Case studies and scientific paper extracts
Water online article, a US competitor describes the market and possible uses. They utilise a very basic large version of the lab experiment where the bars within a casing dissolve until gone-they have a good video on their site explaining their process:
From The Editor | January 24, 2014
Electrocoagulation: A Shocking Approach To Wastewater Treatment
By Laura Martin
The stages of electrocoagulation shown by Advanced Waste & Water Technology Inc. (AWWT), which offers the technology.
Sometimes water and electricity do mix. A growing number of wastewater treatment professionals, especially those in the industrial sector, are turning to electrocoagulation — a water treatment process that uses electric current to remove various contaminants from water.
“Electrocoagulation and similar ideas have been around for years, but the technology is now gaining traction,” said TJ Mothersbaugh, the business development manager for WaterTectonics, which offers the technology.
The technology is most commonly used in the oil and gas, construction, and mining industries to treat emulsified oil, total petroleum hydrocarbons, suspended solids, heavy metals, and other difficult-to-remove contaminants. Changes in regulations and growth in those industries has brought electrocoagulation to the forefront in recent years, said Mothersbaugh.
Electrocoagulation is performed by applying an electric current across metal plates that are submerged in water. Heavy metals, organics, and inorganics are primarily held in water by electrical charges. By applying another electrical charge to the contaminated water, the charges that hold the particles together are destabilised and separate from the clean water. The particles then coagulate to form a mass, which can be easily removed.
Electrocoagulation can be used as a pre-treatment for processes such as clarification, reverse osmosis (RO), and ultra filtration, or as a polish treatment at the end of traditional treatment processes. The technology typically eliminates the need for chemical or biological additives or demulsifiers. Without chemicals, there is also no need for chemical mixing tanks.
This is appealing to environmentally concerned companies, said Mothersbaugh. "People are looking for options other than chemicals because they are dealing with wastewater that is going to be directly released into surface water,” he said. More and more people want to protect the environment.”
Depending on the application, electrocoagulation can sometimes cut back on steps in the typical industrial wastewater treatment process, said Patricia Werner-Els, chief science officer at Advanced Waste & Water Technology Inc. (AWWT), which offers the technology.
When you set up this technology, what it does or does not incorporate depends on the goal or purpose of the water after the process is completed,” said Werner-Els. “We’ve had cases where we just had to use electrocoagulation — no membranes, no settling tanks, no other steps.”
The electrocoagulation process also renders the sludge inert, making it easy to remove and re-purpose or reuse. The ability to recycle sludge, or even water, is the biggest benefit of electrocoagulation, especially in the fracking industry, said Werner-Els.
"There is a site we are working on where they are taking the water they are using in the oil field and are able to reuse it in the drilling process, clean the water, and pipe it to a local area to use for irrigation, all by using electrocoagulation," she said.
Electrocoagulation can also limit the need for injection wells, which are required in traditional fracking practices to dispose wastewater below the aquifer. Using electrocoagulation, fracking wastewater can be treated onsite and used multiple times in the fracking process. The system is portable and can be easily transported from one drilling site to another.
A water recycling system using electrocoagulation could also be implemented at a municipal wastewater treatment facility.
"Instead of cleaning water and releasing it back into the environment, using electrocoagulation we can get the water to a level that it can be reused for irrigation for golf courses and other places like that,” said Werner-Els. “It is a much easier and cleaner way to recycle our water for reuse and to renter it into the ground safely. We really need to think about reuse and recycling the wastewater that we can, because water is such an important resource.”
Electrocoagulation systems can be designed to remediate anywhere from 100 to 500 gallons per minute to 20,000 gallons of water per minute. Electrocoagulation technology is expected to have multiple applications in the coming years, said Mothersbaugh of WaterTectonics.
“Right now there are about a half a dozen companies in the United States working with this technology,” he said. “Most have focused on lower flow applications and industrial wastewater streams. But there is a lot of potential for more. Our main goal is trying to get the word out that water is a resource we want to reuse and this is way to do it.”
