agronomic and public health assessment of reclaimed water quality for landscape irrigation

e Pergamon Wat. Sci. Tech. Vol. 33, No. 10-11, pp. 335-344, 1996.Copyright © 1996 IAWQ. Published by Elsevier Science Ltd

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AGRONOMIC AND PUBLIC HEALTHASSESSMENT OF RECLAIMED WATERQUALITY FOR LANDSCAPE IRRIGATION

Rafael Mujeriego*, Lluis SaIa**, Maria Carb6* andJosep Turet***

* Department ofHydraulic, Coastal and Environmental Engineering,Universidad Politecnica de Cataluna, Gran Capitan, D-I, 08034 Barcelona, Spain** Consorci de la Costa Brava, Plaqa Josep Pia, 4, 17001 Girona, Spain*** Estudis Universitaris de Vic, Miramarges, 4, 08500 Vic, Spain

ABSTRACT

The Mas Nou golf course has been using disinfected secondary effluent for irrigation since September 1989.Although adjusted-SAR values and EC of irrigation water have generally fallen in the non-restrictedirrigation categories, EC values were initially higher than desirable for turf irrigation, due to high effluentchloride concentration. A definite solution was reached in the summer of 1993 with completion of a newsurface water transfer. Since 1993, EC values in summer effluent range from 1.2 to 1.5 dS/m. A new waterand storage pond management system has been proposed to optimize both water and nutrients application,using only the most adequate water source available at a given time. The relatively low iron contributions ofreclaimed water have resulted in occasional spots of ferric chlorosis, which have been recovered withlocalized application of iron compounds. Fertilizer savings have ranged from 0.06 to 0.12 US $/m3 ofreclaimed effluent. Weekly analyses of reclaimed water show that faecal coliforms and faecal streptococciconcentrations lower than 100 cfu/l00 mL can be consistently achieved. By mechanical mixing of topoxygen-rich waters with bottom oxygen-depleted waters in the storage ponds, odor problems have beentotally eliminated. Close collaboration with the greenkeeper has resulted in a more favorable attitude to thewater quality requirements of reclaimed effluent and a more effective and economical fertilization program.The greenkeeper perception has gradually evolved from a passive acceptance of the requirements of usingreclaimed water to a positive recognition of its benefits. Copyright © 1996 IAWQ. Published by Elsevier ScienceLtd.

KEYWORDS

Irrigation; reclamation; reuse; golf l,;ourse; nitrogen; nutrients; phosphorus; ponds; disinfection; wastewater.

INTRODUCTION

The continuous increase in water demands in many semi-arid areas of the world, due to permanent andseasonal population gIOwth, together with the severe and prolonged droughts experienced in some of thoseareas over the last decade1::, and the increasing restrictions on water quality levels for receiving waters havemade clear the limitations of present and planned conventional water supplies to satisfy current and expectedpotable water demands. The coastal resort area of Costa Brava, located in the northern mediterranean coastof Spain, illustrates quite well the problems and alternatives available for water resources management underlimited conventional water supplies, important flow reductions due to seasonal droughts, an eight-foldincrease in water demands due to summer tourist populations, and increasing requirements for aesthetic andpublic health quality of inland and coastal waters. Landscape irrigation and particularly golf course irrigationrepresent a growing water use, due to the tradition of public and private gardens and the significant role ofgolf courses as an added amenity to t01.1rists from central and northern Europe. In this scenario the Consorci

335

R. MUJERlEGO el al.

de la Costa Brava (CCB), the regional water supply and sanitation agency, launched in 1991 a two-yeardemonstration project of a planned water reuse project, in collaboration with the Junta de Sanejament(Catalonia's Sanitation Agency), the Universidad Politecnica de Cataluiia (UPC), and the Mas Nou golfcourse. The objective of this demonstration project was to develop technical and management criteria forreclamation of secondary effluent and irrigation of a golf course whose main water source is the reclaimedeffluent provided by CCB. The Mas Nou golf course demonstration project was subsequently extended underthe joint sponsorship of CCB and UPC, and the results obtained are presented in the following sections.

