Composite wastewater treatment by aerated electrocoagulation and modified peroxi-coagulation processes

doi:10.1016/j.chemosphere.2018.04.141

Chemosphere

Volume 205, August 2018, Pages 587-593

https://doi.org/10.1016/j.chemosphere.2018.04.141 Get rights and content

Highlights

•
Electrochemical treatment of composite wastewater.
•
Enhanced performance of electrocoagulation with external aeration.
•
Superior performance of modified peroxi-coagulation process than aerated electrocoagulation process.
•
Active chlorine generation is irrespective of process and pH.
•
Hydroxyl radicals are superior oxidant responsible for pollutant removal.

Abstract

Treatment of composite wastewater generating from the industrial estates is a great challenge. The present study examines the applicability of aerated electrocoagulation and modified peroxi-coagulation processes for removing color and COD from composite wastewater. Iron plates were used as anodes and cathodes in both electrochemical processes and experiments were carried out in a working volume of 2 L. Aeration enhanced the efficiency of electrocoagulation process significantly. More than 50% of COD and 60% of color were removed after 1 h of electrocoagulation process operated at pH 3 and applied voltage of 1 V. Efficiency of the modified peroxi-coagulation process was significantly higher than that of aerated electrocoagulation. COD and color removal efficiencies of the modified peroxi-coagulation process were found as 77.7% and 97%, respectively after 1 h of electrolysis operated at 1 V, solution pH 3 and 50 mM hydrogen peroxide addition. This improved efficiency of modified peroxi-coagulation compared to aerated electrocoagulation is mainly due to the attack of in-situ generated hydroxyl radicals.

Introduction

Small and medium-sized industries play a vital role in the economic growth and development of every country. It is reported that more than 300000 of small-scale industries are spread all over India and most of these industries are situated in 867 industrial estates (CPCB, 2005). It is estimated that small and medium scale industries are responsible for generating about 50% of industrial wastewater in India (Singh et al., 2008). Wastewater generated from these industries contains a variety of pollutants and should be treated before its discharge into natural waterbodies. Lack of operational space, technical manpower, scale of operation, budget etc. are the main challenges to operate individual wastewater treatment plant for each industrial units. To solve these problems and to protect our environment, Ministry of Environment and Forest, India introduced the concept of common effluent treatment plant (CETP) in 1984 (Pathe et al., 2004). The concept of CETP is to collect effluent generated from different industries and treat them at a common treatment system (Kapley et al., 2007). Effluent generated from each industry transported via tankers or pipeline to the equalization tank of CETPs. This system is similar to a municipal sewage treatment plant system where sewage generating from individual houses is treating in a common treatment plant. CETPs can be planned in such a way that there will be no issue of space in future expansion. Implementation of CETPs reduces the effluent treatment cost for individual industries significantly (Pophali and Dhodapkar, 2011, Singh et al., 2008). CETP eliminates several effluent discharge points and provide a better platform for the effective management of treated effluent and generated sludge.

CETPs can be divided into homogeneous and heterogeneous CETPs, based on the types of industries from which CETPs receiving the effluents. Homogenous CETPs receives effluents from a similar type of industries, while heterogeneous CETPs receive effluents from various types of industries such as textile, tanneries, pharmaceutical, chemical etc. Wastewater treatment in heterogeneous CETPs is quite difficult as compared to that in homogenous CETPs. The quantity and quality of wastewater receiving at heterogeneous CETPs are highly fluctuating than homogenous CETPs. Thus treatment of composite wastewater (mixed industrial wastewater) is a great challenge.

Central Pollution Control Board, India (CPCB, 2005) examined the performance of 78 CETPs operating in India and found that only 20 CETPs are meeting effluent discharge standards for the parameters pH, BOD, COD, and TSS. Only 5 CETPs out of 78 CETPs were meeting parameters including TDS (CPCB, 2005). This poor performance of CETPs is mainly due to the heterogeneous nature of wastewater. Most of the CETPs were designed by extrapolating sewage treatment plant design assumptions. Wastewater receives in STPs are homogeneous in nature, while the inlet wastewater characteristics of CETPs varies with the type of industries and industrial process. More often the industrial effluents contain toxic compounds which retard the performance of secondary treatment system (Roshini et al., 2017). Apart from all, most of the organic compounds present in industrial wastewater are non-biodegradable.

