Case Study XI* - Cyprus

Transcription

1 Water Pollution Control - A Guide to the Use of Water Quality Management Principles Edited by Richard Helmer and Ivanildo Hespanhol Published on behalf of the United Nations Environment Programme, the Water Supply & Sanitation Collaborative Council and the World Health Organization by E. & F. Spon 1997 WHO/UNEP ISBN Case Study XI* - Cyprus * This case study was prepared by I. Papadopoulos XI.1 Introduction Cyprus is situated in the north-eastern part of the Mediterranean Sea, 33 East of Greenwich and 35 North of the Equator (Figure XI.1), and is the third largest island in the Mediterranean with an area of 9,251 km 2, of which 1,733 km 2 are forested, 216,000 ha are cultivated and 38,000 ha are irrigated. Irrigated agriculture contributes more than 50 per cent of the value of the total crop production. The de jure population of Cyprus in 1993 was 722,000 with an annual rate of growth of 1.7 per cent. The economically active population is 46 per cent of the total. Employment in agriculture is continuously declining and in 1993 the proportion of the population engaged in agriculture had fallen to 11.9 per cent. Registered unemployment in 1993 was 2.6 per cent. Life expectancy for males is 74.6 years and for females is 79.1 years (Department of Statistics and Research Development, 1995). The gross national product (GNP) per capita in 1995 was 6,107 Cyprus pounds (US$ 14,045) with a rate of increase of 5.6 per cent. The contribution of different sectors to total production is given in Figure XI.2 (Department of Statistics and Research Development, 1995). XI.2 Water resources XI.2.1 Surface waters The availability of water in Cyprus is dependant on the annual rainfall, which varies from 340 mm in the coastal plains to 1,100 mm in the Troodos mountains. The average annual rainfall throughout the island is about 500 mm, equivalent to 4, m 3. About two thirds of the rainfall occurs during the winter months, December to February. It is estimated that about 80 per cent of the rainfall is lost to the atmosphere by direct evaporation and from the remaining m 3, about m 3 enrich the aquifer and m 3 result in surface run-off. Part of this run-off is used for direct irrigation or is collected in dams and about m 3 is lost to the sea (Water Development Department, 1989). Projects are underway to divert part of the latter run-off to the dams.

2 Figure XI.1 Location map of Cyprus Figure XI.2 Contribution of different sectors to total production in Cyprus

3 Figure XI.3 Increases in the capacity of dams in Cyprus between 1961 and 1991 (Data supplied by the Water Development Department) The annual variations in rainfall and snowfall are quite large leading to deficits in water supplies during low rainfall and to floods during high rainfall. When rainfall is only about 360 mm a -1 or less, drought conditions occur with negligible run-off and groundwater replenishment. This occurs about once every 16 years. During drought conditions, river flow is drastically reduced thereby affecting available domestic and irrigation water supplies. As a result, Cyprus has embarked on and completed a costly storage dam programme for m 3 of water (Figure XI.3) which, when considered per unit area of population, is one of the most intensive in the world. Most of the storage dams are integrated into the southern conveyor system which interconnects all important surface water resources from west to east across the island of Cyprus. XI.2.2 Groundwater Groundwater is a very important source of water for Cyprus. Water infiltrates directly from rainfall (there is no inflow from outside the island) into confined or unconfined aquifers and can be extracted and used either by pumping or sometimes by gravity feeds in the form of springs. Recently, an aquifer west of the city of Limassol (Akrotiri aquifer) was identified as suitable for partial recharge with treated municipal wastewater produced in the city. Precautionary legal and regulatory actions have been taken to protect the quality of the groundwater, the environment and public health. Conservation and use of groundwater resources has to be carried out in parallel, and integrated, with surface water resources. Already many aquifers in Cyprus have been seriously over-pumped and their reliable yield has decreased; in many cases the quality of the water has deteriorated and in coastal areas salt water intrusion has occurred. Due to its extensive storage period, groundwater is ideal as a supplementary water resource in situations of low rainfall and run-off conditions and also as a standby supply