The Mas Nou golf course has been using disinfected secondary effluent for irrigation since September 1989(Mujeriego and Sala, 1991). Secondary effluent from the Castell-Platja d'Aro wastewater treatment plant(WWTP) is disinfected in the 2 200-m pipeline used to bring reclaimed water up to the 300 m elevation ofthe golf course; the disinfectant used is sodium hypochlorite (15% CI2), with doses ranging from 25 to45 mg CI2/L depending mainly on effluent's turbidity and/or ammonia nitrogen concentration. Reclaimedeffluent is stored in two landscape ponds connected in series, each one used for irrigating a different area ofthe golf course. The reclaimed effluent flows into Pond 1, which has a capacity of 13 300 m3

, a maximumdepth of 4.5 m and serves to irrigate 21 ha of turf; water from Pond 1 flows into Pond 2 which has a capacityof 21 ()()() m3

, a maximum depth of 5.5 m and serves to irrigate 13 ha of turf. Secondary effluent and waterfrom both ponds have been intensely monitored for agronomical and microbiological quality since 1989.

CASTELL-PLATJA D'ARO WWTP

The treatment system of Castell-Platja d'Aro WWTP is a conventional activated sludge process, and wasdesigned to treat the combined sewer flows of three nearby resort towns. The residential and tourist characterof the area results in marked flow variations between winter (lower than 10 ()()() m3/day) and summer (higherthan 30 ()()() m3/day). However, operation and maintenance by skilled and motivated personnel results in aneffluent of consistently good quality all year round. Table 1 shows the effluent quality obtained during 1994.

TABLE 1. EFFLUENT QUALITY OF CASTELL- PLATJAD'ARO WWTP IN 1994

Parameter Annual averagepH 8.0Turbidity, NTU 8Suspended solids, mg/L 10BOD5, mg/L 15COD, mg/L 80Electrical conductivity, dS/m 1.34Chloride, mg/L 200Alkalinity, mg CaC03/L 280Sodium, mg/L 190Potassium, mg/L 15Ammonia nitrogen, mg NHrN/L 25.5Nitrite nitrogen, mg N02-N/L 0.2Nitrate nitrogen, mg NOrN/L 0.6Soluble orthophosphate, mg P04-P/L 7.6Boron, mg B/L 0.6

Recla,mation of .secondary effluent has been limited to disinfection with sodium hypochlorite, using the6O-mm contact tnne plug flow reactor provided by the pipeline needed to bring reclaimed water to the first~a~dsc~pe pond of the golf course. Daily flows of reclaimed effluent used by Mas Nou golf course vary withIrngatlO~ ~ater demand, reaching its. maximum value (slightly over 2 ()()() m3/day) in July and August. AsTable 2 mdicates, the volume of reclaImed water used annually for irrigation has ranged from 152000 m3 in

Reclaimed water quality for landscape irrigation 337

1994, when the facilities where practically closed until July, and 280 ()()() m3 during the particularly dry yearsof 1991 and 1993.

TABLE 2. RECLAIMEb EFFLUENT USED FOR IRRIGATIONAT MAS NOU GOLF COURSE

Year1991199219931994

Volume, m3

280100240700280200151 700

AGRONOMIC ASSESSMENT

Water Salinity

Water salinity has been measured by electrical conductivity (EC) , and specific determinations of chlorides,sodium, potassium, calcium and magnesium. Between 1989 and 1991, the EC of summer effluent wasconsidered unfavorable (Crook, 1991) for turf irrigation because of its relatively high values: from 2 to 4dS/m, with occasional values of up to 7 dS/m. Although adjusted-SAR values and EC have generally fallenin non-restricted irrigation categories, according to the criteria developed for the preservation of soilpermeability (Pettygrove and Asa.no, 1984; USEPA, 1992), EC values were higher than desirable for turfirrigation, due to high effluent chloride concentration. During the severe drought of 1989-91, high EC valueswere observed partly due to excessive water supply withdrawals, which favored marine intrusion into thenearby coastal aquifer. The higher rainfall measured during the fall of 1991 and all through 1992 resulted ina significant reduction of the EC of potable water.

A definite solution to the problems caused by high EC values both in potable water and secondary effluentwas reached in the summer of 1993 with completion of a new surface water transfer from EI Pasteralreservoir - 50 km inland - as an additional water supply for the Costa Brava area surrounding Mas Nou golfcourse. Since 1993, EC values in summer effluent range from 1.2 dS/m to 1.5 dS/m. However, majorvariations of effluent EC values have been observed occasionally, due to either seawater intrusion throughthe coastal sewerage system -increasing EC values - or storm water runoff reaching the WWTP - decreasingEC values. In general, and despite irrigation with high EC water during the first years, soil salinity has notincreased except for two poor-drainage areas located in fairways 12 and 15 (Mujeriego et ai., 1994).