Research conducted by Powell water in the USA
This is another US competitor using basic electrocoagulation technology,
Electrocoagulation Vs. Chemical Coagulation
Because Electrocoagulation (EC) utilises methods that precipitate out large quantities of contaminants in one operation, the technology is the distinct economical and environmental choice for industrial, commercial and municipal waste treatment. The capital and operating costs are usually significantly less than chemical coagulation. It is not unusual to recover capital costs in less than one year.
For example a 5 GPM system contrasts the advantages of Electrocoagulation with a typical chemical coagulation system. This system was designed with the following requirements:
Reduce Ni from 8.74 to < 3 mg / I
Reduce Zn from 28.8 to < 3 mg / I
Reduce TSS from 657 to < 250 mg / I
Reduce Oil and Grease from 27 to < 15 mg / I
Reduce phosphorus from 158.75 to < 10 mg / I
Process flow rate of 5 GPM (1,500,000 GPY)
The estimated yearly operating cost saving using Electrocoagulation in place of chemical coagulation is $43,500.00 per year. This does not include labour, sludge transportation or disposal costs.
A second example is a system with requirements to:
Reduce Ni from 25 to < 2.38 mg / I
Reduce Cr from 210 to < 1.71 mg / I
Flow rate of 100 GPM (30,000,000 GPY)
Operating cost: - Chemical Coagulation - Electrocoagulation
per 1,000 gal $14.18 $1.69
per year $425,400.00 $50,700.00
The estimated yearly operating cost saving using Electrocoagulation in place of chemical coagulation is $374,700.00 per year. This does not include labour, sludge transportation, or disposal costs.
Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical state of dissolved and suspended solids and to facilitate their removal by sedimentation. The chemicals used in wastewater treatment include Alum, Ferric chloride, Ferric sulphate, Ferrous sulphate, and Lime. The inherent disadvantages associated with most chemical unit processes (activated carbon adsorption is an exception) is that they are additive processes. (Metcalf & Eddy, Wastewater Engineering Treatment Disposal Reuse, Third Edition, page 301-303). This problem is eliminated in the Electrocoagulation process. These chemicals are not only expensive, but, more importantly, the net increase in the dissolved constituents in the wastewater render it impractical or impossible to reuse.
Electrocoagulation uses electricity to precipitate the dissolved and suspended solids. The total dissolved solids in the liquid usually decrease by 27 to 60 percent. This enables the water to be reused in many applications, such as water reuse in steam cleaning operations. Reuse of the water provides a major advantage because this eliminates all EPA and POTW discharge concerns, to say nothing of the replacement costs of the water itself.
Electrocoagulation produces a cleaner water than either chemical precipitation or sedimentation ( Wastewater Engineering, page 488 ). As discharge requirements become more stringent EC will become more essential.
Constituent: Percentage of removal by:
Electrocoagulation Chemical Coagulation Sedimentation
TSS - 95 to 99% 80 to 90% 50 to 70%
BOD - 50 to 98 50 to 80% 25 to 40%
Bacteria - 95 to 99.999% 80 to 90% 25 to 75%
The handling and disposal of the sludge resulting from chemical precipitation is one of the greatest difficulties associated with chemical treatment. Sludge is produced in great volume from most chemical precipitation operations, often reaching 0.5 percent of the volume of wastewater treated when lime is used. Waste water Engineering, Third Edition, page 489 – 491), estimated the maximal removal of TSS without chemical is up to 60 percent. With the addition of chemicals, ferrous sulphate and lime, TSS removal rates may climb up to 85 percent.
Assume that the following data apply to this situation:
1. Wastewater flow rate = 1.0 Mgal / d
2. Wastewater suspended solids = 220 mg / l
3. Ferrous sulphate (FeSO4 * 7(H2O)) added = 70 lb / Mgal
4. Lime added = 600 lb / Mgal
5. Calcium carbonate solubility = 15 mg / l
A. 99 percent removal of the TSS with EC will produce: 60 percent of the TSS (without chemicals) will produce 1,100 lb/ sludge on a dry matter basis (DMB) (Volume, 285 cubic feet / day)
B. 85 percent removal of the TSS, (with the chemicals) will produce 3,042 lb/ sludge (Volume, 619 cubic feet / day)
1) 1,560 lb / d of sludge from the TSS
2) 27 lb / d of sludge from the Ferric Hydroxide
3) 1,455 lb / d of sludge from the Calcium carbonate
3,042 Total lbs of sludge on a dry basis.
