Analysing the Effluent of Septic Tanks

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About Me

Understanding Cattle Feed Hello! My name is Liam and I live on a small cattle farm in rural Australia. I used to live in the city so when I moved out to the country it was a bit of a culture shock. Not only did I need to get used to the idea of driving many miles to get to the nearest shop, I also needed to start to understand the various pieces of agricultural equipment and supplies. One area I really struggled with was cattle feed. Thankfully, Paul who lives and works on a neighbouring farm has really helped me to understand which type of feed is right for my animals.




Septic tanks serve as effective residential waste management systems. They collect waste from the home and channel it into the surrounding soil. The effluent that is contained in septic tanks consists of many different components; from pathogens and gases to suspended solids and phosphorus.

It is important to know what the effluent composition of most septic tanks is so that proper waste management processes can be put in place. For example, effluent that is high in ammonia concentration may need to be carefully handled due to the poisonous nature of ammonia gas. 

In addition, knowing the effluent composition can assist operators during septic tank cleaning. They can take precautions against potentially harmful components such as bacteria, fungi and parasites.

Suspended solids

As effluent comes out of the home, it contains a large number of suspended solids. These solids arise from both organic and inorganic substances that leave the home's main drainage system. Food wastes, faeces, urine and other solid wastes form a large part of suspended solids in septic effluent.

These solids, together with other items from the garbage disposal such as grease and cellulose, form about an average of 225mg/L or effluent waste. Over time, suspended solids can accumulate within the septic tank and require it to be cleaned before the system blocks.


Bacteria form a large part of effluent from homes. They arise due to the organic matter that is disposed of from the home. Food wastes and human wastes are an attractive target for both aerobic and anaerobic bacteria to use as a nutrient source. In most cases, bacteria are helpful in the surrounding soil because they decompose organic waste and allow for the soil to remain aerated. They also prevent the drainage pipes from blocking and sewage from backing up into the home.

There are also some bacteria that can cause diseases due to the germs they contain. During septic tank cleaning, harmful bacteria should be treated with caution, using safety equipment such as gloves and breathing masks.

Ammonia and Nitrogen

Ammonia is perhaps one of the most hazardous components of septic tank effluent. When this poisonous gas is in high concentrations in surrounding air, it can affect the respiratory system and result in difficulty when breathing. Nitrogen is also a potentially harmful component of effluent. In its dissolved form, it forms nitrates that can contaminate drinking water. Ammonia and nitrogen should be carefully handled during septic tank cleaning to avoid these risks.


Phosphorus, present in effluent at about 10mg/L, plays an important role in adding nutrients to the surrounding soil. Phosphorus allows for vegetation to obtain critical nutrients that they can use to grow and improve soil fertility.

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