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Analysis of water quality criteria in Mexico
~ Pergamon
Wat Sci Tech. Vol. 40. No 10. pp. 169-175. 1999
Pubhshed by Elsevier Science Ltd on behalf of the IAWQ Pnnted in Grelll BOlain. All righls reserved 0273-1223/99 S20.00 + 0.00
PH: S0273-1223(99)00683-6
ANALYSIS OF WATER QUALITY CRITERIA IN MEXICO B. Jimenez, J. Ramos and L. Quezada Instituto de Ingenieria, UNAM, Apdo postal 70-472. Coyoacan 04510. Mexico. D. F.
ABSTRACT During the last decade, it has been acknowledged that, at national level. the availabIlity of water is a trade-off between its temporary and spatial distributIon as well as contammation problems. This situation has urged the Mexican Government to revise the plans and programs for the integrated management of hydric resources by analysing the instItutional system, the legal frame and its effectiveness. Within this context, an essential aspect is to ensure the ordering of the uses and exploitation of water resources. This paper shows that a revision of the effectiveness and apphcability of the current water standards and laws is essential to satisfy the demands, and to have control over the different uses of water (drinking water for human consumption, the use of water for agncultural, municipal, industrial related actlvllles and other purposes). Therefore, in this work. a redefinition of the Ecological Crileria of Water Quality has been proposed. The proposal establishes the Quality Criteria under a new perspective. wherem the set of parameters and their values constitute the goal of quality, in the sense that any type of waler with such characteristics or better ones. cannot only be used as it is. but constitutes the most SUitable water for such use. iC 1999 Pubhshed by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved
KEYWORDS Drinking water; normativity in Mexico; quality criteria ofwater; water uses. INTRODUCTION In the past few years, the availability of water at national level has been a trade-ofT between its temporary and spatial distribution as well as contamination problems. This situation has urged the Mexican Government to revise the plans and programs for the integrated management of hydric resources by analysing the institutional system, the legal frame (consisting of the Ecological Equilibrium and Environmental Protection General Law; National Waters Law and its Regulations; the Federal Law Fees annually updated; the Federation Income Law and the Hydraulic Infrastructure Federal Public Works Betterment Contribution Law) and its effectiveness. Within this context, a fundamental aspect is to ensure the ordering of the uses and appropriate use of water resources. Regarding water use, some policies and strategies have been stated which have stimulated changes in the use of water, these rectify balances according to needs, state priorities and are orientated towards finding alternative supply sources. In the hydraulic policy the reinforcement of the institutional capability of the water sector is emphasised. inclUding the modernisation of the legal frame and the related institutions. the updating of specific hydraulic policies, the improvement of information systems, the technical and administrative procedures. as well as the development of an improved technical and professional capability of the persons and organisations that participate in this sector. 169
170
B. nMENEZ et al.
Specifically, the government is concentrating its efforts as follows: a) To define the goal to be achieved for water quality for every water body in the country. b) To regulate the preservation of the aquifer quality, which is the main human consumption water supply source. c) To regulate the contamination generated by non-point sources. d) To consider the problem of water contamination from rainfall and the dilemma of using comined drainage. e) To develop the management capacity of the government to implement and measure water quality. f) To establish common parameters which allow the identification of how discharge regulation improves the quality of water bodies. In order to satisfy the demands and to keep control over the water activities, full evaluations of the situation must be performed; to know the quantity, quality, demand and uses (water for human consumption and for agricultural, municipal, industrial and other purposes). For this, the effectiveness and applicability of the current water regulations and laws must be analysed, including the documents granting attributions, obligations and responsibilities to the entities of the sector. This will ensure the management of hydric resources in a sustainable and integral way. One of the regulations of special interest is the Ecological Criteria of Water Quality (Criterios Ecol6gicos de Calidad del Agua, CECA). In Mexico as well as other developing countries, the need to qualify water for a specific use is established by the CECA. However, the selected parameters are not appropriate for the needs of the country. The criteria do not define very well the responsibilities in the case that the quality of the water body is not suitable for its use. The reasons for this were mainly political rather than caring for human health. In consequence, the CECA selected a large number of parameters from international regulations where the economical and technological situation were different to the Mexican ones. In addition, the parameter values were so strict that the levels were only reached a few times with the treatment systems available. During the development of the quality criteria it was realised that there was a trade-off between trying exhaustively to define the parameters (which, in fact, it is impossible to do since there are more than 70,000) and to select a set suitable for the countries problems, which are easy to be measured, controlled and followed in a reasonable way. In addilion, their presence should not endanger the use of water. In general, the selection of parameters and values is mainly focused on the protection of public health. Thus, it is essential to establish priorities according to the actual needs and to formulate the criteria according to the economical and technological situation of each country. In theory, the establishment of standards must be based on security, logic, scientific advances and the goal to achieve a measure or estimation of the benefit, whilst minimising the risk at a specific cost. In practice, it is not so easy since the risks and benefits are not known. In the developed countries, to have very strict values results from the pressure ofthe ecological groups. Sometimes, this results in the adoption of standards based on political reasons rather than a scientific or logical reasoning. Most of standards in Europe and America are extremely demanding and the problem to be faced by developing countries is that to copy such values or parameters without analysing the context under which they have been selected is not appropriate. To allow a transcription of the standards already developed for countries with different realities results in implementation of improper and unaffordable technologies, which are not actually translated into desirable objectives. For example, for developed countries to restrict the concentration of nitrogen is easy and affordable, since they have already controlled the DBO, but to apply this to the undeveloped countries is unaffordable and truly insignificant in view of some other problems.
