Characterisation of Indicator Organisms and Pathogens in Domestic Greywater for Recycling

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1 DOI.7/s y Chrcteristion of Indictor Orgnisms nd Pthogens in Domestic Greywter for Recycling R. Birks & S. Hills Received: 3 July 25 /Revised: 27 Jnury 26 /Accepted: 9 Mrch 26 # Springer Science + Business Medi B.V. 27 Abstrct Greywter from bths, showers nd wshbsins ws collected seprtely from ll other domestic wstewter t university block of flts with dul reticultion system nd nlysed for rnge of contminnts including indictor orgnisms nd pthogens. Greywter flow nd temperture were lso monitored nd diurnl vrition ws observed. Physicl nd chemicl wter qulity prmeters were similr to previously published dt, lthough mesured COD nd BOD levels ppered to be lower, possibly due to settlement or biodegrdtion in the storge tnks. Plte counts nd indictor orgnism concentrtions were consistently high suggesting high level of humn bcteril contmintion necessitting biologicl tretment nd disinfection if the wter is to be used for recycling. However, these high levels of indictor orgnisms did not correlte to pthogen presence nd should not be used s pthogen indictors in greywter. One positive count of Slmonell veltereden ws observed s well s low levels of Girdi. Cryptosporidium, Escherichi coli O57:H7, enteroviruses nd Legionell were not identified in ny of the smples. The reserch lso R. Birks (*) : S. Hills Thmes Wter Reserch nd Development, Spencer House, Mnor Frm Rd, Reding RG2 JN, UK e-mil: rebecc.birks@thmeswter.co.uk S. Hills e-mil: sin.hills@thmeswter.co.uk highlighted number of problems with the complexity of this type of smpling progrmme, such s identifying the most likely time to isolte pthogens nd nlysing n unusul wter source. Keywords Domestic. Greywter. Microbiology. Pthogens. Reuse Introduction Of severl lterntive wstewter sources tht cn be reused, greywter is generlly perceived to be more cceptble thn other domestic wstewter, such s blckwter, due to common misconception tht it hs lower levels of contmintion. However, greywter contins significnt microbiologicl contmintion (Birks et l. 24; Lzrov et l. 22; Rose et l. 99; Surendrn nd Whetley 998). By chrcterising the level of contmintion, ssessment cn be mde of the potentil helth risks nd implictions of its use for recycling, the type of tretment tht is necessry nd the ssocited economic vibility. Greywter cn brodly be defined s ll wstewter generted in the household, excluding toilet wste. Greywter cn include wstewter from bthroom sinks, bths nd showers ( light grey ) nd my lso include more contminted wste from lundry fcilities, dishwshers nd, in some instnces, kitchen sinks ( drk grey ). Tble highlights the vrition in rw light greywter qulity tht hs been found in previous studies.

2 Tble Chrcteristics of light greywter from vrious studies Prmeter Line 2 Birks et l. 24; Smith et l. 2 Surendrn nd Whetley 998 Rose et l. 99 Holden nd Wrd 998 Christov-Bol et l. 996 Greywter type B, S, W W B, S, W B, S, W, L B, S, W S, B BOD (mg/l) COD (mg/l) SS (mg/l) Turbidity (NTU) ph Ammoni, s N <. 5 (mg/l) TKN, s N (mg/l) Totl phosphorous (mg/l) Totl coliforms > (cfu/ ml) Fecl coliforms (cfu/ ml) Escherichi coli.5 3 >2.4 6 (cfu/ ml) Fecl enterococci (cfu/ml) 22 C plte >3. 5 counts/ml 37 C plte counts/ml >3. 5 Not stted in the study. B Bth, S shower, W wshbsin, L lundry. The COD nd BOD of greywter cn be reltively high, even in light greywter (see Tble ), but is much incresed if drk greywter (e.g., from kitchen sinks, wshing mchines) is included (Surendrn nd Whetley 998). Greywter generlly contins less suspended solids nd nitrogen thn typicl domestic sewge, s toilet wter is excluded. Generlly, mmoni nd totl Kjeldhl nitrogen concentrtions in greywter re bout times lower thn in domestic wstewter. However, greywter cn contin more phosphorus, lthough this primrily origintes from detergents in wshing powder typiclly found in drk greywter. Greywter cn contin high levels of bcteri (see Tble ). The presence of fecl coliforms, Escherichi coli nd fecl enterococci my indicte pthogenic risk in potble wter nd these orgnisms hve previously been used to ssess the sfety of greywter recycling (Rose et l. 99). However their bsence does not necessrily signify tht wter is pthogen free. This depends both on the type of tretment tht hs been used nd lso the relibility of the indictor orgnisms t predicting the presence of pthogens, which hs previously been questioned (Gerb nd Rose 23). It is reltively rre to hve ccess to lrge rel source of greywter for detiled nlysis. A source ws vilble for this study, with smpling crried out t block of flts with dul reticultion system t Crnfield University in the south of Englnd. The university is postgrdute only university nd the flts house primrily mrried couples, therefore it ws ssumed tht the greywter would be reltively typicl of stndrd block of flts. The greywter collected from the flts is not currently used for recycling but hs been used for number of pilot trils t the university. The primry objective of the

