Generally speaking, environmental valuation techniques are of two types: those relying on revealed preferences or what humans actually do in the markets; and those relying on stated preferences or what humans say they would do in a hypothetical market context. Thus both of these approaches attempt to evaluate human behavior in economic terms but they differ in the sense that the former is based on actual or observed behavior while the latter is based on potential or likely behavior.
As the revealed preference methodologies are based on actual expenditures, they, however, are better able to predict the underlying human preference structure though data difficulties and statistical problems can affect the quality of results.
The revealed preference techniques include production cost analysis (applied to a wide range of impacts including crops, livestock, forest, and ecosystem), travel cost method (applied mainly to recreation demand studies), defensive/averting cost analysis (applied to healthcare studies) and hedonic price analysis (used for property prices and attribute analysis).
Where wastewater irrigation leads to a measurable change in quantity, quality or cost of production, the resulting change can be measured in monetary units using market or shadow prices.
This is called production cost analysis. The travel cost method seeks to quantify the value of travel time and out of pocket or actual travel expenses to provide a measure of the value people place on leisure activities such as angling and sight-seeing. The health effects resulting in morbidity and mortality can generally be quantified by using human capital approach and defensive/
preventive cost analysis. The value of output foregone due to mortality (pre-mature death) or morbidity (sickness) is a proxy for human productivity loss to which actual cost of medical visits, defensive expenditures, and inconvenience cost can be added to derive a cumulative measure of health effects. The mortality-related productivity loss or the value of human statistical life is estimated to be 120 times GDP per capita (Miller 2000). Sickness-related expenses could be calculated from clinical and personal records.
The hedonic price analysis seeks to decompose property prices into: component attributable to property characteristics such as size of the plot, number of rooms, parking spaces, type of heating, north/south aspect, land tax, utility rates, and proximity to civic facilities; and component attributable to environmental variable such as proximity to a landfill or hazardous waste site. Thus the willingness to pay higher property price for being located away from the waste site, for comparable property characteristics, represents the price premium of discomfort associated with proximity to waste site.
The stated preference methodologies, commonly called contingent valuation techniques, are based on surveys where humans are directly questioned by the researchers to place monetary values on goods and services normally not sold in the common market place. Thus, contingent valuation method seeks to replicate hypothetical market conditions to elicit consumer preferences about non-marketed goods: that is, how would they behave if the goods in question were actually sold in market. The consumer preferences are sought either in terms of willingness to pay (WTP) or willingness to accept (WTA). Sometimes, a variant of the contingent valuation method, such as Delphi technique, is used for valuation purposes where experts, instead of consumers, are approached to seek their opinion about a particular environmental resource or issue (Edward-Jones et al. 1995). Contingent valuation techniques can be used to evaluate a number on nonmarketed public or environmental goods such as water quality and quantity improvement projects, natural resource conservation projects, assessment of natural resource injuries such as water pollution
due to hazardous waste or oil spills, enhancement of environmental quality, ecosystem change, and endangered species conservation etc.
The environmental valuation techniques seek to place monetary values on both marketed and non-marketed goods and services and environmental resources: that is; everything in dollars. Hence, the ensuing ethical concerns with the use of contingent valuation method have, lead to the evolution of two nonmonetary approaches to valuation: conjoint analysis; and habitat equivalency analysis (Braden 2000). The habitat equivalency analysis seeks to identify which bundle of natural resources are considered equal to the other damaged resources for example, by the public. No attempt is made to determine their relative importance to the humans, even in physical terms. The conjoint analysis, on the other hand, goes a step further and seeks to: (1) quantify the equivalence in terms of physical units; and (2) assign relative importance in terms of human preference structure.
However, both habitat equivalency analysis and conjoint analysis do not attempt to translate physical units into monetary terms.
The prohibitively high costs of conducting a contingent valuation study has lead researchers to look for existing studies in literature that are sufficiently comparable to the case under question and use the findings of these studies to make inferences about the new situation. This technique called Benefit Transfer, presents a promising valuation alternative in situations where data are hard to come by and public agency has to make strategic policy decisions.