Analysis of water quality criteria in Mexico
171
METHODOLOGY Water Uses The use of water, including extraction and discharge, limits the activities carried out at different levels, for example, at local, regional or international level. Table I shows the compounds that restrict water use. Table 1. Limitation of the water potential uses due to quality degradation Pollutant Drinking Aquatic wildlife, Recreation water fisheries XX XX XX
Pathogens Suspended solids XX XX X Organic matter XX X X Xi Algae X'·· XX Nitrate X X NA Salts' X XX NA Trace elements XX XX X Organic mlcropollutants XX XX X ACidification X XX X XX Marked Impairment causmg major Ireannent or excludmg the desired use. X Minor impairment. NA No applicable. + Degraded water quahty may be beneficial for this specific use. ? Effects not yet fully reahsed.
Uses Irrigation X
X + + + XX
X X
1. 2. 3. 4. 5. 6. 7.
8. 9.
Industrial uses XXi X XX'
XX' XX' XX' X ? X
Power and cooling X
Transport
X'
NA
X'
X' NA NA NA NA X
NA
XX'
X'
NA NA NA NA NA
Food industries. Abrasion.. Sediment settling in channels. Electronic industries. Filter clogging. Odour and taste. In fish ponds higher alga biomass can be accepted. Development of water hyacinth. Ca, Fe, Mn in textile industries, etc.
Adapted from: Chapman, 1992.
The selection of variables to evaluate quality of the water is carried out according to the objectives to be fulfilled in order to ensure its quality for use. A proper selection allows the certainty of an efficient and lower cost use. Each variable must be analysed taking into account the sources, its performance and transformation in the aquatic media, the intervals observed in natural and contaminated waters, its persistence in the same and its handling during the treatment. In addition, it is important to select variables taking into consideration the availability of the analytical methods, the equipment, reactives and personnel available. The level of accuracy and sensitivity must also be considered as criteria Analysis of water Quality criteria jn Mexico In 1989, the National Water Commission (Comisi6n Nacional del Agua) elaborated the Water Use Ecological Criteria (Table 2). In these criteria, the Ecological Equilibrium and Environmental Protection Law gives the power to the Urban Development and Ecological Secretariat to formulate the ecological criteria to be observed for the application of an ecological general policy, paying special aUention to the rational utilisation and prevention, and control ofwater contamination, as well as the aquatic flora and fauna protection. For such purposes, the ecological criteria of water quality were defined. In these criteria, the levels of the parameters and the substances found in the water, their effects and allowable levels are specified. Thus, the relevant authorities will be able to qualify the water bodies as apt to be used as a supply source of drinking wat~r, in entertaining activities with primary contact, for agricultural irrigation, for pecuniary use, for aqulculture use, or for the development and conservation of aquatic life. Such parameters constitute the minimum required quality for the use of water resources in the cases previously mentioned.
172
B. JIMENEZ et a/.
Table 2. Water quality ecological criteria of uses F USES A B D C E In mgll, except when other unit Is ndlcated. Inorganic parameters Alkahnity (as CaCO,) (I) 400 (I) Aluminium 0.2 0.02 5 5 0.05 Antimony 0.09 0.1 0.1 O.04(a) Arsemc 0.05 0.2(a) 0.2 0.1 Asbesto (as FibreslL) 3000 Banum 0.5 I 0.01 Beryllium (III) 0.1 0.00007 0.001 Boron 0.009 I 5 0.7(V) Cadmium 0.0009 0.01 0.01 0.02 (VI) Cyamde (as CN') 0.001 0.02 0.02 0.02 0.005 Chlorine residual 0.0075 0.011 Chloride (as Cn 250 147.5 250 Copper 0.003 I 0.5 (VII) 0.2 Chromium hexavalente 0.05 0.05 I 0.01 I Iron 0.3 0.05 5 I Fluorides (as F") 1.5 1 2 0.5 I Phosphates (as POl') 0.1 (IX) 0.002 Phosphorus elemental 0.0001 0.0001 Manganese 0.1 Mercury (Hg) 0.001 0.003 0.00002 0.00001 Nickel 0.01 I 0.2 0.008 (X) Nitrates (NO,') (as N) 5 90 0.04 Nitrites (N02') (as N) 0.05 0.002 10 Ammonia (as N) 0.01 0.06 Dissolved oxygen 4 5 5 Silver 0.05 0,002 (XIV) Lead 0.05 5 0.1 (XV) 0.006 Selenium (as selenate) 0.01 0.02 0.05 0.4 0.008 500 Sulphate (as SOl) 130 0.005 Sulphide (as H2S) 0.2 0.002 0.002 0.01 Thallium 0,01 0.02 2 50 (XVII) 0.09 5 Zmc USE A: Human consumption supply. USE B: Recreate use. USE D: Livestock. USE E: Freshwater aquatic hfe Primary contact. USE C: Agricultural USE F: Manne aquatic life N.C.: Natural condillons : Like As: Comhmed hmll (III) For continuous irrigation, a maximum of 0.1 mgIL and for alkaline and flOe texture soils a maximum of 0.5 