What is Option A?
Option A is the standard Parawewa configuration: a patented bio septic tank that treats wastewater by natural gravity flow. Effluent passes through biological filter media with no blower, no pump and no electricity, which keeps running costs to a minimum wherever the ground allows it.
How Option A treats wastewater
The design copies the way a natural riverbed or wetland filters organic matter. Instead of an oxygen-starved pit where sludge simply builds up, wastewater moves through distinct biological stages populated by naturally occurring bacteria:
- Primary separation. Heavier solids and grease settle out as wastewater enters, reducing the load on the biological stages that follow.
- Aerobic microbial digestion. Oxygen-favouring bacteria colonise the biological media and digest organic sludge, converting it into liquid and gas rather than letting it accumulate.
- Biological filtration. Effluent rises through filter media layers that trap fine particles and continue the bacterial treatment.
- Clean, low-noise outflow. The water is treated to a level fit for absorption and soaks into the ground.
Read the full explanation in How the Parawewa bio septic tank works without electricity.
Why choose Option A
- No electricity. There is no blower or pump, so the system adds nothing to your power bill.
- Operational during power cuts. Because the flow is passive, a power cut does not stop treatment. Imported mechanical plants rely on a blower running 24/7; see Parawewa vs mechanical STPs.
- No mechanical parts to service or replace. There is nothing in Option A that needs routine mechanical servicing.
- No gully bowser emptying. Continuous biological digestion is designed to avoid the recurring suction-truck visits that a concrete pit needs.
- 10-year written warranty. The manufacturer guarantee covers structural tank integrity, chamber sealing and multi-stage biological filtration performance.
- CEA-oriented performance. Effluent is laboratory-tested against Central Environmental Authority discharge guidelines (BOD and COD limits).
Who Option A suits
Option A is intended for standard inland building plots with normal soil elevation and standard ground water levels. It is used for single and multi-storey houses, offices and commercial buildings, hotels, housing schemes and factories. Where reliable running costs and power-cut resilience matter, the no-electricity design is a clear advantage.
When Option A is not the right choice
Gravity discharge only works where the ground allows water to flow away naturally. On high water table land, marshy plots, coastal sites and flat low-lying land, the better fit is Option B, the Seal Type Parawewa System. A free site inspection confirms which option suits your plot.
Option A or Option B?
| Feature | Option A – Gravity-Fed | Option B – Seal Type Parawewa System |
|---|---|---|
| Best for | Standard ground, normal soil elevation and water table | High water table, marshy, coastal and flat land |
| Discharge | Natural gravity flow | Water-sealed; treated water is lifted to the absorption point |
| Electricity | None – fully passive | Uses some electricity (less than mechanical STPs) |
| Power cuts | Keeps operating | The pump needs power to discharge |
| Treatment | Same patented biological filtration (Sri Lanka Patent #16371) | |
| Warranty | 10-year written manufacturer warranty on both options | |
