Marine sediments in the vicinity of the Cumnija outfall are mostly polluted by lead, and zinc and less so by cadmium and copper, research into sewage outflow in the vicinity.

The report found that in terms of environmental impact the levels of cadmium were particularly of concern.

These are some of the initial findings of a study sponsored by the HSBC Cares For The Environment Fund (HCEF) aimed at assessing the extent of the environmental impact of discharging raw sewage from the Cumnija outfall.

The work which was undertaken by the Marine Ecotoxicology Laboratory of the Department of Biology, University of Malta, under the supervision of Prof. Victor Axiak has now been completed and the first results made available to the relevant authorities. The project extended over a period of nine months and included chemical and biological monitoring in the area under immediate influence of this outfall.

The Cumnija sewage outfall is located in a pristine part of our northern coast in the vicinity of Anchor Bay and Cirkewwa. From here, an estimated 1.6 million m3 of untreated sewage from the northern Malta catchment are discharged per year. Preliminary work in 2003 had shown that the extent of contamination by sewage, and the resultant microbes, may be quite extensive in the area.

Now, the HCEF project has shown that marine sediments in the vicinity of the outfall was mostly polluted by lead, and zinc and less so by cadmium and copper. However in terms of environmental impact the levels of cadmium were particularly of concern. Petroleum hydrocarbons from oils and fuel remains showed up in fairly small concentrations and marginally exceeded levels which may harm the environment only in the closest proximities of the outfall.

Degraded sea grass meadows with signs of stress and unhealthy conditions were evident as from 250 to 300 metres away from the outfall. In the immediate vicinity of the outfall there was a relatively impoverished sandy habitat, typified by small opportunistic worms adapted to living in stressed environments. However, the extent of this damage to the marine environment was rather limited with a relatively rich benthic biodiversity being recorded at 500 metres off the outfall.

This data provides a first contribution on our baseline knowledge of the current state of sediment quality and benthic life in the impacted zone at Ic-Cumnija. It is against such baseline data that the rate of recovery may be monitored when the discharge of untreated sewage in the locality is discontinued by 2007.