A detailed description of the valuation techniques, their application, and problem areas can be found in appropriate text such as James (1994), Hanley and Spash (1993), and Pearce and Turner (1990).
Annex 2. Summary of Empirical Evidence on Public Health Effects of Wastewater Reuse
RECENT EMPIRICAL EVIDENCE ON PUBLIC HEALTH IMPACTS OF WASTEWATER REUSE
Year and Main Objective Methodology Major Findings Implications
Author(S)
Shuval et al. A comprehensive Health risk • Pathogenic microbes in high to low •Proposed guidelines (1986) review of credible assessment model disease risk order are: helminths, for unrestricted
epidemiological and empirical bacteria, and viruses. wastewater irrigation studies on waste- evidence. •Epidemiological evidence suggests viz: 1 nematode egg/l water irrigation. that prevailing wastewater irrigation and 1000 coliform per
standards were overly restrictive. 100 ml.
•Basis for WHO health guidelines.
Brosnan and Impact of cumula- Water sampling •Decline in coliform conc as the results •Water quality O’Shea (1996) tive abatement of and analysis of abatement in wastewater discharges. improvements.
untreated waste- to monitor •Major stimulus: Clean Water Act. •Enhanced recreational water discharges on concentrations of •Affected through: infrastructure resource value.
coliform concentra- total coliforms provision and improvements •Cost savings on tions (concs.) in and fecal such as: construction, upgrading, bathing advisories.
lower Hudson- coliforms. increased surveillance, and maintenance Raritan Estuary. of wastewater distribution system.
•Abetment of illegal connections, wet weather overflows, and reduced discharge.
Olivieri et al. Assessment of Indicator organisms,•Secondary treatment using water •Water Hyacinth (1996) potential health and chemical risk hyacinths plus advanced treatment system as treatment
risk associated assessment of raw generates reclaimed water of alternative.
with potable use water supply vs acceptable potable quality. •Community attitude of advanced treated reclaimed water. •Health risk associated with. to potable reuse?
wastewater. Baseline •Potable use of reclaimed • Financial and
epidemiological water is < existing water supply economic feasibility .
data on reproductive in San Diego.
health and neural tube defects.
Downs et al. Risk screening Risk assessment •High total coliforms in surface •Pathogenic risk (1999) from exposure to based on detection water and lower levels in groundwater. intervention should
contaminated of pathogens, •Fecal contamination of water be a priority.
surface water and ingestion, and resources as a potential risk of •Nitrate pollution risk groundwater due morbidity patterns gastrointestinal disease determination and
to untreated waste- irritation reported. possible treatment.
water irrigation in •Infants and children at risk from.
Mexico. •Frequent diarrhea and skin
nitrate pollution.
•Risk exists outside and inside irrigation district.
Cifuentes et al. Risk factor affecting Household •Children have highest prevalence •Provision of primary
(2000) giardia infections in exposure to of infection. health care and
agri. population in untreated •Risk of infection corelated to •W/water treatment Mexico. wastewater vs unprotected drinking water and facilities.
rain-fed agri. lack of faeces disposal facilities. •Equity and human villages. • Untreated wastewater exposure has no capital formation
excess risk. issues.
•No risk from agri activities.
Habbari et al. Transmission of Disease prevalence •Ascariasis prevalence five times •Adequate treatment (2000) geohelminthic rate in kids in higher in wastewater-impactedregions. of wastewater for
infections among communities with •Contact with wastewater and irrigation.
(primary school) raw wastewater wastewater irrigated land and public •Water supply and children due to raw irrigation vs. no water supply associated with higher sanitation program.
wastewater irrigation raw wastewater infection rates. •Exposure control.
in Morocco irrigation •Trichuris infection rate did not vary. •Public health Role of defensive •Raw wastewater use in Beni-Mallal can education program.
behaviors and lead to a high risk of demographic factors geohelminthic infections.