The corrective measures taken both in the water supply system and the sewerage system, and the evolutionexperienced by reclaimed water salinity clearly illustrate the important role that both potable water qualityand sewerage control measures can play in achieving a reclaimed water of the best agronomical quality.Considering that conventional wastewater secondary treatment does not modify the salinity of the influent, itis of utmost importance to plan water reclamation and reuse using effluents from areas of good potable waterquality and to protect the sewerage system from receiving waters of high salinity, through inadequatedischarges or infiltration-inflow from surrounding brackish aquifers.

Plant Nutrients

Table 1 shows that secondary effluent from Castell-Platja d'Aro WWTP is a water rich in nutrients, speciallyduring the summer, with values reaching consistently 40-45 mg NHrN/L and 8-10 mg P04-P/L. However,Table 3 indicates that, as irrigation water is pumped from either storage pond, nutrients concentrations mayshow a marked variation from the values measured in the reclaimed effluent, depending basically on thehydraulic residence time (HRT) of water in the pond (Mujeriego et ai., 1993). As it could be expected,nutrients concentrations in Pond 1, which receives reclaimed effluent from the WWTP, are greater than in

338 R. MUJERIEGO el al.

TABLE 3. HYDRAULIC RETENTION TIME (HRT), LOSS RATES AND NITROGEN ANDPHOSPHORUS INPUT REDUCTION IN MAS NOU GOLF COURSE LANDSCAPE-STORAGE PONDS DURING 1992 AND 1993

Parameter Year Winter Spring Summer Autumn Average

Pond 1 - Nitrogen

HRT, days 1992 61 15 9 89 191993 87 11 8 142 17

Loss rate, 1992 0.19 0.42 0.94 0.33 0.47g N/m3 pond.day 1993 0.09 1.42 0.83 0.18 0.63

Input reduction, % 1992 64 22 23 117 281993 58 45 15 92 27

Pond 2 - Nitrogen

HRT, days 1992 281 78 52 342 1031993 464 58 42 471 88

Loss rate, 1992 0.02 0.05 0.31 0.10 0.12g N/m3 pond.day 1993 0.04 0.05 0.46 0.18 0.18

Input reduction, % 1992 143 21 60 273 591993 251 17 50 508 57

Pond 1 - Phosphorus

HRT, days 1992 61 15 9 89 191993 87 II 8 142 17

Loss rate, 1992 0.06 0.11 - 0.02 0.02 0.04g P04-P/m3 pond.day 1993 0.04 0.15 0.32 0.04 0.14

Input reduction, % 1992 66 19 -3 33 131993 66 20 24 85 25

Pond 2 - Phosphorus

HRT, days 1992 281 78 52 342 1031993 464 58 42 471 88

Loss rate, 1992 - 0.011 - 0.005 0.059 0.025 0.017g P04-P/m3 pond.day 1993 0.003 - 0.001 0.021 0.078 0.025

Input reduction, % 1992 - 127 - 6 55 207 341993 58 - 1 II 751 33

Pond 2, which receives only water from Pond 1. Annual mass balances of nitrogen and phosphorus in bothponds show similar losses - as percentC\ges of the nutrients mass entering each pond -, except for solubleorthophosphate in Pond 1 (Mujeriego et ai., 1993; Mujeriego et ai., 1994).

As a result of the nutrients loss experienced by the reclaimed effluent during its flow through the waterstorage system, irrigation water from both ponds has very low nutrients concentration in early spring,whereas in summer it shows a considerably increase in nutrients because the reclaimed effluent inflowreaches both its maximum flow rate and nutrients concentration. This increase in nutrients concentration isspecially evident in Pond 1 during the summer, where an HRT of 9 days (less than 7 days from mid-July tomid-August) results in a pond water quality very similar to that of reclaimed effluent. The importantvariations experienced by nutrients concentration in both ponds, together with the different irrigation rateS


a~plied during each season, result in a very irregular turf fertilization rate; furthennore, the important~lfferences between the water application rates imposed by the sprinkler irrigation system in the areas ofmfluence of the two storage ponds further preclude a unifonn turf fertilization rate (Table 4). Although, on

