Chemical solutions for greywater recyclingIntroductionMaterial and methodsSamplingExperimentsFractionationZeta potential and charge densityAnalytical proceduresResults and discussionCharacteristicsCoagulationMIEX reg MIEX reg +coagulationComparison of the systemsDiscussionConclusionAcknowledgementsReferencesTechnical NoteChemical solutions for greywater recyclingMarc Pidoua, Lisa Averya, Tom Stephensonb, Paul Jeffreya, Simon A. Parsonsa,Shuming Liuc, Fayyaz A. Memonc, Bruce Jeffersona,*aCentre for Water Science, School of Applied Sciences, Cranfield University, Cranfield MK43 0AL, United KingdombSchool of Applied Sciences, Cranfield University, Cranfield MK43 0AL, United KingdomcSchool of Engineering, Computer Science and Mathematics, University of Exeter, Exeter EX4 4QF, United KingdomReceived 15 August 2006; received in revised form 24 October 2007; accepted 24 October 2007Available online 21 December 2007AbstractGreywater recycling is now accepted as a sustainable solution to the general increase of the fresh water demand, water shortages andfor environment protection. However, the majority of the suggested treatments are biological and such technologies can be affected, espe-cially at small scale, by the variability in strength and flow of the greywater and potential shock loading. This investigation presents thestudy of alternative processes, coagulation and magnetic ion exchange resin, for the treatment of greywater for reuse. The potential ofthese processes as well as the influence of parameters such as coagulant or resin dose, pH or contact time were investigated for the treat-ment of two greywaters of low and high organic strengths. The results obtained revealed that magnetic ion exchange resin and coagu-lation were suitable treatment solutions for low strength greywater sources. However, they were unable to achieve the required level oftreatment for the reuse of medium to high strength greywaters. Consequently, these processes could only be considered as an option forgreywater recycling in specific conditions that is to say in case of low organic strength greywater or less stringent standards for reuse.Ó 2007 Elsevier Ltd. All rights reserved.Keywords: Coagulation; Greywater; Magnetic ion exchange resin; Recycling1. IntroductionInterest in wastewater recycling has been raised by theincrease of water demand, water shortage due to low rain-fall, economic and environmental issues (Eriksson et al.,2002). Among the different options for water reuse suchas industrial, irrigation, and ground water recharge, waterrecycling within urban environments is the least developed.Urban recycling usually integrates the reuse of black, greyor rain waters. Greywater is defined as domestic wastewa-ter excluding water from the toilet, and generally includeswastewaters from baths, showers, hand basins, washingmachines, dishwashers and kitchen sinks. However, atsmall scale the heavily polluted sources such as washingmachines, dishwashers and kitchen sinks tend to beexcluded whereas at larger scale all sources are used tomaximize water savings. The most common applicationfor greywater reuse is toilet flushing which can reducewater demand within dwellings by up to 30% (Karpiscaket al., 1990). However, other applications such as irrigationof parks, school yards, cemeteries and golf courses, vehiclewashing, fire protection and air conditioning are practiced(Lu and Leung, 2003). The water quality standards forwastewater recycling depend on location and applicationbut generally include parameters based on organic, solidsand microbiological contents of the water. The most strin-gent criteria require a biochemical oxygen demand (BOD)of less than 10 mg l1, a turbidity below 2 NTU and a non-detectable level of either total or faecal coliforms (USEPA,2004; Tajima, 2005). However, other standards which areless restrictive allow higher concentrations of the differentparameters or do not include some of the parameters atall (USEPA, 2004; Gross et al., 2007).0045-6535/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.chemosphere.2007.10.046*Corresponding author. Tel.: +44 0 1234 750111; fax: +44 0 123475167.E-mail address: b.jefferson@cranfield.ac.uk (B. Jefferson).www.elsevier.com/locate/chemosphereAvailable online at www.sciencedirect.comChemosphere 71 (2008) 147–155A large range of technologies has been used for grey-water recycling from simple 2-stage process es (coarse filtra-tion and disinfection) to physical, physicochemical andbiological processes (Jefferson et al., 2000). The latter,widely used in large building (Santala et al., 1998; Suren-dran and Wheatley, 1998; Nolde, 1999; Friedler et al.,2004) suffer from feed source variability and potentialshock loading at smaller scale. Such problems are avoidedwith simple physical processes such as cartridge filters ordepth filtration beds. However, whilst these are effectiveat removing the physical pollution within the greywater,they do not significantly alter the organic fraction (Jeffer-son et al., 2000). As such chemical processes such as coag-ulation and adsorption provide great potential for theremoval of the dissolved organic fraction within greywater.Indeed, coagulation with metal salts remains the main pro-cess utilised in the potable water treatment field for theremoval of high concentrations of dissolved organic carbon(DOC) (Parsons and Jefferson, 2006). In more recent timesa novel magnetic ion exchange resin (MIEXÒ) has been tri-alled and is being used to reduce organic loads onto somewater treatment works, to reduce coagulant demand orimprove the structural properties of the flocs produced(Jefferson et al., 2004a). In opposition to traditi onal ionexchange resins, MIEXÒhas a magnetic component in itsstructure which facilitates agglomeration and settling.Moreover, with an average particle size of 180 lm, 2–5times smaller than traditional ion exchange resins, MIEXÒhas a high surface area for adsorption. And finally, it isdesigned to be added to the water as slurry in a mixed reac-tor. The particles dispersed in the water maximise the con-tact with the organics reducing the contact time neededcompare to a fixed-bed set up (Boyer and Singer, 2005).The aim of the present work is to assess the potential forutilise these chemical processes for greywater recycling.2. Material and methods2.1. SamplingGreywater was collected from a purpose built facilitywhich diverts water from the
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