How to Spot Sewage in the Sea?

Spotting sewage in the sea involves observing specific visual, olfactory, and biological cues that indicate water contamination. Key indicators include flattened waves due to fats and oils, the attraction of seabird flocks, unusual water discolouration, and a distinctive foul odour.

When looking for signs of sewage, it's important to differentiate between general pollution and specific sewage discharge, although they often overlap. Sewage discharges can have distinct characteristics that make them identifiable.

Key Indicators of Sewage in the Sea

Recognizing sewage pollution requires paying attention to several tell-tale signs. These indicators, particularly the presence of fats and oils and the unusual behaviour of marine life, are crucial for detection.

Visual Cues

• Flattened Waves: One prominent sign of sewage discharge is the appearance of waves that are unusually flat around a particular area. This phenomenon is often caused by the presence of fats and oils released from sewage, which calm the water surface.
• Discolouration: While stormwater overflows tend to cause a grey discolouration of the water, especially strongest near an origin like a pipe or outfall, sewage itself can also cause murky, brownish, or cloudy patches. Look for water that appears unnaturally dark or turbid.
• Visible Debris: The most unmistakable visual cue is the presence of human waste. This includes toilet paper, sanitary products, wet wipes, and other non-biodegradable materials that have been flushed down toilets.
• Greasy Sheen or Foam: A film or oily sheen on the water surface can indicate the presence of fats and oils from sewage. Persistent, bubbly foam that doesn't dissipate quickly, especially if it appears greasy, can also be a sign.

Biological Cues

• Seabird Flocks: Sewage discharges can sometimes attract seabird flocks. While birds are naturally drawn to food sources, an unusually high concentration of birds congregating in one area of the sea without an obvious natural food source might indicate they are feeding on organic matter from sewage.

Olfactory Cues

• Foul Odour: Perhaps the most direct sensory indicator is a strong, unpleasant smell. Sewage has a very distinct, putrid odour that is unmistakably associated with human waste. If you detect such a smell while near the water, it's a significant warning sign.

Distinguishing Sewage from Stormwater Overflows

It's important to note the distinction:

• Stormwater Overflows: Tend to cause a grey discolouration of the water, which is often strongest near its origin, such as a pipe or outfall. These overflows primarily consist of rainwater but can carry pollutants from urban runoff.
• Sewage Discharges: Characterized by fats and oils causing waves to flatten and potentially attracting seabird flocks, in addition to containing human waste and associated odours. While stormwater overflows can sometimes mix with sewage (combined sewer overflows), direct sewage discharges have more specific indicators.

What to Do if You Spot Sewage

If you suspect sewage pollution in the sea, it's crucial to take immediate action to ensure public health and environmental protection:

1. Avoid Contact: Do not swim, wade, or engage in any water sports in affected areas. Avoid letting pets enter the water.
2. Document: If possible and safe, take photos or videos of the pollution, noting the date, time, and exact location.
3. Report: Immediately report your observations to the relevant local environmental protection agency or water authority. Providing detailed information, including your documentation, is helpful. Many agencies have dedicated hotlines or online reporting tools.
4. Inform Others: Politely inform other beachgoers or water users about the potential contamination.

Summary of Indicators

Here's a quick reference table for spotting sewage and related pollution:

By being aware of these signs, you can contribute to protecting marine environments and public health from the impacts of sewage pollution.