4 in cases of drought. The Government of Cyprus has recently adopted this policy. In order to harmonise the situation in Cyprus with that of the European Union (EU), legal and institutional regulations to control groundwater and its quality are in the final stages of formulation. The main aquifers of Cyprus are the Western Messaoria, South Eastern Messaoria, Akrotiri and the Kyrenia limestone range. In addition, there are a few minor coastal and some restricted river-valley aquifers. The water from these aquifers is pumped through about 10,000 boreholes and several thousand shallow wells. The total extraction is about m 3 for irrigation, domestic and industrial purposes. The sustainable yield of the aquifers is about m 3 and over-pumping occurs in some areas and losses to the sea occur in other areas. The problem of over-pumping has arisen because there are numerous illegal boreholes and uncontrolled withdrawals but in certain areas, such as Famagusta, Morphou, Limassol and Larnaca, salt water intrusion has became a serious problem. In some locations the saline ground-water is not suitable even for the most salt-tolerant crops. The over-pumping has also resulted in most springs drying up. XI.3 Measures to conserve and replenish groundwater There are many different groundwater conservation and replenishment measures that can be carried out, many of which have been used in Cyprus, although some of them have not been successful because of inadequate management. XI.3.1 Conservation and control measures Aquifers can be declared as conservation areas where laws are enforced for appropriate management action such as: Regulation of pumping and the introduction of water meters and efficient conveyance and water application systems. Charging of water rates per cubic metre based on the type of crop and quantity extracted. Regulation of well drilling, the distance between boreholes and their depth. Controlling the water quality of the aquifer. In order to control water quality, precautionary protection measures and prohibited activities are enforced by law (69/91). The framework of the law defines which substances and/or chemicals are considered toxic or dangerous, as well as pollution by nitrates and other sources (industrial and municipal). Protection measures are proposed for areas recharging ground-water intended for human consumption. These sensitive areas are divided into three zones where different restrictions are imposed. The aim of the law has been to protect groundwater and positive results have been obtained.

5 XI.3.2 Groundwater recharge In Cyprus, where favourable conditions occur, groundwater recharge with river flow has been used efficiently for the replenishment of depleted aquifers. As a result, a number of recharge projects have been carried out in Cyprus including: Recharge dams, such as at Morphou, Famagusta and Kyrenia. Percolation areas downstream of recharge dams such as at Morphou Serrachis valley. A recharge canal downstream of the recharge dams and lake at Paralimni. An infiltration gallery such as the one traversing the Famagusta aquifer. Recharge with treated municipal wastewater. Recharge of groundwater with reclaimed wastewater not used for direct irrigation is a new concept for Cyprus. Based on the "Cyprus approach" that no water should be allowed to reach the sea, it has been decided that all properly treated wastewater should be used either for irrigation or for groundwater recharge. Moreover, it has been realised that in order to protect the marine environment from eventual pollution and particularly from eutrophication, treated wastewater should not be discharged to the sea. The government of Cyprus has attached particular importance to this because the economy of the country is largely dependent on its tourist industry. In line with this decision, no effluent from the city of Limassol can be disposed to the sea. Part of the reclaimed wastewater not used for direct irrigation is expected to be used for recharging the Akrotiri aquifer, which is considered to be the third most important in Cyprus. This water could be used subsequently for irrigation in the area. This concept of wastewater use in Limassol has been accepted and commenced in Under this project, part of the treated effluent (about m 3 a -1 by the completion of the project) will be used for direct irrigation and part will be conveyed to the aquifer for recharge in constructed infiltration basins. Water will be extracted from wells located downgradient of the basins and will be transferred to the existing irrigation distribution systems. The recharge basins can be used throughout the year for reclaimed water but the recharged water need only be recovered by pumping as required for crop irrigation. Additional water quality variables have been set for the treated effluent used for groundwater recharge with a particular emphasis on nitrogen removal. The treatment plant, therefore, has been designed to provide nitrification and denitrification by which the level of nitrogen in the reclaimed water can be controlled. The projected characteristics of the reclaimed water from the treatment plant are given in Table XI. 1. The projected quality of the water should be generally comparable to the quality of the groundwater in the area and is expected to be suitable for the anticipated irrigation and aquifer recharge.

6 Table XI.1 Projected water characteristics for reclaimed wastewater from Limassol Variable Concentration Variable Concentration BOD mg l -1 TSS 2-5 mg l -1 NH 3 -N mg l -1 NO 3 -N mg l -1 Total N mg l -1 Phosphorus 5-10 mg l -1 Total coliform 1 < 2 per 100 ml Sodium mg l -1 Calcium mg l -1 Potassium 1-4 mg l -1 Magnesium mg l -1 Chloride mg l -1 Bicarbonate mg l -1 Sulphate mg l -1 TDS mg l -1 BOD Biochemical oxygen demand TSS Total suspended solids TDS Total dissolved solids 1 Most probable number Source: CHM HILL, 1992 XI.4 Direct use of treated wastewater for irrigation Water resources in Cyprus are limited and, with the rapid development of urban and rural domestic supplies, conventional water resources have been seriously depleted. As a result, the reclamation and use of wastewater has become a realistic option for providing reliable sources of water to meet shortages and to cover water needs, as well as for meeting wastewater disposal regulations aimed at protecting the environment and public health. However, the use of wastewater could itself be associated with severe environmental and health impacts. Therefore, a multidisciplinary research programme was initiated in 1984 to study the agronomical, environmental and health aspects associated with the use of treated wastewaters for irrigation. Most of the chemical and physico-chemical variables associated with wastewaters have been extensively studied by the Agricultural Research Institute and useful results have been obtained for the rational and environmentally-sound use of these waters (Papadopoulos, 1995). Recently, priority has been given to research on animal feeding and human health aspects. The results indicate that with the treatment level required in Cyprus, with the irrigation technology available and with the code of practice suggested, the health and environmental risks fall within acceptable levels (Jenkins et al., 1994; Papadopoulos et al., 1994). XI.4.1 Regulatory considerations In Cyprus, in order to control the treatment and use of wastewater and thereafter to safeguard the environment and public health, very strict guidelines have been formed relating to the quality and the use of treated wastewater (Table XI.2) (Kypris, 1989). In order to allow for the specific situation of Cyprus, these guidelines are more strict than those proposed by the World Health Organization (WHO). In addition, the guidelines are followed by a code of practice intended to ensure protection of public health and the

