MST Small Sewage Treatment System

Publish Date: October 1, 2026

Small Sewage Treatment System (MST) 40–150 PE

The MST, also known as the MF Mechanical Septic Tank or Small Sewage Treatment System (SSTS), is a prefabricated FRP (fibreglass) sewage treatment unit for 40 to 150 PE (population equivalent), with Modified Standard B discharge. The MST is SIRIM certified to MS 2441-2:2014.

The system consists of one single FRP tank, with models ranging from MST-40 to MST-150 and no external piping between tanks. It is an active mechanical treatment system in which settling takes place in the lower part of the tank under anaerobic conditions, followed by an aerobic up-chamber activated sludge stage. Air is pumped through diffusers by air blowers, using an upflow activated sludge treatment process.

The MST is a separate product line from the passive Bio-Filter systems for 6 to 30 PE. It is designed for small developments and temporary or permanent domestic sewage treatment applications, including residential and other suitable small-scale projects. The system is intended for domestic sewage.

Mui Fatt is a SPAN-registered supplier, and the system is built to IWK guidelines. The quality system is ISO 9001:2015.

The MST was the first brand certified under the SIRIM product certification scheme.

Why Choose the Mui Fatt MST System?

• 40–150 PE capacity range — Choose from MST-40 through MST-150 according to the required PE.
• Single FRP tank system — The treatment stages are integrated within the tank.
• Active aeration — The treatment process uses diffused air during the aeration stage.
• 20–30% less space — The system is designed to use less space than comparable systems.
• FRP construction — FRP is corrosion resistant, watertight and light to transport.
• Modified Standard B discharge — The system is designed for Modified Standard B discharge requirements.
• Single-day installation — Installation can be completed in a single day under standard site conditions.
• IWK and SPAN submission support — Mui Fatt can assist with the required submission process and documentation.

How the MST Small Sewage Treatment System Works

The MST uses an upflow activated sludge process. Wastewater first passes through an anaerobic settling stage, followed by an aerobic aeration stage where diffused air is introduced. The treated wastewater then passes through the clarification stage before discharge.

1. Settle — Wastewater enters the anaerobic settling stage.
2. Aerate — The wastewater moves into the aeration chamber where air is introduced through the built-in air diffuser.
3. Clarify — The wastewater passes through the clarification stage.
4. Discharge — Treated wastewater is discharged from the system.

MST Small Sewage Treatment System Model Range: 40–150 PE

The MST range covers treatment requirements from 40 to 150 PE. Select the model according to the calculated population equivalent for the project.

Common dimensions: 2,400 mm width, 2,650 mm height, 2,000 mm water level and 150 mm inlet/outlet pipe diameter. Desludging is required once every 2 years.

How to Calculate the Required PE

Population equivalent (PE) is used to determine the required treatment capacity. The selection guide uses 1 PE = 60 g BOD₅ per person per day at 200 litres per day as the Malaysian design basis.

For example, a project with 100 factory workers represents 30 PE, while 500 m² of office gross floor area represents 15 PE. The combined requirement is 45 PE. Because this exceeds the 30 PE Bio-Filter ceiling, the example moves into the MST range, with MST-50 indicated in the selection guide.

Integrated Tank Design with Less On-Site Piping

The MST supply includes the tank, primary and aeration sections, a built-in air diffuser, and the transfer pipe, VCP pipe and inspection chamber combined into the unit. This reduces the need for additional piping work between the treatment components on site.

The integrated arrangement also contributes to the system's stated 20–30% space saving compared with comparable systems.

MST Supply Scope

The MST supply includes the treatment tank and integrated components required for the selected PE capacity, together with the relevant product documentation and submission support.

Supplied by Mui Fatt

• Primary and aeration tank — sized according to the required PE capacity.
• Built-in air diffuser — integrated into the tank.
• Transfer pipe, VCP pipe and inspection chamber — built into the MST unit.
• SIRIM certificate and product documents.
• IWK and SPAN submission support, including free submission drawings.

Provided by the Contractor or Installer

• Civil and structural works.
• Base slab and concrete plinth foundation.
• Screen and distribution chambers.
• Air blowers — one duty blower and one standby blower.
• Control panel.
• Mechanical and electrical connections.
• Excavation, shoring and backfill.
• Fencing and site works.
• CCTV inspection with the IWK officer.

The typical lead time is 4 to 7 working days.

Installation Time

Under standard site conditions, the MST system can be installed in one day. The integrated tank arrangement reduces the amount of additional piping work required on site.

IWK and SPAN Submission Support

Mui Fatt can assist with the IWK and SPAN submission process for applicable MST projects. Submission support covers the required drawings and documentation needed for the approval process.

Free submission drawings are available to support the submission process. Contact Mui Fatt with the project's PE requirement to discuss the required system, drawings and submission documents.

MST Approval Process

1. Design and sizing — Calculate the PE requirement and prepare the system design.
2. Submission — Prepare and submit the required SWA, SWC and e-SWAP documentation.
3. Installation and testing — Install and test the system according to the approved requirements.
4. Inspection — Complete the applicable PDC6, PDC7 and PDC8 inspection forms.
5. Surat Sokongan — Complete the approval process and obtain the support letter.

MST Warranty and Design Life

The MST system carries a 5-year warranty against manufacturing defects. The warranty covers workmanship and does not cover misuse or installation that does not follow the installation manual.

