Biological treatments, which use organisms to break down organic substances in wastewater, are widely used around the world.
Unlike other wastewater treatments methods, which use only mechanical or chemical processes, biological treatments include the use of bacteria, nematodes, or other small organisms.
The effluent is a mixture of water with suspended cells and drastically reduced BOD content. This mixture is then passed through a clarifier (settling tank) where the solids (mostly cells, called sludge at this stage) are separated from the water. The system is commonly operated in continuous mode (as opposed to batch mode). This process involves confining naturally occurring bacteria at much higher concentration, in tanks. From here this bacteria, together with some protozoa and other microbes (collectively referred to as activated sludge) are treated in an anaerobic and an aerobic process. They are then returned to the anaerobic phase to eliminate sludge production and waste.
Activated sludge process is a proven biological wastewater (sewage) treatment widely used for the treatment of both domestic and industrial wastewaters. It is particularly well suited for treating waste streams high in organic or biodegradable content. The Ecotech Africa WWTP is a system in which pre-treated sewage (i.e. having passed through primary treatment) is aerated to promote the growth of bacteria (cells) that gradually consume the organics in the sewage. The result is the development of cellsacclimated to the particular mix of substances present in the sewage and a significant consumption of the organic material.
The system is properly speaking an activated sludge system when a portion of the sludge (cells) collected from the bottom of the clarifier is returned to the anaerobic phase. The treated effluent can be utilized for various reclamation uses such as agriculture, irrigation, duct suppression or can be discharged to the environment as plants are designed to either comply to SA Special Limits or General Discharge Limits dependant on requirements.
Advantages of the EcoTech Africa Systems
Ecotech Africa Biological Waste Water Treatment Process
Screening takes place at the point of entrance in the WWTP to remove any gross solids and inorganic material. This can be done manually or automatically.
Influent enters the anaerobic phase. The de-nitrification cycle takes place in this phase. This function is responsible for the breaking down of nitrates to nitrogen gas.
In this third phase the digestion takes place in an aerated environment. This phase can be divided into two or three bioreactors added together. This phase is called aerobic digestion or simpler terms is Bioreactor. This phase takes the smaller solids and bio-degrade them further. The type of bacteria that operates in this environment is called aerobic bacteria. It is very important to aerate this phase to enrich the liquid with oxygen. The bacteria perform at their optimum in an oxygen enriched environment. In the aerobic phase the nitrification takes place. This process breaks down the ammonia to nitrites and the nitrites to nitrates.
Secondary settling takes place in the fourth phase. The cell material and settle able solids settle in this phase and form the so-called sludge blanket . The sludge blanket is very important for the process. When the blanket matures it is re-circulated to the primary settling tank in phase one to seed or inoculate the raw sewerage entering into the plant and to alter the nitrates to nitrogen gas. This cycle is called the re-activated sludge cycle. This technology improves the efficiency of the process and the plant.
In the fifth and final phase the final effluent is prepared for final discharge. The effluent is disinfected or sterilized to prevent any dangerous or harmful bacteria from entering our environment. This is achieved by either dosing with chlorine or treatment by means of Ozone.