Septic, settling, sewage-A A +A
Wednesday, July 4, 2012
YEARS ago the colloquial term for Davao's drinking water utility was Nawasa. At the time I had no idea what the word meant - later I'd find out that Nawasa was an acronym for the National Water and Sewage Authority. Nawasa moved on, via the Davao Metropolitan Waterworks, to the Davao City Water District, our familiar DCWD, a company which got on with the business of supplying potable water but ignored unfortunately the sewage part of its old title; unfortunately because instead of a city developing side by side with a growing sewage removal and treatment infrastructure it fell back on septic tanks or, rather, settling tanks and there's a difference.
Septic tanks were originally conceived for rural areas - farms, country houses, isolated residences which were far from any piped sewage connection and had plenty of room to install a proper septic tank, which consists of a concrete settling tank - divided nowadays to encourage settlement and decomposition - and a separate gravel filter bed where various organisms can munch their way through whatever gunk is remaining. The water which finally seeps away from the gravel filter is hardly drinkable nor will it poison the subsoil (Which in itself acts as another filter as the water permeates down to the water table).
My septic tank, and yours, and thousands of others in the city, are no such thing but rather settling tanks which theoretically allow much of the solid sediment to settle before emptying. Theoretically because the majority of the tanks I've seen are way too small - token tanks - which, given continual use and continuous activity - the rush of water - fill quickly and soon vent liquid raw sewage from the overflow pipe into... what?
Settling tanks without gravel filters or separate buried filter tanks would work if they were connected to a piped sewage system but that's something we don't have nor do we have sewage treatment facilities; that raw sewage usually flows into a roadside canal thence into a bigger canal or stream and finally into the sea or a handy river.
Here at Buhangin Hollows the original subdivision developer (Not the current owner) ignored the topography and existing drainage system, bulldozing culvert-less road embankments whilst forgetting to construct an alternative. On one side of the road the overflow from 'septic tanks' finds its way into a small and noxious stream. On the other side a later canal collects the waste water and funnels it into a natural hollow where a green-fingered and enterprising gardener cultivates prize-winning kangkong daily snapped up by the local market. Human waste is, after all, stuffed with nutrients, a rich organic fertilizer and if you don't believe me just look at the rampant plant life in your local roadside canal.
Published in the Sun.Star Davao newspaper on July 04, 2012.