Development and simulation of the operation of a two-tier sedimentation tank for urban wastewater treatment

Abstract

Abstract One of the main reasons for the increase in the ecological tension of aquatic ecosystems remains the discharge into water bodies of domestic wastewater containing toxic substances and pathogenic microorganisms. This is due to the imperfection of water treatment technologies, including due to wear and tear of utility networks and violations in the technological process, accompanied by salvo emissions. Reducing the anthropogenic load on water bodies is possible by retechnologizing various stages of wastewater treatment. The paper describes the design of a sedimentation tank with aeration elements for clarification of urban wastewater, providing an increase in the efficiency of sedimentation of suspended solids. Spraying fine air bubbles contributes to the collision and enlargement of aggregate-unstable elements without the use of coagulants and flocculants. The paper presents a mathematical algorithm for calculating the required deposition surface, taking into account the wastewater flow rate, the nominal diameter of the dispersed phase particles and the required degree of purification. Numerical experiments have shown that for a settlement with a population of 100,000 people, a treatment plant with a standard sedimentation tank is required, the area of which is 130 m2. The use of a sedimentation tank with aeration elements in similar conditions allows reducing the required clarification surface to 120.9 m2 without reducing the clarification efficiency. It has been proven that the spraying of finely dispersed air bubbles helps to reduce the required settling area of the sump by 8%.