C. 99 percent removal of the TSS with EC will produce:
1) 1,817 lb / d of sludge from the TSS
2) 8 lb / d of sludge from the aluminium chambers
1,825 Total lbs of sludge on a dry basis (Volume, 285 cubic feet / day)
The total sludge generated by EC contains less than 0.5 percent added coagulant. Total sludge generated by Chemical precipitation contains 49 percent added coagulant. The added sludge generated by chemical precipitation effectively doubles the sludge disposal volume. The hazardous waste issue may increase the cost 20 to 30 fold.
“When compared with alum treatment, Electrocoagulation provided approximately 83% less sludge volume and a 76% improvement in filtration rate.”
Sludge disposal costs are significant. A Class II landfill in Northern California only disposes or treats non hazardous waste. The landfill charges $18.00+ /- yard tipping fees for Class II land fill, non-leachable solids in the 20% moisture range. Non hazardous waste recyclers in Northern California charge processing fees from $0.45 – $3.00 per gallon depending on solids and / or hydrocarbon content. Hazardous waste tipping fees for F listed sludge in North-eastern Colorado range from $400 to $600 per yard.
Hauling charges are significant and may be more than the tipping fee. Hauling charges range from $55 to $70 per hour for short runs and $2.20 to $2.50 per loaded mile for runs over 100 miles for a 3,500 to 7,000 gallon (10 to 20 Yard) truck. In addition there is a $200 truck washing fee. The hauling savings generated from EC as compared to chemical precipitation is usually more than the cost to operate and maintain the Electrocoagulation system marketed by Raintech.
In example B, above, 85 percent of the TSS was removed with chemicals, producing 3,042 lbs of sludge on a Dry Matter Base (DMB). The volume of this sludge was 619 cubic feet /day, of which 49%, (1,490 lbs DMB totalling 303 cubic feet / 11 cubic yards) came from the added chemicals required to achieve the removal of the TSS. Assuming a two-hour run for a 10-yard truck at $55 per hour with a $200 truck washing fee, the extra hauling cost for chemical added sludge is $310.
Electrocoagulation of oxygenated municipal sewerage water is summarised:
Constituent Raw Treated % Removal
BOD (mg/l) 1,050 14 99%
TSS (mg/l) 4,620 7 99%
Bacteria (cfu) 110,000,000 2,700 99%
The Electrocoagulation cost was $0.24 / 1,000 gallons for electricity and chamber repair. The Electrocoagulation operating cost is $240.00 per 1.0 MGPD. That is a $70 per day savings ($310-$240) with Electrocoagulation on hauling alone after deducting the Electrocoagulation operating cost.
Electrocoagulation can produce an environmentally friendly sludge in the 6 to 7 pH range. The metals in the sludge at this pH range are stabilised in a non hazardous form as Oxides, that will pass the U.S. Environmental Protection Agency (EPA) Toxic Classification Leaching Procedure (TCLP), and California Title 22 STLC & TTLC leach tests.
Chemical precipitation on the other hand, usually creates a sludge in the caustic pH range above 10. The metals precipitate as hydroxides, a hazardous form because the metals will become soluble again at the natural pH range around 7.
For example chemical precipitation of phosphorus is brought about by the addition of the salts of multivalent metal ions that form precipitates of sparingly soluble phosphates. The multivalent metal ions used most commonly are calcium (Ca++), Aluminium (Al+++), and Iron (Fe+++).
Chemical coagulation necessitates the addition of calcium, usually introduced in the form of lime. As the pH of the wastewater increases beyond 10, excess calcium ions will then react with the phosphate. The quantity of lime required to precipitate the phosphorus in wastewater is typically about 1.4 to 1.5 times the total alkalinity expressed as CaCO3. Because a high pH value is required to precipitate phosphate, the pH usually requires adjustment before the subsequent treatment or disposal.