3 smpling progrmme ws to chrcterise rel rw greywter with specific reference to microbiology. This ws chieved by nlysing for bsic physicl nd chemicl prmeters, microbiologicl indictor orgnisms nd rnge of wterborne pthogens t vrious times both during the dy nd, lso, the yer. 2 Mterils nd Methods 2. Greywter collection At Fedden flts hll of residence, light greywter is collected vi dedicted pipework from the bths, showers nd hndbsins of 8 of the 72 flts nd directed to subsurfce collection sump (Tnk A) in the grounds of the hlls of residence (see Fig. ). This is then pumped to collection tnk (Tnk B) in n djcent portcbin where smples cn be tken. When the greywter volume in Tnk B drops below certin level, low level flot switch in the tnk ctivtes the sump pump in Tnk A to pump more greywter into Tnk B. The greywter in Tnk B flows to drin vi n outlet pipe ner the bottom of the tnk when the tnk is full. There is lso n overflow t the top of the Tnk B in the cse of very high greywter flows. 2.2 Greywter flow nd temperture monitoring The greywter flow from the flts ws mesured using flowmeter ( M in Fig. ) on the outlet pipe ner the bottom of Tnk B. The pipework fter the flowmeter ws the height of the top of the tnk (see Fig. ) so tht greywter would only flow through the flowmeter nd out of the tnk when the tnk ws full. The greywter temperture in both Tnks A nd B ws mesured using two floting dt loggers, which logged the temperture every 5 min. Both the temperture nd flow dt were used to predict when the greywter ws likely to be fresh nd when stgnnt so the two extremes could be smpled ech dy during the smpling progrmme. 2.3 Greywter smpling Greywter smples were tken from Tnk B (see Fig. 2). The smpling rtionle ws for it to be crried out in three phses with review of the results fter ech phse. This is summrized in Tble 2. SAMPLING POINT OVERFLOW TO DRAIN GREYWATER COLLECTED FROM BATHS, SHOWERS AND WASHBASINS IN THE HALLS OF RESIDENCE GREYWATER FLOW = pprox. 4l/h OVERFLOW TO DRAIN M DRAIN TANK B m 3 COLLECTION TANK IN PORTACABIN ADJACENT TO THE HALLS OF RESIDENCE FLOAT SWITCH TO ACTIVATE SUMP PUMP IN TANK A AT LOW WATER LEVEL PUMP TANK A 5 LITRE SUBSURFACE SUMP TANK IN THE GROUNDS OF THE HALLS OF RESIDENCE Fig. Schemtic of the greywter collection system t Fedden flts

