Oil and gas production operations from depleted oil and gas fields often result in the production of enormous amount of water. Even though, disposal of this oil-field produced water itself is a challenging task, however at the same time, treated oil-field produced water can provide an unconventional source of water that could be used for certain beneficial reuses.
The present study reports on the review of various currently available oil-field water treatment technologies with a focus on heavy metals removal technologies.It appears that the photo catalyticmethods are the most promising methods for removing heavy metals from oil-field produced water. However, several factors including the initial metal concentration, the component of the wastewater, capital investment and operational cost, plant flexibility and reliability, environmental impact, and utility of the treated water have a great influence on the selection of the most suitable treatment techniques.
Extraction of oil and gas from underground reservoirs often is accompanied by water or brine, which is referred to as produced water. Produced water is the largest waste-stream of oil and gas exploration which includes water trapped in underground formations and water injected into the stratum to drive out the crude oil . In early stages of oil production, water content is usually low but can rise to as high as 80% during the later years of the well . As reservoirs mature, especially if secondary or tertiary recovery methods are used, the quantity of water climbs and often exceeds the volume of the hydrocarbons before the reservoir is exhausted. It has been observed that in some of the oil-fields this ratio is 1:15 where 15 parts of water accompany just 1 part of oil. Global produced water production is estimated at about 250 million barrels per day compared with about 80 million barrels per day of oil .The chemical composition and behaviour of produced water varies when compared with the surface waters because they are constrained within an aquifer and has distinctive characteristics due to the presence of organic and inorganic matters, high salinity, BTEX, PAH, heavy metals etc. which can cause toxicity to the environment.Generally, produced water is composed of dissolved and dispersed oil components, dissolved formation minerals, productionchemicals, dissolved gases (including CO2 and H2S) and produced solids. There is a wide variation in the level of its organic and inorganic composition due to geological formation, lifetime of the reservoir and the type of hydrocarbon produced. Also, this produced water contains various microorganisms which result in microbial corrosion of the inner surfaces of pipesby forming biofilms on the metal surfaces .The constituents of produced water vary and can differ from well to well with pH in the range of 6-8.5 . Produced water is increasingly being considered to supplement limited freshwater resources in many parts of the US as well as other countries. The cost of producing, handling, and disposing of the produced water often defines the economic lifetime of a field and the actual hydrocarbon reserves; therefore, understanding and predicting the aspects, behaviour, and problems induced by the produced-water flow is important.
Composition of oil-field produced water
Oil field produced water generally consists of dispersed and dissolved oil components those are mixture ofhydrocarbons including BTEX (benzene,toluene,ethylbenzeneandxylene), PAHs (polyaromatic hydrocarbons) and phenols. Dissolved oils are the polar constituent organic compounds in produced water, while small droplets of oil suspended in the aqueous phase are called dispersed oil [8-10]. BTEX, phenols, aliphatic hydrocarbons, carboxylic acid and low molecular weight aromatic compound are classified as dissolvedoil, while less-soluble PAHs and heavy alkyl phenols are present in produced water as dispersed oil . Dissolved and dispersed oil has to be removed in order to utilize this produced water for some efficient reuse.
Dissolved inorganic compounds or minerals are usually highin concentration, and classified as cations and anions, naturallyoccurring radioactive materials and heavy metals. Cations andanions play a significant role in the chemistry of producedwater. Na and Cl2are responsible for salinity, ranging from afew milligrams per litre to 300000 mg/L. Cl2, SO4,CO3, HCO, Na, K, Ca2, Ba2, Mg2, Fe2 and Sr2affect conductivity and scale-forming potential. Typical oilfieldproduced water contains heavy metals in varied concentrations,depending on the formation geology and the age of oil well and its concentration is usually higher than those of receiving water (for enhanced oil recovery) and those found in sea water.226Ra and 228Ra are the most abundant naturally occurringradioactive elements present sometimes in oilfield produced water.Radioactivity of produced water results primarily fromradium that is co-precipitated with barium sulphate (scale)or other types of scales .
Current scenario of oil-field produced water disposal
At present,oil and gas operators manage the produced water by following one or more of the options. Some try to avoid production of water by blocking the water fractures by polymer gel or downhole water separator;but this option is not always possible as water would generally be produced during secondary and tertiary extraction process of oil. Another is injecting the produced water back into the formations. However, this demands transportation of water, and treatment to reduce fouling and bacterial growth. In the long term, the stored produced water may pollute the underground waters. Also, some follows its discharge in to the environment if it meets onshore and offshore discharge regulations. Petroleum industry may try reusing minimally treated produced water for drilling and work over operations. Finally, it could be utilized for beneficial domestic purposes such as for irrigation, wildlife consumption and industrial water, but this may involve significant treatment [3,15].
Environmental concerns and the prospect of beneficial uses have driven research into the treatment of produced water. Current conventional treatment technologies are targeted at removal of heavy metals, oil and grease, suspended solids, and desalination, which often lead to the generation of large volumes of secondary waste. For instance, heavy metals are removed as sludge using current treatment technologies . This article reviews current produced water efficient, eco-friendly and cost effective treatment technologies for removal of heavy metals thereby rendering the produced water for reuse with minimal negative impact on the environment.
Pre-treatment methods for oil-field produced waters
The first pre-treatment process of the oil-field produced waters containing traces of oil is the oil-water separation. Theconventional rectangular-channel separators, developed by the American PetroleumInstitute (API) are wildly used for this purpose, and their design criteria are summarized inthe publication API, 1990. Many other separators had been developed based on the oil-waterseparation theory and some of them, as the parallel plate and corrugated plate separators,had been implemented in the petroleum refineries . The oilseparators removeonly the fraction of free oil, whereas the emulsified and the dissolved oil remain in the separator effluent in the form of oil-water emulsions. These emulsions could be destabilized using chemical destabilizers followed by separation using dissolved air flotation technique (DAF)[19-21]. Different biologicaltreatment processes that have been utilized for treating produced water are aeratedponds, activated sludge, biological contactors, sequential bath reactors and moving bedreactors[22-25]. Initial researches that had been done for recycling of the biologically treated refinery effluent involved the use of activated carbon adsorption alone or in combination with ozonation or sandfiltration [26-28].Themembrane technology development allowed additional options, such as ultrafiltration andreverse osmosis[29-32].The implementation of the advanced treatment technology allowedreusing of the biologically treated wastewater and freshwater savings in the refineries.
Effects of heavy metals
Heavy metals are generally considered to be those whose densityexceeds 5 g per cubic centimetre and atomic weights between 63.5 and 200.6. Most heavy metals are well-known toxic and carcinogenic agents and it represent a serious threat to the human population and the fauna and flora of the receiving water bodies. Heavy metals have a great tendency to bio-accumulate and end up as permanent additions to the environment and have detrimental effect on human health .Oncethey enter the food chain, large concentrations of heavymetals may accumulate in the human body. If the metals concentrations are ingested beyond the permitted value, they can cause serious health disorders. A large number of elementsfall into this category, but the ones discussed here are those of relevance in the environmental context. Arsenicis usually regarded as a hazardous heavy metal even thoughit is actually a semi-metal. Heavy metals cause serious healtheffects, including reduced growth and development, cancer,organ damage, nervous system damage, and in extreme cases,death. Exposure to some metals, such as mercury and lead,may also cause development of autoimmunity, in which aperson’s immune system attacks its own cells. Thiscan leadto joint diseases such as rheumatoid arthritis, and diseases ofthe kidneys, circulatory system, nervous system, and damagingof foetus’s brain. Wastewater regulationswere established to minimize human and environmental exposureto hazardous chemicals. This includes limits on the typesand concentration of heavy metals that may be present in thedischarged wastewater[34-35].