In the case of alum and iron, 1 mole will precipitate 1 mole of phosphate. These chemical precipitation reactions must be considered in light of the many competing reactions, their associated equilibrium constants, the effects of alkalinity, pH, trace elements, and ligands found in wastewater. Therefore, dosages are generally established on the basis of bench scale tests and occasionally by full-scale tests (Wastewater Engineering, page 308).
When chemical precipitation is used, anaerobic digestion for sludge stabilisation may not be possible because of the toxicity of the precipitated heavy metals. (Wastewater Engineering, page 756). For land application of sludge, concentrations of heavy metals often limit the sludge application rate and the useful life of the application site to which it is applied (Wastewater Engineering, page 772).
Land application of sludge has been practices successfully for decades. Sludge may be applied to (1) Agricultural land, (2) Forest land, (3) Disturbed land, and (4) Dedicated land disposal sites. Sludge acts as a soil conditioner to facilitate nutrient transport, increase water retention, and improve soil tilth. Sludge also serves as a partial replacement for expensive chemical fertilisers. Characteristics of sludge that affect its suitability for land application or affect the design of land application systems include organic content (usually measured as volatile solids), nutrients, pathogens, metals, and toxic organics. (Wastewater Engineering, page 903). EC can eliminate the concerns regarding pathogens, and metals.
Metals are a major concern in sludge as shown in the following table (Wastewater Engineering, page 772). Typical metal content in wastewater sludge:
Dry sludge, mg / kg
Metal Range Median
Arsenic (As) 1.1-230 10
Cadmium (Cd) 1 – 3,410 10
Chromium (Cr) 10 – 99,000 500
Cobalt (Co) 11.3 – 2,490 30
Copper (Cu) 84 – 17,000 800
Iron (Fe) 1,000 – 154,000 17,000
Lead (Pb) 13 – 26,000 500
Manganese (Mn) 32-9,870 260
Mercury (Hg) 0.6 – 56 6
Molybdenum (Mo) 0.1 – 214 4
Nickel (Ni) 2 – 5,300 80
Selenium (Se) 1.7 – 17.2 5
Tin (Sn) 2.6 – 329 14
Zinc (Zn) 101 – 49,000 1,700
EPA concerns about toxic leachable metal build up in soils may cause many sludges to be deposited in hazardous waste landfills. This not only increases the disposal cost several fold, it eliminates the beneficial soil additive effect discussed earlier.
The reality of the Hazardous waste limits can be illustrated by acceptable disposal limits at non hazardous disposal facilities like Forward, Inc. Stockton, CA. Forward, Inc. can only accept waste for disposal with levels of metals below the following leach-ability listed limits:
Element Title 22 STLC (mg/l) Title 22 TTLC (mg/kg)
Antimony (Sb) 15.00 500
Arsenic (As) 5.00 500
Barium (Ba) 100.00 10,000
Beryllium (Be) 0.75 75
Cadmium (Cd) 1.00 100
Chromium (Cr) 560.00 2500
Hexavalent (Cr+6) 5.00 500
Cobalt (Co) 80.00 8,000
Copper (Cu) 25.00 2,500
Lead (Pb) 5.00 1,000
Mercury (Hg) 0.20 20
Molybdenum (Mo) 350.00 3,500
Nickel (Ni) 20.00 2,000
Selenium (Se) 1.00 100
Silver (Ag) 5.00 500
Thallium (T) 7.00 700
Vanadium (V) 24.00 2,400
Zinc (Zn) 250.00 5,000
Forward has no fixed limit for petroleum hydrocarbons except:
Benzene at 0.5 mg / l (TCLP).
Electrocoagulation may soon move from the optional treatment method to the essential treatment method as the US EPA begins to enforce the laws protecting the environment from toxic wastes, including heavy metals. Electrocoagulation cleans most wastewater streams better, with less operating cost, producing less sludge, with the sludge being a better quality than chemical precipitation. The reuse opportunities for the water is increased because dissolved solids are not added to the waste water stream; and usable products are harvested because the metal oxides pass leach-ability tests, allowing the sludge to be utilised as a soil additive.