4 Tble 2 Summry of the smpling progrmme Phse Frequency Durtion Determinnds No. of repets/ smple Twice dy (8 A.M. nd 3 P.M.) every dy Review results 2 3 times week (2 in week, t weekend) 2b 3 times week (2 in week, t weekend) Review results 3 3 times week (2 in week, t weekend) 2 weeks Indictors (E. coli, totl coliforms, fecl enterococci, 22 & 37 C plte counts) 3 months Indictors (s bove); physicl & chemicl (BOD, soluble BOD, COD, SS, ph, turbidity, conductivity, TKN, P) 3 months Pthogens (Slmonell, Girdi. Cryptosporidium, E. coli O57:H7, enteroviruses nd Legionell) week Indictors; physicl nd chemicl; pthogens (ll s bove) 3 Phse ws n intense 2 weeks of smpling during which smples were tken in triplicte dily (t 8 A.M. in the morning nd 3 P.M. in the fternoon). From nlysis of the temperture nd flow dt it ws believed t 8 A. M. there would be fresh greywter nd t 3 P.M., more stgnnt greywter, so tht the two extremes of wter qulity could be nlysed for. During Phse, the greywter ws monitored for indictor orgnisms nd generl physicl nd chemicl prmeters. The wter qulity results of Phse of smpling were reviewed nd used to design Phse 2 of the smpling progrmme. Phse 2 smpling ws crried out for 3 months, with less frequent smples tken thn in Phse nd greywter nlysed for indictor orgnisms, generl physicl nd chemicl prmeters nd some pthogens. Smpling times were bsed on the results of Phse. In Phse 3, indictor orgnisms, generl physicl nd chemicl prmeters nd pthogens were nlysed for one week, lter in the yer, s repliction of Phse 2. The complexity nd high cost of the pthogen nlysis ment tht smples in Phse 2 nd 3 were nlysed for pthogens only when there ws 3 ~8:m: Fresh greywter increses tnk temperture ~5:: Temperture levels level off from miniml use, therefore, no fresh greywter 3 25 Generl cooling of the greywter during the night Generl cooling of the greywter during the night Tnk A temp 25 Tnk B temp flow (l/h) 2 5 ~5: nd 5:: Lulls in greywter production ~8: nd 22:: Peks in greywter production 2 5 Tnk temperture (C) 5 5 :: :5:3:4: 5:3: 7:2:9:: :: 2:5:4:4: 6:3: 8:2:2:: 22:: 23:5: Time Fig. 2 Diurnl vrition in greywter flow nd temperture

5 mg/l no 9 45 published 4 dt no 5 4 published dt COD SS BOD soluble TKN Totl P conductivity turbidity ph BOD rnge of mesured prmeters men previous published dt us/cm NTU Fig. 3 Greywter qulity (from Phse, 2 nd 3) physicl nd chemicl properties very high probbility tht there would be positive count (i.e., when it ws predicted tht there would be high levels of indictor orgnisms in the greywter). 3 Results nd Discussion 3. Greywter flow nd temperture Diurnl vrition in greywter production ws observed with pek flows t 8 A.M. ndp.m. nd lulls t 5 A.M. nd 3 P.M. (see Fig. 2). Temperture dt followed similr pttern to flow, with lower tempertures observed during times of low greywter flow nd high tempertures when high volumes of fresh greywter were being produced (see Fig. 2). The occupnts were primrily mrried couples nd the verge per cpit consumption (pcc) ws comprble to Thmes Wter dt for two-person households t 85 l/p/d (Thmes Wter internl dt from 23 for two-person households gives n verge pcc of 87 l/p/d). 3.2 Greywter qulity physicl nd chemicl properties Physicl nd chemicl wter qulity prmeters were similr to previously published dt for light greywter, lthough mesured COD nd BOD levels ppered to be lower (see Fig. 3), possibly due to settlement or biodegrdtion in the storge tnks. Concentrtions of turbidity nd suspended solids incresed during the smpling period (from 25 to 3 NTU nd 3 to 52 mg/l respectively), possibly from deteriortion in the clenliness of the storge tnks (see Fig. 4). Levels of phosphorous were consistently low (<4 mg/l) s this light greywter did not contin ny detergents from wshing mchine powders. Tble 3 summrises the results of the physicl nd chemicl prmeter nlysis. 3.3 Greywter qulity microbiologicl properties The plte counts nd indictor orgnism concentrtions were high (see Fig. 5) probbly due to biodegrdtion in the tnks nd multipliction in nutrient rich environment (men totl coliforms t cfu/ ml, E. coli t cfu/ ml nd fecl enterococci t cfu/ ml, see Tble 3). The 37 C plte counts were generlly s high s the 22 C plte counts (men of.3 7 cfu/ml nd.5 7 cfu/ml respectively, see Tble 3) suggesting high level of humn bcteril contmintion (from bcteri on the skin, fecl contmintion etc.). For both plte counts nd indictor orgnisms, the