mglL. (IV) Boron sensitive cultures. a maximum of 0.75 mgIL; others, up to 3 mgIL. (V) The 4-day penod average concentration of cadmium in IlgIL must not exceed more than one time every 3 years the value of the followmg equation: C(llgIL)-exp(0.7852[In(hardness)]-3.49) Hardness=rngIL as CaCO, (VI) The 4-day period average concentration of copper in IlglL must not exceed more than one time every 3 years the value of the following equation: C(llglL)·exp(0.8545[ln(hardness))-1.465) Hardness=rngIL as CaCO, (IX) In influents of reservoirs. phosphorus must not be over 0.05 mgIL; within the reservoir, lower than 0.0059 mgIL; and for the rivers up to 0.1 mgIL. (X) The 4.day period average concentration of nickel in IlglL must not exceed the numeric value in the following equallon: Ni(llgIL)·exp(0.846[In(hardness)]+1.645) Hardness-mgIL as CaCO, (XIV) The silver concentration in giL must not exceed the numeric value provided by the following equation: Ag(llglL)-exp(\.72[ln(hardness)]-6.52) Hardness-mgIL as CaCO, (XV) The 4-day period average concentration of lead in IlgIL must not exceed more than one time every 3 years the numeric value in the following equation: Pb(llgIL)·exp( 1.273[ln(hardness)]-4.075) Hardness-mgIL as CaCO, (XVII) The 4-day penod average concentration of zinc in IlgIL must not exceed more than one time every 3 years the numeric value 10 the following equation: Zn(llgIL)-exp(0.8473[ln(hardness)]+10.3604) Hardness=rngIL as CaCO, (XVIII) The total dissolved gas concentration must not exceed 1.1 times the saturation value under the prevailing hydrostatic and atmospheric conditions. (XIX) With conventional treatment (coagulation, filtration and disinfection). SOURCE: ECOLOGICAL CRITERIA OF WATER QUALITY PUBLISHED IN THE FEDERAnON OFFICIAL GAZETTE, 13'" OF DECEMBER, 1989.
Analysis of water quality criteria in Mexico
173
As observed, five groups were identified for six uses amounting to 126 parameters. Table 2 shows only the inorganic parameters group. The uses of drinking water supply and aquatic life protection have the highest number of parameters with guideline values. The analysis of quality criteria determines that: •
In relation to the listed parameters, it is important that the Mexican criteria conform to the 56 parameters of the Quality Criteria established by the EPA in 1972, with more strict values in 68% from the total. Equally, it is worth mentioning that after identifying the toxic substances regulated by the EPA in 126 compounds listed in 1978, Mexico considered 71 (77%) parameters as suitable to be standards to regulate water quality.
These considerations generated problems relative to the effectiveness to reach and measure the proposed values. Therefore, it is necessary to revise the listed parameters in the Mexican criteria so that the parameters established in the developed countries are not selected since they do not necessarily constitute a substantial factor for countries in development. •
The criteria are not consistent with the different uses defined by the Law (Table 3). In fact, there is no correspondence. This situation is worse when the regional normativity analysis is included (e.g. in Mexico City, the "hospital use" is defined for which no quality criteria has been proposed).
•
They provide the same weight and significance to restrictive parameters of use as those that may be recommended. For example, to exceed 15 times the content of turbidity represents a minimum risk to health since it may be controIled in drinking treatment equipment. This does not apply if the value of mercury is exceeded since it implies a total prohibition ofwater consumption.
•
There is no technology available to influence the numerical value of parameters. For example, it is not necessary to limit the concentration of Fe to 0.3 mgIL in water to prepare drinking water. Since there are systems to make drinkable water by removing higher concentrations at an affordable cost. Table 3. Water uses in the different regulating instruments
I. 2.
3.
4. 5.
6. 7.
8. 9.
Water Federal Law Water Quality Ecological Criteria (January 11, 1972) (December 13, 1989) Domesbc uses. Water Supply I. Dnnking Urban Public Services. Source eanle drinking trough. with primary 2. Recreative Land sprinkling: of public grazing Conllct. pasture, common lands and private 3. Agncultural spnnkling. properties. 4. Pecuniary. Industries: 5. Protection of Aquatic Life. S.l Electric power generation for S.l Fresh Water. Pubhc Service. 5.2 Sea Water (coastal areas). 5.2 Other Industries. Aquaculture. Generation of Electric Power for Private Service. Land Washing and Fertilising with s,lt or slime. Olben.
