Prevention of hydrogen sulfide formation
Hydrogen sulfide (H2S) has an unpleasant odour and is toxic even in small amounts. The formation of hydrogen sulfide begins when dissolved oxygen and nitrates have been consumed from water, and the remaining sulphates begin to be reduced. If waste water is delivered in long closed pipelines, the microbes contained in the water and chemical reactions have enough time to consume all oxygen in the water, creating favorable conditions for the formation of hydrogen sulfide. The prevention of hydrogen sulfide formation is the most cost-efficient alternative. The addition of pure oxygen enables the oxygen content of the water to be kept at a sufficient level without unpleasant odors.
Improving the efficiency of the activated sludge process
Biological waste water treatment utilizes natural microbial decomposition processes. In most cases the actual decomposition is caused by aerobic bacteria, which need oxygen to be able to split organic matter. Traditionally, the supply of oxygen in aerobic biological decomposition has been secured by using surface aerators, various types of bottom aerators, or membrane units with blower input. The addition of pure oxygen instead of air (oxygen content only 21%) increases oxygen content by a factor of 4.8. The higher oxygen content in the interface between gas and liquid significantly improves oxygen dissolution. Oxygen addition is widely used to increase the capacity of biological waste water treatment plants, and to facilitate the treatment of seasonal and daily peak loads.
Neutralization of alkaline waste waters using CO2
Carbon dioxide is a weak acid which, unlike mineral acids, is naturally found in water, and can therefore be safely used to replace mineral acids in the neutralization of alkaline waste waters. While the use of strong acids may lead to sudden changes in pH, the neutralization curve is considerably more gentle when using CO2. This means that pH values are easier to set and adjust. The use of CO2 also increases the buffering capacity of treated waste water.