Produced water management techniques
The general objectives for operators treating produced water are: de-oiling (removal of dispersed oil and grease), desalination, removal of suspended particles (salts) and sand, removal of soluble organics, removal of dissolved gases, removing traces of heavy metals, removal of naturally occurring radioactive materials (NORM), disinfection and softening (to remove excess water hardness) . In this current review,different methods to remove heavy metals from oil-field produced waters have been discussed in detail. These methods includechemical precipitation, coagulation, flocculation,ion-exchange, adsorption, membrane filtration,Reverse Osmosis, floatation, electrochemicaltreatment technologies, Electrodialysis, Photocatalysis and biological methods.
Chemical Precipitation, Coagulation and Flocculation
The conventional method for heavy metal removal from industrial wastewater generally involves achemical precipitation process[36-39].Of the varioustreatment methods employed to remove heavymetals, hydroxide precipitation is the most commontreatment technology. Heavy metals are removed byadding alkali such as caustic, lime or soda ash toadjust the wastewater pH to the point where themetals exhibit a minimum solubility. Then a proper solid-liquid separation technique removes the metal precipitation such as sedimentationand filtration. The conventional heavy metalremoval process has some inherent shortcomingssuch as requiring a large area of land, a sludgedewatering facility, skilful operators and multiplebasin configurations.The conceptual mechanism of heavy metal removal by chemical precipitation is presented in Eq. (1) M2+ + 2(OH)– ↔ M(OH)2,.
Where, M2+ and OH represent the dissolved metal ions and the precipitant, respectively, while M(OH)2 is the insoluble metal hydroxide. Adjustment of pH to the basic conditions (pH range of 9–11) is the major parameter that significantly improves heavy metal removal by chemical precipitation. Lime and limestone are the most commonly employed precipitant agents due to their availability and low-cost in most countries [42- 43]. Lime precipitation can be employed to effectively treat inorganic effluent with a metal concentration of higher than 1000 mg/L and other advantages of using lime precipitation include the simplicity of the process, inexpensive equipment requirement, and convenient and safe operations. To enhance lime precipitation, fly ashwas used as a seed material. The fly ash- limecarbonationtreatment increased the particle size of the precipitateand improved the efficiency of heavy metal removal. In hydroxide precipitation process, the addition of coagulantssuch as alum, iron salts, and organic polymers can enhance theremoval of heavy metals from wastewater Another researcher employed chemical coagulation and precipitation by lime to treatsynthetic wastewater.Sulphide precipitation is also an effective process for the treatmentof toxic heavy metal ions. One of the primary advantages ofusing sulphides is that the solubility’s of the metal sulphide precipitatesare dramatically lower than hydroxide precipitates and sulphide precipitates are not amphoteric. Also, this process can achieve a high degree of metal removal overa broad pH range compared with hydroxide precipitation. Metalsulphidesludge also exhibit better thickening and dewateringcharacteristics than the corresponding metal hydroxide sludge.However, there are potential dangers in the use of sulphide precipitation process as it many times results into evolution of toxic H2S fumes. However, chemical precipitation has been successful in combination with other methods and a reported literature shows that sulphide precipitation can reuse and recover heavy metalions by employing nanofiltration as a second step.There are some reports on chemical precipitation in combination with ion-exchange treatments. Here nickel was removed with the help of ion-exchange in combination of chemical precipitation .Another novel method is nucleation precipitation which is a simple cost effective method to strip off heavy metals in a fluidized sand bed. In operation, the metal-bearing wastewater is pumped through afluidized sand column with a simultaneous injection of carbonatesolution to raise pH metal precipitation to occur and then deposit onthe sand surface (nucleated precipitation) rather than to formdiscrete metal original sand grains are 0.2-0.3mm in diameter, butquickly grow to a much larger size (up to 2 or 3mm) uponcontinuous coating of metal precipitates. The larger coated sandparticles sink to the bed bottom from which they can be easilyremoved and new sand can then be added from the top of the stripper.Since the coated particle contains a high level of metal mineral, theycan be collected for mineral recovery.However, chemical precipitation requires large amounts of chemicals to reduce metals to an acceptable level for discharge along with excessive sludge formation that requires further treatment, slow metal precipitation, poor settling, the aggregation of metal precipitates, and the long-term environmental impacts of sludge disposal . Coagulation is one of the most important methods for wastewater treatment, but the main objects of coagulation are only theHydrophobic colloids and suspended particles. Flocculation is the action of polymers to form bridges between the flocs and bind the particles into large agglomerates or clumps. Once suspended particles are flocculated into larger particles, they can usually be removed or separated by filtration, straining or floatation. Today many kinds of flocculants, such as PAC, polyferric sulphate (PFS) and polyacrylamide (PAM), are widely used in the treatment of wastewater; however, it is nearly impracticable to remove heavy metal very well from wastewater directly by these current flocculants.
Ion exchange may be defined as the exchange of ions between the substrate and surrounding medium. The most useful ion exchange reaction is reversible, whereby the reaction is reversible and the ion exchanger can be regenerated and reused many times. Generally, resins aremanufactured in the spherical, stress and strain free form to resist physical degradation.They are stable at high temperatures and applicable over a wide pH range. Ion exchangeresins, which are completely insoluble in most aqueous and organic solutions, consist of across linked polymer matrix to which charged functional groups are attached by covalent bonds . Typical ion exchangers are produced with a particle size distribution in the range 20-50mesh (for separation of anions from cations or of ionic species from nonionic ones). Formore difficult separations, materials of smaller particle size or lower degrees of cross linking are necessary. Depending on the type of functional groups of exchanging certain ions, the ion exchangerswith strongly acidic e.g., sulphonate -SO3H, weakly acidic e.g, carboxylate -COOH, stronglybasic e.g., quaternary ammonium -N+R3 and weakly basic e.g., tertiary, and secondary amine-N+R2H and -N+RH2 should be mentioned. The strong acidic cation exchangers are welldissociated over a wide pH range and thus reaching its maximum sorption capacity.There are also amphoteric exchangers, which depending on the pH of the solution mayexchange either cations or anions. More recently these ion exchangers are called bipolarelectrolyte exchange resins (BEE) or zwitterionic ion exchangers .
