Pollution and water quality

Solent Protection Society (SPS) has been working for many years to monitor the impact of pollution in the Solent, long before the topic was given much wider focus through mainstream media. The many sources of this pollution include human waste, household chemicals, pharmaceuticals and micro-plastics together with nitrates and phosphates generated from livestock waste and agricultural fertilisers.

Southern Water’s ‘Beachbuoy’ display of CSO discharge status – 24 October 2022

While technical reports commissioned by local authorities and water companies often cite ‘coastal sources’ or ‘coastal background’ nitrogen as the most significant factor in Solent pollution, we have found no analysis of that constituent. However, considering the relatively weak flow clearing the Solent water body from west to east, it is likely, though unproven, that a significant part of this ‘coastal background’ comes from wastewater treatment sources, effluent from which will wash back and forth over several tidal cycles before, finally, leaving the Solent.

The subject has been brought into sharp focus in recent years by the inability of the wastewater treatment operations to cope with the ever-increasing load on our antiquated Victorian system of combined sewers. In the combined sewer system, rainwater runoff from rooftops and roads drain into the public sewer, potentially overloading the system during and immediately after rainstorms. Under such storm conditions, local wastewater treatment plants can use ‘combined sewer overflows’ (CSOs) to enable a level of emergency discharge into a watercourse to relieve pressure on local properties. Further downstream at the main treatment works, additional flow is captured in storm water storage tanks.

However, when the combined volume of sewage and rainwater in these tanks reaches capacity, something has to give. The excess effluent which spills out from more than 300 CSOs in our region flows into the Solent, either directly via offshore outfalls or indirectly via outfalls which discharge into the rivers, harbours and estuaries.

The amount of untreated effluent that a water utility company can legally discharge is limited by licences granted by the Environment Agency, licences which are now recognised as being inadequate for the sewage overflow Spills. With insufficient storage capacity, the excess effluent is being discharged by the water utility companies simply to keep the combined load moving and prevent the backing-up of sewage into urban properties.

For several years, the SPS pollution team has been monitoring historical CSO discharges by Southern Water, using data publicly available from Environment Agency annual reports. The team spends many hours analysing the data, extracting the specific detail relevant to the Solent, and using the locations of known CSOs, highlighting its conclusions about the state of pollution in the Solent. SPS also takes a keen interest in the sometimes-confusing assortment of regulatory bodies and their related initiatives, engaging in public consultations where the opportunities arise.

We were encouraged by the passing into law of the Environment Act 2021, heavily influenced by a private member’s bill sponsored by the Rt. Hon. Philip Dunne MP. The SPS Council had raised concerns that the scope of the bill should extend to the estuaries and inshore waters into which the river basins drain. Consequently, we wrote to each of the MPs with constituencies bordering the Solent, seeking their support for the legislation as it passed through parliament. Responses were mixed, but those who took the time to respond were supportive and the bill eventually passed onto the statute book, though not before a number of unsatisfactory amendments had watered down some of its goals.

In a forthcoming post, we will summarise the many Government departments, initiatives and quangos which are intended to monitor the quality of the UK water and its sources.