TABLE 4. ANNUAL MACRONUTRIENT CONTRIBUTIONS TO MAS NOUGOLF COURSE BY IRRIGATION WITH RECLAIMED WATER

Year and N P20 S K20 Irrigatioq Total irrig~ti&Ppond (kg/ha) (kg/ha) (kg/ha) water, (m ) water, (m )1991

Pond 1 219 177 193300Pond 2 46 69 85200 278500

1992Pond 1 194 121 196 171 600Pond 2 48 48 111 64400 236000

1993Pond 1 270 156 256 186400P~Hd2 79 72 163 77500 263900

1994 a

Pond 1 66 38 30 79000Pond 2 38 35 41 47800 126800

(a) The golf course remained closed until July.(b) Volumes of irrigation water are slightly different from those of

reclaimed water pumped to Pond 1 due to evaporation from the ponds,rainfall, and minor contributions from golf course water wells.

an annual basis, nutrients contributions are quite similar to nutrients requirements in the turf area irrigatedwith water from Pond 1, monthly mass balances show important disparities, with overfertilization in summerand insufficient fertilization in winter. Nevertheless, if very little or no mineral fertilizer is applied afterApril, turf is able to overcome the fertilizer excess with no evident damage or important quality loss.

To reduce the unbalance between seasonal nutrients contributions and turf requirements, a new water andpond management system has been proposed (Sala et ai., 1994). To optimize both water and nutrientsapplication, the source of irrigation water should be the same for the all the golf course turf, and it should bepossible to choose at a given time among the different water sources available at the golf course: a) reclaimedeffluent coming from the WWTP, b) water from Pond 1, or c) water from Pond 2, in the case of Mas Nougolf course. Water source selection would be made based on nutrients concentrations in irrigation water andnutrients requirements of the turf. In winter months, when irrigation is scarce, reclaimed effluent will bemore suitable for the turf because its nutrients concentrations are greater than those of pond water; insummer, when irrigation rates are the highest, the choice will be water from Pond 2 (the last in a series ofinterconnected ponds) because its nutrients concentrations are the lowest and nutrients contributions ofirrigation water will be enough to satisfy turf requirements. Water from Pond 1 would be selected during thespring and fall seasons.

An added benefit of the proposed strategy is a lower risk of aquifer contamination with nitrates, bypreventing the deep percolation of the excess amounts of nitrogen species that otherwise are applied duringthe summer period when both irrigation rates and nitrogen concentration in irrigation water are the highest.

The relatively low iron contributions of reclaimed water, as compared to those of nitrogen and phosphorus,have resulted in occasional spots of ferric chlorosis in the Mas Nou golf course. Those incidents have beenrecovered with localized application of iron compounds. As reported by Mancino and Pepper (1994), themain effect of using reclaimed water for turf irrigation is late summer ferric chlorosis due to both an excessof nitrogen in the irrigation water, which stimulates plant growth beyond the capacity of the roots for ironuptake, and the formation of insoluble iron phosphate salts in high pH soils. However, according toHayes et ai. (1990), ferric chlorosis may be easily corrected with foliar applications of iron sulfate or iron

R. MUJERIEGO el al.

chelates. Confinning Hayes I (1990) conclusions. plot trials with iron sulfate (7 g FeSO41m2

, 18,5 % Fe) andiron chelates (10 g/m2

, 6% Fe) on turf areas affected by ferric cWorosis have shown an evident recovery inapproximately two weeks.

Other turf nutritional deficiency observed is the lack of potassium and occasionally of nitrogen, whichusually become evident when irrigation with reclaimed water is totally or substantially discontinued for acertain time due to high rainfall or to low water needs. However, correct mineral fertilizer applications helpthe turf to recover its adequate nutritional status. Furthennore, some fungal infections have been observed inthe fall season, mainly due to Puccinia coronata, Marasmius oreades, Laetisaria fusiformis, Sclerotiniahomeocarpa and Fusarium roseum, which are favored by excessive nitrogen contributions with irrigationwater during the summer. Fungicide applications have been used to prevent and eliminate those infections.

Significant savings in fertilizers cost can be achieved by irrigation with reclaimed water. The savingsachieved at Mas Nou golf course have been calculated assuming that all the nitrogen applied with irrigationwater had to be provided as a mineral fertilizer. Although this may be considered a questionable assumption.particularly in the light of the excess nitrogen applications observed during the summer season, preliminarycost estimations for 1994 indicate that an improved irrigation strategy (using reclaimed effluent during thewinter) has made practically unnecessary the addition of mineral fertilizer while maintaining the golf coursein excellent conditions all year round.

