There are various biological processes in wastewater treatment plants that are carried out by the diverse group of organisms. It is very hard to say which species are present as their dependency is based on external conditions.

The organisms-

All organisms in wastewater treatment must have their origin from outside as they come from refuse, air, the soil, and animals etc. An important aspect regarding biological treatment process is the presence of pathogenic organisms. This isn’t the important aspect but one should know that during biological treatment of water the pathogenic microorganisms are present at every stage of wastewater treatment. The organisms in wastewater can be subcategorized as:

• 1. Bacteria
• 2. Fungi
• 3. Algae
• 4. Protozoa
• 5. Metazoa

Wastewater treatment plants are of two main types: activated sludge and bio filters. The variation of living organisms can be found diverse in bio filters whilst in activated sludge based plants the distribution of organisms are uniform. Bacteria occur vastly in both plants and are relatively more in activated sludge based plants. The main responsibility is degradation of organic matter and transformation into products which can be disposed of safely. Fungi are of competitive nature to bacteria for food (biodegradable matter). This competition is normally an added advantage to bacteria and hence they are found more in treatment plants. Algae are usually found in bio filters where conditions are favorable (sunlight and food). Protozoa occurs in varying number in activated sludge based plants and depends upon the loading rate of plant. Metazoa have same distribution pattern as protozoa and are higher animals. The species are Rotifers, Crustaceans, animals and insects.

Selection

The basics of selection are based on threshold diversity of species for doing specific work inside a plant. This can be understood simply by a statement as quoted: More the number of species, greater is the chance for them to flourish under different environmental conditions. The two main types of mechanism as discussed above are mainly based on selection criteria. The selection is a bit tough in activated sludge type plants. The prime factors for selection of living life in treatment plants are: pH, temperature, oxygen, growth rate, suspended life forms, settling, death rate and food.

Conversions in biological treatment system

There are ample numbers of organism dependent conversions which are vitally important. It is concerned with: hydrolysis, microorganism growth and death (decay). In addition to that adsorption should be added (this doesn’t actually hinder with the process) which may have an impact to the process.

The flowchart designed below will show how the process works:

Biological Conversion in Treatment Plants

The most vital part of reactor plants is that only a certain quantity is to be removed is immediately accessed by living organisms inside the plant. The biological growth, decay or death rate and hydrolysis needs to be understood in order to understand the living world inside of a wastewater plant. The complexity of living world is so high that even scientific explanations might seem unsatisfactory.