Tackling potential impacts from offline sewage treatment systems
Offline sewage treatment systems can have a big impact on freshwater wildlife. Our Think Tank project aims to reduce the impacts of small offline sewage systems in the New Forest through raising awareness of the risks and providing local communities with actions they can take to reduce the environmental impacts of their systems.
An Important Freshwater Landscape
Boasting pristine streams, ponds and mires bursting with rare species, the New Forest is one of the UK’s most significant freshwater and coastal landscapes. Freshwater Habitats Trust have identified 24 Important Freshwater Landscapes (IFLs) across England and Wales, extensive regions with nationally significant concentrations of freshwater biodiversity, rich in threatened plants and animals. The New Forest and Dorset Heaths IFL has the highest number of rare species records, likely as a result of the historic practice of traditional grazing and areas with clean water, free from pollution.
The New Forest catchment spans 300km2 and is made up of 12 major rivers with many streams and tributaries, as well as over 1,000 mapped ponds, extensive coastal habitat, the best examples of valley mire systems in Europe and many important headwater streams. Headwaters and the surrounding catchments are incredibly important ecologically, making up more than 70% of Britain’s river network and providing habitats for a wide variety of freshwater species.
A typical headwater stream in the New Forest.
Coral Necklace thrives in the New Forest due to the presence of grazing and clean water.
Rare species like this Oblong-leaved Sundew are abundant in the New Forest.
A New Forest pond, abundant with rare wetland plants.
Kickstarting nature recovery
In the New Forest, many rivers and streams begin in the boggy heathland mires. These ecologically sensitive headwater streams are at risk, their small size and seasonally low volume of water mean that any pollutants entering the water have a higher concentration due to the lack of dilution. Any discharge from nearby offline sewage treatment reaching the watercourse will have a negative impact causing water quality declines and potential loss of freshwater species.
This actually provides an opportunity – to kickstart nature recovery by maintaining and upgrading offline sewage treatment systems in headwater catchments like the New Forest. Because of their position in the river network, headwater streams are not affected by cumulative upstream pressures in the same way as larger rivers. As such, removing sewage input can in some cases be a solution to water pollution in the stream. This means that by maintaining and upgrading offline systems around New Forest headwater streams, we can make huge improvements to water quality.
- Signs of pollution are not always obvious but can be impacting freshwater biodiversity all the same. Testing water quality and chemistry can be a useful way to identify pollutants that don’t cause any observable signs.
There is also a growing concern over new and emerging contaminants from septic tanks and other wastewater discharge including Active Pharmaceutical Ingredients (APIs) as these may contribute to concentrated loads in rivers and other water bodies impacting on aquatic life. There is particular concern in more rural locations, where a recent study found that APIs were widespread in 52 of the 54 sites sampled across all of England’s National Parks.
Wastewater is a particular issue in rural settings like the New Forest National Park, where many properties are not covered by the mains sewer network. Wastewater from most properties (i.e. residential and businesses) connects via drains and sewers to wastewater treatment works, where it is treated and returned to the environment. But not all properties benefit from this – some rely on private systems to collect and treat their waste. Recent mapping found that around 35% of all properties (residential and business) in the New Forest are ‘offline’.
Types of offline sewage treatment systems
If your home or business is not connected to the mains sewerage system or a cess pit, the wastewater from your toilets, baths, showers, sinks and washing machines will drain into one of the following systems:
Septic Tanks are underground chambers where bacteria safely break down the waste. Solids sink to the bottom forming sludge and the liquid flows into a ‘drainage field’ where bacteria further treats it as it soaks into the ground. These systems must not discharge to watercourses.
Small Sewage Treatment Systems work in a similar way, but use powered mechanical parts to aerate the bacteria. This makes them more effective at treating wastewater and means they can discharge treated sewage into a soakaway or directly into flowing water.
If not working properly, both systems can release raw sewage, polluting the water in the ground, in rivers and streams, and at the coast. There are environmental risks associated with these off-mains systems, especially if they are faulty, incorrectly sited or not properly maintained. Whilst incorrectly operated systems pose the greatest risk of pollution, any system that discharges will be introducing nutrients and pollutants into the surrounding environment. This is a particular cause for concern in the New Forest, where many offline properties are located near sensitive waterbodies.
- Gemma Stride carrying out water quality testing.
Next steps
- A campaign to raise awareness of the environmental impacts of offline systems and promote simple actions that New Forest locals with offline properties can take to reduce the environmental impact and improve the efficiency of their system.