Electrochemical water and wastewater treatment methods have received great attention due to its simplicity, efficiency, lower operating cost compared to other treatment processes etc. (Brillas et al., 2009, Brillas and Martínez-Huitle, 2015, Martínez-Huitle et al., 2015, Nidheesh and Gandhimathi, 2012, Vasudevan and Oturan, 2014). Electrochemical treatment methods such as electrocoagulation (Shankar et al., 2014), electrochemical oxidation (Bhatnagar et al., 2014), anodic oxidation (Panizza and Cerisola, 2006), electro-Fenton process (Nidheesh and Gandhimathi, 2015, Roshini et al., 2017), peroxi-coagulation process (Nidheesh and Gandhimathi, 2014a), etc. are found very effective for the treatment of various industrial wastewater. Higher dissolved solid concentration present in the industrial wastewater is also helpful for the performance of electrochemical methods. The present study examines the performance of two electrochemical processes, namely aerated electrocoagulation process and modified peroxi-coagulation process for the treatment of composite wastewater. Efficiency of the processes was monitored in terms of color and COD removal.

Section snippets

Chemicals

Sulphuric acid (98% pure), sodium hydroxide and hydrogen peroxide (30% pure) were purchased from Merck and used for the experiments without further purification or treatment. Deionized water was used for reagent preparation.

Composite wastewater

Composite wastewater was collected from the inlet point of a heterogeneous common effluent treatment plant situated in Gujarat, India. This composite wastewater contains effluents from various chemical industries, textile industries etc. Sufficient amount of wastewater was

Composite wastewater treatment by aerated electrocoagulation

Electrocoagulation process is widely accepted electrochemical process in which pollutants are removed from the water medium by in-situ generated hydrolyzable metal cations (Anantha Singh and Ramesh, 2013, Nidheesh and Singh, 2017, Vasudevan and Oturan, 2014). This process is found highly effective for removing various contaminants from synthetic water medium and to treat real wastewater (Aswathy et al., 2016, Eiband et al., 2014, Garcia-Segura et al., 2017, Mithra et al., 2017). Efficiency of

Conclusions

Electrochemical processes were found effective for COD and color removal from composite wastewater. Efficiency of electrocoagulation process using iron electrodes was improved significantly with external aeration. Aerated electrocoagulation process was found effective at pH 3 and 7.7, and more than 60% color and 50% COD were removed at pH 3. Performance of modified peroxi-coagulation process was found quite high compared to aerated electrocoagulation process. Color and COD removal efficiencies

Acknowledgments

Authors are thankful to the Director, CSIR-NEERI, Nagpur, India for providing encouragement, and kind permission for publishing the article.

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Composite wastewater treatment by aerated electrocoagulation and modified peroxi-coagulation processes

Highlights

Abstract

Introduction

Section snippets

Chemicals

Composite wastewater

Composite wastewater treatment by aerated electrocoagulation

Conclusions

Acknowledgments

New trends in electrocoagulation for the removal of dyes from wastewater: a review

Environ. Eng. Sci.

Standard methods for the examination of water and wastewater. Stand. Methods

Removal of organics from bilge water by batch electrocoagulation process

Separ. Purif. Technol.

Treatment of landfill leachate by using electro-Fenton method

J. Hazard Mater.

Process Chemistry for Water and Wastewater Treatment

Electrocoagulation and effect of cathode materials on the removal of pollutants from tannery wastewater of Rouïba

Desalination

Electrochemical oxidation of textile industry wastewater by graphite electrodes

J. Environ. Sci. Health. A. Tox. Hazard. Subst. Environ. Eng

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Electrochim. Acta

Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. An updated review

Appl. Catal. B Environ.

Electro-Fenton process and related electrochem- ical technologies based on Fenton’s reaction chemistry

Chem. Rev.

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Decolorization of orange II by electrocoagulation method

Separ. Purif. Technol.

Electrochemical removal of pollutants from agro-industry wastewaters

Separ. Purif. Technol.

Elimination of Pb2+through electrocoagulation: applicability of adsorptive stripping voltammetry for monitoring the lead concentration during its elimination

J. Electroanal. Chem.

Electrocoagulation and advanced electrocoagulation processes: a general review about the fundamentals, emerging applications and its association with other technologies

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Treatment of dye solution containing colored index acid yellow 36 by electrocoagulation using iron electrodes

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Environ. Eng. Manag. J

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Textile wastewater treatment by electro-fenton process in batch and continuous modes

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