The former Eastern Bloc countries were notoriously known for giving little weight to public health and other basic individual needs. Since the fall of the Iron Curtain, Bulgarian water experts have finally regained control over the most precious of all resources and, additionally spurred by EU requirements, can already boast important achievements in the provision of sound and healthy drinking water.

What has contributed to these achievements is the vital and fruitful exchange of experiences and know-how with foreign colleagues mainly from Germany throughout many years. This collaboration has so far found its peak in a major survey assessing the quality of drinking water in Bulgaria, with the objective that the obtained data lead to immediate recommendations.

The recently concluded project meets all these requirements. The Bulgarian population and potential investors will thus soon have a clearer picture of the current water situation, based on which further improvements in Bulgarian water management can be made. Quality deviations and their impact on human health were assessed by means of a guidance specially designed for use by regional health authorities in this specific project; this guidance derives its contents from Article 9 of the EU Drinking Water Directive.

Analysis

In Bulgaria, more than 28 regional health service departments (RIPHP) are in charge of drinking water quality monitoring and data transmission to the Ministry of Health. These departments have no computer-aided data collection and evaluation tools whatsoever at their disposal. This is why they work together closely with regional water suppliers (WVU). At present not even all the laboratories run by the latter are properly equipped to meet EU standards. This also goes for quality monitoring.

This situation causes Bulgaria to increasingly engage in joint projects with the "old" EU member states to improve its water management system. During its numerous fact-finding visits of the country, the project team has found that the raw waters used for drinking water production are either derived from groundwater (47.6 % of total supply) or from surface waters (52.4 %).

The proportion abstracted from surface waters (direct abstraction or abstraction through bank-filtered water) is drawn from impoundment reservoirs (45.4 %) and watercourses (7 %). In many regions, too little of the land adjoining wells and bank filtration plants is spared from agricultural use. As a result, pollutants need to cover only short distances to pass through the soil into water.

Wells drilled in flood zones and within the boundaries of river dams pose additional problems for the provision of high-quality drinking water. Groundwater is chlorinated before use and apart from this usually undergoes no extra conditioning. The conditioning of surface water for use as drinking water is limited to a few impoundment reservoirs and direct abstraction from rivers or bank-filtered waters. The steps of conditioning usually comprise precipitation/flocculation, filtration and disinfection by chlorination and occasionally by UV radiation.

Most of the conditioning plants are in full operation, but on account of their long service life they are becoming increasingly unreliable. All plants the expert team has visited are badly in need of restoration. The drinking water in the project was analysed by using fact sheets (update 2003–2004 or later) which were provided by the RIPHP.

In some of the known critical areas, the German experts were asked to analyse specific parameters in more detail and were in fact able to identify excessive pollutant concentrations and public health risks. Nitrate: the biggest problem Excessive nitrate concentrations were the most common problem identified by the project team.

Mainly groundwater aquifers near the surface in the area of smaller settlements are affected. Nitrate concentrations of 4-15 mg/l, as they typically occur throughout the country, are yet below the permissible limit of 50 mg/l NO3. Significantly higher concentrations (commonly also above 130 mg/l) are found in the northeast and southeast of the country, with peaks of 250 mg/l and higher.

These are mainly caused by uncontrolled use of nitrogen fertilizer in agriculture, which can only be countered effectively by a significant reduction of fertilizer amounts. Relevant cooperation models between agricultural and water management stakeholders also ought to be initiated in Bulgaria.

Excessive nitrite concentrations were far less common. These typically occur in near-surface groundwater aquifers in areas of agricultural land use. Measured concentrations were found to range from 0.002 to 1.8 mg/l and occasionally coincide with elevated nitrate concentrations. Ammonium concentrations exceeding the permissible limit are only of importance in a local environment. They are caused by discharge of untreated municipal sewage and effluents from animal farms.

Elevated manganese concentrations are of geogenic origin and primarily found in the bank-filtered water of the larger rivers (Danube, Maritsa, Kamchyia, etc.). This phenomenon tends to occur in episodes such as in impoundment reservoirs or after dry periods when water levels are low. Extremely high concentrations are at times also measured in the households, resulting from the release of manganese deposits into the system.

Concentration levels exceeded the permissible limits dramatically when in 2001 the threshold was reduced to match EU Drinking Water Directive requirements. Some 68,000 people or 0.85 % of the total population in Bulgaria are affected by the problem with manganese, with the regions hardest hit being Haskovo and V.Tarnovo.

Chromium constitutes a very specific problem of geogenic origin. 16 small towns with as many as 19,000 inhabitants in the regions of Montana and Pleven in Bulgaria’s north are affected. The current countermeasure is to dilute with uncontaminated water to keep above-threshold concentrations to a minimum. Above-threshold concentrations of lead are in most cases also of geogenic origin and, unlike in Germany, not the result of old leaden pipes. Throughout the country elevated concentrations are occasionally measured.

When disinfection with chlorine gas or other oxidants combines with bromide, large proportions of organic matter or heavy turbidity of the raw water, this may lead to the formation of by-products such as bromate and trihalogen methane. These two substances can seriously impact human health. Since the RIPHP’s regular analytical programme fails to look at by-products, some samples were taken and examined in the framework of the project. No above-threshold concentrations were found.