Assume that the following data apply to this situation:
1. Wastewater flow rate = 1.0 Mgal / d
2. Wastewater suspended solids = 220 mg / l
3. Ferrous sulphate (FeSO4 * 7(H2O)) added = 70 lb / Mgal
4. Lime added = 600 lb / Mgal
5. Calcium carbonate solubility = 15 mg / l
Scientific research papers from Sciencedirect.com
Treatment of chemical mechanical polishing wastewater by electrocoagulation: system performances and sludge settling characteristics
Treatment of copper chemical mechanical polishing (CMP) wastewater from a semiconductor plant by electrocoagulation is investigated. The CMP wastewater was characterised by high suspended solids (SS) content, high turbidity (NTU), chemical oxygen demand (COD) concentration up to 500 mg l−1 and copper concentration up to 100 mg l−1. In the present study, electrocoagulation was employed to treat the CMP wastewater with an attempt to simultaneously lower its turbidity, copper and COD concentrations. The test results indicated that electrocoagulation with Al/Fe electrode pair was very efficient and able to achieve 99% copper ion and 96.5% turbidity removal in less than 30 min. The COD removal obtained in the treatment was better than 85%, with an effluent COD below 100 mg l−1. The effluent wastewater was very clear and its quality exceeded the direct discharge standard. In addition, sludge settling velocities after electrocoagulation were measured and the data were employed to verify the empirical sludge settling velocity models. Finally, the sludge settling characteristic data were also utilized to establish the relation between the solids flux (G) and the initial solids concentration.
Algae Removal by Electro-coagulation Process, Application for Treatment of the Effluent from an Industrial Wastewater Treatment Plant
GH Azarian, AR Mesdaghinia, F Vaezi, R Nabizadeh, D Nematollahi
Iranian Journal of Public Health 2007. 36(4):57-64.
Background: Although stabilisation ponds and lagoons are suitable treatment processes due to simplicity of operation and low per capital costs, the effluents of these systems have too high of a total suspended solids concentration to be discharged into receiving waters. This problem is mainly caused by algae. In this study, an electro-coagulation reactor was examined to remove algae from the final effluent of the wastewater treatment plant belong to Bu-Ali Industrial Estates (Hamadan City).
Methods: For the continuous flow electro-coagulation reactor used in these experiments three aluminium anodes were utilized. This type of metal was selected because it could introduce the flocculation agent into the effluent, thereby algae could be removed by both mechanisms of electro-flotation and electro-flocculation.
Results: The results of treatment were remarkably good and the efficiencies of total suspended solids (TSS) and chlorophyll a removal reached to as high as 99.5% and about 100% by applying a power input of about 550 W. In fact, this level of power input was needed for complete removal of algae in a low retention time of 15 minutes. Meanwhile, by applying less power input of about 100Wdm-3, the required time for a relatively same treatment was reached to 30 minutes.
Conclusion: It is expected that this method which is also known as a multiple contaminants removal process will be considered as a suitable alternative for final polishing of effluents from lagoons and similar treatment systems.
Volume 124, Issues 1–3, 30 September 2005, Pages 247–254
Arsenic removal via electrocoagulation from heavy metal contaminated groundwater in La Comarca Lagunera México
Arsenic contamination is an enormous worldwide problem. A large number of people dwelling in Comarca Lagunera, situated in the central part of northern México, use well water with arsenic in excess of the water standard regulated by the Secretary of Environment and Natural Resources of México (SEMARNAT), to be suitable for human health. Individuals with lifetime exposure to arsenic develop the classic symptoms of arsenic poisoning. Among several options available for removal of arsenic from well water, electrocoagulation (EC) is a very promising electrochemical treatment technique that does not require the addition of chemicals or regeneration. First, this study will provide an introduction to the fundamental concepts of the EC method. In this study, powder X-ray diffraction, scanning electron microscopy, transmission Mössbauer spectroscopy and Fourier transform infrared spectroscopy were used to characterise the solid products formed at iron electrodes during the EC process. The results suggest that magnetite particles and amorphous iron oxyhydroxides present in the EC products remove arsenic(III) and arsenic(V) with an efficiency of more than 99% from groundwater in a field pilot scale study.
