From 2018 until now, continuous blooming of Lake Sevan has become one of the main environmental problems of our country. Aquatic biologists say there are several reasons for the lake’s bloom.
One of them is the domestic and economic waste water of the settlements of the Sevan basin, which are rich in various organic and inorganic substances and are poured into the lake without any treatment. These substances create a favorable environment for the development of cyanobacteria (blue-green algae) that cause blooms. Warm weather also contributes to their vigorous growth. The fact that as a result of the artificial lowering of the lake level is of significant importance In Great Sevan, the cold bottom layer, the hypolimnion, has completely disappeared, which performs a protective function, preventing the biomaterials accumulated in the bottom from re-entering the lake and contributing to the bloom of algae. In Little Sevan, which is relatively deeper, the hypolimnion has partially disappeared. This is also the reason why Big Sevan is blooming more. On the other hand, there are more rivers flowing into the Great Sevan, therefore more dirty water and various substances are poured here. And, of course, the rotting of the vegetation of the coastal layer that was covered with water in parallel with the even slight increase in the level of the lake in recent years is of great importance, which again produces biomass. However, the biggest challenge among the above-mentioned factors leading to the blooming of Sevan is the organic and inorganic substances coming to the lake from the rivers that fill Sevan. These substances are mainly the result of human activity. Evelina Ghukasyan, the head of the Institute of Hydroecology and Fisheries, also states that the main reason for the flowering of Sevan is the influence of the catchment basin on the lake. «When it comes to the temperature factor, we can hardly control it, and the flowering phenomena become more active with the temperature. But for that you need to have a material basis. And it is the amount of biogenic elements entering the lake from the catchment basin.» Among other rivers of Armenia, the water quality of the rivers flowing into Sevan is also regularly examined. The scientist also highlights the self-cleaning properties of rivers. «As a rule, the springs are always cleaner compared to the middle and lower streams. If the river has a long length, during which it manages to get rid of these biological elements through self-purification, the picture at the mouth is good, but if it is short and has large sources of pollution in the middle stream, that is, there are settlements distributed, then the pollution increases, and up to reaching the mouth of the river, it is not enough to clean it all, and a rather polluted stream flows into the lake.»
As a solution to the problem, «Khimmaster» LLC offers:
• Build a biological treatment plant in each city based on the rationed water consumption.
• In parallel with the construction of the stations, repair and re-equip the existing sewage lines, add new networks until 100% sewerage of the cities.
• Give priority to directing all volumes of wastewater to existing treatment plants and subsequent biological treatment plants. If not feasible, design local (district) stations.
• In order to avoid the spread of infection of Sevan Lake water, especially hepatitis, HIV and other complex diseases, it is necessary to plan a disinfection node at the design stage of any station.