I sugget you consult the book, " Standard Methods for the Examination of Water and Wasrewater". The latest edition is available on line as of January 2023. The book is jointly published by the "American Public Healthe Association" and the American Water Works Association".

There are various microorganisms involved in different stages of wastewater treatment. Some of the key microorganisms used in wastewater treatment include:

Bacteria: responsible for the decomposition of organic matter in sewage. The process of bacterial decomposition is known as aerobic and anaerobic digestion, depending on the presence or absence of oxygen.

Aerobic Bacteria: require oxygen to survive and break down organic materials. They are commonly used in the initial stages of sewage treatment to digest readily biodegradable organic matter rapidly.

Anaerobic Bacteria: can function in the absence of oxygen and are utilized in anaerobic digestion processes. They break down complex organic compounds and produce biogas (methane and carbon dioxide) as a byproduct.

Protozoa: prey on bacteria and other small particles in the wastewater. They contribute to the biological breakdown of organic matter and help clarify the water by consuming suspended solids.

Fungi: can be found in some wastewater treatment systems. They play a role in decomposing complex organic compounds that bacteria may struggle to break down.

Algae: used in ponds or lagoons to remove nutrients like nitrogen and phosphorus from the water through nutrient uptake.

The role of microbes in sewage and wastewater treatment systems includes the following key processes:

Primary Treatment: processes like screening and sedimentation remove large solid materials from the wastewater. Microorganisms, especially bacteria, aid in the breakdown of organic solids that settle at the bottom of the sedimentation tanks.

Secondary Treatment: microorganisms, primarily bacteria and protozoa, break down dissolved and suspended organic matter through aerobic and anaerobic digestion. This step reduces the biological oxygen demand (BOD) and chemical oxygen demand (COD) of the water, making it less harmful to the environment.

Tertiary Treatment: In some advanced wastewater treatment systems, tertiary treatment involves using specific microbes or algal systems to remove nutrients, such as nitrogen and phosphorus, from the water.

Sludge Treatment: anaerobic bacteria digest the organic matter in sludge to produce biogas. The remaining sludge can be further treated and stabilized before disposal.

Dr Mohd Ariff Ahmad Nazri thank you for your contribution to the discussion

Biological wastewater treatments employ microorganisms to remove organic matter from water. Organic matter or pollutants stem from number of sources, such as drainage systems or acid rain. The use of microorganisms in wastewater treatment results in the Fats, Oil and Grease removal. Wastewater is always contaminated with different biological agents such as bacteria, viruses, protozoa, fungi, flatworms or roundworm.Microorganisms have several vital roles in ecosystems: decomposition, oxygen production, evolution, and symbiotic relationships. Decomposition is where dead animal or plant matter is broken down into more basic molecules. This process only happens because of the microorganisms that find their way into the dead matter. The secondary stage of treatment removes about 85 percent of the organic matter in sewage by making use of the bacteria in it. Wastewater entering a treatment plant is aerated to provide oxygen to bacteria that degrade organic material and pollutants. Microbes consume the organic contaminants and bind the less soluble fractions, which can then be filtered off. Activated sludge (AS) is composed of aerobic and anaerobic microorganisms such as bacteria, archaea, fungi, and protists. A microbial culture for wastewater treatment is a microbe that is added to the aeration tank to encourage the breakdown of different materials and to lower BOD, COD, and SS concentrations. A solid type formulation and a liquid type formulation of microbial culture for wastewater treatment are both available.Here in, microbes carry out the decomposition of organic matter by utilizing carbon and nitrogen as the energy sources along with oxygen and water, ensuring the production of water, carbon dioxide, heat, and soil-enriching compost.To do this the liquid is fed into an aeration tank containing a complex community of microbes. The contents of the tank are mixed mechanically with air or air is bubbled through the tank. The microbes then use the organic material in the sewage as their source of carbohydrate for respiration. The aerobic bacteria in the sludge digest the organic material around them in order to reproduce and grow, and change the chemical makeup of the sludge, oxidizing ammonia into nitrate and nitrite in a process of nitrification

Bacterial communities are responsible for the degradation of organic matter in the waste water

Dr Preethi Shetty thank you for your contribution to the discussion