Wastewater treatment is a process used to remove contaminants from wastewater and convert it into a product that can be returned to the water cycle. The treatment process takes place in a wastewater treatment plant. There are two wastewater treatment plants namely chemical or physical treatment plants, and biological wastewater treatment plants. Biological waste treatment plants use biological matter and bacteria to break down waste. Alternatively, Physical waste plants use chemical reactions as well as physical processes to treat wastewater.

U.S. wastewater treatment plants process an estimated 34 billion gallons of wastewater every day. Biological treatment systems are ideal for treating wastewater from households and business premises. Whereas physical treatment plants are used to treat industrial wastewater. There’s a lot more that goes into wastewater treatment than you might think. Traditional wastewater treatment methods have three distinct steps. Here’s a look at the three steps involved.

Primary Wastewater Treatment

Wastewater is full of contaminants including bacteria, chemicals, and other toxins. Firstly, and most importantly treatment aims at reducing the contaminants to acceptable levels. In order to discharge the water back into the environment treatment must first take place. Primary treatment of wastewater involves sedimentation of solid waste within the water. Larger contaminants are first filtered out of the water. After that several tanks and filters separate water from contaminants. The resulting “sludge” is then fed into a digester, for further processing. This primary batch of sludge contains nearly 50% of suspended solids within wastewater.

Secondary Wastewater Treatment

Secondary treatment of wastewater makes use of oxidation to further purify wastewater. Oxidation can take place in one of three ways.


Biofiltration removes additional sediments from the wastewater. The removal of this sediment uses sand filters, contact filters, or trickling filters. Of the three filters, trickling filters are typically the most effective for small-batch wastewater treatment.


Aeration is a long, but effective process that entails mixing wastewater with a solution of microorganisms. This process is based on pumping air into a tank, which promotes the microbial growth in the wastewater. The microbes feed on the organic material, forming flocks which can easily settle out. After settling in a separate settling tank. The bacteria that form the “activated sludge” flocks are then continually aerated for up to 30 hours at a time. As a result of this constant aeration the rate of decomposition increases.

Oxidation Ponds

Also called lagoons or stabilization ponds, are large, shallow ponds designed to treat wastewater through the interaction of sunlight, bacteria, and algae. Algae grow using energy from the sun and carbon dioxide and inorganic compounds released by bacteria in water. During the process of photosynthesis, the algae release oxygen needed by aerobic bacteria.

Tertiary Wastewater Treatment

Removing phosphates and nitrates from the water supply is the final step. The most common materials used in this step are sand and activated carbon. Wastewater treatment may entail a bit more than these three steps, but they are the basis of how traditional wastewater treatment facilities operate.

Why is Wastewater Treatment Important?

Wastewater treatment is one of the most important environmental conservation processes. Most treatment plants treat wastewater from homes and businesses. Industrial wastewater comes from plants, refineries, and manufacturing plants. Onsite facilities are used to treat industrial wastewater. It’s illegal for disposing untreated wastewater into rivers, lakes, oceans, or into the environment. As a result these facilities are designed to ensure that industrial wastewater is properly treated. This will not just help save water thereby paving the way towards a healthy and sustainable environment, but it will also prevent water-borne hazards that put millions of human lives at stake.

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