Turbidity of drinking water, together with other sensory parameters (taste, smell), is a common phenomenon in Bulgaria which particularly occurs in periods of heavy rainfall, snow melt and algal bloom. Since the numerous water supply facilities with their poor technical equipment are unable to cope with this problem, drinking water conditioning plants urgently need to be complemented by the required process stages and receive financial backing. A large number of organic parameters taken into account by the EU Drinking Water Directive can at present not be tested in Bulgaria. Any potential discharge from old contaminated sites or from other unexamined pollution sources are therefore still unknown.

Guidance for assessment

Whether and to what extent excessive concentrations of certain substances in the drinking water lead to health problems depends on the properties of the relevant substance, drinking water consumption and exposure time. Excessive concentrations need not automatically result in health risks. The project team has developed a guidance and conducted training courses, which shall support the RIPHP in identifying excessive concentration levels.

The guidance basically:

• answers fundamental questions relating to competencies, necessary measures, etc.,
• compares the legal situation,
• describes drinking water pollutants and provides a list of priority measures to be taken in case of a potential hazard,
• identifies risk assessment methods and
• suggests a relevant risk management strategy including programmes of measures.

Results of assessment

Based on the large number of evaluated data, the following conclusions can be drawn:

• A major proportion of the drinking water obtained from surface waters is distributed to customers without prior conditioning in accordance with Regulation 12/2002 governing the quality of surface waters for drinking water supply.
• With respect to drinking water derived from groundwater reservoirs, the country has merely two conditioning plants for manganese elimination servicing 150,000 inhabitants.
• Drinking water in Bulgaria is “traditionally” chlorinated before it is supplied to customers. Especially in smaller supply units, water disinfection has proven to be inefficient owing to the lack of modern dosing facilities. The problem of microbial contamination is particularly severe in mountain springs where access is difficult and which are therefore rarely and insufficiently maintained.
• More than two thirds of the distribution pipes are made of asbestos cement and about one third of metals. Plastic pipes, which began to be installed ten years ago, today account for 2 %. Most of the pipes are old, in poor condition and are incompatible with the physical-chemical properties of the water. This results in heavy corrosion and excessive water losses respectively.
• It would be essential to either modernise the existing water conditioning plants or alternatively build new ones where needed.
• Resource protection, especially in drinking water protection zones, is simply inadequate.
• No one knows whether and how industrial plants, landfills and other suspected sites impact drinking water quality. Critical parameters are at present neither investigated nor analysed.
• In some water supply areas seasonal low precipitation leads to water shortage, which puts drinking water quality and supply under additional pressure.

Considerable investment is needed to solve the problems outlined above. This relates to the construction of new plants as well as the restoration of existing plants. We generally suggest and recommend the following procedures: To condition raw water from impoundment reservoirs, flocculation and filtration plants need to be constructed or completed. In critical cases complementary ozone treatment or powdered activated carbon dosage is additionally needed. Potassium permanganate may be required in individual cases to eliminate manganese efficiently.

Flocculation must basically be a permanent process. According to the EU Drinking Water Directive, water turbidity prior to disinfection should be < 1 FNU, although substantially lower values are suggested. The cost of constructing a conditioning plant for impounded water with a daily capacity of 20,000 m3 and potassium permanganate dosage, flocculation, two-layer filter and pH control equipment is estimated at 100 e/m3/d.

If river water of poor quality is directly abstracted and bank filtration cannot be used, the water must at least be subjected to the same treatment as water from impoundment reservoirs. The treatment of bank-filtered water with elevated iron and manganese concentration levels requires rapid filtration. Water from rivers exposed to anthropogenic impact may need additional treatment. Nitrate can be eliminated by means of various different techniques. In smaller units mostly reverse osmosis and/or ion exchange are used.

Biological methods are recommended for larger units. The prime goal, however, must be to reduce agricultural water pollution! Chromium VI can only be eliminated through special ion exchangers or precipitation with ferrous hydroxide under alkaline conditions. Also the installation of permeable reactive walls made of ferrous materials in the area of the inflow was tested. At any rate, thorough investigation of the relevant background conditions is required. Rapid filtration units are required to ensure efficient elimination of iron and manganese.

Bulgaria has already gathered some experience within this field; the encountered problems basically result from a lack of financial power. Microbially contaminated catchments or wells need to be restored to prevent surface water from seeping in. If this is not possible, the water needs to be subjected to the same treatment as surface water.

For smaller units slow sand filtration may be used. Irrespective of whether there is a need to build conditioning plants like the ones described above, disinfection techniques have to be safe and reliable to ensure that drinking water remains unaffected by microbial contamination. For this purpose, it is essential that adequate funding is provided as soon as possible.

Regional concepts need to be developed which form the basis for a sustainable water supply and devise solutions to existing problems by drawing on water consumption forecasts and current water supply data. After comparing different alternative approaches, a regional development concept needs to be drafted based on which funds should be allocated. Without the pursuit of this strategy there is the risk that costly "individual solutions" are to be expected. Also measures to reduce grid losses shall be implemented.
(Source: aqua press Int. 4/2006, Dr. Hans-Martin Mulisch et al.)

Contact & Information:

Umweltbüro DI Mulisch GmbH
Dr. Hans-Martin Mulisch
Dennis-Gabor-Str. 2; D-14469 Potsdam
Tel.: +49/331/62 53 40