Frequently Asked Questions

A single BMS Blivet unit treats up to 500 population equivalents (PE), approximately the size of a 40-foot shipping container, and is the practical maximum for road and international transport. However, the units are fully modular and can be expanded in 500-PE increments. The largest temporary installation BMS has completed to date was 5,000 PE at Lusk, Co. Dublin, where ten units were added in stages as the housing development grew, ahead of the Portrane municipal plant coming on stream.

Yes, and this is one of the most common applications in Ireland and internationally. Most municipal plants are organically overloaded rather than hydraulically overloaded, meaning they cannot treat any additional organic load (BOD, suspended solids, ammonia) but can still accept additional flow. If the on-site package STP treats sewage to the required standard, typically BOD 25 mg/l and SS 35 mg/l (European Wastewater Discharge Standard), it can discharge to the sewer. Treated effluent dilutes and improves the incoming load at the municipal plant, benefiting the utility. Irish Water and planning authorities in Ireland have accepted this approach at multiple locations, including Arklow, Middleton, Kingscourt and others.

Temporary STPs are typically planned for 1–10 years, with a median of around 3 years in BMS's experience. In practice, they frequently operate longer than originally projected, often because municipal infrastructure upgrades are delayed. The BMS Blivet at Ringaskiddy, Cork, has been operating for nearly 10 years. The Lusk installation operated for nearly 15 years. Units are designed for a 25–30+ year operational life, so extended temporary use does not compromise the asset. Units can be refurbished and redeployed after temporary use, for example, a BL4000 from Lusk was refurbished and is now operating in Brittany, France.

Yes, planning permission is typically required. BMS provide a full customised design service suitable for planning submission, including PE calculations, effluent standard confirmation, site layout, civil works specification, and supporting documentation. BMS have prepared planning submissions in Ireland, France, and other jurisdictions. Planning authorities in Ireland have approved temporary STP proposals at multiple locations where housing development is outpacing municipal infrastructure. BMS can assist with responses to planning queries and liaise with Irish Water where a sewer connection or discharge agreement is involved.

Discharge to a watercourse requires a licence from the EPA or local authority and typically requires more stringent treatment than discharge to sewer. Standard secondary treatment (BOD ≤25 mg/l, SS ≤35 mg/l) is the minimum. For watercourse discharge, ammonia removal (NH₄ ≤5 mg/l) is commonly required, along with total nitrogen reduction (requiring anoxic denitrification) and phosphorus removal (typically via ferric or aluminium sulphate dosing). Ireland has some of the most stringent effluent discharge standards in Europe, and BMS have extensive experience designing systems to meet these requirements. A receiving water capacity study may also be required.

This distinction is critical for designing a temporary STP solution. A hydraulically overloaded plant cannot accept any additional flow volume; the physical pipework, tanks and outfall are at capacity. An organically overloaded plant can accept additional flow but cannot biologically treat any more organic load, BOD, suspended solids, ammonia, or phosphorus. The majority of overloaded municipal plants in Ireland are organically rather than hydraulically overloaded. This means a package STP treating on-site sewage to a standard that removes organic load can discharge its treated effluent to the sewer. The municipal plant handles the hydraulic flow. In contrast, the package plant handles the organic treatment.

Biological sewage treatment processes treat organic matter, not water volume. Sizing a plant based solely on flow consistently leads to undersizing. For example, an office building with 165 staff produces 4,950 litres per day of flow, which, divided by 200 l/PE/day, suggests 25 PE. But the actual BOD load from office staff (20g BOD/person/day) amounts to 3,300g BOD/day, equivalent to 55 PE. The plant would be undersized by over 100% if sized on flow alone and would fail to meet discharge standards. The Irish EPA population equivalent table provides flow and BOD/SS values for a wide range of building types and should be used for all initial sizing.

Yes. With the addition of UV disinfection at the end of the treatment process, treated effluent from a BMS Blivet meets the standard for non-potable reuse. On construction sites, this has been used for toilet flushing (80–90% of site water use), wheel and road washing, dust suppression, and road cleaning. BMS supplied and operated this solution at Centre Parcs Longford Forest during construction by Sisk and Roadbridge, with a payback period of under one year compared to tankering untreated sewage. Biodegradable toilet blocks eliminate any residual colour or odour when treated water is reused for flushing.

Standard guidance recommends a setback of approximately 50 metres from housing. However, setbacks can be significantly reduced with the right system and mitigation. BMS installed two BL4000 Blivet units in Co. Offaly, just 5 metres from houses, by housing them in a ventilated Steeltech-type agricultural shed, eliminating odour impact. Residents were reportedly unaware that the units were present. The shed approach is a practical solution where site constraints make standard setbacks impossible.

Yes, and this is one of the key advantages of an all-in-one package STP over a built-in-situ system. Because the BMS Blivet is a self-contained manufactured unit with a resale value, it can be financed by hire purchase, spreading the capital cost over the operational period. This is particularly relevant for housing and commercial developers, where cash flow management is critical. Hire purchase financing is only available for self-contained portable units — systems requiring concrete surrounds or permanent civil installation cannot be financed in this way.

Once the municipal plant is upgraded or a sewer connection becomes available, the temporary STP is decommissioned. For a BMS Blivet, this involves: fully emptying the unit via a suction tanker, disconnecting the inlet and outlet pipework and electrical connections, and lifting the unit from its position. If installed above ground or without a concrete surround, there are minimal civil decommissioning works. The unit can then be sold on, relocated to another site, or refurbished for reuse. Units retain significant resale value, for example, a 15-year-old BL4000 from Lusk was refurbished and redeployed to Brittany, France. A BL2000 from the same project is now operating in Mayotte in the Indian Ocean.

Once the municipal plant is upgraded or a sewer connection becomes available, the temporary STP is decommissioned. For a BMS Blivet, this involves: fully emptying the unit via a suction tanker, disconnecting the inlet and outlet pipework and electrical connections, and lifting the unit from its position. If installed above ground or without a concrete surround, there are minimal civil decommissioning works. The unit can then be sold on, relocated to another site, or refurbished for reuse. Units retain significant resale value, for example, a 15-year-old BL4000 from Lusk was refurbished and redeployed to Brittany, France. A BL2000 from the same project is now operating in Mayotte in the Indian Ocean.

Yes. Biological sewage treatment functions in very cold conditions because sewage temperature is typically warmer than ambient air temperature in cold climates. BMS have operated Blivet systems in Newfoundland, Canada, at temperatures down to minus 40°C, and in the Middle East at temperatures over plus 35°C. The biological process slows in cold conditions but does not stop, provided adequate sewage flow is maintained. Additional insulation or housing may be considered for extreme environments.