Design life: 15–20+ years for the composite.

Desludging: once every 2 years.

Modified Standard B Effluent Requirements

Modified Standard B is the treated-water quality limit the MST is designed to meet before discharge. Under MS 2441-2:2014, Clause 6.1.2, the effluent is tested over three test periods and must meet the following limits:

Standard B applies to septic tanks from 5 to 30 PE, while Modified Standard B applies to small sewage treatment systems (SSTS) from 31 to 149 PE.

The MST achieves the required treatment through an anaerobic sludge blanket in the lower zone followed by an aerobic activated sludge stage in the up chamber. Air is supplied through diffusers, after which the flow passes to a clarifier. A scum baffle and set effluent weir length help prevent suspended solids from carrying over into the discharge.

Small Sewage Treatment System FAQs

What PE range does the MST Small Sewage Treatment System

The MST / Small Sewage Treatment System covers 40 to 150 PE, with models from MST-40 to MST-150.

Which MST model should I choose?

The required model depends on the project's calculated population equivalent (PE). Select the model according to the required PE capacity. The available models, capacities and tank lengths are shown in the MST model table above.

How is PE calculated for an MST system?

PE is calculated using the applicable wastewater loading basis. The selection guide uses 1 PE = 60 g BOD₅ per person per day at 200 litres per day, with 5 PE per typical house, 0.3 PE per factory worker and 0.03 PE per m² of office gross floor area.

For example, 100 factory workers represent 30 PE, while 500 m² of office gross floor area represents 15 PE, giving a total of 45 PE. Since this exceeds the 30 PE Bio-Filter ceiling, the applicable MST model for this example is MST-50.

What are the MST rental terms?

Rental terms are available on request and depend on the selected MST model and rental period.

View MST Small Sewage Treatment System Rental

When do I need an MST instead of a Bio-Filter?

An MST is used when the treatment requirement is above 30 PE. The PE Bio-Filter covers 6 to 18 PE, the FRP Bio-Filter covers 8 to 30 PE, and the MST range covers 40 to 150 PE.

Why are two air blowers required?

Two air blowers are required as one duty blower and one standby blower. The air blowers and control panel are provided by the contractor or installer, together with the required mechanical and electrical connections.

What does Mui Fatt supply and what does the contractor provide?

Mui Fatt supplies the MST treatment unit and its integrated components, while the contractor or installer is responsible for the required civil, structural, mechanical and electrical works.

Mui Fatt's supply includes the primary and aeration tank, built-in air diffuser, transfer pipe, VCP pipe and inspection chamber integrated into the unit, together with the SIRIM certificate and product documentation.

The contractor or installer provides the base slab, concrete plinth foundation, screen and distribution chambers, air blowers, control panel, mechanical and electrical connections, excavation, shoring, backfill, fencing, site works and CCTV inspection with the IWK officer.

Is the MST suitable for domestic sewage?

Yes. The MST is intended for domestic sewage and is designed for small developments requiring treatment from 40 to 150 PE.

Does the MST require external piping between treatment tanks?

No. The MST uses one single FRP tank, with the transfer pipe, VCP pipe and inspection chamber integrated into the unit. There is no external piping between separate treatment tanks.

What is Modified Standard B discharge?

Modified Standard B is the treated-water quality limit that the MST is designed to meet before discharge. See the Modified Standard B Effluent Requirements section above for the applicable limits under MS 2441-2:2014, Clause 6.1.2.

Does Mui Fatt assist with IWK and SPAN submissions?

Yes. Mui Fatt provides IWK and SPAN submission support, including free submission drawings and the required product documentation for the submission process.

What are the MST warranty, design life and desludging requirements?

The MST carries a 5-year warranty against manufacturing defects. The warranty covers workmanship only and does not cover misuse or installation that does not follow the installation manual.

The stated composite design life is 15–20+ years, and the MST requires desludging once every 2 years.

Technical Expertise and Attribution

Technical specifications and product information on this page are attributed to Danny Ng Shin Lai, Director & Lead Composite Technical Specialist, and the Mui Fatt Technical Engineering Support Team. Danny Ng studied Materials Science and Engineering at UC Berkeley and oversees technical design, composite fabrication standards, engineering design, and technical compliance for FRP/GRP products, including compliance with MS 1390:2010 and MS 2441-2:2014 in Malaysia.

Request an MST System for Your Project

Have a wastewater project requiring treatment from 40 to 150 PE? Send Mui Fatt your calculated PE requirement and project details to discuss the appropriate MST model, system documentation and submission requirements.

Mui Fatt can provide drawings, SIRIM certificates and IWK submission documents on request.

Mui Fatt Marketing Sdn Bhd — Contact Details

Request a Quote

Looking for a Small Sewage Treatment System (MST) for your project? Contact Mui Fatt to discuss your required PE capacity, project requirements and wastewater treatment needs.

Mui Fatt provides Small Sewage Treatment Systems covering 40–150 PE, with models from MST-40 to MST-150.

Working hours: Monday to Friday, 8:30am to 5:30pm

Send us your project's PE requirement to discuss the suitable MST system, available models, drawings and submission documentation.

Call +603 3134 3888 for a Quote

Email Mui Fatt for an MST Quote