Annex 3. Summary of Empirical Evidence on Effects of Wastewater Irrigation on Crops
EMPIRICAL EVIDENCE ON EFFECTS OF WASTEWATER IRRIGATION ON CROPS
Year and Main Objective Methodology Major Findings Conclusions/ * ESD
Author(s) Implications Assessment
Day et al. Effect of treated municipal Well water+normal Wastewater irrigation Treated w/w: a +ve$$
(1975) wastewater irrigation on NPK dose vs. well leads to: potential source of +ve♠♠
wheat growth, yield and water+simulated NPK • Higher wheat grain yields. irrigation water plus NA♣♣
quality parameters. dose vs treated • Higher protein content in grains. a rich source of +ve∅
wastewater, no • No change in total fiber content fertelizer.
fertilizer. and thus feed quality. • Fertilizer cost Wastewater supplied more savings.
PFN than control thus Higher potential giving more tillers and yields.
higher yield and protein content.
Mortvedt Effect of Zn and Cr Soil application of high • Higher corn forage yields • Irrigation with +ve$$
and contamination (high Zn and Cr municipal (in general). tannery wastewater -ve♠♠
Giordano in tannery wastewater) wastes. Successive • Zn available to maize. under careful +ve♣♣
(1975) on maize crop. maize crop vs control. • Lower Zn concentrations management may +ve∅
and no change in Cr conc. be possible.
in maize tops.
• Cr uptake but no effect on crop growth.
Sidle et al. Uptake of heavy metals by Wastewater irrigation • Higher Cu and Zn conc. • Animal feed +ve$$
(1976) reed canary-grass and for 11 years. and total uptake in reed program (Cu level -ve♠♠
maize over time. Base year as control. canary-grass. in w/w irrigated -ve♣♣
•Lower Cu and Zn conc. and r-grass may be -ve∅
total uptake in Maize than a problem for reed canary-grass. sheep feed).
• Highest heavy metal • Loadings+ removal accumulation in soil sown @ modeling to r-grass.(low removal rate). evaluate life of a
•Plant conc. of Cu and Zn do land disposal sys.
not pose hazard to food chain.
•Heavy metal removal through crop plant uptake.
Day and Effect of treated municipal Well water+ normal Wastewater irrigation lead to: • Treated w/w: a +ve$$
Tucker wastewater irrigation on NPK dose vs. well • Higher leaf length (more potential source +ve♠♠
(1977) sorghum growth, yield and water+ simulated NPK forage) and maturity period. of irrigation NA♣♣
quality parameters. dose vs treated (low cropping intensity). water plus a rich +ve∅
wastewater, no fertilizer. • Higher sorghum grain yields. source of fertilizer.
• Similar protein content, but • Fertilizer cost
•Less amino acid content in savings.
Bole and Suitability of five forage Lagoon treated municipal • Higher alfalfa yields than other • w/w supplied enough +ve$$
Bell species for optimal wastewater. grass sp. P but not N for +ve♠♠
(1978) utilization of municipal Relative growth • Double N-yield of alfalfa. forage production. -ve♣♣
wastewater irrigation and nutrient utilization. • N uptake by all grass, except • A system of forage +ve∅
system for forage Efficiency of: alfalfa, wheat-grass, exceeds sp. such as alfalfa
production. reed canary-grass, brome- w/w N supply. and reed
canary-grass, wild rye, and tall • P supply in w/w exceeds plant grass may be
• For optimal utilization of waste- utilization and water, alfalfa is most suitable disposal of w/water.
forage crop (max. N and water uptake). Alfalfa can optimize w/w utilization as it has its own N supply system (nodules).
•For optimal wastewater disposal, reed canarygrass is more suitable as it can remove most nutrients and withstand flooding.
Marten Effect of municipal waste- Parameters: feed quality, • Maize more digestible than • Perennial grasses +ve$$
et al. water irrigation on feed dry matter, digestible . r-grass. have superior quality +ve♠♠
(1980) quality and yields of maize Dry matter of maize • Higher dry matter and digestible than maize to -ve♣♣
vs reed canary-grass. vs r-grass. dry matter yields for maize. remove w/w +ve∅
Two rates (levels) of • Differences decline progressively nitrogen treated municipal with higher amounts of w/w • A managed r-grass wastewater irrigation. applications in maize. and maize sys.