6 25 Phse 2 Phse 3 Turbidity (NTU) & SS (mg/l) Jn-3 Feb-3 Turbidity (FTU) Dte Suspended solids (mg/l) Fig. 4 Levels of turbidity nd SS in the greywter (mg/l) (from Phse 2 nd 3) Mr-3 Apr-3 Oct-3 levels of contmintion were higher thn for previously published dt (see Fig. 5). However, for plte counts, the previous published dt vilble ws from wshbsins only (Birks et l. 24, see Tble ) nd not shower nd bth wter, s in this study, so this would be expected. The presence of totl coliforms, E. coli nd fecl enterococci shows fecl contmintion, indicting the possible presence of pthogens. 3.4 Greywter qulity pthogens The untreted greywter ws lso nlysed for rnge of pthogens nd only two were identified. In ll of the smples tken, one positive count of Slmonell (Slmonell veltereden) ws found (see Tble 4). This is common species ssocited with food poisoning from prtilly cooked met nd shellfish nd presumbly pssed into the greywter by n infected person Tble 3 Summry of men nd SD of the physicl, chemicl nd microbiologicl prmeters compred to the previously published dt shown in Tble Physicl nd chemicl prmeters Microbiologicl prmeters Prmeter Men SD Published dt Prmeter Men SD Published dt ph C plte counts/ml >3. 5 Turbidity, NTU C plte counts/ml >3. 5 SS, mg/l Totl coliforms/ ml > TKN, mg/l Escherichi coli / ml >2.4 6 Totl P, mg/l Fecl enterococci/ ml BOD, mg/l Soluble BOD, mg/l 3.2 N/A COD, mg/l Conductivity, μs/cm N/A N/A No dt vilble.

7 cfu/ml (plte counts) C plte counts 37C plte counts rnge of mesured prmeters Totl coliforms men E.coli Fecl enterococci previous published dt cfu/ml (indictor orgnisms) Fig. 5 Greywter qulity (from Phse, 2 nd 3) microbiologicl properties wshing or possibly the wshing of uncooked met in bthroom wshbsin. Interestingly, this ws t time when the levels of indictor orgnisms were t the lower end of the rnge identified. Girdi ws lso identified in 63% of the smples nlysed (see Tble 4), lthough these were not t levels to be of cuse for concern s they were below the infective does of to 25 cysts (positive Girdi smples were ll <.5 cysts/litre). Cryptosporidium, E. coli O57:H7 nd Legionell were not identified in the smples; however, the likelihood of their presence is low s they re not common cuses of illness (compred to pthogens such s Slmonell). Enteroviruses were not identified, despite being one of the more common groups of pthogens. 3.5 Generl trends in the greywter qulity Some trends in the greywter qulity were observed during Phse, 2 nd 3, such s the concentrtions of turbidity nd suspended solids incresing during the smpling period (see Fig. 4). However, no significnt difference ws observed between the week nd the weekend smples for indictor orgnisms or 37 C plte counts, lthough 22 C plte counts were significntly higher in the week thn t the weekend (t test t the 95% confidence level). It is uncler s to why the concentrtions of environmentl microorgnisms would be higher in the week compred to the weekend nd my simply be dt nomly. There ws lso no significnt difference in the Tble 4 Summry of results of the pthogen nlysis Pthogen Positive smples (%) Rnge identified Pthogen Positive smples (%) Rnge identified Girdi/l 63%.5.5 Legionell pneumophil, sg,2 4 Slmonell, MPN/l 3% b Legionell sp. (non-pneumophil) Cryptosporidium/l Enterovirus enumertion/ l Cmpylobcter/l Escherichi coli O57:H7/l Ech pthogen shown nlysed eight times during the smpling progrmme. b Identified s Slmonell weltevreden.