7 environment even further and they should be considered to be part of the guidelines (Box XI. 1). It is important to stress that when the guidelines were being formulated, the Technical Committee specifically recognised that the conditions affecting the acceptable risk for reuse of reclaimed water may change, that knowledge of real risk may be improved, and that treatment technologies may also be improved in future. Therefore, the Technical Committee considers the guidelines and the code of practice to be open for further modifications based on the latest knowledge and experience gained from ongoing actual use, and from research. XI.5 Pollution of water resources Potential pollution of water resources in Cyprus is related to groundwater over-pumping and the intrusion of sea water to aquifers as already discussed above, to wastewater use and to intensive agriculture. Industrial activities are rather limited in Cyprus and therefore the main sources of pollutants are, and will increasingly be, urban sewage plants and the use of the effluents. For this reason guidelines and a code of practice have been formulated and legally enforced to protect human health and the environment (Table XI.2 and Box XI.1). Recently, there has been a considerable increase in the application of fertilisers and pesticides in order to enhance agricultural production. In Cyprus, because of the limited amount of agricultural land and the high cost of labour and water, increases in production through the application of fertilisers and pesticides have become very important, but have also resulted in some groundwater pollution. Pollution of groundwater by nitrates is becoming a serious problem in areas of intensive agriculture. Measures are taken by the Ministry of Agriculture to minimise the application of fertilisers and pesticides and a code of practice concerning fertilisers and other chemicals, similar to the code of practice for wastewater use, has been formulated. Farmers are advised to apply suitable fertilisers and other chemicals using an appropriate method at the best time of year and to keep their fertiliser and pesticide activities away from rivers and open wells.

8 Table XI.2 Guidelines for the quality of wastewater used for irrigation in Cyprus Irrigation area 80% limit 1 Amenity areas of unlimited access Crops for human consumption; amenity areas of limited access BOD (mg l -1 ) SS(mg l -1 ) Faecal coliforms (No. per 100 ml) Max. allowed 80% limit 1 Max. allowed 80% limit 1 Max. allowed Intestinal -worm (No. per litre) Treatment required Nil Secondary, tertiary and disinfection ,000 Nil Secondary, storage > 1 week and disinfection, or tertiary and disinfection na na na na 200 1,000 Nil Stabilisation using maturation ponds with a total retention time > 30 days or secondary and storage > 30 days Fodder crops ,000 5,000 Nil Secondary and storage > 1 week or tertiary and disinfection na na na na 1,000 Nil Stabilisation using maturation ponds with total retention time > 30 days or secondary and storage > 30 days Industrial crops na na 3,000 10,000 na Secondary and disinfection na na na na 3,000 10,000 na Stabilisation using maturation ponds with a total retention time > 30 days or secondsecondary and storage > 30 days BOD Biochemical oxygen demand SS Suspended solids na Not applicable 1 These values must not be exceeded in 80% of samples per month Irrigation of vegetables is not allowed. Irrigation of ornamental plants for trade purposes is not allowed. No substances accumulating in the edible parts of crops and proved to be toxic to humans or animals are allowed in the wastewater effluents.