•Higher crude protein in r-grass, and can be used for
•Higher crude protein yield per efficient renovation
hectare. of w/w effluent
Ajmal and Effect of textile factory • Untreated textile • Textile effluent rich in BOD, • Diluted textile +ve$$
Khan effluents on soil effluent in dilutions COD, Cl, SO4, and trace effluent may be used +ve♠♠
(1985) chemistry, and of v/v 25, 50, 75, metals such as Ns, K, Ca, for crops without NA♣♣
germination and growth and 100% vs Mg and highly alkaline. affecting soil quality +ve∅
of two vegetables viz • Normal irrigation • Higher dilution applications • Textile effluent. as kidney beans and lady’s water as control led to higher conc. of a source of water
fingers. • Effect on kidney these elements in soil and nutrients
beans and lady’s with top-soil conc. • Industrial policy
fingers higher than subsoil. design
•Plant Na increased
Ali Risk assessment of • Sprinkler application of • Non detectable fecal • Scientific evidence +ve$$
(1987) reclaimed municipal secondary treated + coliforms on summer squash for wastewater +ve♠♠
wastewater for chlorinated w/w after 24 hours of sprinkler reuse guidelines NA♣♣
irrigation of food crops • With and without irrigation. for KSA +ve∅
such as alfalfa, onions, fertilizer treatments • Nondetectable fecal coliforms • Middle of the road summer squash • Fecal coliform counts on onions after 15 days of approach with
on vegs. irrigation. flexible permit
• Secondary treated wastewater + sy. for w/w irrigation chlorination may be used for
Singh Effect of urea plant • Untreated urea plant • Highly alkaline urea • Urea factory effluent +ve$$
and effluent on soil effluent in dilutions plant effluents. as a source of -ve♠♠
Mishra and germination, of v/v 2.5, 5, 10, • Chemical properties of soil liquid fertilizer. -ve♣♣
(1987) growth, dry matter, and 50% vs Tap water adversely affected by • Diluted fertilizer +ve∅
and pigment contents irrigation as control by effluent conc. of >10%. industry effluent
of corn and rice • Higher growth and protein content may be used for
of corn and rice with 2.5 and 5% crop irrigation.
effluent conc. (N absorption and • Point source
utilization). pollution control.
•Adverse effect on seed • Eutrophication control.
germination, dry matter and pigment contents, and yield of both rice and corn for effluent applications with conc. > 10%.
Misra and Effect of paper industry Untreated paper • Germination %, growth, and • Pollution regulation -ve$$
Behera effluent on growth, industry effluent pigment, carbohydrate, and for pulp and paper -ve♠♠
(1991) carbohydrates, and Various dilutions vs protein contents decline with industry. NA♣♣
protein content of rice distilled water increase in effluent conc. • Evaluation of -ve∅
Effect on rice seedlings and exposure time. phytotoxicity and as a function of effluent • Protein content most sensitive pollution risk.
con and exposure time. to effluent conc. • Point source.
• Protein and protein enzymes as pollution control.
bioindicators of effluent • Eutrophication
phyto-toxicity. control.
• Pulp and paper industry effluent not suitable for irrigation.
Aziz et al. Effect of crude oil Treated oil refinery • Treated oil refinery w/w met • Treated wastewater +ve$$
(1995) refinery wastewater wastewater vs ground- irrigation standards, hence has no adverse effect -ve♠♠
irrigation on growth water as control. suitable for crop irrigation. on soil quality and -ve♣♣
and yield parameters Same dose of fertilizer • Wastewater irrigated soil show can be used for -ve∅
of four varieties of Growth p-meters: no change in soil properties. crop irrigation.
wheat. shoot length, leaf#, fresh • Higher growth, protein, • Need for long-term and dry weight/plant carbohydrate, and grain yield impact evaluation.
