490.
  • Mameri, N.; Yeddou, A.R.; Lounici, H.; Belhocine, D.; Grib H.; Bariou, B. 1998. Defluoridation of septentrional Sahara water of north Africa by electrocoagulation process using bipolar aluminium electrodes. Water Research 32: 1604-1612.
  • Mahvi, A.H.; Ebrahimi, S.J.A.; Mesdaghinia, A.; Gharibi, H.; Sowlat, M.H. 2011. Performance evaluation of a continuous bipolar electrocoagulation/electrooxidation-electroflotation (ECEO-EF) reactor designed for simultaneous removal of ammonia and phosphate from wastewater effluent. Journal of Hazardous Materials 192: 1267-1274.
  • Mari, A.; Secco, D.; Kunz, A.; Edwiges, T.; Maro Junior, A.; Frigo, E.; Alves, H. 2014. Performance of up-flow anaerobic digester in solids removal and biogas production. International Journal of Food Agriculture and Environment 12: 1135-1139.
  • Merzouk, B.; Madani, K.; Sekki, A. 2010. Using electrocoagulation-electroflotation technology to treat synthetic solution and textile wastewater, two case studies. Desalination 250: 573-577.
  • Mezzari, M.P.; Silva, M.L.B.; Nicoloso, R.S.; Ibelli, A.M.G.; Bortoli, M.; Viancelli, A.; Soares, H.M. 2013. Assessment of N2O emission from a photobioreactor treating ammonia-rich swine wastewater digestate. Bioresource Technology 149: 327-332.
  • Molinuevo, B.; García, M.C.; Karakashev, D.; Angelidaki, I. 2009. Anammox for ammonia removal from pig manure effluents: effect of organic matter content on process performance. Bioresource Technology 100: 2171-2175.
  • Mollah, M.Y.A.; Schennach, R.; Parga, J.P.; Cocke, D.L. 2001. Electrocoagulation (EC) science and applications. Journal of Hazardous Materials 84: 29-41.
  • Nanseu-Njiki, C.P.; Tchamango, S.R.; Ngom, P.C.; Darchen, A.; Ngameni, E. 2009. Mercury (II) removal from water by electrocoagulation using aluminum and iron electrodes. Journal of Hazardous Materials 168: 1430-1436.
  • Park, J.; Jin, H.F.; Lim, B.R.; Park, K.Y.; Lee, K. 2010. Ammonia removal from anaerobic digestion effluent of livestock waste using green alga Scenedesmus sp. Bioresource Technology 101: 8649-8657.
  • Tezcan Ün, Ü.; Koparal, A.S.; Öğütveren, Ü.B. 2009. Hybrid processes for the treatment of cattle-slaughterhouse wastewater using aluminum and iron electrodes. Journal of Hazardous Materials 164: 580-586.
  • Tezcan Ün, Ü.; Ozel, E. 2013. Electrocoagulation of yogurt industry wastewater and the production of ceramic pigments from the sludge. Separation and Purification Technology 120: 386-391.
  • Vasudevan, S.; Lakshmi, J.; Kamaraj, R.; Sozhan, G. 2013. A critical study on the removal of copper by an electrochemically assisted coagulation: equilibrium, kinetics, and thermodynamics. Asia-Pacific Journal of Chemical Engineering 8: 162-171.
  • Zhang, S.; Zhang, J.; Wang, W.; Li, F.; Cheng, X. 2013. Removal of phosphate from landscape water using an electrocoagulation process powered directly by photovoltaic solar modules. Solar Energy Materials & Solar Cells 117: 73-80.

Publication Dates

  • Publication in this collection
    Sep-Oct 2016

History

  • Received
    02 July 2015
  • Accepted
    05 Nov 2015
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