Ion-exchange processes have been widely used to remove heavymetals from oil-field produced water and other waste waters due toadvantages such as hightreatment capacity, high removal efficiency and fast kinetics . Ion-exchange resin, either synthetic or natural solidresin, has the specific ability to exchange its cations with the metalsin the wastewater; however, synthetic resins are commonly preferred as they areeffective to nearly remove the heavy metals from the solution.Hydrogen ions in the sulfonicgroup or carboxylic group of the resin can serve as exchangeableions with metal cations. The uptake of heavy metal ions by ion-exchange resins is ratheraffected by certain variables such as pH, temperature, initial metalconcentration and contact time . Ioniccharge also plays an important role in ion-exchange process which could be incurred from the study of removal of Ce4, Fe3 and Pb2from aqueous systems by cation-exchange resin purolite C100 . Similarresults for Co2, Ni2 and Cr3in an Amberlite IRN-77 cationexchangeresin were previously obtained .
Besides synthetic resins, natural zeolites, naturally occurringsilicate minerals, have been widely used to remove heavy metalfrom aqueous solutions due to their low cost and high abundance.Many researchers have validated that zeolitesexhibit good cation-exchangecapacities for heavy metal ionsunder different experimental conditions .Clinoptilolite isone of the most frequently studied natural zeolites that havereceived extensive attention due to its selectivity for heavymetals. It has been studied that the surface of clinoptiloliteloaded with amorphous Fe-oxide species would significantly improve its ion-exchange capacity. Doula employedclinoptilolite-Fe system to simultaneously remove Cu, Mn and Zn from drinking water and found that the system has very large metaladsorption capacity and for most of the cases the treated watersamples were suitable for human consumption or agricultural use.
Adsorption is now recognized as an effective and economicmethod for heavy metal wastewater treatment. The adsorptionprocess offers flexibility in design and operation along with producing high-quality treated effluent. It is also very efficient becauseadsorption is sometimes reversible, adsorbents can be regeneratedby suitable desorption process. In recent years, the search for lowcostadsorbents that have metal-binding capacities has beeninvestigated . The adsorbents may be of mineral, organicor biological origins, zeolites, industrial by-products,agricultural wastes, biomass, and polymeric materials .Various other effective adsorbents are activated carbon, carbon nanotubes, low-cost adsorbents, bioadsorbents.There are many adsorbents that can be used for the removalof metal ions from wastewater and, certainly, cost plays animportant role for determining which one is applicable. Activated carbon (AC) adsorbents are widely used in the removalof heavy metal contaminants due to itslarge micropore and mesopore volumes and the resulting highsurface area. A large number of researchers are studying the use ofAC for removing heavy metals .
Nowadays, the depleted source of commercial coal-based AC has resulted into increase in its price thereby opting other additives along with AC such as alginate, tannic acid and magnesium [63-65].Converting carbonaceous materials intoAC for heavy metals remediation have been reported. The use of AC from eucalyptusbark in the binary component sorption of Cu2 and Pb2and poultry litter to manufacture AC for treating heavy metal-contaminated water was explored [66-67].Carbon nanotubes (CNTs) discovered by Iijima ,have been widely studied for their excellent properties and applications as new adsorbents possessing great potential for removing heavy metal ions such as lead,cadmium , chromium, copper andnickel fromwastewater.CNTs are divided into two types: (1) single-walled CNTs(SWCNTs) and (2) multi-walled CNTs (MWCNTs) .The mechanisms by which the metal ions are adsorbed ontoCNTs are very complicated and appear attributable to electrostaticattraction, sorption-precipitation and chemical interactionbetween the metal ions and the surface functional groups of CNTs.The sorption capacities of metal ions by raw CNTs are very lowbut significantly increase after oxidized by HNO3, NaClO andKMnO4 solutions.
Despite these recently developed adsorbents the search for low cost and easily available adsorbents has become main research focus today. Studies have been carried out for adsorption of a few heavy metals on natural and modified kaolinite and montmorillonite , chemically modified plantwastes , industrial by-products such as lignin, diatomite ,clino-pyrrhotite, lignite,aragonite shells , natural zeolites ,clay ,kaoliniteand peat etc.Another report showed zinc and copperremoval from aqueous solutions using brine sediments, sawdust,and the mixture of both materials.The potential to remove boron and arsenic from petrochemical wastewater by using aquatic booster wasinvestigated in batch experiment process and the results were measured by inductively coupled plasma massspectrometry (ICPMS). The main parameters influencing arsenic and boron adsorption onto the aquatic boosterwere contact time, size of particle, agitation speed, and dosage. The adsorption efficiency of arsenic andboron increases with longer contact time as well as more aquatic booster dosage and higher agitation speed. The removal efficiency for boron was around 60.36% by 35g/L dosage, 80 rpm anda particle size of 0.60 mm at of 390 minutes. As for the arsenic, the condition where it gives the removal percentagearound 71.83% is that particle size of 0.6 mm, 300 minutes contact time, agitation speed of 80 rpmand dosage of 45g/L. Hydrogels, which are crosslinked hydrophilic polymers, arecapable of expanding their volumes due to their high swellingin water and hence are being used in purificationof wastewater. Various hydrogels were synthesized and theiradsorption behavior for heavy metals was investigatedwhile Barakat and Sahiner(2008) prepared poly(3-acrylamidopropyl)trimethyl ammoniumchloride hydrogels for As(V) removal .
Biosorption of heavy metals from aqueous solutions is a relativelynew process that is effective and inexpensive and has been confirmed a very promisingprocess in the removal of heavy metal from dilute waste waters such as oil field produced water. Typical biosorbents can be derived from threesources as follows: (1) non-livingbiomass such as bark, lignin, shrimp, krill, squid, crab shell, etc(2) algal biomass; (3)microbial biomass, e.g. bacteria, fungi and yeast.Different forms of inexpensive, non-living plant material such aspotato peels, sawdust ,black gram husk, Rice husk [90-91], coffee husks ,eggshell, seedshells,sugar-beet pectin gels .and citrus peels ,sugarcane bagasse , coconut husk , oil palm shell , neem bark , fly ash have been widely investigated as potentialbiosorbents for heavy metals.
Algae, a renewable natural biomass proliferates ubiquitouslyand abundantly in the littoral zones of world has attracted theattention of many investigators as organisms to be tested and usedas new adsorbents to adsorb metal ions. Several advantages inapplying algae as biosorbent include the wide availability, low cost,high metal sorption capacity and reasonably regular qualityResearch works on the metal biosorption using algal biomass include the biosorption of Cu2 andZn2 using dried marine green macroalgaChaetomorphalinum, the biosorption of Cu2, Cd2, Pb2, andZn2 using dried marine green macroalgaCaulerpalentillifera, the biosorption of chromium from wastewaterusing green alga Ulva lactuca, and thebiosorption of lead (II) from wastewater by green algae Cladophorafascicularis. Microbial removal of metal ions from wastewater has beenindicated as being highly effective. Biosorption of heavy metals inaqueous solutions by bacteria includes Bacillus cereus , Escherichia coli ,Pseudomonas aeruginosa .Fungi and yeasts are easy to grow, produce high yields ofbiomass and at the same time can be manipulated genetically andmorphologically. Fungi biosorbents include Aspergillus niger,Rhizopusarrhizus,Saccharomyces cerevisiae andLentinusedodes.
