【正文】 m and have been widely used for the treatment of produced water. Nearly 8 million barrels per day of produced water can be treated with hydrocyclones . They are used in bination with other technologies as a pretreatment process. They have a long lifespan and do not require chemical use or pretreatment of feed water. A major disadvantage of this technology is the generation of large slurry of concentrated solid waste. 3 ELECTROCHEMISTRY AND PRODUCED WATER TREATMENT Electrochemistry is rarely employed in produced water treatment, even though it has been widely used in the treatment of other wastewaters. So far, only ED and EDR are established electrochemical treatment technologies of produced water and are mainly useful when removing salts from produced water for irrigation use. However, heavy metals, oil, produced solids and other contaminants present in produced water can be as harmful to the soil as its salt content. Progress in electrochemistry knowledge and research suggests that electrochemistry could be the future treatment technology of produced water. Although current treatment technologies have been used to carry out desalination, deoiling, removal of suspended solids and in some cases NORM removal from produced water, they are acpanied by many setbacks. High treatment cost, production and discharge of secondary waste, high energy requirement and use of chemicals in some cases are mon problems facing these technologies. Electrochemistry on the other hand is a relatively cheap green technology. It does not generate secondary waste nor involve the use of additional chemicals, and offers improved beneficial uses of produced water. It can generate and store energy, remove anics, produce clean water and recover valuable materials from produced water with little or no negative impact on the environment. This is achievable by harmonizing photoelectrochemistry (photoelectrolysis, photocatalysis and photoelectrocatalysis), water electrolysis, fuel cell, electrodeposition and other electrochemical techniques into a single electrochemical process technology. Photoelectrolysis is a chemical process of breaking down molecules into smaller units by light . This process has played significant roles in hydrogen production and removal of anics from wastewater . Fujishima and Honda first reported the photocatalytic deposition of water on TiO2 electrodes. This method has been investigated for the removal of anics from produced water and used successfully for a variety of anic pollutant treatment. . Photodegradation of anics has been enhanced by the addition of oxidants such as hydrogen peroxide, peroxymonosulphate (oxone) and peroxydisulphate, but the presence of hydrogen peroxide may induce corrosion process . Semiconductor photocatalysis has been reported to effectively reduce hydrocarbon content in produced water by 90% in 10 min . Photoelectrocatalysis is reported to be a more efficient process for the removal of anics from waste water. Li et al. reported that COD removal efficiencies by photoelectrocatalysis from synthetic produced water are much higher than removal by photocatalysis and electrochemical oxidation. Results showed that photoelectrocatalytic degradation of anic pollutants is much favoured in acidic solution than in neutral and/or alkaline solutions. In another experiment, Li et al. found that photoelectrocatalysis exhibited a superior capability to reduce genotoxicity to photocatalysis, while photocatalysis did not cause appreciable change in mutagenicity. Ma and Wang set up a catalytic electrochemical pilotscale plant for the removal of anics from oilfield produced water, using double anodes with active metal and graphite, and iron as the cathode and a noble metal catalyst with big surface . They found that COD and BOD were reduced by over 90% in 6 min, suspended solids by 99%, Ca2+ content by 22%, corrosion rate by 98% and bacteria (sulphate reducing bacteria and iron bacteria) by 99% in 3 min under 15V/120A. Photoelectrolysis also offers a great promise for inexpensive production of hydrogen and has widely been reported for the generation of hydrogen through water splitting . Although not yet petitive on a mercial scale, photoelectrolysis has the potential to bee a major hydrogen production process. Powder semiconductor photocatalysts, nanophotocatalysts, photoanodes and several metal oxides are being investigated for improved hydrogen production from water . As these technologies develop, generation of hydrogen from produced water would bee a reality. Thus, it may be possible to reduce the energy cost of produced water treatment significantly if removal of anics and generation of hydrogen from produced water is efficiently carried out by photoelectrolysis. Fuel cell is another major electrochemical technology that is important in the future of produced water treatment technology. Fuel cell converts chemical energy contained in, for example, H2 gas into electricity and generates water and heat as byproducts . This technology is important in converting produced water into drinking water. Hydrogen generated from photoelectrolysis of produced water can be fed into a fuel cell to produce clean water which upon further treatment can be converted into drinking water. Fuel cell is a particular choice technology for converting produced water into drinking water because it also generates electricity and heat which can be recycled into the treatment process. The application of fuel cell technology to future produced water treatment depends on successful research into its cost reduction, efficiency improvement and increased life span . Electrodeposition is a mature technology that is widely applied in various fields of electrochemistry, particularly in material coating, fabrication of magic films and metal recovery . It is a cathodi