TABLE 5. ECONOMIC VALUE OF ANNUAL FERTILIZER CONTRIBUTIONS BYIRRIGATION WITH RECLAIMED WATER AT MAS NOU GOLF COURSE

Parameter 1991 1992 1993 19943

Nitrogen contribution, kg 5099 4603 6807 1 852Pumped effluent, m3 280100 240700 280200 151 700Economic value, US $ b 33200 25400 27700 9200Unit savings, US $/m3 effluent 0.12 0.11 0.10 0.06

3 The golf course remained closed until July.b Cost of mineral fertilizer and N content have varied over the years.

1 US $ = 130 ptas.

The results shown in Table 5 are based on the nitrogen contribution and the cost of mineral fertilizer for eachyear. As Table 5 indicates, the economic value of nitrogen contributions by reclaimed water have variedbetween US$ 9 000 and US$ 33000 from 1991 to 1994, which represents a unit savings of 0.06•0.12 US $/m3 of reclaimed effluent.

Heavy Metals

The heavy metals content of reclaimed water was detennined during 1992 both in the reclaimed effluent andin the water of both ponds. All metals analyzed (cadmium, chromium, copper, lithium, manganese, nickeland lead) had concentrations lower tha.i the limits recommended for irrigation waters which had to be usedduring a minimum of 20 years (Pettygrove and Asano, 1984; USEPA, 1992). This is in accordance with thepredominantly residential character of the sewerage catchment area.

PUBLIC HEALTH ASSESSMENT

Systematic weekly analyses of indicator bacteria in reclaimed water entering Pond 1 show that faecalc~liforms ~nd faecal str:ptococci concentrations lower than 100 cfu/100 mL can be consistently achievedWIth cWonne doses rangmg from 25 to 45 mg C12/L. When secondary effluent turbidity remains stable and


below 15 NTU, as observed during the summer of 1994, most samples show no detectable faecal coliformsor streptococci colonies in 100 mL, which represents more than 6 log removal for faecal coliforms(see Table 6).

TABLE 6. ANNUAL AVERAGE OF DISINFECTION PERFORMANCE ATCASTELL-PLATJA D'ARO WWTP

Year Effluent type and Faecal coliforms Faecal streptococcidisinfection parameters log cfu/100 mL log cfu/loo mL

1991 Secondary effluent 5.8 4.2Reclaimed effluent 1.1 0.3Average reduction, log 4.7 3.9Chlorine dose, mg ClzL 24 24

1992 Secondary effluent 6.4 4.7Reclaimed effluent < 0.7 < 0.3Average reduction, log > 5.7 > 4.4Chlorine dose, mg ClzL 24 24



Despite these high disinfection rates, a certain regrowth of what seems to be indicator bacteria has beenobserved occasionally in the ponds. Although confirmatory testing for those indicator bacteria-like colonieswas not within the scope of this project, it is suspected that they might be microorganisms other thanindicator bacteria, but able to grow in the selective culture media used, specially in m-FC Broth Base.Although regular tests for Salmonella enterica in secondary effluent were always positive, similar tests inwater from both ponds did never detect the presence of Salmonella enterica, even with regrowth coloniesconcentrations up to 1 000 cfu/l00 mL in f(!ecal coliform tests. It has to be pointed out that sunlightradiation, and daily variations of pH (up to 9,4 in July and August) and dissolved oxygen concentration inthe ponds are unfavorable conditions for the survival of microorganisms originating in the digestive tract ofwann-blooded animals, such as Salmonella enterica and faecal coliforms and faecal enterococci indicators.

To improve the reliability and the disinfection performance of the water reclamation process, a 4 000 m3/daymulti-media two-stage rapid sand filtration process has been designed and it is expected to becomeoperational by the end of 1995. The more stable and lower turbidity values expected in the filtered effluentshould contribute to a more efficient use of the disinfectant while achieving a better and more consistentmicrobiological quality of the reclaimed water (Asano et al., 1991; Asano and Mujeriego, 1994).