Membrane filtration technologies with different types ofmembranes show great promise for heavy metal removal for theirhigh efficiency, easy operation and space saving. The membraneprocesses used to remove metals from the wastewater are ultrafiltration,reverse osmosis, nanofiltration and electrodialysis.
Ultrafiltration (UF) is a membrane technique working at lowtransmembrane pressures for the removal of dissolved andcolloidal material. Since the pore sizes of UF membranes are largerthan dissolved metal ions in the form of hydrated ions or as lowmolecular weight complexes, these ions would pass easily through UF membranes, hence to obtain high removal efficiency of metal ions, themicellar enhanced ultrafiltration (MEUF) and polymer enhancedultrafiltration (PEUF) was proposed.MEUF was first introduced by Scamehorn et al. in the 1980s forthe removal of dissolved organic compounds and multivalent metalions from aqueous streams .This separation technique isbased on the addition of surfactants to wastewater in a quantity beyond its critical micelle concentration (CMC), the surfactant molecules willaggregate into micelles that can bind metal ions to form largemetal-surfactant structures. The micelles containing metal ions canbe retained by a UF membrane with pore sizes smaller than micellesizes, whereas the untrapped species readily pass through the UFmembrane. To obtain the highest retentions, surfactants of electriccharge opposite to that of the ions to be removed must be used and metal removal efficiency by MEUF depends on the characteristicsand concentrations of the metals and surfactants, solution pH,ionic strength, and parameters related to membrane operation. PEUFuses water-soluble polymer to complex metallic ions and forma macromolecular, having a higher molecular weight than themolecular weight cut off of the membrane which will be retained when they are pumped through UF membrane.The reverse osmosis (RO) process uses a semi-permeablemembrane, allowing the fluid that is being purified to pass throughit, while rejecting the contaminants and accounts for more than 20% of the world’s desalination capacity .Cu2 and Ni2 ions were successfully removed by the RO processand the rejection efficiency of the two ions increased up to 99.5% byusing Na2-EDTA .The major drawback of RO isthe high-power consumption due to the pumping pressures, andthe restoration of the membranes. Nanofiltration (NF) is the intermediate process between UF and RO and is a promising technology for the rejection of heavy metalions such as nickel,chromium,copper,and arsenic  from wastewater. NF process benefits from ease ofoperation, reliability and comparatively low energy consumption aswell as high efficiency of pollutant removal; however reports have been published on use of NF and RO in combination for removal of copper from process waste water. Electrodialysis (ED) is another membrane process for the separationof ions across charged membranes from one solution toanother using an electric field as the driving force where ion-exchange membranes are used. This process has been widely used for the production f drinking and process water from brackish water and seawater,treatment of industrial effluents, recovery of useful materials fromeffluents and salt production .
Flotation has nowadays found extensive use in wastewatertreatment and has been employed to separate heavy metals from a liquid phase using bubble attachment originated in mineralProcessing. Dissolved air flotation (DAF), ion flotation and precipitationflotation are the main flotation processes for the removal ofmetal ions from solution.DAF is to allow micro-bubbles of air to attach to the suspendedparticles in the water, developing agglomerates with lower densitythan water, causing the flocs to rise through the water and accumulatingat the surface where they can be removed as sludge. Ion flotation method is based on imparting the ionic metal species in wastewatershydrophobic by use of surfactants and subsequent removalof these hydrophobic species by air bubbles . Potential of ion flotation was investigated to remove cadmium, lead and copper from dilute aqueoussolution with a plant-derived biosurfactant tea saponin. Precipitate flotation process is another alternative of flotationmethod, based on the formation of precipitate and subsequentremoval by attachment to air bubbles. Depending on the concentrationof the metal solution, the precipitation may proceed by formation of metal hydroxide or as a salt with a specific anion (sulfide,carbonate, etc.) .
Electrochemical methods involve the plating-out of metal ionson a cathode surface and can recover metals in the elemental metalstate; however these wastewater treatment technologies involve relativelylarge capital investment and the expensive electricity supply, sothey haven’t been widely applied. Electrocoagulation (EC) involves the generation of coagulants insitu by dissolving electrically either aluminum or iron ions fromaluminum or iron electrodes where, metal ion generation takes place at the anode, and hydrogen gas is released from the cathode that helps to float the flocculated particles out of the water . This technique has been used with aluminium electrodes for removing Zn2, Cu2, Ni2, Ag and Cr2O7.Electroflotation (EF) is a solid/liquid separation process thatfloats pollutants to the surface of a water body by tiny bubbles ofhydrogen and oxygen gases generated from water electrolysis. EFhas wide range applications in heavy metals removal from industrial wastewater and application of the optimized parameters on the separation of someheavy metal ions such as iron, nickel, copper, zinc, lead andcadmium was studied.TheElectrodeposition has been usually applied for the recovery ofmetals fromwastewater and is called a “clean” technology with no presenceof the permanent residues for the separation of heavy metals.
In the recent years, photocatalytic process in aqueous suspensionof semiconductor has received considerable attention inview of solar energy conversion and this photocatalytic processwas achieved for rapid and efficient destruction of environmentalpollutants. Upon illumination of semiconductor-electrolyte interface with light energy greater than thesemiconductor band gap, electron-hole pairs (e-/h+) areformed in the conduction and the valence band of the semiconductor,respectively .These charge carriers which migrate to the semiconductor surface, are capable ofreducing or oxidizing species in solution having suitable redoxpotential. Various semiconductors have been used: TiO2, ZnO,CeO2, CdS, ZnS, etc. also a study showed photocatalytic degradation using UV-irradiated TiO2 suspension for destroying complex cyanide with a con-current removal of copper .
Several studies were reported for the photocatalytic reductionof Cr(VI), which is mobile and highly toxic, compared toCr(III), which is immobile and less harmful. Heterogeneous photocatalytic oxidation of arsenite toarsenate in aqueous TiO2 suspensions has also been provedrecently to be an effective and environmentally acceptabletechnique for the remediation of arsenite contaminated water.The process was performed using an adsorbent developed byloading iron oxide and TiO2 on municipal solid waste meltedslag.
Various biological treatments, both aerobic and anaerobic can be used for heavy metal removal. A fixed activated sludge system (FAS) for treatment of wastewater containing heavy metal compounds (chromium, lead and nickel was carried out . There results showed that a reduction of 84%, 75% and 80%, respectively was observed in chromium, lead and nickel on using fixed activated sludge at concentration of 1 mg/L. However, a reduction of 90%, 84% and 87%, respectively was observed by increasing concentration of them to 5 mg/L. Mechanism of activated sludge process was studied which showed that the carboxylic and amino groups are two main groups responsible for the binding properties of the biomass . A novel biofiltration technique was utilized for the treatment of heavy metals mainly nickel, and their mechanism for heavy metals removal along with the kinetics of biofilters and its modeling aspects were studied .The success in microbial cloning technique may improve the removal efficiency and hence the reduction in treatment cost. Trickling filter was used for removal of heavy metals, whereby the indigenous bacterial populations provided a certain advantage and ensured durability under various operating conditions. They operated the system in three different ways i.e. batch, continuous and sequencing batch reactor (SBR) with recirculation . The use of an attached growth system provides the necessary surface for the development of biofilm structures. Biofilms provide high biomass concentration per unit volume, while bacteria can remain in the reactor for unlimited time, thus allowing the bacteria better adjustment to the environmental conditions. The studies on the metal removal from an aerobically digested sludge by chemical treatment and microbial leaching processes in laboratory reactors were carried out by addition of ferric sulphate that resulted intoacidification of the sludge and elution of heavy metals from the sludge.The investigation also showed that with an increase in the amount of iron added and decrease in the sludge concentration, the pH of the sludge decreased. They also observed that the Ferric iron eluted cadmium, copper and zinc effectively than sulphuric acid. This chemical method was found to be useful for the removal of heavy metals from aerobically digested sewage sludge. Attached growth waste stabilization ponds were used for heavy metal removal where experiments were conducted to investigate the performance of AGWSP units that received Cd and Cr shock loadings. Per the investigation, the waste stabilization pond (WSP) units without attached-growth media had more concentrations of the applied heavy metals present in the effluents than waste stabilization ponds.