Bilge/Ballast water treatment
Int. J. Electrochem. Sci., 9 (2014) 2316 - 2326
International Journal of ELECTROCHEMICAL SCIENCE
Electrocoagulation Process Application in Bilge Water Treatment Using Response Surface Methodology
Received: 26 September 2013 / Accepted: 23 January 2014 / Published: 2 March 2014
Marine pollution problems have been noted in increasing manner depending on the increment in sea transportation every succeeding day. Bilge water can be count as one of the main pollution source, which contains petroleum, oil and hydrocarbons in high concentrations. Due to interference of seawater to the bilge water, it contains in high chloride concentration; and therefore it is high in conductivity. This feature is an advantage for treatability of bilge water by electrochemical processes. High conductivity leads to increment of current intensity and decrements in voltage and energy costs. Contrary to conventional chemical treatment, extra consumption of chemicals can be avoided by electrochemical treatment methods. In this study, treatment of bilge water by electrocoagulation/electroflotation process is investigated. The experiments were carried out in accordance with statistical runs assigned by response surface methodology. Before optimisation via response surface methodology, a pre-study was performed and the highest removal efficiencies in all pre-studies are obtained in original pH (pH6,95). in consideration of pre-studies, statistical runs were carried out and, the optimum removals of both COD and Oil & Grease were obtained under 9,87 mA/cm2 of current density in approximately 13 minutes and in approximately 29º C of inlet temperature; optimum COD and Oil & Grease were removed by 90,3% and 81,7%, respectively.
Keywords: Bilge water, Electrochemical Treatment, Electrocoagulation, Response Surface Methodology, Central Composite Design.
In recent years increment in transportation by ships and tankers has brought along the marine problem arisen from these vehicles. Besides the countries which have coasts, sea pollution problem has become a global topic. Every succeeding day, uncontrolled discharges of wastewater from the ships such as domestic waste-waters, bilge water, slop, sludge and contaminated ballast water are posed a serious threat to the seas and bilge water takes an important part within these waste-waters.
Int. J. Electrochem. Sci., Vol. 9, 2014 2317
Bilge water stored in bilge tanks consists of waste-waters from machinery department such as cooling waters, oil leaks and also the sludgy waste-waters from oil storage tank; hence it contains oil in high concentration. Some conventional physical and chemical treatments such as centrifugation, filtration, coagulation, sedimentation and flotation had been applying for the treatment of bilge water. Due to the fact that the majority of bilge water’s oil content is emulsified, physical treatment applications are to be insufficient. It is also reported by Caplan et al. and Woytowich et al. that conventional oil/water separation systems cannot separate the emulsified oil droplets under 20 microns. As stated before, conventional treatments are not effective for oil containing wastewater, and for bilge water treatment there are also a limited number of studies in which ultrafiltration, UF/membrane distillation water oxidation, biotechnology, electrocoagulation, photocatalytic methods are applied.
Within advanced wastewater treatment processes, electrochemical wastewater treatment is one of the fastest advancing, most applied processes and will be the most applicable process in more applications in the future. Besides electrochemical treatment of domestic wastewater is applied successfully, it is proved to be effective in treatment of phenol, aniline, olive oil, cyanide and industrial waste-waters from leather tanning, textile, paint industry.
As an electrochemical wastewater treatment process, electrocoagulation is a process based on dissolving Al+3, Fe+2 and Fe+3 ions as coagulant, which forms metal hydroxides with high adsorption capacity in water, via aluminium and iron electrodes. Electrically charged metal ions can form high-gravity flocks by binding emulsified materials, suspended solids and colloidal materials. In addition, H2 gas produced in cathode generates large surface areas for the adsorption of flocs and precipitates, and removes them by floating (electroflotation process).
Electrochemical treatment applications to treat bilge water are very few in number. In the electrocoagulation research with aluminium and iron electrodes by Woytowich et al, it is stated that electrocoagulation becomes gaining acceptance compared to the much higher cost conventional treatment processes.