AESTHETIC ASSESSMENT

Water extraction from the two storage ponds takes place from the bottom layers, through a pipelineconnected to a nearby wet well, from where it is pumped into the irrigation system. This design arrangementhas resulted in oxygen depletion and odor generation in irrigation water, particularly during the warm period

R. MUJERIEGO el al.

from June to September. To prevent oxygen depletion in bottom layers and its subsequent odor generationand spreading during onset of irrigation, especially in the residential area nearby Pond 1, an electric motor•driven aerator (AIRE-02, Aeration Industries International, Inc., Minneapolis, MN, USA) has been installed;by introducing fine air bubbles directly into the deep layers of the pond (4-5 m) and also by mixing topoxygen-rich waters with bottom oxygen-depleted waters, offensive odors have been totally eliminated.Considering the reliability and efficiency of this device in controlling odors during the summer period, asecond device will be installed in Pond 2 during 1995.

Systematic control of mosquito populations has been achieved with a suspension of enthomopathogenicBacillus thuringiensis var. israeliensis (SKEETAL, Biokontrol Novo Industri NS, Denmark). Mosquitolarvae have been detected particularly during spring and summer in the shores of Pond 1 and the wet wells ofboth ponds. Regular cutting and removal of emerging vegetation on pond sides has proved an effectivemeasure to prevent the spreading of mosquito populations.

MANAGEMENT OF RECLAIMED WATER

Disinfection of secondary effluent was initially (1989-1993) the responsibility of golf course operators, underthe supervision of CCB technical personnel. The -technical requirements of the process and the lack ofreliability of disinfectant supply made quite evident to the Consorci de la Costa Brava the need to discontinuethat management strategy. A contractual agreement was established in 1993 between CCB and Mas Nou golfcourse, by which CCB takes the responsibility of providing reclaimed water of adequate quality and MasNou golf course satisfies the cost of reclaiming the secondary effluent. Included in that cost is an assistanceservice by technical staff of the CCB, by which the water user is regularly informed about the chemical andmicrobiological quality of the reclaimed water (with prompt notice in case of high electrical conductivityvalues) and the estimated fertilization rates achieved by using the reclaimed water, either directly from theplant or from the two storage ponds. Close and regular collaboration with the greenkeeper has resulted in amore favorable attitude to the water quality requirements of reclaimed effluent and a more effective andeconomical fertilization program, preventing the occasional turf overfertilization episodes observed inprevious years. The greenkeeper perception has gradually evolved from a passive acceptance of therequirements of using reclaimed water to a positive recognition of the benefits derived from using thisalternative source of water, that he expresses clearly to golf course visitors, landscape professionals andmanagers of golf courses interested in irrigation with reclaimed water.

Based on this demonstration project, and following well established criteria (Asano and Mills, 1990; Richardand Crites, 1994), the CCB has prepared a preliminary water reclamation and reuse program for the 1995-98period, covering specific areas of 16 municipalities of Costa Brava, with the objective of promotingagricultural irrigation, golf course irrigation, landscape irrigation and environmental restoration of rivers andwetlands. The maximum annual flow of secondary effluent expected to be reclaimed by 1998 is 15 hm3/year,which would be applied to 2 600 ha of agriculture and landscape land.

CONCLUSIONS

Salinity of reclaimed effluent is an essential quality parameter to be considered when planning a landscapeirrigation project. Completion of a new surface water transfer to the study area resulted in EC values insummer effluent of 1.2-1,5 dS/m, more adequate than the 2-4 dS/m previously observed.

A new water and pond management system has been proposed to optimize water and nutrients application:the source of irrigation water should be the s.ame ~or the all the golf course turf, and it should be possible tochoose the most adequate water source at a given time among those available at the golf course.

The relatively low iron contributions of reclaimed water, as compared to those of nitrogen and phosphorus,


have resulted in occasional spots of ferric cWorosis. Those incidents have been recovered with localizedapplicat~on of iron compounds. Plot trials with iron sulfate (7 g FeS04/m2

, 18,5% Fe) and iron chelates(10 g/m , 6% Fe) on turf areas affected by ferric chlorosis have shown an evident recovery in approximatelytwo weeks.

Some fungal infections have been observed in the fall season, favored by excessive nitrogen contributionswith irrigation water during the summer. Fungicide applications have been used to prevent and eliminatethose infections.

Significant savings in fertilizers cost can be achieved by irrigation with reclaimed water. Assuming that allthe nitrogen applied with irrigation water had to be provided as a mineral fertilizer, the economic value ofnitrogen contributions by reclaimed water have varied between US$ 9000 and US$ 33000 from 1991 to1994, which represents a unit savings of 0.06-0.12 US $/m3 of reclaimed effluent.