National Waten Law (December 1,1992) I. Urban Public. 2. Agriculture. 3. Generation of Electric power. 4. Other producllve activitJes. 5. Control of avenues and protection against floods.
Under this perspective, it is fundamental to redefine the Water Quality Ecological Criteria. RESULTS AND DISCUSSION In order to exemplify the changes to the Quality Criteria for Water, the analysis to determine the criteria for human consumption was used. In the first place, the compounds listed by the WHO were analysed one by one, according to the groups presented by the same: (I) microbiological components, (2) inorganic
B. nMENEZ et al.
174
components, (3) organic components, (4) radioactive components and (5) acceptance related components. This revision was exhaustively carried out, identifying for each compound: its presence in the water (superficial and underground), its negative effects on human health (toxic substances, carcinogens, mutagenics, etc.). Likewise, the positive effects were considered which may affect the acceptance for consumer or user (colour, odour, corrosion, etc.). Subsequently, the origins of the selected compounds were analysed taking into consideration the sources of origin as follows: natural, municipal, industrial, agricultural, pertaining to cattle, and those related to water handling. From the above, the importance for each compound was determined considering the risk that this represented for the human health. A selection of compounds and their values was performed at two levels: • •
Without treatment (quality goal) With conventional treatment (guidelines of possible use)
The value for each parameter was established to comply with the stated limits according to the Mexican Official Standard (Norma Oficial Mexicana NOM-127-SSA-I-1994), the CECA and the guidelines values of WHO. Also, acceptable analytical techniques were considered to identify the presence of these compounds as well as the monitoring requirements. On the other hand, a comparison of the maximum and minimum values of the National Monitoring Network was carried out between 1987 and 1997. Both in superficial and underground bodies, and then finally, the selection of the first list of guidelines (52 parameters) was obtained. A second selection allowed the elimination of those compounds due to the lack of information or due to the poor definition of risk. In this way, a reduction of 13 compounds took place. At the end, the Water Criteria for Human Consumption remained as follows: • • • • • •
Inorganic compounds: Arsenic; Barium; Boron; Cadmium; Chromium; Fluoride; Manganese; Mercury; Molybdenum; Nickel; Lead. Microbiological: Escherichia Coli; Faecal Choliforms; Faecal Streptococcus. Organic Components: Carbon tetrachloride; 1,2-dichloroethane; Vinyl chloride; Tetrachloroethane; Benzene; Styrene; Formaldehyde; Trichloroacetic Acid; 2-Ethylexile Phthalate. Pesticides: Alachlorine; Atrazine; Bentazone; Simazine. Radioactive Components: Alpha and beta emissions. Compounds Included by critical value due to Don-sanitary reasons: Colour; Turbidity; Ammonia; Hardness; Iron; Manganese; pH; Dissolved Solids; Zinc.
Pesticides should be especially highlighted. The guidelines established for Mexico do not coincide with the total pesticides considered by the WHO. The selection of pesticides was carried out based on their toxicity, mobility in soil, and frequency of use. The result is a list of 4 pesticides among which the herbicides stand out. According to the revision carried out by Funari and Bighi (1995) these are of more interest in drinking water. CONCLUSIONS According to Mexican Government programs, to carry out the plans and implementations for water, it is important to identify the parameters that define the use of water as a function of the activity to be developed. In this context, the Ecological Criteria of Water Quality were redefined. These criteria were renamed as "Criteria of Water Quality" and use a new procedure for the selection of parameters. In the criteria are two values: the goal of quality and the criteria itself. The goal of quality allows the use of any type of water with such characteristics or better ones and cannot only be used as it is, but constitutes the most suitable water for such use. The criteria depend on the possibility to treat the water to reach the proposed values.
Analysis of water quality criteria in Mexico
17S
In addition, the establishment of guideline values are not only dictated by the need to regulate a set of parameters potentially dangerous for humans, but also to solve different needs. For example, those where each State can define which of these parameters are of higher priority for its region and which have a second priority according to the climatological conditions in the country. REFERENCES AWWA (1987). Radionuclides in Drinking Water. AWWA Seminar Proceeding, American Water Works Association. pp. t6S. Kansas City, USA. Biswas A. (1997). Development of a Framework for Quality Monitoring in MeXICO. Water International, Official Journal of the InternatIOnal Water Resources AssocIation, 22(3),179-186. Bloem A.A., Laker M.C., La Grange L.F and Smit C.J. (1991). Kriteria vir die aanpassing van die ontwerp en bestuur van oorhoofte besproeiingstelsels by die ilfiltreerbaarheid van grond, WRC Report No. 208/1191. Bowman H.l.M. (1979). Environmental Chemistry ofthe Elements. AcademiCS Press London. Canadian EnVIronmental Protection Act. (1995). Strengthening Environmental Protection in Canada: A Guide to the New Legislation. Government of Canada, pp. 15, Canada. CanadIan Guidelines (1987). Canadian Water Quality Guidelines. Prepared by Resource and Environment Ministers. Canada. Chapman D. (1992). Water Quality Assessments. A guide to the use of biota. sedIments and water in environmental monitoring. UNESCO, WHO and UNEP. Vol. I and II, pp. 565. Grain Britain. EnVIronmental Protection Agency (1972). Water Quality Criteria 1972. A Report of the Committee on Water Quality Criteria. pp. 594, Washmgton, D.C., USA. Environmental Protection Agency (1988). Federal RegIster Vol. V: Guidelines to evaluate suspicious toxic affecting the development. Pan-American Centre of Human Ecology and Health, OPS and WHO. Metepec, Mexico, pp. 44. Federal Register (1992). Water Quality Standards. Establishment of numeric criteria for pnority toxic pollutants. States' Compliance. Fmal Rule (40 CFR part 131). Water Environment FederatIon, 57(246), 60848-60923. Government of Canada (1995). Vers une protection renforcee de I 'environnement au Canada. pp. I S, Government of Canada. Gustafson D. (1993). Pesticides in Drinking Water. Van Nostrand Reinhold, pp. 241. USA. WHO (1993). Guidelines for Drinking Water Quality, Vol. I Recommendations., 2nd edn., World Health Organisation, Geneva, pp.195.
