ARTICLE IN PRESS WAT E R R E S E A R C H 42 2008 2260 2268 Available at www sciencedirect com journal homepage www elsevier com locate watres Essential oils for the disinfection of grey water Gideon P Winwarda Lisa M Averyb Tom Stephensona Bruce Jeffersona a Centre for Water Sciences Cranfield University Building 39 Bedfordshire MK43 0AL UK Macaulay Institute Macaulay Drive Craigiebuckler Aberdeen AB15 8QH UK b ar t ic l e i n f o abs tra ct Article history Although the antimicrobial properties of many plant essential oils EOs are well known Received 7 October 2007 their application for the disinfection of water has received little attention In this study Received in revised form their use as alternative natural disinfectants for grey water reuse was assessed Toxicity 28 November 2007 screening of eight EOs and their components highlighted origanum oil Thymus capitatus Accepted 6 December 2007 and carvacrol as exerting the most antimicrobial activity Over a 30 min contact time Available online 15 December 2007 origanum EO concentrations of up to 94 mg L 1 had minimal effect on total coliform Keywords Grey water Essential oil Oregano Water reuse Regrowth Coliform concentrations in the grey water while a concentration of 468 mg L 1 rendered total coliforms non detectable in 100 mL grey water Coliform inactivation was found to increase with EO contact time Organic concentration and particulate size in grey water were shown to reduce the efficacy of disinfection with origanum EO Origanum EO prevented regrowth of coliform bacteria in reed bed treated grey water for up to 14 days at a concentration of 468 mg L 1 with or without prior disinfection by ultraviolet UV light Based on the disinfection data reported here the production of sufficient origanum EO for the disinfection of grey water for reuse with toilet flushing would require approximately 35 times the average land area of a UK household 2007 Elsevier Ltd All rights reserved 1 Introduction Small scale decentralised reuse of water is increasingly viewed as a viable way forward for water conservation in the urban environment Anderson 1996 Fane et al 2002 Small scale reuse schemes can range from individual households to clusters of homes such as blocks of flats or commercial premises like hotels Water reuse schemes typically involve treatment and disinfection of the source water prior to reuse for applications such as toilet flushing and irrigation Grey water can be defined as all wastewater flows exiting a building with the exception of toilet waste black water Depending on the quantity or quality of water required for reuse grey water is frequently limited to the bathroom streams of hand basin shower and bath water which are less polluted in terms of organics and bacteria Friedler 2004 Jefferson et al 2004 Faecal contamination of grey water and the reported presence of pathogenic microorganisms Ottoson and Stenstro m 2003 Birks et al 2004 dictates that treatment and disinfection of grey water is important to control the potential health risks emanating from reuse applications The type of treatment and disinfection employed can vary according to the desired application and regional standards for water reuse Treatment options for grey water reuse include coarse filtration March et al 2004 direct membrane filtration Ramon et al 2004 constructed wetland Dallas and Ho 2005 rotating biological contactor Nolde 1999 and membrane bioreactor Jefferson et al 2000 Chlorine is a leading contender for the disinfection of grey water for reuse due to its widespread use for the disinfection of wastewater and potable water Drawbacks of chlorination Corresponding author Tel 44 1234 754813 fax 44 1234 751671 E mail addresses g p winward cranfield ac uk G P Winward l avery macaulay ac uk L M Avery t stephenson cranfield ac uk T Stephenson b jefferson cranfield ac uk B Jefferson 0043 1354 see front matter 2007 Elsevier Ltd All rights reserved doi 10 1016 j watres 2007 12 004 ARTICLE IN PRESS WAT E R R E S E A R C H include the formation of disinfection by products that can cause adverse health effects Morris et al 1992 Nieuwenhuijsen et al 2000 and limited efficacy in the presence of particles and organics Winward et al 2007 Alternative disinfectants that are perceived as being environmentally friendly would be an attractive option for operators of smallscale water reuse systems Such alternatives include ultraviolet UV light and plant essential oils EOs EOs are aromatic liquids extracted from plant material typically by steam distillation Sangwan et al 2001 EOs and their components have been shown to possess antibacterial Hammer et al 1999 Burt 2004 antiviral Edris 2007 antiparasitic Anthony et al 2005 antifungal Sokovic and van Griensven 2006 insecticidal Isman 2000 and herbicidal Tworkoski 2002 properties Research into the antimicrobial properties of EOs and their components has been largely directed towards their use as food preservatives EOs and their components have been shown to inhibit bacterial growth in meat fish and vegetable products Burt 2004 The principal mechanism of bacterial inactivation by EOs is considered to be the disruption of the cell membrane causing leakage of cell contents and eventual cell lysis Burt 2004 This action of certain EOs can be explained by the presence of phenolic compounds common in many EOs such as carvacrol thymol and eugenol which are known to cause such disturbance of the cell membrane Sikkema et al 1995 The effective use of EOs and their components as inhibitors of microbial growth in foods points to their potential as residual regrowth inhibitors in reused water This study investigates the disinfection potential of EOs for grey water reuse including the impact of organics and particles and their application as residual regrowth inhibitors in reed bedtreated grey water following UV disinfection 2 Materials and methods 2 1 Water sample collection 2261 42 2008 2260 2268 Grey water was collected from bathroom sinks baths and showers of 18 specially plumbed student flats on Cranfield University campus The grey water was collected by gravity in an underground sump and then pumped into a continuously circulating holding tank 700 L capacity The grey water was supplemented with a 10 v v shampoo Tesco Value in tap water to create a high strength grey water Fig 1 The supplementary solution and the real grey water were pumped at fixed intervals into a second holding tank at a ratio of 1 55 A self contained vertical
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