On 04.07.2025, the Summer Internship in Biological Control and Water Treatment for students from the MSc program "Environmental Biotechnology" was completed, as well as the internships for MSc programs "Applied Hydrobiology and Aquaculture", "Eco-management" and "Bio-business and Bio-entrepreneurship". The internship was divided into 2 modules related to: 1/ technologies for treatment and purification of drinking water, wastewater, and waste, as well as control of technological processes; 2/ environmental monitoring of water, sediments, and air. The internship was organized by lecturers from the Department of General and Applied Hydrobiology of the Faculty of Biology at Sofia University "St. Kliment Ohridski" and researchers from the Center of Competence Clean&Circle.

Students visited the mineral water bottling plant "Bankya" in Bankya and had the opportunity to speak with the management team. Adelina Petrova - Head of Production Center Bankya; Shteryo Spasov - Health and Safety Specialist, and Aleksandar Anastasov - Shift Manager, Bottling Lines, together with their colleagues, introduced them to the technological processes and control indicators, as well as the responsibilities and challenges in the treatment of spring water and the distribution of the finished product.

They followed the path from the spring to the packaging of the product, along with the path of wastewater and waste generated at the plant. They became acquainted with the quality systems ISO 9001, ISO 14001, ISO 22000 and with the set indicators (Key Business Indicators; Equipment Sanitization Indicators; Waste Recycling; Cost Management, etc.) and the target values achieved by the plant. During their visit, the students also learned about the established educational program of Coca-Cola HBC Bulgaria - #YouthEmpowered, which aims to support young people between 16 and 25 years of age in one of the key stages of their lives - the transition from education to professional realization.

Visit to the spring in Bankya

Production line for bottling natural mineral water

During their visit to the Kubratovo WWTP, the MSc students became acquainted with the water cycle in Sofia, with the technological scheme and operation of the treatment plant, with the new facilities along the path of water and sludge, as well as with the control parameters of the treatment processes and the water quality at the plant’s outlet. They also visited the Laboratory Testing Complex of the Accredited Laboratory of "Sofiyska Voda" JSC to see the processing of samples under the guidance of Mrs. Vesela Stefanova.

Biological basins at the Kubratovo WWTP, where Sofia’s wastewater is biologically treated

After the training in front of the Laboratory Testing Complex of "Sofiyska Voda" JSC

At the Municipal Waste Treatment Enterprise (MWTE), the students visited both sites of the enterprise and became acquainted with the integrated waste management system of Sofia. They reviewed the technological scheme and operation of the biogas, composting, and wastewater treatment facilities. They also learned about the control parameters for treatment processes and for the quality of water, compost, and biogas.

Visit to MWTE, Sadinate site

At the composting facility of MWTE, Han Bogrov site

Treatment of liquid fraction of digestate from Kubratovo WWTP with plasma source surfaguide

Grown colonies on Endo medium before and after treatment of digestate from Kubratovo WWTP with plasma source β-device and surfaguide

Grown colonies on Salmonella Differential Agar medium before and after treatment of digestate from Kubratovo WWTP with plasma source β-device and surfaguide

The MSc students visited the University of Forestry, a partner of the CC Clean&Circle. They participated in a discussion concerning real results on the state of air in Sofia, key indicators, and methods for air quality analysis. Together with Prof. Eng. Dr. Ekaterina Todorova and Assist. Prof. Dr. Aleksandrina Kostadinova, they characterized waste samples and discussed opportunities for utilizing different groups of waste.

Presentation of results and discussion on air quality in Sofia

Characterization of waste in a UF laboratory and discussion on opportunities for their utilization in CC Clean&Circle

The students visited the Institute of Fish Resources in Varna, where Assoc. Prof. Dr. Sonya Uzunova and her colleagues introduced them to opportunities for fish resource cultivation and process control

Discussion on the state and specifics of the Black Sea in front of the Institute of Fish Resources in Varna

At the Institute of Oceanology – BAS in Varna, Assoc. Prof. Dr. Kremena Stefanova and her colleagues held discussions on indicators for monitoring marine ecosystems.

Discussions at the Institute of Oceanology – BAS in Varna with the students

Students worked in the field with Assoc. Prof. Dr. Dimitar Kozhuharov, Assist. Prof. Dr. Zornitsa Zakharieva and biologist Lachezar Spasov, taking samples from the Black Sea and analyzing on site indicator groups of organisms for the state of the marine ecosystem. They visited the Dalboka Mussel Farm in the village of Balgarevo, getting acquainted with the cultivation of black mussels; the biology of the species and the ecological significance of mussel farms and their impact on the environment.

Collecting samples for assessment of the marine environment based on the biological quality element plankton

Analysis of biodiversity in the studied sampling points in the Black Sea

Visit to Dalboka Mussel Farm

Cultivation of mussels of the species Mytilus galloprovincialis

 The conducted Summer Internship presented to students and lecturers real ecological and technological cases, reinforced theoretical knowledge based on "learning by doing" and "learning through solving real problems from the practice of clean technologies and environmental management". The spirit of positivity and collegial partnership contributed to the motivation of the MSc students to work in the field of water resource and waste management and to participate in the creation of innovative clean technologies.

We express our heartfelt gratitude to our partners who made possible and engaging the practical training of the MSc students from the Department of General and Applied Hydrobiology, who are also studying at the CC Clean&Circle.

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