8 9 8 7 Phse Phse 2 Phse 3 Totl coliform smples nlysed here t insufficient dilutions cfu / ml Oct-2 Dec-2 Jn-3 Mr-3 My-3 Oct-3 Dte Totl coliforms E.coli Fecl enterococci Fig. 6 Trends in indictor orgnism concentrtion over the smpling period physicl nd chemicl prmeters nlysed for in the week nd weekend smples, with the exception of totl phosphorous which ws significntly higher in the smples tken during the week (t the 95% confidence level). Figure 6 shows the concentrtions of indictor orgnisms found throughout the smpling period. No significnt difference ws observed between the morning nd fternoon smples for plte counts, totl coliforms or ny of the physicl nd chemicl prmeters nlysed. However, E. coli nd fecl enterococci levels were significntly higher in the fternoon smples, when it ws thought tht the greywter would hve been stored for longer, compred to the morning smples predicted to contin fresher greywter (t test t the 95% confidence level). This indictes tht more biodegrdtion hd occurred in the greywter which hd been left for few hours. However, s this did not correlte with the BOD nlysis (i.e., there ws no significnt difference in the BOD morning nd fternoon smples), no firm conclusions cn be drwn from this trend without further greywter qulity nlysis to confirm or refute the trend. It should be noted tht, lthough the best ttempts were mde to predict times during the dy when the greywter ws the most fresh nd most stgnnt from the temperture nd flow dt this my hve been inccurtely estimted. Therefore, vritions in the greywter qulity from being stored for different lengths of time my hve been indvertently missed. 4 Conclusions The reserch showed tht consistently high levels of potble wter indictor orgnisms (totl coliforms, E. coli nd fecl enterococci) cn be found in rw untreted greywter. However, these high levels of indictors do not necessrily signify the presence of pthogens nd, therefore, should not be used for pthogen indiction in greywter. The potentil for humn pthogens to be present in detectble numbers in greywter ws confirmed. The high levels of microorgnisms nd BOD necessitte biologicl tretment to reduce contmintion, if greywter is to be reused. Disinfection is lso essentil to eliminte pthogens nd to provide residul to minimise biofilm growth in the pipework. This reserch hs highlighted number of difficulties nd the complexity of the smpling progrmme, prticulrly, the expense of nlysis for pthogens, identifying the most likely time to isolte pthogens,

9 nlysing n unusul wter source nd estimting when the greywter will be fresh or stgnnt. There ws much vrition in the results for ech microbiologicl contminnt. However, the vrition ws much less during Phse of the smpling when the nlysis ws crried out in triplicte, due to the incresed ccurcy of lrger smple. However, lrger smple obviously incurs n dditionl cost, which must be considered in ny smpling progrmme. Acknowledgments The uthors would like to cknowledge collegues throughout Thmes Wter nd Crnfield University nd ll others who hve worked on projects described in this pper. Any views expressed re those of the uthors nd not necessrily those of RWE Thmes Wter Plc. References Birks, R., Colbourne, J., Hills, S., & Hobson, R. (24). Microbiologicl wter qulity in lrge in-building recycling fcility. Wter Science nd Technology, 5(2), Christov-Bol, D., Eden, R. E., & McFrlne S. (996). An investigtion into greywter reuse for urbn residentil properties. Deslintion, 6, Gerb, C. P., & Rose, J. B. (23, November). The indictor concept in wstewter reclmtion: Pst, present nd future. Pper presented t the 4th Interntionl Symposium on Wstewter Reclmtion nd Reuse, Mexico City. Holden, B., & Wrd, M. (998, December). An overview of domestic nd commercil re-use of wter. Pper presented t the IQPC Conference on Wter Recycling nd Effluent Re-use, London. Line, A. (2). Technology for greywter recycling in buildings. PhD thesis, Crnfield University, Crnfield, Bedfordshire, UK. Lzrov, V., Hills, S., & Birks, R. (22). Using recycled wter for non-potble, urbn uses: A review with prticulr reference to toilet flushing. Wter Science nd Technology: Wter Supply, 3(4), Rose, J. B., Sun, G. S., Gerb, C. P., & Sinclir, N. A. (99). Microbil qulity nd persistence of enteric pthogens in grywter from vrious sources household sources. Wter Reserch, 25(), Smith, A, Hrdy, P., & Lodge, B. (2). Alterntive wter sources nd technologies for non-potble reuse. Pper presented t WEFTEC 2, Atlnt. Surendrn, S., & Whetley, A. D. (998). Greywter reclmtion for non-potble reuse. Journl of the Chrtered Institution of Wter nd Environmentl Mngement, 2,