On-site Sand Filters as Alternative Sewage Treatment Options

Posted on: 14 October 2015

Homeowners seeking to remodel their homes and add new bedrooms and baths may be faced with the challenge of waste water treatment and management, especially if the home is built on land with a raised water table or the depth of unsaturated soil above the water table has considerably shrunk over the years. In such a situation, the best alternative would be to acquire on-site alternative water treatment systems. The local government has to be informed prior to the installation of such systems for their consent. Once tests have been done and consent given, one type of alternative septic tank system available would be sand filter systems.


 Sand is an excellent filter. The particles can be varied from one chamber to the next to offer varying filtration levels. Sand is also an excellent medium for bacterial growth. In sand filters, aerobic bacteria grow on the upper levels while anaerobic bacteria grow in the deeper, less exposed regions. Sand is also a good material since it equalizes temperature; it does not freeze when buried deep within the earth during cold seasons. Burying the sand deep protects the sand considerably from cold air influxes. A few feet thickness of sand can, therefore, effectively remove a lot of pathogens and impurities from waste water.


When wastewater leaves the existing septic tank, it is directed to the sand filters via a pump. A recirculation tank may or may not be present between the septic tank and the sand filters. Once the wastewater hits the sand filters, the different microorganisms break down impurities while the sand particles act as fine sieves. The emerging water is safe to be discharged to the ground, water collection system or even rivers.

In the case of recirculating sand filters, the pump sends water to the filters and circulates it through the filter a couple of times before it is discharged.  These usually achieve high levels of filtration and treatments.

Installation and maintenance

Sand filters are relatively cheap to construct. This is because the materials required are usually locally available. The structure simply entails a concrete box dug into the soil and either covered or left open. Vents and tubes connect to and from the box.

Maintenance of sand filters is required periodically. Sand filtration systems used for primary waste water treatment must be pumped out periodically. The upper layer of a sand filter also needs occasional raking. This prevents the clogging of the filter's surface. The upper sand may also need changing now and then. To ensure even distribution and filtration of the waste water, the effluent distribution piping at the top of the filter, must also be flushed periodically.