Designed to fit a 20ft container
Reiken Solutions ordered two polypropylene process tanks from AquaTelos for a membrane bioreactor (MBR) wastewater-treatment system serving an operator in the country's oil and gas industry.
Both tanks had to fit inside a single 20-foot container while leaving sufficient space for a small technical room. The container therefore determined the available footprint, but its corrugated steel walls could not be relied upon to support the water load.
Each tank therefore had to be self-supporting, with the two structures together carrying more than 20 tonnes of water.
Engineering before fabrication
To determine how the PP tanks could safely withstand the resulting water pressure, Reiken Solutions worked with Baloo Design to engineer their structures through FEA.
Finite element analysis, or FEA, is a computer simulation used to predict how a structure will behave under stress. In this case, it modelled the forces acting continuously against the tank floors and walls once filled.
The calculations considered the tank geometry, material properties, operating temperature, creep behaviour, intended lifespan, reinforcement configuration and appropriate safety margins.
Why polypropylene for wastewater
Wastewater tanks are commonly constructed locally from coated steel, concrete or GRP fibreglass. Each presents its own limitations.
Coated steel depends on an intact protective layer. Scratches, impact damage or coating imperfections can expose the underlying steel and allow corrosion to develop.
Concrete is heavy, requires substantial site work and may crack or remain porous unless properly protected. An additional lining is often needed under aggressive wastewater conditions.
GRP is lightweight and corrosion-resistant, but its performance depends heavily on the selected resin and the quality of the laminate. Joints and repairs are bonded, while damage can expose the reinforcing fibres or lead to delamination.
Polypropylene (PP) requires no protective coating. It is corrosion-free, resistant to wastewater and many treatment chemicals, lightweight and easy to clean. Its panels and reinforcement can be thermally welded into a homogeneous, leak-tight tank structure.
From tacking to structural welding
Fabrication began by positioning the polypropylene panels and tacking them together. This established the tank geometry before the permanent welds were made.
The joints were then hot-air welded, followed by structural extrusion welding. Hot-air welding secures and seals the initial joint, while extrusion welding applies a larger bead of molten polypropylene to create the required structural connection.
Verifying every seam
Engineering calculations demonstrate that the structure will withstand its intended load. Spark testing checks the completed welds for pinholes or other small discontinuities that could cause leakage.
Before the joints were closed, conductive aluminium tape was positioned behind them. Once welding was complete, a spark tester was passed over the finished seams. Any discontinuity would allow the electrical current to reach the aluminium backing and reveal the precise location of the defect.
This provides a direct quality-control check before the tanks leave the workshop and are placed into service.
Two tanks, one HIAB
Both completed tanks were loaded onto one conventional HIAB crane truck for the journey from our Apapa workshop.
The same vehicle transported the tanks and provided the lifting capacity required at their destination. Both tanks were lowered into the same 20-foot container, together occupying most of the available space while leaving room for the adjoining technical section.
This combination of workshop fabrication and direct crane installation reduced the amount of specialist work required on site.
From workshop to operation
The completed MBR system was commissioned in one of Nigeria’s oil-producing states.
The installation brought together structural simulation, controlled workshop fabrication, verified thermoplastic welding and coordinated transport. Once installed and connected, the two self-supporting tanks became part of the operational wastewater-treatment process.
AquaTelos designs and fabricates thermoplastic tanks for water, wastewater and industrial process applications.
Send us the intended tank dimensions, operating conditions, liquid characteristics and installation constraints. AquaTelos can review the appropriate material, structural requirements, fabrication method and delivery scope before detailed design.