A Description of a Designing of a Biosand Filtration System

Biosand Filtration System


The PVC outlet tubes of a biosand filtration forms a very crucial part of the system. This is what made us to undertake a serious mission during the fall term in order to establish the best parameters to use in the designing of a biosand filtration system. This was made mainly on the online sources including the use of electronic journals. This allowed us to come up with a number of key diameters for which we made a selection. However, The PVC outlet tubes that are attached to the filters do not allow for a sufficient pressure differential compared to the filter itself (difference in diameters). This needed to be described in order to establish what could be the problem and seek to improve in the future.

A Description of a Designing of a Biosand Filtration System

Designed biosand filtration systems in many will fail to give the best results (New England Water Treatment Technology Assistance Center, 2012). This is attributed to a number of factors which upon understanding them, one will be able to avoid them during the designing process. They include the failure by the PVC outlet tubes attached to the filters to allow for a sufficient pressure differential in comparison to the filter. This is in regard to the diameters. To understand on how to make the right adjustments is imperative in the efforts to help in cleaning of water for health and environmental sustainability purposes.

In order to make the right adjustments on the diameter of PVC outlet tube it is necessary to understand the factors behind the rate of flow in view to the biosand filter. They include the sand size, diffuser plate configuration and the under drain type (Kikkawa, 2008).. For example, flow rate should be slow because a high rate will lead to flushing of microbes into the filtrate preventing their removal. This is the same reason why the diameter of the outlet tube should meet appropriate standard. Generally, there has been a lot of research to establish the correct diameter of an outlet for Biosand filter.

Designing of a reliable biosand filter can be seen in an example designed by EWB Project. The water obtained had shown a remaining 10% bacteria after the process. This could be told of the problem that caused it. It would be from the water or inside the bucket used to make the biosand filter. It should be noted that the sand layer was initially 19 inches. The water was on top of the sand with 2 inches. Then water quality was tested later while the sand layer was at depth of 15.5 inches. At this second time, the standing water depth was at 5.5 inches (Tyner et al, 2013). The conclusion was that the large amount of water standing caused the oxygen to loose it value yet it was needed for the purification process. One is supposed to build a good level of sand for this matter for effectiveness of the biosand filter.

Generally, certain amount of filtration sound normally settles after the installation of biosand filter. It is recommended that proper adjustments be made because of the possible increase of the level of the standing water. This will increase effectiveness noting that further increments of standing water is a common trend with biosand filters (Tyner et al, 2013). In addition, it is advisable to use containers with lesser cross sectional areas than those with large ones.

Similarly, 1” PVC outlet pipe was used in the first place. It was realized that the flow was too small for the outlet amounting a trickle. It was found to be effective and it was recommended as to be used. Therefore it was realized that the best functioning of a biosand filter depended on a number of factors. This includes a small diameter of the outlet pipe and thin containers than wide ones (Tyner et al, 2013).

In another context, an outlet pipe of 0.5 inch PVC pipe was used which was rigid. In addition, there was a vertical pipe was put vertically to the rigid PVC pipe so that the outlet pipe was 2 inches higher on the top of the sand layer. This still produced good results. It shows that different individuals design the Biosand filters with different diameters. The functioning depends on other factors including the size of the container and the level of sand. The important thing is to avoid large diameter in comparison to other factors mentioned.


In the designing of a biosand filter, one should pay attention to the reducing of the flow rates. This is possible through the use of finer sand and reduced flow board. The size of the container should not be too large and yet not too small to fail to meet the demands. Depending on the cross- sectional area, the PVC outlet tube should not be of small size to increase the effectiveness.  A diameter of 1” to ¼” with consideration of the level of water at pause period has always worked.

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