Wastewater systems containing heavy metals with otherorganic pollutants, the presence of one species usually impedesthe removal of the other. For instance, hydrometallurgy, aclassical process to recover metals, is inhibited by the presenceof organic compounds and a pre-treatment step, to remove ordestroy organics, is generally required, pyrometallurgy whichcan decontaminate systems from organic pollutantsand recover metals suffers from lack of controllability,demanding extremely high temperatures. The most promisingmethods to treat such complex systems are the photocatalyticones which consume cheap photons from the UV-near visibleregion. These photo catalysts serve as electron relays, from theorganic substrates to metal ions. Thus, they induce bothdegradation of organic pollutants and recovery of metals inone-pot systems, operable at traces of the target compounds(less than ppm). Although all above techniques can be employed for the treatmentof heavy metal wastewater, it is important to mention thatthe selection of the most suitable treatment techniques depends onthe initial metal concentration, the component of the wastewater,capital investment and operational cost, plant flexibility and reliability, environmental impact, utility of the treated water etc.7February,2017
- Deng S, Chen BR, Jian JP, Yu Z, Zhou G, et al. (2002)Produced water from polymer flooding process in crude oil extraction: Characterization and treatment by a novel crossflow oil-water separator. Separation and Purification Technology 29: 207-216.
- Lu J, Wang X, Shan B, LiX, WangW (2006) Analysis of chemical compositions contributable to Chemical Oxygen Demand (COD) of oilfield produced water. Chemosphere 62: 322-331.
- Fakhru’l-RaziA, Pendashteh A, Abdullah LC,Biak DR, Madaeni SS, et al. (2009) Review of technologies for oil and gas produced water treatment. J Hazard Mater 170: 530-551.
- Wemedo SA, Akani NP,Eke CE (2009) Fungi in an oilfield wastewater in Nigeria. Asian J Biol Sci 2: 54-57.
- Puyate YT, Rim-RukehA (2008) 2D model for diffusion of oxygen with biochemical reaction during biofilm formation process in static aqueous medium. J Applied Sci 8: 1560-1565.
- Cakmakce M, Kayaalp N, KoyuncuI (2008) Desalination of produced water from oil production fields by membrane processes. Desalination 222: 176-186.
- Xu P, Drewes JE, HeilD (2008)Beneficial use of co-produced water through membrane treatment: Technical-economic assessment. Desalination 225: 139-155.
- Hayes T, Arthur D (2004)Overview of emerging produced water treatment technologies. In: The 11th Annual International Petroleum Environmental Conference, Albuquerque, NM.
- Khosravi J, Alamdari A (2009)Copper removal from oil-field brine by coprecipitation. J Hazard Mater166:695–700.
- Stephenson MT, Ray JP, Engelhardt FR (1992)A survey of produced water studies. Produced Water: Technological/Environmental Issues and Solutions. Plenum Publishing Corp1-12.
- Veil JA, Puder MG, ElcockD, Redweik RJ Jr (2004)A White Paper Describing Produced Water from Production of Crude oil, Natural Gas, and Coal Bed Methane. US. D. o. E, Argonne National Laboratory.
- Roach RW, Carr RS, Howard CL, Cain BW (1993)An assessment of produced water impacts at two sites in the Galveston Bay system. United States Fish and Wildlife Service, Clear Lake Field Office unpublished report. Houston, Texas.
- Utvik TIR (2003) Composition, characteristics of produced water in the North Sea. In: Produced Water Workshop, Aberdeen, Scotland.
- Jerez Vegueria SF, Godoy JM, Miekeley N(2002)Environmental impact studies of barium and radium discharges by produced waters from the ‘Bacia de Campos’ oil-field offshore platforms, Brazil. J Environ Radioactivity62:29-38.
- Daniel Arthur J, Langhus BG, Patel C (2005)Technical Summary of Oil & Gas Produced Water Treatment Technologies. NETL.
- KhosraviJ, Alamdari A (2009) Copper removal from oil-field brine by coprecipitation. J Hazard Mater166:695-700.
- API (American Petroleum Institute) (1990) Design and operation of oil-water separators. API Publication. Washington D.C.
- WEF (Water Environment Federation) (1994) Pretreatment of industrial wastes. Manual ofPractice FD-3, Alexandria, USA
- Eckenfelder WW (2000)Industrial Water Pollution Control, 3rded, McGraw-Hill.
- Galil N ,Wolf D (2001) Removal of hydrocarbons from petrochemical wastewater by dissolved air flotation. Water Sci Technol 43: 107-113.
- Al-Shamrani AA, James A, Xiao H (2002) Destabilisation of oil–water emulsions and separation by dissolved air flotation. Water Research36:1503-1512.
- Galil N,Rebhum M (1992) Waste management solutions at an integrated oil refinery based on recycling of water, oil and sludge. Water Science and Technology 25:101-106.
- Baron C, Equihua LO, Mestre JP (2000) B.O.O.Case: water manajement project for the use of reclaimed wastewater and desalted seawater for the “Antonio Dovali Jayme” refinery, Salina Cruz, Oaxaca, Mexico. Water Science and Technology42: 29-36.
- Lee LY, Hu JY, Ong SL, Ng WJ, Ren JH,et al. (2004) Two stage SBR for treatment of oil refinery wastewater. Water Science and Technology50: 243-249.
- Schneider EE, Cerqueira ACFP, Dezotti M (2011) MBBR evaluation for oil refinery wastetreatment with post-ozonation and BAC, for water reuse. Water Science and Technology63: 143-148
- Misković D, Dalmacija B, ŽivanovŽ, Karlović E, Hain Z, et al. (1986) An investigation of the treatment and recycling of oil refinery wastewater. Water Science and Technology18: 105-114.
- Guarino CF, Da-Rin BP, Gazen A,Goettems EP (1988) Activated carbon as an advanced treatment for petrochemical wastewaters. Water Science and Technology 20:115-130.
- Farooq S, Misbahuddin M (1991) Activated carbon adsorption and ozone treatment of a petrochemical wastewater. Environmental Technology12:147-159.
