Farm waste disrupting sewage treatment plants

The uncontrolled disposal of farmland waste into the drainage system is causing operational problems to the Tac-Cumnija waste treatment plant, which treats sewage before it gets safely disposed in to the sea.

In its annual report for 2011, the Water Services Corporation said the plant was being overloaded with organic pollutants from uncontrolled farm discharges.

"The plant is still facing operational problems due to a significant amount of farmyard waste it receives. At times this exceeds both the plant's design and installed spare capacity, particularly during the summer peaks."

Sludge from animal farms is being deposited into the drainage system, substantially increasing sewage treatment costs for the WSC.

The effluent from the Tac-Cumnija plant was sampled on 48 occasions, as opposed to the legal minimum of 12, with 56.3% of the samples failing to conform to the legal requirements.

The WSC is currently working on upgrading the plant's treatment capacity to cater for the additional treatment needs particularly during summer. Moreover, national waste agency Wasteserv is working on measures to reduce the pressures exerted by the farmyard waste industry.

"These discharges were meant to be disconnected from the public sewer system or at least pre-treated before the wastewater treatment plants began operating."

The WSC also embarked on an extensive assessment of incoming wastewater received at the plant during the summer of 2011, upgrading the plant to cushion the seasonal increase in the loads that are so typical of the catchment area served by the plant.

Problems with farmland waste were also experienced at the Ta' Barkat sewage treatment plant, caused by surges of storm water, industrial discharges "and the most problematic of all, farmyard waste." 28.6% of the samples of treated effluent marginally exceeded the limits set in the law.

Less problems were experienced at the Gozo plant (Ras il-Hobz), which was sampled on 50 occasions - only 8% of the samples have failed to conform, thus being still within legal notice requirements.

Groundwater warning

The annual report also refers to another problem faced by the WSC caused by the high rates of nitrates in Malta's ground water.

Deteriorating groundwater quality is forcing the corporation to supplant groundwater production with desalinated water, WSC chief executive Marc Muscat said in his report, a process which results in increased expenditure for the corporation.

Nitrate concentration in groundwater has continued to increase over recent years, causing the WSC to increase the blending ratio of reverse osmosis water to groundwater, to ensure that the water in consumers' taps respects EU legislation.

During 2011, RO-water production increased by 600,000 cubic metres over the previous year, but is still less than that the amount of water produced in the early 1990s. At just under 17 million cubic metres per annum, desalinated water comprised 56% of potable water production.

Water production figures from 1941 to 2011 demonstrate that last year's groundwater abstraction is down to the same levels of the late 1950s.

Over a number of years the WSC had to close down numerous pumping stations and boreholes due to long-term nitrate contamination, or sudden contamination from oil spills.

During 2011 the corporation made use of 93 boreholes and 12 pumping stations. The largest single source was Ta' Bakkja pumping station, producing 5,420 cubic metres per day, which is equivalent to approximately 15% of total groundwater production.