HISTORY

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3 HISTORY Protecting the environment and meeting all requirements of the national and the EU legislation in this area are a major priority and inseparable part of the business strategy of Sofiyska Voda JSC. BGN 38.5 M has been invested by the Company in in the wastewater treatment plant in Kubratovo since the start of the Concession (2000). The investments were made in order to implement projects for modernization, increase of the efficiency of the Plant and provision of the required quality of wastewater and sludge September 4th, 1984, the first day of operation of Sofia s Wastewater Treatment Plant (WWTP) in Kubratovo. It was designed in the period It is the first big urban wastewater treatment plant in Bulgaria m 3 per day per day design capacity 600 decares area of the Plant Municipality of Sofia and the management of the treatment plant make successful steps under the PHARE Program of the European Commission for the allocation of a grant for reconstruction of the water treatment line. The project included mechanical and biological treatment. The provided financial support is at the amount of EUR 17.3 M for the execution of the first stage of the reconstruction assigned to the German company VA TECH WABAG. The stage was commissioned in Partial reconstruction of the sludge treatment facilities was carried out with funds provided by the Municipality of Sofia. The aim was to create conditions for stabilization and dewatering of the whole amount of sludge generated at the Plant. The German company Roediger won the tender through a proposal ensuring stabilization and dewatering of the whole volume of sludge. Within the scope of the project, three drum thickeners Roefilt for surplus activated sludge with total capacity 58 m3 per hour were delivered and installed. Provided were also four belt filter presses Roepress for digested sludge with total capacity 96 m3 per hour. Due to the lack of funding at the time the reconstruction of the digesters was not implemented and they were commissioned in The Company commissioned the largest cogeneration installation in the WSS sector for generation of electricity and heat from biogas. Cogeneration is a technology for combined generation of heat and electricity. Kubratovo WWTP recovers the biogas produced in the process of digestion and stabilization of the sludge separated from wastewater. For this purpose, Sofiyska Voda implemented a major investment project worth BGN 5 M for modernization and rehabilitation of the sludge and gas lines in order to capture this biogas. Afterwards, three CHP devices were installed which produce heat and electricity from the biogas. Each of them has a capacity of 1063 kw electricity and 1088 kw heat, which is sufficient to meet the energy needs of a small Bulgarian village November: Veolia, a world leader in the provision of WSS, energy and waste services, became the majority shareholder of Sofiyska Voda and applied its 160-year experience in the management of utility companies in Sofia. Using great expertise, innovations and resourcing the world are key in the development of wastewater treatment facilities of Veolia around the world In the first year since Veolia took over the Company, nitrogen and phosphorus started to be removed from wastewater. This ensures life and biodiversity in the Iskar River Sofiyska Voda JSC, by virtue of a 25-year Concession Agreement signed with the Municipality of Sofia, took over the provision of water supply and sewerage services to the capital city and the WWTP became part of the assets of the Company. 3

4 TECHNOLOGY FOR WASTEWATER TREATMENT Every day about 400,000 m3 of wastewater is treated in order to protect the environment from pollution Sofia s wastewater treatment plant is designed to treat the city s mixed wastewater (domestic, industrial and stormwater) to an extent which allows for it to be discharged into the Iskar River, the receiving water body. The city s sewerage is of mixed type and so surface wastewater from rainfalls and snowmelt enter the plant. This necessitates the facilities through which wastewater passes to take hydraulic load equal to twice the maximum hourly flow in dry weather. The wastewater flows by way of gravity through the sewerage system of Sofia to the WWTP. The length of the sewers and collectors is over 1, 700 km. The wastewater treatment process includes two main lines: a line for treating water and a line for treating the sludge separated from wastewater. 4 1 Sofiyska Voda part of Veolia