Yield p-meters: grain yield, with wastewater irrigation. • Industrial pollution protein, and carbohydrate • Better crop performance due abatement policy.
contents. to availability of additional • National food security nutrients in treated w/w. policy.
• Varied response of wheat cultivars.
Aziz et al. Long-term effects Treated oil refinery • Treated oil refinery w/w met • With out crops, +ve$$
(1996) of petrochemical wastewater vs. irrigation standards, hence fixing of heavy -ve♠♠
refinery wastewater Lake water as control for suitable for crop irrigation. metals in soil may -ve♣♣
irrigation on heavy 8 years •Negligible accumulation of pose future threat -ve∅
metal accumulation Same dose of commercial heavy metals in soil and grains of food chain in soil and grain fertilizer • Grain metal content below transfers.
and yield parameters Effect on soil permissible limit, thus seed fit • Industrial pollution of six cereals and Effect on seed yield of for human consumption. abatement policy.
legumes viz. wheat, crops • Higher seed yield for all • National food
triticale, chickpea, crops, except moong, security policy.
lentil, pigeon pea, with w/w irrigation.
and summer moong.
Howe Effect of paper mill Untreated paper • Biomass production of c-wood • Problem: Na +ve$$
and wastewater irrigation industry wastewater affected by gypsum application accumulation in -ve♠♠
Wagner and gypsum application with not pH. paper mill effluent -ve♣♣
(1996) on growth rates and Four gypsum application Stem biomass dependent irrigated soils; -ve∅
sodium uptake by Freser rates ww 100, 175, 325, on pH. Management action:
cottonwood and soil 625 mg Cl/l w/w on ww • Higher growth of c-wood gypsum application.
water pH and gypsum • Stem and leave Na conc. w/w irrigation application rate affected by gypsum application management . Dep. variables for rate, not w/w pH. • Potential long-cottonwood: biomass, • Infiltration rate affected by term effects need stem Na, and Ca, K, and both gypsum application and attention.
Na in leaves w/w pH.
El Hamouri Effect of wastewater Domestic origin waste- • WSP treatment produces effluent • Treated w/w irrigation +ve$$
et al. irrigation on micro- water with: of WHO’s guidelines quality for instead of groundwater +ve♠♠
(1996) biological quality of Raw wastewater vs unrestricted irrigation. for growing salt -ve♣♣
soil and yield and waste stabilization. • For salt sensitive crops: cucumber sensitive crops in arid +ve∅
hygienic quality of Pond treated w/w vs yield is worst affected by high salinity; and saline areas has salt-sensitive (cucumber, groundwater. negative yield effect is more for advantages viz: low turnips) and salt tolerant Four irrigation methods raw w/w and less for treated salinity effect on (alfalfa, corn, zucchini, (surface, 2 sy. drip, w/w, thus . growth and yield, beans, tomato) crops. sprinkler). • High salinity of w/w affects low soil and aquifer
Fecal coliform and yield negatively. salinization, fertilizer helminth eggs on crop • For salt tolerant crops: small cost savings.
and in soil. differences in yield among w/w • Arid and saline zone types and groundwater, thus. development policy.
• Much lower salinity effect. • Wastewater treatment
• No helminth eggs found on technology.
treated w/w irrigated crops and soils.
• Helminth eggs found on raw w/w irrigated crops and soils.
• Raw wastewater not suitable for irrigation.
• Drip irrigation gives highest performance and crop yield.
Shahalam The suitability of Treated wastewater • Yield trends: • No risk to crops, +ve$$
et al. wastewater irrigation below WHO standard • Alfalfa: freshwater with fert. soil, humans or +ve♠♠
(1998) for alfalfa, tomato, vs standard freshwater. > w/w with fert. environment from NA♣♣
and radish crops and With and without fertilizer• Radish: w/w use insignificant below guidelines +ve∅
and radish crops and With and without fertilizer• Radish: w/w use insignificant below guidelines +ve∅