Due to the high chloride concentration, conductivity of bilge water is high and this makes it appropriate to treat by electrochemical methods by considering the advantages of low energy consumption and less chemical usage. High conductivity leads to increment of current intensity and decrements in voltage and energy costs. Besides the number of researches on treatment of bilge water by electrochemical processes are few in literature; researches on waste-waters contaminated with oil and/or diesel fuel which is thought to be main pollution of bilge water are exist [10-19]. In these studies it is demonstrated that the removal of O&G is carried out by being adsorbed on metal hydroxides produced in electrocoagulation process or by floating via produced gasses [11-12]. In the treatment of oily waste-waters, generally, aluminium and iron electrodes are used and in researches it is specified that aluminium electrodes are more effective than iron electrodes in the treatment of oily waste-waters by proving that O&G adsorption capability of ferrous hydroxides are considerably lower than the adsorption capability of aluminium hydroxides.
The removal of Phosphates from agricultural run off
Available online at Available online at
Treatment of Water Loaded With Orthophosphate by Electrocoagulation
Available online 20 March 2012
In this study, the effective performance of electrocoagulation process in the treatment of water solution that is loaded with orthophosphate was investigated using sacrificial iron electrodes. Various operating parameters (e.g., pH, current intensity and supporting electrolyte concentration) were studied in an attempt to achieve a higher removal capacity. Results obtained with synthetic wastewater revealed that the most effective removal of orthophosphate could be achieved when the pH was kept between 5 and 8. The optimum concentration of supporting electrolyte was found to be 2 g/L, which was adjusted using proper amount of NaCl with the orthophosphate concentration of 10 mg/L. In addition, the increase of current intensity, in the range 0.6–2.0 A, enhanced the treatment rate without affecting the energy consumption. The method was found to be highly efficient and relatively fast compared to conventional existing techniques.
A comparative study of chemical precipitation and electrocoagulation for
treatment of coal acid drainage wastewater
The present study provided a quantitative comparison between chemical precipitation and
electrocoagulation (EC) for removal of heavy metals such as Fe, Al, Ca, Mg, Mn, Zn, Si, Sr, B, Pb, Cr and As from coal mine drainage wastewater (CMDW) at a laboratory scale. The optimum pH for removal of most of heavy metals from CMDW by the chemical precipitation using sodium hydroxide was 8 except for Ca, Sr and B (pH 10 or higher). The removal efficiencies at the optimum pH were varied from 28.4% to 99.96%. Inﬂuence of current density and operating time in the EC process was explored on the removal efficiency and operating cost. Results from the EC process showed that the removal of metals present in CMDW increased with increasing current density and operating time. The EC process was able to achieve higher removal efficiencies (>99.9%) at an electrocoagulation time of 40 min, a current density of 500 A/m2 and pH of 2.5 as compared to the results obtained with the chemical precipitation at pH 8. The operating costs at the optimum operating conditions were also determined to be 1.98s/m3 for the EC and 4.53s/m3 for the chemical precipitation. The EC process was more effective than the chemical precipitation with respect to the removal efficiency, amount of sludge generated and operating cost. Electrocoagulation has the potential to extensively eliminate disadvantages of the classical treatment techniques to achieve a sustainable and economic treatment of polluted wastewater.
This study dealt with removal of metal ions from CMDW by the chemical precipitation and electrocoagulation processes. The chemical precipitation was performed with NaOH, whereas the EC process was evaluated via an electrolytic cell using iron plate electrodes. In the chemical precipitation, the residual metal concentrations from CMDW were reduced with increasing pH values between 4 and 10 but not for Ca, Mg, Sr and B. The optimum pH value for majority of metal ions presents in CMDW was determined to be 8. Effects of current density (200–500 A/m2) and operating time (0–40 min) at pH 2.5 on the removal of metal ions from CMDW were investigated for the ﬁrst time by the EC process.
The residual metal ion concentrations varied from 0.00001 to 0.104 mg/L in the EC process were below the limiting value for CMDW discharge. The ﬁnal effluent pH for the EC process was 6.96 at 500 A/m 2 and 40 min and fell into the discharge limit values. The operating cost for removal of metal ions from CMDW by the chemical precipitation was 2.29s/m3 times higher than that of the EC process. Therefore, it can be concluded that the EC process has the potential to be utilised for cost-effective removal of heavy metals from water and wastewater.