Faecal coliforms and faecal streptococci concentrations lower than 100 cfu/lOO mL can be consistentlyachieved with chlorine doses ranging from 25 to 45 mg C12/L. When secondary effluent turbidity remainsstable and below 5 NTU, most samples show no detectable faecal coliforms or streptococci colonies in100 mL. Although regular tests for Salmonella enterica in secondary effluent were always positive, similartests in irrigation water did never detect the presence of Salmonella enterica.

Mechanical introduction of fine air bubbles directly into the deep layers of a pond provides a practical andeconomical alternative for mixing top oxygen-rich waters with bottom oxygen-depleted waters, preventingodor problems during onset of irrigation. Mosquito populations has been systematic control with asuspension of enthomopathogenic Bacillus thuringiensis var. israeliensis.

Close and regular collaboration with the golf course greenkeeper has resulted in a more favorable attitude toreclaimed water quality requirements and a more effective and economical fertilization program.Greenkeeper perception has gradually evolved from a passive acceptance of using reclaimed water to apositive recognition of the benefits derived from using this alternative source of water.

ACKNOWLEDGMENTS

This study was financially supported by the Junta de Sanejament of the Generalitat de Catalunya, and theConsorci de la Costa Brava. The authors are grateful to the Castell Platja d'Aro WWTP staff, the Mas Nougolf course management and personnel, and the research assistants Joan Garcia, Jordi Sala and SandraMartinez for their assistance and collaboration since the beginning of the project in 1989.

REFERENCES

Asano, T. and Mujeriego, R (1994). Water quality guidelines for water reuse. In: Bios6lidos y aguasdepuradas como recursos, Ed. by R Mujeriego and L. Sala. Consorci de la Costa Brava. Girona,Spain.

Asano, T, Richard, D., Crites, RW., and Tchobanoglous, G. (1991). Evolution of tertiary treatmentrequirements in California. Water Envir. and Techn., 4 (2): 36-41.

Asano, T. and Mills, R (1990). Planning and analysis for water reuse projects. Journal of the AmericanWater Works Association, 82 (1).

Crook, J. (1991). Quality Criteria for Reclaimed Water. Water Sci. and Techn., 24(9): 109-121.Hayes, A.R, Mancino, C.F., Forden, W.Y., Kopec, D.M., and Pepper, I.L. (1990). Irrigation of turfgrass

with secondary sewage effluent: n. Turf quality. Agron. J., 82: 943-946.Mancino, C.F. and Pepper, Ian L. (1994). Irri!(ation of turfgrass with wastewater. In: Wastewater Reuse for

Golf Course Irrigation. Lewis Publishers, Chelsea, Michigan.

R. MUJERIEGO el al.

Mujeriego, R, Sala, L., Garcia, J., and Carbo, M. (1994). Gestio de l'aigua residual regenerada empradaper al reg del camp de golf Mas Nou (IV). 4a Memoria del Projecte de Demostraci6 conjunt entre laJunta de Sanejament, el Consorci de La Costa Brava, la Secci6 d'Enginyeria Sanitaria i Ambiental deLa Universitat Politecnica de Catalunya i la Zona Residencial Mas Nou.

Mujeriego, R., Sala, L., and Turet, J. (1993). Nutrient losses in two landscape ponds used for golf courseirrigation. Second IAWQ International Conference on Waste Stabilization Ponds and the Reuse of PondEffluents, Berkeley, USA.

Pettygrove, G.S. and Asano, T. (1984). Irrigation with Reclaimed Municipal Wastewater - A GuidanceManual. Lewis Publishers, Inc.

Richard, D. and Crites, W.C. (1994). Planning for a major water reclamation program: balancing costswhile building consensus. In: Biosolidos y aguas depuradas como recursos, Ed. by R Mujeriego andL. Sala. Consorci de La Costa Bruva. Girona, Spain.

Sala, L., Turet, J., and Mujeriego, R (1994). L'tis de l'aigua regenerada per a la fertirrigacio: efectes del'emmagatzematge en llacs. IV Trobades de Biotecnologia de l'Euroregi6, Toulouse.

US. EPA and US. AID (1992). Manual on Guidelines for Water Reuse. EPA/625/R-92/004. September1992. Center for Envir. Res. Inform. Cincinnati, Ohio.

agronomic and public health assessment of reclaimed water quality for landscape irrigation

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