Septic Tank poor performance
We have been assessing the performance of a septic for a village in Java, Indonesia. The tank, which serves about 75 houses with on average of 4 people per household, comprises a tank with approximate dimensions 2 x 9m followed by a leachate field with dimensions 3 x 9m. The tank is immediately adjacent to a small river and there is a constant discharge of clear foul smelling liquid into the river. We are unclear on how the discharge pipe is connected to the system, whether it is connected to the tank or is from a separate surface water system. We were unable to see inside the tank, but we have been told its not been emptied in 6 years.
We are looking for some advice on what could be potentially wrong with the system so we can advise the village leaders on their next steps. The discharge does not directly impact their community but they are keen to protect the environment and promote themselves as an eco-village.
We think the problem might be one, or a combination, of the below: - the septic tank is full of sludge - the pipes in the leachate field are blocked - the tanks and the leachate field are undersized - the ground conditions are unsuitable for the infiltration from the leachate field.
We have initially advised that the villagers that they should at the very least get the tank emptied.
Does anyone else have any thoughts or experience to draw on similar situations?
Collecting the nfomation suggsted by Tim Foster may help narrow the options and is supported. However ultimately you will almost certainly have to access the septic tanks, if not to identify problems then to effect remediation. Speculating is unlikely to beneficial, so adopting a systematic process of elimination with easiest tasks / access first would be my suggestion. Its a relatively simple calculation to calculate the expected accumulated volume in the tank (based on pit type and if water is used for flushing / anal cleansing, number of people per household, cubic volume of pit [plumb the depth if need be]) and this may give an idea if the tank is due for cleaning. I would suggest based on the limited information and a rough calculation with assumed pit depth and anal cleansing / flushing practice and , there is a good chance the pit is due for cleaning and this would in any event be a good starting point, and routine maintenance. It may produce initial mprovement provide access to the tank (if adequate access / cleaning hole). It is not clear from the post if it is discharging into the leachate field or directly to the river (latter is what seems suggested). The next step then seems to be to expose the connection of the pipes to ascertain connection to the tank and if the pipes are blocked - again possibly routine maintenace required. RedR manual and Helvetas latrines manual give guidance on infiltration rates for differing soils, however remember infiltration reduces over time. It is quite simple to do a rough infiltration field test and this may remove another variable as to soil suitability.
It would be interesting to hear whether you were able to find a solution. Worth remembering that any water that comes out of the septic tank will be highly polluted so if it does not soak away properly, any surplus flow will inevitably be foul smelling. Septic tanks settle out solids but do not treat as such. Good luck.
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