Wat Sci Tech. Vol. 40. No 10. pp. 169-175. 1999
Pubhshed by Elsevier Science Ltd on behalf of the IAWQ Pnnted in Grelll BOlain. All righls reserved 0273-1223/99 S20.00 + 0.00
PH: S0273-1223(99)00683-6
ANALYSIS OF WATER QUALITY CRITERIA IN MEXICO B. Jimenez, J. Ramos and L. Quezada Instituto de Ingenieria, UNAM, Apdo postal 70-472. Coyoacan 04510. Mexico. D. F.
ABSTRACT During the last decade, it has been acknowledged that, at national level. the availabIlity of water is a trade-off between its temporary and spatial distributIon as well as contammation problems. This situation has urged the Mexican Government to revise the plans and programs for the integrated management of hydric resources by analysing the instItutional system, the legal frame and its effectiveness. Within this context, an essential aspect is to ensure the ordering of the uses and exploitation of water resources. This paper shows that a revision of the effectiveness and apphcability of the current water standards and laws is essential to satisfy the demands, and to have control over the different uses of water (drinking water for human consumption, the use of water for agncultural, municipal, industrial related actlvllles and other purposes). Therefore, in this work. a redefinition of the Ecological Crileria of Water Quality has been proposed. The proposal establishes the Quality Criteria under a new perspective. wherem the set of parameters and their values constitute the goal of quality, in the sense that any type of waler with such characteristics or better ones. cannot only be used as it is. but constitutes the most SUitable water for such use. iC 1999 Pubhshed by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved
KEYWORDS Drinking water; normativity in Mexico; quality criteria ofwater; water uses. INTRODUCTION In the past few years, the availability of water at national level has been a trade-ofT between its temporary and spatial distribution as well as contamination problems. This situation has urged the Mexican Government to revise the plans and programs for the integrated management of hydric resources by analysing the institutional system, the legal frame (consisting of the Ecological Equilibrium and Environmental Protection General Law; National Waters Law and its Regulations; the Federal Law Fees annually updated; the Federation Income Law and the Hydraulic Infrastructure Federal Public Works Betterment Contribution Law) and its effectiveness. Within this context, a fundamental aspect is to ensure the ordering of the uses and appropriate use of water resources. Regarding water use, some policies and strategies have been stated which have stimulated changes in the use of water, these rectify balances according to needs, state priorities and are orientated towards finding alternative supply sources. In the hydraulic policy the reinforcement of the institutional capability of the water sector is emphasised. inclUding the modernisation of the legal frame and the related institutions. the updating of specific hydraulic policies, the improvement of information systems, the technical and administrative procedures. as well as the development of an improved technical and professional capability of the persons and organisations that participate in this sector. 169
