Mellieha sewage treatment plant to expand in response to population growth

The Mellieħa sewage treatment plant will expand to cater for population growth and increased tourism with plans showing it will triple its capacity.

The plans for the extension of the Ċumnija Wastewater Treatment Plant (WWTP) were presented by the Water Services Corporation (WSC). The new facility will take up 6,500sq.m of agricultural land next to the existing plant.

The proposed expansion includes the construction of an additional treatment unit and an underground inlet flow pipe to connect to the existing pumping station.

The WWTP, operational since 2009, currently processes 6,700 cubic metres of wastewater daily, serving a catchment population of 49,620 residents across Mellieħa, St Paul’s Bay, and Mġarr. However, the plant frequently exceeds its capacity during the peak tourist season in summer, increasing the urgency of the proposed upgrades.

As outlined in the Project Description Statement presented by the WSC, the proposal aims to increase the plant’s capacity to 20,000 cubic metres per day, which would accommodate up to 121,000 residents and meet projected demand until 2040.

The expanded facility will encroach on agricultural land, which consists of terra rossa soil, characterised by its reddish colour and clayey texture.

The upgrade also promises some environmental benefits. The new unit will incorporate advanced Membrane Bioreactor (MBR) technology, enabling more efficient treatment and better pollutant removal before the water is disposed of in the sea.

Another significant benefit is that the system will increase the production of ‘new water’ – treated wastewater that is made suitable for reuse in agriculture. The system is expected to generate up to 8,000 cubic metres of new water daily, reducing farmers’ reliance on groundwater resources to water their fields. However, the treatment plant will still discharge treated effluent into the sea via the existing outflow point, with an increased daily volume of up to 20,000 cubic metres, up from the current 12,000 cubic metres.

Although the proposed extension will not disturb ecologically sensitive habitats, the project site lies near Natura 2000 areas, including Għadira Nature Reserve and coastal cliffs that provide habitats for sensitive seabird species, such as the Yelkouan Shearwater and Cory’s Shearwater.

In its screening of the project, while acknowledging the environmental benefits – particularly in preventing untreated wastewater discharge – the Environment and Resources Authority (ERA) expressed concern regarding the potential impact of noise, light emissions, and operational disturbances on nearby protected sites.

The construction team expects to keep the construction phase confined to the site boundaries, minimising dust and spillages through standard containment measures. However, the long-term effects of intensified operations, including noise and light pollution, require further assessment to ensure compliance with the conservation objectives of the surrounding Natura 2000 sites.

ERA has also recommended measures to mitigate these effects, including limiting exterior lighting to current levels and adopting advanced odour abatement systems. The upgraded plant is expected to improve air emissions by using biological filters and odour control technology.

Despite these challenges, ERA does not object to the proposed extension, recognising the necessity of land uptake to address the increasing demands for wastewater treatment. Furthermore, the authority noted that the additional unit would be located to the east of the existing facility, preventing any encroachment into sensitive coastal areas or garrigue habitats.

ERA's screening report concludes that the proposal does not warrant a full Environmental Impact Assessment but calls for further detailed studies to address uncertainties surrounding light, noise, and operational risks.