According to recent data, DEFRA (Department for Environment, Food and Rural Affairs) reports approximately 330,000 kilometres of public sewers in England and Wales. Consequently, this remains the most common method for managing sewage and wastewater.
However, many rural locations lack mains access. As a result, these sites require independent systems to manage waste, which remains the responsibility of all building owners.
Furthermore, developers increasingly install treatment plants or septic tanks on new greenfield sites. Although these systems are more frequent, people often use the wrong terminology for them. This creates confusion regarding their names and how they function.
To address this, we have decided to provide a breakdown of each approach. This guide will simplify and help you understand each system.
Main Sewers
Main sewers consist of an underground network of pipes. These pipes carry wastewater from homes, businesses, and other buildings to treatment plants. This wastewater enters the system from various sources, including toilets, sinks, showers, and washing machines.
Gravity moves the wastewater through the pipes. As it flows, it combines with wastewater from other buildings. Manufacturers typically use durable materials like concrete or PVC plastic for these pipes. These materials withstand the weight of the waste and any present debris.
The pipes carry the wastewater to a sewage treatment plant. Here, the water undergoes several processes to remove contaminants and harmful substances. These treatments include physical, biological, and chemical methods like sedimentation, filtration, and disinfection.
Once treated, the system typically releases the water into nearby rivers or oceans. These bodies of water safely dilute and disperse the treated liquid. In some cases, industries reuse this water for agricultural irrigation or cooling.
Pro’s
- Easy to connect to
- A monthly/ annual fee paid to the Wastewater Management company for maintenance and service
Con’s
- Not available throughout the country
- System is old and will often take rainwater which risks overflooding and untreated water releasing in the sea
Cesspits
A cesspit is an underground tank designed to hold untreated sewage and wastewater. Manufacturers usually build these tanks from concrete, brick, or plastic. Furthermore, they ensure the structure is watertight to prevent sewage from leaking into the surrounding soil and groundwater. The size of the cesspit depends on the number of users and the total volume of wastewater generated.
In terms of operation, the cesspit collects and stores wastewater from toilets, sinks, and other sources until it reaches capacity. At this point, you must call a licensed waste contractor to empty the tank. They then transport the sewage to a treatment plant for proper disposal.
Consequently, cesspits require regular maintenance and cleaning to prevent overflowing and ensure they function properly. If you do not maintain the system, it can lead to unpleasant odours, health hazards, and environmental pollution.
Overall, cesspits offer a basic, temporary solution for managing waste in areas without mains sewer access. However, they remain less convenient and more expensive to maintain than other options. They also pose a greater risk to public health and the environment if they are not managed correctly.
Pro’s
- Solution for when mains connection, or septic tank or treatment plant are not allowed
- Suitable for contaminated waste
Con’s
- Very expensive to maintain and need to be regularly emptied
- If not maintained and tank is damaged can be a huge environmental risk
Septic Tanks
A septic tank is an underground system used to treat and dispose of household wastewater. These are common in rural areas where a connection to a mains sewer is unavailable or impractical.
Structurally, manufacturers typically build these tanks from concrete, fibreglass, or plastic. They are designed to hold untreated wastewater and allow it to separate into three distinct layers. The top layer consists of scum, including oils, grease, and other floating substances. The middle layer contains clarified wastewater, also known as effluent. Finally, the bottom layer consists of sludge made of heavy solids that settle to the tank floor.
In terms of the process, as wastewater enters the tank, it undergoes natural decomposition. Bacteria present in the water break down and digest organic materials. This biological action produces the sludge at the bottom and releases gases like methane into the air.
Subsequently, the system discharges the effluent layer into a drain field or leach field. This field uses a network of perforated pipes or chambers to allow the liquid to percolate slowly into the soil. The soil then acts as a natural filter. It removes harmful bacteria and contaminants from the effluent before the water returns to the groundwater.
However, septic tanks require regular maintenance and pumping. This removes the accumulated sludge layer and prevents overflow. If you do not maintain the tank properly, it can lead to unpleasant odours, health hazards, and environmental pollution.
Pro’s
- Great solution for sites without mains
Con’s
- Limits what can go into wastewater as bleach and other household items can kill off the required bacteria which breakdowns the matter.
- Cannot be installed in a flood risk zone
- Requires highly permeable ground for the drainage field
- Only removes 30% of pollutants
Sewage Treatment Plants
Sewage treatment plants treat and dispose of wastewater from individual households. These systems typically consist of several key components. These include a septic tank, a treatment unit, and a drainage field.
Initially, wastewater from toilets, sinks, and other sources enters the underground septic tank. Once inside, solid matter settles to the bottom to form a layer of sludge. Simultaneously, grease, oils, and other floating substances form a layer of scum on the surface.
Following this, the liquid layer between the sludge and scum, known as effluent, moves to the treatment unit. This unit is typically a biofilter or a treatment chamber. Inside the unit, microorganisms break down the remaining organic matter and pollutants.
After treatment, the effluent moves to the drainage field. This network of perforated pipes or chambers allows the liquid to percolate slowly into the surrounding soil. The soil then acts as a natural filter to remove any remaining contaminants. Once the soil treats and filters the effluent, the water safely returns to the ground water.
Pro’s
- The wastewater is treated safely and can prevent environmental damage
- A great solution when septic tanks aren’t suitable
Con’s
- Requires power
Professional Guidance and Regulations
If you require an alternative sewage management system, you must seek professional advice. Furthermore, you must obtain a licence from the Environment Agency to allow any wastewater to enter the waterways.
Recently, Paul Howe and Will Hadler from Kingspan visited our office in Hove. They delivered an informative presentation on ‘Old Cesspits, Septic Tanks & Environmental Regulations’.
Kingspan ranks as one of the largest manufacturers of treatment plants and septic tanks. They provide an excellent design service to ensure you install the right type of kit for your specific needs. You can visit their website here.