170
B. nMENEZ et al.
Specifically, the government is concentrating its efforts as follows: a) To define the goal to be achieved for water quality for every water body in the country. b) To regulate the preservation of the aquifer quality, which is the main human consumption water supply source. c) To regulate the contamination generated by non-point sources. d) To consider the problem of water contamination from rainfall and the dilemma of using comined drainage. e) To develop the management capacity of the government to implement and measure water quality. f) To establish common parameters which allow the identification of how discharge regulation improves the quality of water bodies. In order to satisfy the demands and to keep control over the water activities, full evaluations of the situation must be performed; to know the quantity, quality, demand and uses (water for human consumption and for agricultural, municipal, industrial and other purposes). For this, the effectiveness and applicability of the current water regulations and laws must be analysed, including the documents granting attributions, obligations and responsibilities to the entities of the sector. This will ensure the management of hydric resources in a sustainable and integral way. One of the regulations of special interest is the Ecological Criteria of Water Quality (Criterios Ecol6gicos de Calidad del Agua, CECA). In Mexico as well as other developing countries, the need to qualify water for a specific use is established by the CECA. However, the selected parameters are not appropriate for the needs of the country. The criteria do not define very well the responsibilities in the case that the quality of the water body is not suitable for its use. The reasons for this were mainly political rather than caring for human health. In consequence, the CECA selected a large number of parameters from international regulations where the economical and technological situation were different to the Mexican ones. In addition, the parameter values were so strict that the levels were only reached a few times with the treatment systems available. During the development of the quality criteria it was realised that there was a trade-off between trying exhaustively to define the parameters (which, in fact, it is impossible to do since there are more than 70,000) and to select a set suitable for the countries problems, which are easy to be measured, controlled and followed in a reasonable way. In addilion, their presence should not endanger the use of water. In general, the selection of parameters and values is mainly focused on the protection of public health. Thus, it is essential to establish priorities according to the actual needs and to formulate the criteria according to the economical and technological situation of each country. In theory, the establishment of standards must be based on security, logic, scientific advances and the goal to achieve a measure or estimation of the benefit, whilst minimising the risk at a specific cost. In practice, it is not so easy since the risks and benefits are not known. In the developed countries, to have very strict values results from the pressure ofthe ecological groups. Sometimes, this results in the adoption of standards based on political reasons rather than a scientific or logical reasoning. Most of standards in Europe and America are extremely demanding and the problem to be faced by developing countries is that to copy such values or parameters without analysing the context under which they have been selected is not appropriate. To allow a transcription of the standards already developed for countries with different realities results in implementation of improper and unaffordable technologies, which are not actually translated into desirable objectives. For example, for developed countries to restrict the concentration of nitrogen is easy and affordable, since they have already controlled the DBO, but to apply this to the undeveloped countries is unaffordable and truly insignificant in view of some other problems.
Analysis of water quality criteria in Mexico
171
METHODOLOGY Water Uses The use of water, including extraction and discharge, limits the activities carried out at different levels, for example, at local, regional or international level. Table I shows the compounds that restrict water use. Table 1. Limitation of the water potential uses due to quality degradation Pollutant Drinking Aquatic wildlife, Recreation water fisheries XX XX XX
Pathogens Suspended solids XX XX X Organic matter XX X X Xi Algae X'·· XX Nitrate X X NA Salts' X XX NA Trace elements XX XX X Organic mlcropollutants XX XX X ACidification X XX X XX Marked Impairment causmg major Ireannent or excludmg the desired use. X Minor impairment. NA No applicable. + Degraded water quahty may be beneficial for this specific use. ? Effects not yet fully reahsed.
Uses Irrigation X
X + + + XX
X X
1. 2. 3. 4. 5. 6. 7.
8. 9.
Industrial uses XXi X XX'
XX' XX' XX' X ? X
Power and cooling X
Transport
X'
NA
X'
X' NA NA NA NA X
NA
XX'
X'
NA NA NA NA NA
Food industries. Abrasion.. Sediment settling in channels. Electronic industries. Filter clogging. Odour and taste. In fish ponds higher alga biomass can be accepted. Development of water hyacinth. Ca, Fe, Mn in textile industries, etc.
Adapted from: Chapman, 1992.
The selection of variables to evaluate quality of the water is carried out according to the objectives to be fulfilled in order to ensure its quality for use. A proper selection allows the certainty of an efficient and lower cost use. Each variable must be analysed taking into account the sources, its performance and transformation in the aquatic media, the intervals observed in natural and contaminated waters, its persistence in the same and its handling during the treatment. In addition, it is important to select variables taking into consideration the availability of the analytical methods, the equipment, reactives and personnel available. The level of accuracy and sensitivity must also be considered as criteria Analysis of water Quality criteria jn Mexico In 1989, the National Water Commission (Comisi6n Nacional del Agua) elaborated the Water Use Ecological Criteria (Table 2). In these criteria, the Ecological Equilibrium and Environmental Protection Law gives the power to the Urban Development and Ecological Secretariat to formulate the ecological criteria to be observed for the application of an ecological general policy, paying special aUention to the rational utilisation and prevention, and control ofwater contamination, as well as the aquatic flora and fauna protection. For such purposes, the ecological criteria of water quality were defined. In these criteria, the levels of the parameters and the substances found in the water, their effects and allowable levels are specified. Thus, the relevant authorities will be able to qualify the water bodies as apt to be used as a supply source of drinking wat~r, in entertaining activities with primary contact, for agricultural irrigation, for pecuniary use, for aqulculture use, or for the development and conservation of aquatic life. Such parameters constitute the minimum required quality for the use of water resources in the cases previously mentioned.