5 MECHANICAL TREATMENT THE WAY TO THE RIVER During mechanical treatment, larger objects, grit, suspended impurities and oils are removed from the wastewater. At this stage the so-called primary sludge is also removed. The water goes through 10 coarse and 10 fine screens automated screens. All large impurities brought by the inflow are caught by the screens. The retained mass is gathered in containers and transported for disposal. The major part of mineral waste (grit, glass etc.) is separated from water in aerated grit removal tanks. Water flows slowly here and all mineral impurities settle at the bottom. The separated mass, which is provisionally called grit is dewatered by classifiers. The retained grit can be reused. Suspended solids, which are mainly organic, are separated in primary settling tanks (four radial tanks with diameter 54 m and depth 5.5 m). Waste with relative weight lower than the weight of water detaches and reaches the surface as flowing substances, and waste which weighs more settles at the bottom as sludge. This is primary sludge which is brought to a primary sludge pumping station and then to the sludge stabilization unit. SECONDARY TREATMENT After the mechanical treatment remain organic pollutants which need to be removed. This requires the use of technology for biological treatment of water during which, under maintained special conditions, natural microorganisms use organic pollutants as food thus reducing them to a level that is safe for discharge into the Iskar River. In this process, the microorganisms or the so-called activated sludge multiplies and increases in volume. In order to maintain optimum conditions of the environment some of the activated sludge is removed from the system in the form of surplus activated sludge. AERATION TANKS There are six aeration tanks, each with length 150 m, width 36 m and depth 5.8 m. At the aeration tanks, wastewater is mixed with aerobic microorganisms (activated sludge) and oxygen which they need in order to live. The biochemical treatment of water lasts between 8 and 12 hours. NITROGEN AND PHOSPHORUS RE- MOVAL Another important process is carried out in the aeration tanks. Nitrogen and phosphorus are removed from water before it is discharged fully clarified into the Iskar River. High levels of nitrogen and phosphorus lead to fast multiplication of certain types of algae and deterioration of water quality as well as reduction of the self-clarifying capacity of water. That is why, removing nitrogen and phosphorus from wastewater is extremely important in order to ensure purity of rivers and ecological balance in nature. SECONDARY SETTLING TANKS There are 10 secondary settling tanks, which are the same cylindrical tanks as the primary settling tanks. Here the treated water, which is to be discharged into the Iskar River. Settles at the bottom of the secondary settling tanks, the necessary part of it is pumped back into the aeration tanks to be included in a new treatment cycle. The surplus activated sludge is directed elsewhere to the facilities where sludge is treated sludge digesters. 5

6 THE WAY OF SLUDGE AND GREEN ENERGY By resourcing the world and recovering waste we protect the environment and nature. 6 1 Sofiyska Voda part of Veolia

7 SLUDGE DEWATERING The sludge digested in the aeration tanks is not solid mass yet. It has to be dewatered mechanically as the water content is high (about 96%) so that it becomes more compact. Thus from the aeration tanks the sludge goes through belt filter presses. In this way, not only its volume decreases but also the transportation expenses decrease. The sludge which has gone through the sludge digesters is dewatered mechanically until a sludge cake is produced where the dry substance content is about 25%. The dewatered sludge is a reliable and harmless end product that is applied in agriculture. SLUDGE STABILIZATION The primary and surplus activated sludge contains pollutants removed from water organic substances and microorganisms. If left in nature, they decay and have an unpleasant smell, pollute groundwater, air and soil. Sludge is treated in order to protect the environment and people from these hazardous impacts. The process is called stabilization and during this process most of the organic substances is dissolved, mineralizes and becomes harmless. Anaerobic microorganisms (microorganisms living in a non-oxygen environment) participate in the process. Organic substances are dissolved to biogas that contains methane (CH4, the socalled biogas), carbon dioxide (СО2), hydrogen sulphide (H2S), water (Н2О), etc. The optimal temperature for the process is 33о-37о. GENERATION OF GREEN ENERGY The generated biogas is a high-calorific fuel and is used for the generation of energy which is used for the needs of the Plant. In order to produce green heat and electricity from biogas, a cogeneration installation was installed in the WWTP in In 2014, the WWTP achieved 98% selfsufficiency, producing almost all of the electric energy needed for wastewater treatment. SLUDGE RECOVERY Sofiyska Voda JSC has permits for use of sludge on agricultural land, the permits being issued by the Bulgarian Food Safety Agency at the Ministry of Agriculture and Food. The permits have been issued after detailed chemical analyses aimed to check whether the sludge contained heavy metals and other hazardous substances which could pollute the soil, groundwater or could lead to negative consequences for biodiversity. The analyses have shown that the sludge in Kubratovo WWTP is very suitable to be used as fertilizer on agricultural land. 7

