Criteria for water recycling and reuse in the Mediterranean countries

Though rapid changes are likely to occur, until recently most Mediterranean countries had neither water reuse regulations nor guidelines. Countries where reuse is developing within an organized institutional setting have elaborated and implemented their own regulations or guidelines. Some countries (France, Tunisia) and regions (Andalusia and Balearic Islands in Spain and Sicily in Italy) have adopted a set of water quality criteria based on the WHO guidelines, while other countries (Cyprus, Italy, Israel) elaborated regulations or guidelines close to the more conservative California’s Water Recycling Criteria. Though the need for sharing common regulations or, at least, a common rationale for developing water reuse standards on both sides of the Mediterranean has been acknowledged, this objective does not appear reachable in a near future. Among the factors that might be evoked to explain the dramatic discrepancies in the Mediterranean criteria, the lack of a clear rationale supported by scientifically established data as a solid basis for setting up water reuse guidelines has a major importance. A deterministic approach, such as the one adopted in the draft of Australian National Guidelines for Water Recycling may, despite several drawbacks and uncertainties, pave the way to reach a regional consensus.

Several factors that explain the dramatic discrepancies in the Mediterranean regulations of water reuse have been found in their elaboration Table 2 Quality guidelines for water reuse in Andalusia Type of application Faecal coliforms/100mL Nematode egg/L Irrigation of sport fields and parks with public access Vegetables to be consumed raw Production of biomass intended for human consumption and refrigeration in open circuits Recreational lakes Refrigeration in semi-closed circuits Industrial crops, cereals, dry fodder seeds, forests and conserved or cooked vegetables Irrigation of green areas with no public access, production of biomass not intended for human consumption and impoundments with access prohibited <200 <1000 <1000 <1 <1 None <2000 <10,000 None <1 None <1 None None Table 3 Planned Spanish standards for the reuse of treated effluent (Associación Española de Abastecimiento de Agua y Saneamiento, 2005) Uses of reclaimed wastewater Nematode eggs1 E. coli (cfu/100 mL) SS (mg/L) Turbidity (NTU) Residential uses <1/10 L <10 <2 Urban uses and facilities Greenhouse irrigation <1/L <200 <20 Other criteria <10 Legionella spp. 100 cfu/100 mL Irrigation of vegetables Irrigation of fodder <1/L <1,000 <35 No limit set Watering of crops eaten cooked Irrigation of industrial crops Irrigation of wooden areas Industrial cooling <1/L <1/L No limit set <10,000 No limit set <10,000 <35 <35 <35 No limit set No limit set <1/L <200 <35 No limit set No limit set <10,000 <35 No limit set <1/L <1,000 <35 No limit set <1/L <10 <2 Ponds, etc. for recreational purposes (public contact allowed) Ponds, etc. for recreational purposes (public contact is not allowed) Aquifer recharge: localized percolation Aquifer recharge: direct injection process and, particularly in the reference to the benchmark standards, i.e. the State of California Title 22 criteria and WHO guidelines. Beyond these factors, the lack of a clear rationale supported by scientifically established data as a solid basis for setting up or adapting water reuse guidelines explains the heterogeneity of the Mediterranean guidelines and regulations. Most guidelines and regulations reflect more a perception of a risk hierarchy – which differs from one country to another – than scientifically based risk assessments. Therefore, some doubts might be introduced on the consistency of the reuse criteria and their ability to provide an efficient protection to the public Taenia saginata and T. solium <1 egg/L Legionella spp. <10 cfu/100mL Total nitrogen <50 mg/L Total nitrogen <15 mg/L health and the environment. As a result, governments may be tempted to turn towards the most conservative and costly regulations or to prioritize other resources, such as seawater desalination. Two conditions should be fulfilled to increase the credibility of water reuse guidelines and regulations and, at the same time, facilitate the reduction of the discrepancies between the regulations adopted by Mediterranean countries. (a) The first one is the harmonization of healthbased guidelines related to different water uses. Water reuse guidelines should be part of a set of consistent water regulations applying to drinking water, bathing water, irrigation and Table 4 Proposed minimal criteria for reuse of reclaimed wastewater in Greece [10] Water quality criteria a Recommended uses I.N. ≤ 0.1 eggs/L FC ≤ 10 cfu/100mL SS ≤ 10 mg/L Tb ≤ 2 NTU (a) Residential areas with high public contact (b) Toilet flushing and air conditioning (c) Car washing (d) Direct injection to the groundwater I.N. ≤ 1 egg/L FC ≤ l00 cfu/100mL SS ≤ 20 mg/L Τ ≤1 NTU (a) Ponds, bodies of water, and streams with high public contactc,d (b) Fountains and other recreation places (c) Streets cleaning and fighting (d) Irrigation of vegetables to be eaten uncooked I.N. ≤ 1 egg/L (a) Irrigation of fodder crops for livestocke, crops for canning, vegetables to be eaten cooked, plant nurseries, etc. (b) Aquaculture (c) Groundwater recharge (by surface spreading)g FC ≤ 1000 cfu/100mL SS ≤ 35 mg/L I.N. ≤ 1 eggs/L FC ≤ 10,000 cfu/100 mL SS ≤ 35mg/L (a) Irrigation of wooden areas, industrial wooden areas, greenbelts, and areas where the public is not allowed to enter (b) Industrial use (except for food industry)h (c) Ponds, bodies of water and streams where the public contact is not allowed Limits for T are not applicable Limits for NO3– should be required e Limits for Taenia sp. (< 1 egg/L) should be required g Minimal depth of 5 m is required h Limits for Legionella pneumophila should be required for industrial cooling. c d discharge in the environment. Guidelines on water reuse and other water exposures (e.g. drinking water and recreational water contact) should assure equivalent protections. (b) The second is that setting up health guidelines should be supported by a methodology based on epidemiologic investigations and quantitative microbiological health risk assessment (QMRA). In this respect, the deterministic approach adopted in the draft of Australian National Guidelines for Water Recycling and Reuse [11] is, despite some methodology limitations, a major breakthrough in the methods implemented for the elaboration of reuse guidelines. Its mathematic formulation should allow a more efficient dialogue between the countries and significant progress in the adop- tion of common policies. In the same time, it makes easier pointing out the uncertainties attached to the relationships between the microbial quality of the reused water and heath risks and, by the way, stressing the research needed to reinforce the scientific basis of reuse guidelines. The WHO guidelines for the safe use of wastewater in agriculture have been recently revised according to the same principles; this work was also based on an updated and comprehensive review of epidemiological investigations and QMRA results [12,13]. This revision should help revitalize the dialogue between European and Mediterranean countries and pave the way towards a regional consensus.