172
B. JIMENEZ et a/.
Table 2. Water quality ecological criteria of uses F USES A B D C E In mgll, except when other unit Is ndlcated. Inorganic parameters Alkahnity (as CaCO,) (I) 400 (I) Aluminium 0.2 0.02 5 5 0.05 Antimony 0.09 0.1 0.1 O.04(a) Arsemc 0.05 0.2(a) 0.2 0.1 Asbesto (as FibreslL) 3000 Banum 0.5 I 0.01 Beryllium (III) 0.1 0.00007 0.001 Boron 0.009 I 5 0.7(V) Cadmium 0.0009 0.01 0.01 0.02 (VI) Cyamde (as CN') 0.001 0.02 0.02 0.02 0.005 Chlorine residual 0.0075 0.011 Chloride (as Cn 250 147.5 250 Copper 0.003 I 0.5 (VII) 0.2 Chromium hexavalente 0.05 0.05 I 0.01 I Iron 0.3 0.05 5 I Fluorides (as F") 1.5 1 2 0.5 I Phosphates (as POl') 0.1 (IX) 0.002 Phosphorus elemental 0.0001 0.0001 Manganese 0.1 Mercury (Hg) 0.001 0.003 0.00002 0.00001 Nickel 0.01 I 0.2 0.008 (X) Nitrates (NO,') (as N) 5 90 0.04 Nitrites (N02') (as N) 0.05 0.002 10 Ammonia (as N) 0.01 0.06 Dissolved oxygen 4 5 5 Silver 0.05 0,002 (XIV) Lead 0.05 5 0.1 (XV) 0.006 Selenium (as selenate) 0.01 0.02 0.05 0.4 0.008 500 Sulphate (as SOl) 130 0.005 Sulphide (as H2S) 0.2 0.002 0.002 0.01 Thallium 0,01 0.02 2 50 (XVII) 0.09 5 Zmc USE A: Human consumption supply. USE B: Recreate use. USE D: Livestock. USE E: Freshwater aquatic hfe Primary contact. USE C: Agricultural USE F: Manne aquatic life N.C.: Natural condillons : Like As
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As observed, five groups were identified for six uses amounting to 126 parameters. Table 2 shows only the inorganic parameters group. The uses of drinking water supply and aquatic life protection have the highest number of parameters with guideline values. The analysis of quality criteria determines that: •
In relation to the listed parameters, it is important that the Mexican criteria conform to the 56 parameters of the Quality Criteria established by the EPA in 1972, with more strict values in 68% from the total. Equally, it is worth mentioning that after identifying the toxic substances regulated by the EPA in 126 compounds listed in 1978, Mexico considered 71 (77%) parameters as suitable to be standards to regulate water quality.
These considerations generated problems relative to the effectiveness to reach and measure the proposed values. Therefore, it is necessary to revise the listed parameters in the Mexican criteria so that the parameters established in the developed countries are not selected since they do not necessarily constitute a substantial factor for countries in development. •
The criteria are not consistent with the different uses defined by the Law (Table 3). In fact, there is no correspondence. This situation is worse when the regional normativity analysis is included (e.g. in Mexico City, the "hospital use" is defined for which no quality criteria has been proposed).
•
They provide the same weight and significance to restrictive parameters of use as those that may be recommended. For example, to exceed 15 times the content of turbidity represents a minimum risk to health since it may be controIled in drinking treatment equipment. This does not apply if the value of mercury is exceeded since it implies a total prohibition ofwater consumption.
•
There is no technology available to influence the numerical value of parameters. For example, it is not necessary to limit the concentration of Fe to 0.3 mgIL in water to prepare drinking water. Since there are systems to make drinkable water by removing higher concentrations at an affordable cost. Table 3. Water uses in the different regulating instruments
I. 2.
3.
4. 5.
6. 7.
8. 9.
Water Federal Law Water Quality Ecological Criteria (January 11, 1972) (December 13, 1989) Domesbc uses. Water Supply I. Dnnking Urban Public Services. Source eanle drinking trough. with primary 2. Recreative Land sprinkling: of public grazing Conllct. pasture, common lands and private 3. Agncultural spnnkling. properties. 4. Pecuniary. Industries: 5. Protection of Aquatic Life. S.l Electric power generation for S.l Fresh Water. Pubhc Service. 5.2 Sea Water (coastal areas). 5.2 Other Industries. Aquaculture. Generation of Electric Power for Private Service. Land Washing and Fertilising with s,lt or slime. Olben.
National Waten Law (December 1,1992) I. Urban Public. 2. Agriculture. 3. Generation of Electric power. 4. Other producllve activitJes. 5. Control of avenues and protection against floods.