- Zubarev SV, Alekseeva NA, Ivashentsev VN ,Yavshits GP, Matyushkin, et al.(1989) Purification of wastewater in petroleum refining industries by membrane methods. Chemistry and Technology of Fuels and Oils 25:588-592.
- Elmaleh S,Ghaffor N (1996)Upgrading oil refinery effluents by cross-flow ultrafiltration. Water Science and Technology34:231-238.
- Teodosiu CC, Kennedy MD, van Straten HA, Schippers JC (1999) Evaluation of secondary refinery effluent treatment using ultrafiltration membranas. Water Research33:2172-2180.
- Wang D, Tong F, Aerts P (2011) Application of the combined ultrafiltration and reverse osmosis for refinery wastewater reuse in Sinopec Yanshan Plant. Desalination and Water Treatment 25: 133-142.
- Dhokpande SR and Kaware JP (2013) Biological Methods for Heavy Metal Removal- A Review, International Journal of Engineering Science and Innovative Technology (IJESIT) 2.
- Babel S,Kurniawan TA (2003) Low-cost adsorbents for heavy metals uptake from contaminated water: a review. J Hazard Mater 97: 219-243.
- Babel S, Kurniawan TA (2003) various treatment technologies to remove arsenic and mercury from contaminated groundwater: an overview. In: Proceedings of the First International Symposium on Southeast Asian Water Environment, Bangkok, Thailand 24-25: 433-440.
- Kim BM (1981) Treatment of metal-containing waste-water with calcium sul®de. AICHE Symp 77: 39-48.
- Basta N (1983) Getting the metal out of spent plating baths. Chem Eng 90: 22-25.
- Thomas E H, Vernon E S (1984) Combined removal of Cr, Cd and Ni from wastes. Environ. Prog 3:12-25.
- Chowdhury J (1987) New routes buoy efforts to trim heavy-metal wastes. Chem Eng 94: 26-27.
- Zhou P, Huang JC, Alfred M, Li WF, Wei S (1999) heavy metal removal from wastewater in fluidized bed reactor. Wat Res 33: 1918-1924.
- Wang LK, Vaccari DA, Li Y, Shammas NK (2004) Chemical precipitation. In: Wang, L.K., Hung, Y.T., Shammas, N.K. (Eds.), Physicochemical Treatment Processes, Humana Press, New Jersey 3: 141-198.
- Mirbagherp SA and Hosseini SN (2004) Pilot plant investigation on petrochemical wastewater treatment for the removal of copper and chromium with the objective of reuse. Desalination 171: 85-93.
- Chen CL, Hu J, Shao DD, Li JX, Wang XK (2009) Adsorption behavior of multiwall carbon nanotube/iron oxide magnetic composites for Ni(II) and Sr(II). J Hazard Mater 164: 923-928.
- Charerntanyarak L (1999) Heavy metals removal by chemical coagulation and precipitation. Wat Sci Technol 39: 135-138.
- González-Muñoz MJ, Rodríguez MA, Luquea S, Álvareza JR (2006) Recovery of heavy metals from metal industry waste waters by chemical precipitation and nanofiltration. Desalination 200: 742-744.
- Papadopoulos A, Fatta D, Parperis K, Mentzis A, Haralambous KJ, Loizidou M (2004) Nickel uptake from a wastewater stream produced in a metal finishing industry by combination of ion-exchange and precipitation methods. Sep Purif Technol 39: 181-188.
- HuangJC (2005) Nucleated precipitation for heavy metal removal and resource recovery, Science Council of Asia, May 12th.
- Aziz HA, Adlan MN, Ariffin KS (2008) Heavy metals (Cd, Pb, Zn, Ni, Cu and Cr(III)) removal from water in Malaysia: post treatment by high quality limestone. Bioreso Technol 99: 1578- 1583.
- Sherrington DC (1998) Preparation, structure and morphology of polymer supports, Chemical Communications 30: 2275-2286.
- Nesterenko PN, Haddad PR (2000) Zwitterionic ion-exchangers in liquid chromatography, Analytical Sciences 16: 565-574.
- Kang SY, Lee JU, Moon SH, Kim KW (2004) Competitive adsorption characteristics of Co2þ, Ni2þ, and Cr3þ by IRN-77 cation exchange resin in synthesized wastewater. Chemosphere 56: 141-147.
- Alyüz B, Veli S (2009) Kinetics and equilibrium studies for the removal of nickel and zinc from aqueous solutions by ion exchange resins. J Hazard Mater 167: 482-488.
- Gode F, Pehlivan E (2006) Removal of chromium (III) from aqueous solutions using Lewatit S 100: the effect of pH, time, metal concentration and temperature. J Hazard Mater 136: 330-337.
- Abo-Farha SA, Abdel-Aal AY, Ashourb IA, Garamon SE (2009) Removal of some heavy metal cations by synthetic resin purolite C100. J. Hazard. Mater 169: 190-194.
- Kang SY, Lee JU, Moon SH, Kim KW (2004) Competitive adsorption characteristics of Co2, Ni2, and Cr3 by IRN-77 cation exchange resin in synthesized wastewater. Chemosphere 56: 141-147.
- Motsi T, Rowson NA, Simmons MJH (2009) Adsorption of heavy metals from acid mine drainage by natural zeolite. Int J Miner Process 92: 42-48.
- Doula MK, Dimirkou A (2008) Use of an iron-overexchanged clinoptilolite for the removal of Cu2 ions from heavily contaminated drinking water samples.J. Hazard. Mater 151: 738-745.
- Doula MK (2009) Simultaneous removal of Cu, Mn and Zn from drinking water with the use of clinoptilolite and its Fe-modified form. Water Res 43: 3659-3672.
- Fu F,Wang Q (2011) Removal of heavy metal ions from wastewaters: A review, Journal of Environmental Management 92: 407-418.
- LeungWC, WongMF, Chua H, Lo W, YuPH, et al. (2000)Removal and recovery of heavy metals by bacteria isolated from activated sludge treating industrial effluents and municipal wastewater. Water Sci Technol41: 3.
- KurniawanTA, ChanGYS, Lo WHS, Babel S(2005)Comparisons of low-cost adsorbents for treating wastewaters laden with heavy metals. Sci Total Environ 366:409.
- Jusoh A, Shiung LS, Ali N, Noor MJMM (2007) A simulation study of the removal efficiency of granular activated carbon on cadmium and lead. Desalination 206: 9-16.
- Park HG, Kim TW, Chae MY, Yoo IK, (2007) Activated carbon-containing alginate adsorbent for the simultaneous removal of heavy metals and toxic organics. Process Biochem 42: 1371-1377.
- Üçer A, Uyanik A, Aygün SF (2006) Adsorption of Cu(II), Cd(II), Zn(II), Mn(II) and Fe(III) ions by tannic acid immobilised activated carbon. Sep Purif Technol 47:113-118.
- YanagisawaH, Matsumoto Y, Machida M (2010) Adsorption of Zn(II) and Cd(II) ions onto magnesium and activated carbon composite in aqueous solution. Appl Surf Sci 256: 1619-1623.