8 QUALITY OF THE TREATED WASTEWATER AND SLUDGE In order to avoid environment pollution and to act in accordance with the requirements of the Permit for Wastewater Discharge into Water Bodies issued by the Danube Region Basin Directorate, the Wastewater Sector of the Laboratory Testing Complex (LTC), situated at Kubratovo WWTP, ensures continuous and regular monitoring of the wastewater at the different treatment stages. Every day certified laboratory specialists of Sofiyska Voda JSC take samples at more than 20 points in WWTP. They are analyzed for more than 30 physical and chemical indicators and also by some microbiological and hydrobiological indicators. The Wastewater Sector of LTC also performs analyses of key indicators of industrial wastewater flowing in the city sewerage. 8 1 Sofiyska Voda part of Veolia

9 LTC OF SOFIYSKA VODA JSC Qualified specialists work in the LTC. Applied are both classical and high-technology instrumental test methods. Full traceability is ensured for each sample submitted to the LTC, from the moment of the sample taking to the issuing of the test protocol. Reliability of the analytical results and continuous control on the test methods are ensured as only chemicals and high-purity reagents, certified reference materials, and calibrated technical devices are used and also everyday control on the factors of the work environment is ensured. In June 2008, a Quality Management System developed as per the requirements of the standard BDS EN ISO was implemented at the LTC of Sofiyska Voda JSC. In November 2008, Sofiyska Voda JSC submitted the required documents and started a procedure for accreditation of the LTC in line with the requirements of the Bulgarian Accreditation Service. All the samples of potable water, wastewater and sludge are tested at LTC in line with the principles of good laboratory practice (GLP) and in line with the procedures and rules of the Management System. In February 2010, the LTC received an accreditation certificate as per the standard BDS EN ISO/IEC 17025:2006. The scope of accreditation includes taking water samples and testing potable water, surface water and wastewater. After a successful re-accreditation assessment carried out by Executive Agency Bulgarian Accreditation Service, the LTC received a certificate and order for accreditation for the period Apart from the reaccreditation, the LTC obtained a permit concerning its scope. The scope already includes the groundwater matrix. 9

10 INVESTMENTS IN KUBRATOVO WWTP Over its 30-year life, Kubratovo WWTP has treated more than 4 billion m3 wastewater or about 8 times the volume of Iskar Dam and almost 2 billion tons of sludge. More than BGN 38 M has been invested in the reconstruction and maintenance of the facility by Sofiyska Voda JSC and another BGN 60 M under the ISPA program Sofiyska Voda part of Veolia

11 Since 2001 a large-scale rehabilitation program has been implemented in the wastewater treatment plant. During the implementation of the investment projects, there are periods when fewer facilities are included in the technological cycle and then the plant functions at reduced capacity. In these cases the management of the WWTP has always managed to optimize the control of the technological processes and establish organization so that the quality parameters of the water at the outlet of the plant to meet the statutory requirements. The large-scale capital investments required for modernization of the wastewater treatment plant are ensured with own funds of Sofiyska Voda JSC and via EU funding of infrastructure projects. Completed investments financed with EU funds Project for the reconstruction and modernization of the water line stage I The implementation of the project commenced in 2001 and was completed in The funds amounting to BGN 36 M are a grant to the Municipality of Sofia under PHARE program from the European funds for large-scale infrastructure. The contractor under the project is the German Company VA TECH WABAG, and the supervisor the Swedish Company VAIVA. This stage of the project includes: Construction of three aerated grit removal tanks; Construction of a new distribution and metering device upstream the primary settling tanks; Repair of the primary sludge pumping station; Rehabilitation of four aeration tanks with replacement of the aeration system; Replacement of the electrical and control and measurement equipment of four air blower facilities; Construction of a new three-direction distribution device in front of the secondary settling tanks; Construction of two new pumping stations for activated sludge recirculation; Construction of two new secondary settling tanks; Implementation of SCADA system (monitoring, management, control and data collection). P M BGN investments provided for the project under the ISPA program for rehabilitation of existing facilities and implementation of a system for removal of nitrogen and phosphorus. 1. Checkpoint - main gate 2. Administrative building 3. Grease chamber 4. Screens 5. Aerated grit removal tanks 6. Primary radial settling tanks 7. Primary sludge pumping station 8. Grit drying beds 9. Emergency chamber upstream the aeration tanks 10. Air blowers upstream the aeration tanks 11. Aeration tanks 12. Three-direction distribution device 13. Secondary radial settling tanks 14. Digested sludge dewatering 15. Digested sludge thickener 16. Drying beds 17. Surplus activated sludge thickeners 18. Sludge digesters 19. Cogeneration installation 20. Gasholders 21. Contact reservoir 22. Reservoir for sludge water 11

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