Under this perspective, it is fundamental to redefine the Water Quality Ecological Criteria. RESULTS AND DISCUSSION In order to exemplify the changes to the Quality Criteria for Water, the analysis to determine the criteria for human consumption was used. In the first place, the compounds listed by the WHO were analysed one by one, according to the groups presented by the same: (I) microbiological components, (2) inorganic
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components, (3) organic components, (4) radioactive components and (5) acceptance related components. This revision was exhaustively carried out, identifying for each compound: its presence in the water (superficial and underground), its negative effects on human health (toxic substances, carcinogens, mutagenics, etc.). Likewise, the positive effects were considered which may affect the acceptance for consumer or user (colour, odour, corrosion, etc.). Subsequently, the origins of the selected compounds were analysed taking into consideration the sources of origin as follows: natural, municipal, industrial, agricultural, pertaining to cattle, and those related to water handling. From the above, the importance for each compound was determined considering the risk that this represented for the human health. A selection of compounds and their values was performed at two levels: • •
Without treatment (quality goal) With conventional treatment (guidelines of possible use)
The value for each parameter was established to comply with the stated limits according to the Mexican Official Standard (Norma Oficial Mexicana NOM-127-SSA-I-1994), the CECA and the guidelines values of WHO. Also, acceptable analytical techniques were considered to identify the presence of these compounds as well as the monitoring requirements. On the other hand, a comparison of the maximum and minimum values of the National Monitoring Network was carried out between 1987 and 1997. Both in superficial and underground bodies, and then finally, the selection of the first list of guidelines (52 parameters) was obtained. A second selection allowed the elimination of those compounds due to the lack of information or due to the poor definition of risk. In this way, a reduction of 13 compounds took place. At the end, the Water Criteria for Human Consumption remained as follows: • • • • • •
Inorganic compounds: Arsenic; Barium; Boron; Cadmium; Chromium; Fluoride; Manganese; Mercury; Molybdenum; Nickel; Lead. Microbiological: Escherichia Coli; Faecal Choliforms; Faecal Streptococcus. Organic Components: Carbon tetrachloride; 1,2-dichloroethane; Vinyl chloride; Tetrachloroethane; Benzene; Styrene; Formaldehyde; Trichloroacetic Acid; 2-Ethylexile Phthalate. Pesticides: Alachlorine; Atrazine; Bentazone; Simazine. Radioactive Components: Alpha and beta emissions. Compounds Included by critical value due to Don-sanitary reasons: Colour; Turbidity; Ammonia; Hardness; Iron; Manganese; pH; Dissolved Solids; Zinc.
Pesticides should be especially highlighted. The guidelines established for Mexico do not coincide with the total pesticides considered by the WHO. The selection of pesticides was carried out based on their toxicity, mobility in soil, and frequency of use. The result is a list of 4 pesticides among which the herbicides stand out. According to the revision carried out by Funari and Bighi (1995) these are of more interest in drinking water. CONCLUSIONS According to Mexican Government programs, to carry out the plans and implementations for water, it is important to identify the parameters that define the use of water as a function of the activity to be developed. In this context, the Ecological Criteria of Water Quality were redefined. These criteria were renamed as "Criteria of Water Quality" and use a new procedure for the selection of parameters. In the criteria are two values: the goal of quality and the criteria itself. The goal of quality allows the use of any type of water with such characteristics or better ones and cannot only be used as it is, but constitutes the most suitable water for such use. The criteria depend on the possibility to treat the water to reach the proposed values.
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In addition, the establishment of guideline values are not only dictated by the need to regulate a set of parameters potentially dangerous for humans, but also to solve different needs. For example, those where each State can define which of these parameters are of higher priority for its region and which have a second priority according to the climatological conditions in the country. REFERENCES AWWA (1987). Radionuclides in Drinking Water. AWWA Seminar Proceeding, American Water Works Association. pp. t6S. Kansas City, USA. Biswas A. (1997). Development of a Framework for Quality Monitoring in MeXICO. Water International, Official Journal of the InternatIOnal Water Resources AssocIation, 22(3),179-186. Bloem A.A., Laker M.C., La Grange L.F and Smit C.J. (1991). Kriteria vir die aanpassing van die ontwerp en bestuur van oorhoofte besproeiingstelsels by die ilfiltreerbaarheid van grond, WRC Report No. 208/1191. Bowman H.l.M. (1979). Environmental Chemistry ofthe Elements. AcademiCS Press London. Canadian EnVIronmental Protection Act. (1995). Strengthening Environmental Protection in Canada: A Guide to the New Legislation. Government of Canada, pp. 15, Canada. CanadIan Guidelines (1987). Canadian Water Quality Guidelines. Prepared by Resource and Environment Ministers. Canada. Chapman D. (1992). Water Quality Assessments. A guide to the use of biota. sedIments and water in environmental monitoring. UNESCO, WHO and UNEP. Vol. I and II, pp. 565. Grain Britain. EnVIronmental Protection Agency (1972). Water Quality Criteria 1972. A Report of the Committee on Water Quality Criteria. pp. 594, Washmgton, D.C., USA. Environmental Protection Agency (1988). Federal RegIster Vol. V: Guidelines to evaluate suspicious toxic affecting the development. Pan-American Centre of Human Ecology and Health, OPS and WHO. Metepec, Mexico, pp. 44. Federal Register (1992). Water Quality Standards. Establishment of numeric criteria for pnority toxic pollutants. States' Compliance. Fmal Rule (40 CFR part 131). Water Environment FederatIon, 57(246), 60848-60923. Government of Canada (1995). Vers une protection renforcee de I 'environnement au Canada. pp. I S, Government of Canada. Gustafson D. (1993). Pesticides in Drinking Water. Van Nostrand Reinhold, pp. 241. USA. WHO (1993). Guidelines for Drinking Water Quality, Vol. I Recommendations., 2nd edn., World Health Organisation, Geneva, pp.195.