- KongsuwanA, Patnukao P, Pavasant P (2009) Binary component sorption of Cu(II) and Pb(II) with activated carbon from Eucalyptus camaldulensis Dehn bark. J Ind Eng Chem 15: 465-470.
- Guo MX, Qiu GN, Song WP (2010) Poultry litter-based activated carbon for removing heavy metal ions in water. Waste Manage 30: 308-315.
- Iijima S (1991) Helical microtubules of graphitic carbon. Nature 354: 56-58.
- Kabbashi NA, AtiehMA, Al-Mamun A, Mirghami MES, Alam MDZ, et al. (2009) Kinetic adsorption of application of carbon nanotubes for Pb(II) removal from aqueous solution. J Environ Sci 21: 539-544.
- Kuo CY, Lin HY (2009) Adsorption of aqueous cadmium (II) onto modified multiwalled carbon nanotubes following microwave/chemical treatment. Desalination 249: 792-796.
- Pillay K, Cukrowska EM, Coville NJ (2009)Multi-walled carbon nanotubes as adsorbents for the removal of parts per billion levels of hexavalent chromium from aqueous solution. J Hazard Mater 166: 1067-1075.
- Kandah MI, MeunierJL (2007) Removal of nickel ions from water by multi-walled carbon nanotubes. J Hazard Mater 146: 283-288.
- Odom TW, Huang JL, Kim P, Lieber CM (1998) Atomic structure and electronic properties of single-walled carbon nanotubes. Nature 391: 62-64.
- Rao G.P, Lu C, Su F (2007) Sorption of divalent metal ions from aqueous solution by carbon nanotubes: a review. Sep Purif Technol 58: 224-231.
- Bhattacharyya KG, Gupta SS (2008) Adsorption of a few heavy metals on natural and modified kaolinite and montmorillonite: a review. Adv Colloid Interface Sci 140: 114-131.
- Wan Ngah SW, Hanafiah MAKM (2008) Removal of heavy metal ions from wastewater by chemically modified plant wastes as adsorbents: a review. Bioresour Technol 99 : 3935-3948.
- Betancur M, Bonelli PR, Velásquez JA, Cukierman AL (2009) Potentiality of lignin from the Kraft pulping process for removal of trace nickel from wastewater: effect of Demineralization. Bioresour Technol 100: 1130-1137.
- Sheng GD, Wang SW, Hua J, Lu Y, Li JX et al. (2009) Adsorption of Pb (II) on diatomite as affected via aqueous solution chemistry and temperature. Colloid Surf. 339: 159-166.
- Mohan D, Chander S (2006) Removal and recovery of metal ions from acid mine drainage using lignite: a low cost sorbent. J Hazard Mater 137: 1545-1553.
- Kohler SJ, Cubillas P, Rodriguez-Blanco JD, Bauer C, Prieto M (2007) Removal of cadmium from wastewaters by aragonite shells and the influence of other divalent cations. Environ Sci Technol 41: 112-118.
- Apiratikul R, Pavasant P (2008) Sorption of Cu2, Cd2 and Pb2 using modified Zeolite from coal fly ash. Chem Eng J 144: 245-258.
- Al-Jlil SA, Alsewailem FD (2009) Saudi Arabian clays for lead removal in wastewater. Appl Clay Sci 42: 671-674.
- Gu XY, Evans LJ (2008) Surface complexation modelling of Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) adsorption onto kaolinite. Geochim Cosmochim Acta 72: 267-276.
- Agoubordea L, Navia R (2009) Heavy metals retention capacity of a non-conventional sorbent developed from a mixture of industrial and agricultural wastes. J. Hazard. Mater 167: 536-544.
- Ismail MHS, Zhang XT, Lazim MFM (2013) Removal of Boron and Arsenic from Petrochemical Wastewater by Using Aquatic Booster as Adsorbent, Pol. J. Environ. Stud 22: 403-408.
- Barakat MA, Sahiner N (2008) Cationic hydrogels for toxic arsenate removal from aqueous environment. J. Environ. Manage 88:955–961.
- Aman T, Kazi AA, Sabri MU, Bano Q (2008) Potato peels as solid waste for the removal of heavy metal copper(II) from waste water/industrial effluent. Colloid Surf 63: 116-121.
- Kaczala F, Marques M, Hogland W (2009) Lead and vanadium removal from a real industrial wastewater by gravitational settling/sedimentation and sorption onto Pinus sylvestris sawdust. Bioresour Technol 100: 235-243.
- Saeed A, Iqbal M, Akhtar MW (2005) Removal and recovery of lead(II) from single and multimetal (Cd, Cu, Ni, Zn) solutions by crop milling waste (black gram husk). J Hazard Mater 117: 65-73.
- Srinivasan K, Balasubramaniam N, Ramakrishna TV (1998) Studies on chromium removal by rice husk carbon.Indian J Environ Health 30: 376-387.
- Munaf E, Zein R (1997)The use of rice husk for removal of toxic metals from wastewater.Environ Technol 18: 359-362.
- Oliveira L, Franca AS, Alves TM, Rocha SDF (2008) Evaluation of untreated coffee husks as potential biosorbents for treatment of dye contaminated waters. J. Hazard. Mater 155: 507-512.
- Jai PH,Wook JS, Kyu YJ, Gil KB, Mok LS (2007) Removal of heavy metals using waste eggshell. J. Environ. Sci 19: 1436-1441.
- Amudaa OS, Adelowoa FE, Ologunde MO (2009) Kinetics and equilibrium studies of adsorption of chromium (VI) ion from industrial wastewater using Chrysophyllumalbidum (Sapotaceae) seed shells. Colloid Surf 68:184-192.
- Mata YN, Blázquez ML, Ballester A, González F, Muñoz JA (2009) Sugar-beet pulp pectin gels as biosorbent for heavy metals: preparation and determination of biosorption and desorption characteristics. Chem. Eng. J 150: 289-301.
- Schiewer S, Patil SB (2008) Modeling the effect of pH on biosorption of heavy metals by citrus peels. J. Hazard. Mater 157: 8-17.
- Khan NA, Ali SI, Ayub S (2001) Effect of pH on the removal of chromium (Cr) (VI) by sugar cane baggase, Sci. Technol 6: 13-19.
- Tan WT, Ooi ST, Lee CK (1993) Removal of chromium (VI) from solution by coconut husk and palm pressed fibre, Environ. Technol 14: 277-282.
- Khan NA, Shaaban MG, Hassan MHA (2003) Removal of heavy metal using an inexpensive adsorbent, in: Proc. UM Research Seminar organized by Institute of Research Management and Consultancy (IPPP), University of Malaya, Kuala Lumpur.
- Ayub S, Ali SI, Khan NA (2001) Efficiency evaluation of neem (Azadirachtaindica) bark in treatment of industrial wastewater, Environ. Pollut. Control J 4: 34-38.
- Ajjabi LC, Chouba L (2009) Biosorption of Cu2þ and Zn2þ from aqueous solutions by dried marine green macroalgaChaetomorphalinum. J. Environ. Manage 90: 3485-3489.
