What is an aerated package treatment plant?
An aerated package plant is a prefabricated wastewater treatment unit, typically a fibre-reinforced plastic (FRP) tank, that treats wastewater through combined anaerobic and aerobic stages. Suppliers describe these units as compact, factory-built and quick to install above or below ground. The aeration that keeps the bacteria supplied with oxygen comes from electric air blowers.
What is Parawewa?
Parawewa is a Sri Lankan bio septic system, invented in 1996 and protected by Sri Lanka Patent #16371. It comes in two forms: Option A, a gravity-fed system with no electricity, and Option B, the Seal Type Parawewa System for high water table land. Both carry a 10-year written manufacturer warranty.
The main difference: how oxygen reaches the bacteria
Aerobic treatment needs oxygen. An aerated package plant supplies it with air blowers, which means electricity is the plant’s running input and the blowers are the part that has to keep working. Parawewa’s design uses a naturally aerated, oxygen-present process built into the geometry of the tank, so Option A has no blower and no compressor. Option B uses a small amount of power only to lift the treated water where gravity discharge is not possible.
For a detailed look at that difference with mechanical plants in general, read Parawewa vs mechanical STPs: Option A vs Option B.
Side-by-side comparison
| Feature | Parawewa | Aerated package plant |
|---|---|---|
| Origin and technology | Sri Lankan, patented system (Patent #16371, invented 1996) | Prefabricated aerated treatment unit |
| Tank body | Hermetically sealed concrete body | Fibre-reinforced plastic (FRP) unit |
| How oxygen reaches the bacteria | Natural, passive aeration built into the tank geometry (Option A) | Electric air blowers |
| Electricity | Option A: none. Option B: low (less than mechanical STPs) | Required for the blowers |
| During a power cut | Option A keeps operating | Depends on the blower; ask the supplier in writing |
| Footprint | Sized to the site’s occupancy; confirmed at inspection | Compact; usually the smaller footprint |
| Installation | Site-specific installation by the Parawewa team | Prefabricated, quick to install above or below ground |
| High water table | Option B is engineered for it | Sealed units are generally suitable; confirm per model |
| Warranty | 10-year written manufacturer guarantee | Varies by supplier; ask for the terms in writing |
| Local manufacture | Manufactured and installed in Sri Lanka by Parawewa | Check where it is made and what local support exists |
Where an aerated package plant may suit you better
- Very limited space. Prefabricated aerated units are generally the more compact option.
- Above-ground or relocatable installations. Suppliers describe units that can be placed above ground or moved later.
- Modular capacity. Some units can be combined to expand capacity.
- Reliable power and a service contract. If power is dependable and you are comfortable maintaining blowers, the electricity requirement matters less.
Where Parawewa may suit you better
- You want no electricity. Option A has no blower and no pump, so nothing is added to your power bill.
- Power cuts are a concern. A passive system keeps operating when the power goes off.
- High water table or marshy land. Option B is engineered for waterlogged and coastal sites.
- Local manufacture and a long written warranty. Parawewa manufactures and installs in Sri Lanka and issues a 10-year written guarantee.
- No gully bowser emptying. Continuous biological digestion is designed to avoid recurring suction-truck visits.
Questions to ask any supplier
- How much electricity does the system use, and what happens during a power cut?
- What does the warranty cover, for how long, and is it in writing?
- Can I see a laboratory test report for the treated water against CEA discharge limits?
- What routine servicing is needed, and who provides spare parts locally?
- How much space does the installation need, and how deep is the excavation?
Parawewa’s laboratory test report and patent documents are shown in the certificates section of the home page.
Notes about aerated package plants summarise publicly available supplier descriptions. Specifications, electricity use and warranty terms vary by model and manufacturer, so please confirm details with the supplier.
