Off-Grid Waste Management
When living off the grid you have to consider the management of your home’s wastewater. There are many systems available to safely, cleanly, and greenly dispose of your waste. When designing a new off grid home, you can opt to recycle some of your water, and to process the waste that you cannot reuse.
The most important element to this will be how you choose to dispose of your sewage.
In new-build off grid systems, it is common practice to recycle grey water, and to treat and dispose of black-water.
What kind of treatment do I need?
There are two types of waste in your home:
Greywater is the wastewater that comes from showers, washing machines, and sinks. It may contain particles, but they are not dangerous.
Blackwater is the sewage wastewater, from toilets and dishwashers, which contain solid food particles and human waste. These solids are considered harmful to humans, and therefore cannot be directly released to soil or watercourses.
How Does Off-Grid Sewage Treatment Work?
Whether sewage treatment occurs in your garden, or on a huge city-sized operation, it follows the same basic process. Firstly, there is a primary “separation” stage, and then a filtration stage. The separation stage simply allows solids in the wastewater to fall away from the liquids, so the liquid effluent can be treated.
The secondary treatment of the liquid effluent is almost exactly the same as the process that occurs in an aquarium filter. It requires no chemicals and is extremely simple. The liquid will be biologically filtered, this is when naturally occurring friendly bacteria will substantially degrade the biological content of the wastewater. This stage requires oxygen and is known as aerobic digestion.
Finally, there is a tertiary treatment phase, in which the wastewater is mechanically filtered to remove any particles, and render the effluent fully treated and safe for disposal into the environment.
Why should I process my own waste-water?
Wastewater management has been an environmental concern for a very long time. In an off-grid property, it is typical to run a septic tank or cesspool.
A septic tank requires a drainage field, and many properties will not be able to find a site that meets the Environmental Agency (EA) mandatory soakaway tests. This can make a traditional septic tank system impossible to install.
Cesspools are now considered to be of environmental concern, and it is advised to choose another option if possible. Cesspools are banned in Scotland and France, and legislation could potentially move that way in England and Wales too. Not only do cesspools have huge volume requirements, but they also require costly and polluting tanker collections. There are ways to incorporate further treatment in to a septic tank off-grid waste system, to make it compliant. A more complete approach would be to install an all in one sewage treatment plant for your property. This may allow you to discharge your wastewater directly to a watercourse or to ground.
What are the Options?
A Cesspool / Cesspit
A cesspool is simply a large tank, that holds your untreated wastewater, until it can be collected by a waste management company. This is an expensive and very inefficient way to manage off-grid waste. It requires a huge amount of space, and the carbon footprint from the regular tanker collections can really add up over time. Cesspools are such an inefficient method of managing waste, that they have been banned in Scotland and France. We always recommend a system that allows you to dispose of your waste yourself.
A Septic Tank System
A septic tank is an underground tank where solids sink to the bottom, and the liquid flows out. With a septic tank system, secondary treatment of waste water occurs in the ground. In general, the liquid from the septic tank is sent to a drainage field, or reed bed, which treats/filters the water before it drains through to the groundwater.
A Sewage Treatment Plant System
A sewage treatment plant, or package treatment plant, is a miniaturized treatment facility. It produces fully treated effluent, that may be discharged directly to a watercourse, such as a river or stream, or to ground through a drainage field, depending on EA regulations.
A complete sewage treatment plant system is by far the easiest way to get approval from the Environmental Agency to process your own off- grid waste. Some systems come pre-approved for discharge to a watercourse at certain volumes.
The entire system takes up a small amount of above-ground space, and is low maintenance. Different systems may have different requirements. Some require annual services and frequent desludging whereas others are much more hands-off.
There are now systems that can run without any electrical input, which allows the system to be as green as possible.
Recommended Sewage Treatment Systems
All in One
Biorock Monoblock Systems
The Biorock Monoblock systems are some of the greenest all in one options on the market. They are one of the few non-electric septic systems. The system relies on a natural aerobic digestion process, that does not require any electrical pumping or aerating.
The Monoblock system uses no chemicals, and the process is completely natural. It is a low maintenance system, that releases high quality effluent, that can be discharged to water or ground.
As a complete off-grid waste system, this is as close to “plug and play” as you can get.
Quality Waste Disposal
For sites that require the highest quality off-grid waste treatment, normally when discharging in protected areas, the Biorock Ecorock systems are a zero electric, quiet, and odourless option.
The Ecorock produces the highest quality effluent of any sewage treatment system on the market. The Ecorock is a modular system that can be scaled up to any project size, including buildings and complexes with a capacity up to 100 people.
In properties with a capacity of over 8 persons, the Ecorock is the go to option.
For an overview of the Ecorock system, see Biorock’s video here: https://www.youtube.com/watch?v=EC6XZC00R4I
All Natural Option
Reed-beds and plant based treatment
Reed-beds provide a fantastic, natural way to treat wastewater from your home. A reed-bed is an engineered structure, rather like a pond, that harnesses natural ecological processes, to breakdown the organic matter in your wastewater. A reed-bed is filled with sand and gravel and is planted with reeds. Depending on the type of reed-bed, wastewater is applied over the surface, or at one end, and the naturally occurring bacteria and oxygen rich atmosphere, effectively process the off-grid waste, to produce treated effluent, which can be returned to the ground, through a drainage field, or dispersed into a watercourse.
Most reed-bed systems will require pre-treatment with a septic tank to remove solids, however those with enough land may be able to manage without.
A reed-bed is an inexpensive system to run and is completely natural. They do require a larger above ground area than an all in one sewage treatment system, and are not suitable for all properties.
Greywater recycling is a very good off-grid water-saving option for a new build home. Due to the requirement for a separate grey-water system, it is rarely practical to re-plumb a home as a retrofit. As greywater does not contain harmful particles, it can be recycled simply for use in flushing toilets. With more processing, it can even be made to meet the requirements for the European Bathing Water Regulation 2006/7/EG. At this stage, it can be used for showers, sinks, baths, and washing machines.
At a basic level grey-water can be filtered, chemically dosed, and then returned to the property for flushing toilets. Products such as the Aquawiser 210 can be used for this purpose.
On a new-build property, greywater recycling should be considered, as you could recycle up to 50% of your domestic water. This not only saves you money, but also reduces the strain on the water supply network. For those who rely on rain or bore water, greywater recycling can help reduce your water requirement, and help your system function more efficiently.