- Pavasant P, Apiratikul R, Sungkhum V, Suthiparinyanont P, Wattanachira S, et al. (2006) Biosorption of Cu2, Cd2, Pb2, and Zn2 using dried marine green macroalgaCaulerpalentillifera. Bioresour. Technol 97: 2321-2329.
- El-Sikaily A, Nemr AE, Khaled A, Abdelwehab O (2007) Removal of toxic chromium from wastewater using green alga Ulva lactuca and its activated carbon. J. Hazard. Mater 148: 216-228.
- Deng LP, Su YY, Su H, Wang XT, Zhu XB (2007) Sorption and desorption of lead (II) from wastewater by green algae Cladophorafascicularis. J. Hazard.Mater 143: 220-225.
- Pan JH, Liu RX, Tang HX (2007) Surface reaction of Bacillus cereus biomass and its biosorption for lead and copper ions. J. Environ. Sci 19: 403-408.
- Souiri M, Gammoudi I, Ouada HB, Mora L, Jouenne T, et al. (2009) Escherichia coli-functionalized magnetic nanobeads as an ultrasensitive biosensor for heavy metals. Proced. Chem 1: 1027-1030.
- Gabr RM, Hassan SHA, Shoreit AAM (2008) Biosorption of lead and nickel by living and non-living cells of Pseudomonas aeruginosa ASU 6a. Int. Biodeterior. Biodegradation 62: 195-203.
- Amini M, Younesi H, Bahramifar N (2009) Statistical modeling and optimization of the cadmium biosorption process in an aqueous solution using Aspergillus niger. Colloid Surf 337: 67-73.
- Aksu Z, Balibek E (2007) Chromium(VI) biosorption by dried Rhizopusarrhizus: effect of salt (NaCl) concentration on equilibrium and kinetic parameters.J. Hazard. Mater 145: 210-220.
- Chen C, Wang JL (2008) Removal of Pb2, Ag, Csand Sr2 from aqueous solution by brewery’s waste biomass. J. Hazard. Mater 151: 65-70.
- Bayramoglu G, Arica MY (2008) Removal of heavy mercury (II), cadmium(II) and zinc(II) metal ions by live and heat inactivated Lentinusedodes pellets. Chem. Eng. J 143: 133-140.
- Landaburu-Aguirre J, Pongrácz E, Perämäk P, Keiski RL (2010) Micellarenhanced ultrafiltration for the removal of cadmium and zinc: use of response surface methodology to improve understanding of process performance and optimisation. J. Hazard. Mater 180: 524-534.
- Shahalam AM, Al-Harthy A, Al-Zawhry A (2002) Feed water pretreatment in RO systems in the Middle East. Desalination 150: 235-245.
- Mohsen-Nia M, Montazeri P, Modarress H (2007) Removal of Cu2 and Ni2 from wastewater with a chelating agent and reverse osmosis processes. Desalination 217: 276-281.
- Murthy ZVP, Chaudhari LB (2008) Application of nanofiltration for the rejection of nickel ions from aqueous solutions and estimation of membrane transport parameters. J. Hazard. Mater 160: 70-77.
- Muthukrishnan M, Guha BK (2008) Effect of pH on rejection of hexavalent chromium by nanofiltration. Desalination 219: 171-178.
- Cséfalvay E, Pauer V, Mizsey P (2009) Recovery of copper from process waters by nanofiltration and reverse osmosis. Desalination 240: 132-142.
- Nguyen CM, Bang S, ChoJ, Kim KW (2009) Performance andmechanismof arsenic removal fromwater by a nanofiltration membrane. Desalination 245: 82-94.
- Erikson P (1988) Nanofiltration extends the range of membrane filtration. Environ. Prog 7: 58-62.
- Sadrzadeha M, Mohammadi T, Ivakpour J, Kasiri N (2009) Neural network modeling of Pb2 removal from wastewater using electrodialysis. Chem. Eng. Process 48: 1371-1381.
- Lundh M, Jönsson L, Dahlquist J (2000) Experimental studies of the fluid dynamics in the separation zone in dissolved air flotation.Water Res 34: 21-30.
- Polat H, Erdogan D (2007) Heavy metal removal from waste waters by ion flotation. J. Hazard. Mater 148: 267-273.
- Yuan XZ, Meng YT, Zeng GM, Fang YY, Shi JG (2008) Evaluation of tea-derived biosurfactant on removing heavy metal ions from dilute wastewater by ion flotation. Colloid Surf 317: 256-261.
- Capponi F, Sartori M, Souza ML, Rubio J (2006) Modified column flotation of adsorbing iron hydroxide colloidal precipitates. Int. J. Miner. Process 79: 167-173.
- Chen GH (2004) Electrochemical technologies in wastewater treatment. Sep. Purif. Technol 38: 11-41.
- Heidmann I, Calmano W (2008) Removal of Zn (II), Cu(II), Ni(II), Ag(I) and Cr(VI) present in aqueous solutions by aluminium electrocoagulation. J. Hazard. Mater152: 934-941.
- Khodir M, Belkacem M, Abdelkrim S (2008) Treatment characteristics of textile wastewater and removal of heavy metals using the electroflotation technique. Desalination 228: 245-254.
- Issabayeva G, Aroua MK, Sulaiman NM (2006) Electrodeposition of copper and lead on palm shell activated carbon in a flow-through electrolytic cell. Desalination 194: 192-201.
- Herrmann JM (1999) Heterogeneous photocatalysis: fundamentals and applications to the removal of various types of aqueous pollutants. Catal. Today 53: 115-129.
- Barakat MA (2005) Adsorption behavior of copper and cyanide ions at TiO2–solution interface. J Colloid Interface Sci 291: 345-352.
- Zhang FS, Itoh H (2006) Photocatalytic oxidation and removal of arsenite from water using slag–iron oxide–TiO2 adsorbent. Chemosphere 65:125-131.
- Hassani AH, Hossenzadeh I, Torabifar B (2010)Investigation of Using Fixed Activated Sludge System for Removing Heavy Metals (Cr,Ni and Pb) From Industrial Wastewater. Journal of EnvironmentalStudies 36: 22-24.
- Pagnanelli F, Mainelli S, BornoroniL, DionisiD, Toro L (2009)Mechanisms of heavy-metal removal by activated sludge Chemosphere 75: 1028-1034.
- SrivastavaNK, MajumderCB (2008)Novel bio filtration methods for the treatment of heavy metals from industrial wastewater. J Hazard Mater 151: 1-8.
- DermouE, VelissariouA, XenosD, Vayenas DV (2005) Biological Chromium (VI) Reduction using a trickling filter. Journal of Hazardous Materials: 78-85.
- Ito A, Takahashi K, AizawaJ, Umita T (2008)Enhanced heavy metals removal without phosphorus loss from anaerobically digested sewage sludge. Water Sci Technol 58: 201-206.
- PolprasertC, Charnpratheep K (1989)Heavy metal removal by attached growth waste stabilizationpond. 23: 625-631.
Citation:Rakhi NMand Dayanand S (2017)Efficient Removal of Heavy metals from Oil-field Produced Water: A Review of Currently Available Techniques.Arch Petro Environ Biotechnol 2017: APEB-105.