For industries producing wastewater in Australia as part of their process, biological wastewater treatment is usually necessary to ensure discharge regulations and safety precautions are met. The most appropriate system for wastewater treatment will help companies avoid harming the human health, environment and the process and products of the company. It will also help the company curb heavy fines in case the wastewater is being discharged improperly into the publicly owned treatment works (POTW) or to the environment.
Typically, biological treatment of wastewater can be economical and efficient technologies that help in breaking down and removing contaminants from the organic-laden wastes e.g. those produced in beverage and food, oil and gas, chemical manufacturing and municipal industries.
Biological systems of wastewater treatment
This is a technology that uses some protozoa, bacteria and other speciality microbes to treat water. When the microorganisms break down the organic pollutants in wastewater for food, they get to stick together and this leads to a flocculation effect that allows the organic substances to settle out from the solution. This, in turn, produces a sludge that is easier to manage and is then dried and disposed of as solid waste.
There are three main categories of treating wastewater biologically in Australia:
- Aerobic – this is when microorganisms use oxygen to break down organic matter in wastewater to form microbial biomass and carbon dioxide.
- Anaerobic – this is when microorganisms don’t use oxygen to break down organic matter in wastewater to form carbon dioxide, methane and excess biomass. Methane is then burned to produce electricity for the biological wastewater treatment plant.
- Anoxic – this is when microorganisms use different molecules that are not oxygen for growth, such as removing nitrate, sulfate and selenite.
These microorganisms decompose organic contaminants that are often measured in BOD or biological oxygen demand. This refers to the amount of dissolved oxygen that is needed for the organisms to break down organic matter and yield smaller molecules. High levels of biological oxygen demand indicate an elevated concentration of biodegradable matter present in wastewater and can be caused by pollutants introduction such as domestic faecal wastes, industrial discharges or fertilizer runoff.
BOD can deplete the oxygen needed by aquatic organisms when pollutants levels are elevated. This may lead to fish kills, algal blooms and harmful changes to the aquatic ecosystem where the harmful wastewater is discharged. Many facilities are therefore required to treat their waste before discharging it to natural water bodies. However, it is the level of inorganic and organic pollutants concerning their discharge requirements that dictates what specific unit operations a wastewater treatment system will need and how they are operated and sequenced.
Biological wastewater treatment systems in Australia make use of the naturally occurring process of microorganism decomposition to break down harmful industrial wastewater contaminants so that unwanted materials can be removed to make the water safe. This process may replace the chemical and physical treatments or may sometimes be used along with the chemical and physical treatments which can be among the expensive alternatives. A biological treatment system may be composed of different processes depending on the wastewater’s chemical makeup.