9 Box XI.1 Code of practice for treated domestic sewage effluent used for irrigation in Cyprus 1. The sewage treatment and disinfection plant must be kept and maintained continuously in satisfactory and effective operation for as long as treated sewage effluent is intended for irrigation. 2. Skilled operators should be employed to attend the treatment and disinfection plant, following formal approval by the appropriate authority that the persons are competent to perform the required duties, necessary to ensure that the conditions of clause 1 are satisfied. 3. The treatment and disinfection plant must be attended every day and records must be kept of all operations performed. 4. All outlets, taps and valves in the irrigation system must be secured to prevent their use by unauthorised persons. All such outlets must be coloured and clearly labelled to warn the public that the water is unsafe for drinking. 5. No cross-connections with any pipeline or works conveying potable water are allowed. All pipelines conveying sewage effluent must be satisfactorily marked with red tape to distinguish them from domestic water supply. In unavoidable cases where sewage effluent and domestic water supply pipelines must be laid close to each other, the sewage or effluent pipes should be buried at least 0.5 m below the domestic water pipes. 6. The irrigation methods allowed and the conditions of application differ between different plantations as follows: a. Park lawns and ornamental gardens in amenity areas of unlimited access: Subsurface irrigation methods. Drip irrigation. Pop-up, low angle, low pressure and high precipitation rate sprinklers. Sprinkling should preferably be practised at night and when people are not around the amenity areas. b. Park lawns and ornamental gardens in amenity areas of limited access, industrial and fodder crops: Sub-surface irrigation methods. Drip irrigation. Surface irrigation methods. Spray or sprinkler irrigation is allowed with a buffer zone of about 300 m. For fodder crops, it is recommended to stop irrigation at least one week before harvesting. No animals supplying milk should be allowed to graze on pastures irrigated with sewage. c. Vines: Drip irrigation. Minisprinklers and sprinklers (irrigation should stop two weeks before harvesting). d. Trees with fruits eaten raw without peeling: Drip irrigation.

10 Hose basin irrigation. Bubbler irrigation. No fruits to be collected from the ground. e. Trees with fruits eaten after peeling, nuts and similar fruits: Drip irrigation. Minisprinklers (stop irrigation one week before harvesting). No fruits to be collected from the ground except nuts. Other irrigation methods could also be considered. 7. In order to meet the required standards, tertiary treatment is essential when treated effluent is intended for irrigation of fruit trees and amenity areas of unlimited access. The following tertiary treatment methods are acceptable: Sedimentation by storage for not less than 30 days in open basins without agitation. Coagulation plus flocculation followed by rapid sand filtration. Any other method which may secure the total removal of helminth eggs and reduce faecal conforms to acceptable levels. 8. Appropriate disinfection methods should be applied when sewage effluents are to be used for irrigation. In the case of chlorination the residual free or total level of chlorine in the effluent should be equal to or more than 0.5 and 2 mg l-1 respectively at the point of use. 9. Suitable facilities for monitoring the essential water quality variables, should be available at the treatment site. XI.6 Conclusions and recommendations Based on experimental data and on the application of wastewater for irrigation in Cyprus, the following conclusions and recommendations can be put forward: Wastewater, when properly treated, used and managed, could be considered as an additional, innovative and reliable water resource with particular application in agriculture. With the use of all treated wastewater for direct irrigation or irrigation following groundwater recharge, the irrigated land in Cyprus will be expanded by 6 per cent. Similarly, the equivalent amount of freshwater could be saved for other purposes. The treatment and use of wastewater for irrigation, within the acceptable level of risk for the environment and for public health, is considered, under the conditions found in Cyprus, to be the best option for long-term sustainable agriculture with a sound environmental basis. Wastewater reclamation and use may contribute to the protection of the environment but inappropriate treatment and use may also adversely affect the environment and

11 human health. Therefore, the formulation of guidelines and a code of practice concerning treatment and use of wastewater are essential. In order to be effective, the guidelines and code of practice should be followed by legal enforcement. XI.7 References Department of Statistics and Research Development 1995 Statistical Abstract Ministry of Finance, Nicosia. CHM HILL 1992 Limassol Sewage Effluent and Sludge Reuse Study. Final Report. CHM HILL, Nicosia. Jenkins, C.R., Papadopoulos, I. and Stylianou, Y Pathogens and wastewater use for irrigation in Cyprus. In: Land and Water Resources Management in Mediterranean Region, Volume IV. Proceedings of a conference held in Ban, Italy, 4-8 September CIHEAM, Kypris, D Considerations for the quality standards for the reuse of treated effluent. In: Wastewater Reclamation and Reuse. Proceedings of a conference held in Cairo, Egypt, December 1988, United Nations Food and Agriculture Organization, Rome. Papadopoulos, I Non conventional water resources: Present situation and perspective use for irrigation. In: International Seminar on Economic Aspects of Water Management in the Mediterranean Area. Proceedings of a seminar held in Marrakech, Morocco, May, CIHEAM, Papadopoulos, I., Economides, S., Stylianou, Y., Georgiades, E. and Koumas, A Use of treated wastewater for irrigation of sudax for animal feeding. In: Land and Water Resources Management in Mediterranean Region, Volume IV. Proceedings of a conference held in Bari, Italy, 4-8 September CIHEAM, Water Development Department 1989 Fifty Years of Water Development, , in Cyprus. Water Development Department, Nicosia.