- Targeted water quality monitoring at offline sewage ‘hotspots’ to identify the impact of improving awareness and upgrading offline sewage systems.
- Working with local communities to establish suitable options for collective pump out and maintenance schemes.
What can you do?
As a property owner there is a legal obligation to ensure that your offline sewage system is compliant with the UK Government’s General Binding Rules or that you have an environmental permit.
If the system belonging to your property meets the required legal standards, follow these Best Practice Guidelines to ensure that your system is properly maintained to minimise the impact on your local freshwater environment.
General Binding Rules
Below are some of the key General Binding Laws that must be followed. Please refer to the official Government website for the full list of laws.
Fix faults and perform regular maintenance
Gurgling pipes, discoloured effluent, odours, foam, a swampy soakaway, lush grass growth, and sewage fungus (that looks like grey cotton wool) in local waterways can all indicate that your system isn’t working properly. The most common problems are that tanks are full and need to be emptied, or that pipes are blocked – these can be cleared with boiling water or drain rods. Problems must be fixed immediately, preventing pollution, health risk, and escalating repair bills. Accredited engineers can fix more serious faults and carry out servicing.
Empty regularly
All systems need to be emptied of sludge on a regular basis. Frequency will depend on levels of use, and on how well you treat your system, but having it emptied annually by a registered waste carrier will help to ensure that it functions properly and doesn’t cause pollution.
Buyer beware
If you sell your property, you must inform the buyer in writing that it has a septic tank or small sewage treatment plant. Being able to provide them with records and a maintenance guide will reassure them that the system isn’t a liability.
Check the lawBest Practice Guidelines
1 Get to know your system
Where is your tank? A metal or concrete lid should be visible, usually in the ground downhill from your property. Is it shared? Ask your neighbours. Where does it discharge to? Locate your soakaway. This gravel or grassed area cleans and filters the liquid effluent from your tank.
2 Check your system
Check that the soakaway isn’t waterlogged, and that there are no pools of water running into ditches or watercourses. Effluent inside the inspection chamber should be clear or pale, and odour-free.
3 Don’t upset the balance
Using products marked as ‘suitable for septic tanks’ or ‘environmentally friendly will keep the bacteria in your tank healthy. The bacteria break down your waste, so the tank could cause health risks and environmental problems without them. Avoid harsh chemicals like bleach, caustic soda, disinfectants and anti-bacterials, and use cleaning products and detergents sparingly. Domestic sewage systems can’t remove phosphates from the effluent so using phosphate-free product will help to protect your local rivers and streams.
4 Bin your waste
Household waste can block or damage your system and should be binned instead of flushed. Kitchen towels, ‘flushable’ wipes, tissues, cotton buds, nappies and sanitary items will all block your tank or pipes leading to expensive repair bills. Oils, fat and grease will solidify and block pipes and soakaways. Use a kitchen sink strainer to prevent food waste filling up your tank, or it will need to be emptied more frequently. Paints, solvents and chemicals can kill your tank bacteria and should be disposed of at a civic amenity site. Medicines can also kill your bacteria.
5 Don’t over-water
Large volumes of water can overwhelm your tank, flushing out untreated sewage. Ensure that roof gutters carrying rainwater aren’t connected to your system, and avoid running dishwashers and washing machines several times in one day.
6 Keep good records
Keeping a record of maintenance, emptying and servicing will help contractors to fix any problems that arise, and will be useful if you want to sell your home.
7 Report signs of pollution and suspected sewage spills
If you notice signs of pollution (such as discolouration, unusual odour, a cotton-wool like substance called sewage fungus or foam/bubbles) report this to the Environment Agency incident hotline, here.
8 Spread the word!
Let your neighbours and community know about the importance and benefits of caring for your system and encourage them to do the same.
Benefits of caring for your offline system
Save money. Maintaining your system helps to ensure that it’s running smoothly and reduces the risk of unexpected repair costs.
Reduce your environmental footprint. Caring for your offline sewage system prevents toxic effluent from entering valuable waterbodies across the New Forest, improving water quality and supporting species to thrive.
Save time. Keeping records will save you time and effort when it comes to selling your home in the future. Your future self will thank you!
Read our reports
Freshwater Habitats Trust in the New Forest
Blue Horizons
Through Blue Horizons, we’re improving the running and standing water network in the New Forest.
New Forest Catchment Partnership
We’re working in partnership to protect freshwater habitats in the New Forest catchment.
The Freshwater Network
The New Forest is part of an Important Freshwater Landscape in a national network of wilder, wetter, cleaner, connected habitats.