Mana eco House Project

Drainage

Well let’s start with the facts about our drainage. We won’t be using a flush toilet so there is no sewage system to drain to. Our grey water from the sinks, shower and washing machine will yield about 60 litres per day.

Our drainage design therefore is a simple one which does not involve standard solutions like package treatment plants or septic tanks. All of the liquid toilet waste is used as fertiliser for plants around the garden and all the solids waste is composted for 12 months and used as mulch around fruit trees. The grey waters coming from the rest of the house will go into our WET System which will be designed and built by Jay Abrahams of Biologic Design.

The only treatment required for this flow is from the kitchen sink which needs to have solids and oils etc. removed before entering the WET System. This will be achieved using a commercial grease trap. 

Wetland Ecosystem Treatment (WET) Systems created by Biologic Design are regenerative, nature-based water purification systems. They can be described as being horizontal plug-flow, multi-species, soil biome-based, constructed wetlands, with wet woodland and orchards. Biologic Design has been creating Wetland Ecosystem Treatment (WET) Systems since 1993. Locally in Herefordshire they have created large industrial-scale systems for Westons Cider, Hereford Livestock Market and Pontrilas Timber.

The WET System for Mana eco House comprises a productive tree-based water purification system. It is also soil-based, and because the subsoil is permeable, the whole of the wastewater system will be lined with an impermeable geosynthetic bentonite clay liner, to prevent any untreated wastewater from leaving the site and entering groundwater. Unlike conventional mechanical wastewater treatment systems, and reedbed treatment systems, a WET System integrates wastewater purification with both biomass resource production and enhanced biodiversity, through the creation of a lush, species-rich, diversely planted wetland habitat.

 

Within a WET System phosphate is not seen as an expensive problem, but as a crucial biologically active molecule to be absorbed and used within this living, nature-based system. Greywater, from the dwelling, will be processed within a sub-surface flow WET System planted with willow coppice. These trees absorb nutrients, the nutrients are then removed with the Willow coppice when harvested.

 A WET System is a tree-based ecosystem which relies on the energy transactions of the trees planted, to power the purification of the wastewater entering it. Coppiced willows can be harvested annually to produce a yield of basketry willow wands, which also removes the nutrients from the system.  The root zone of the trees is where the products of photosynthesis, the simple sugars and oxygen, create an environment favourable to aerobic microbes, especially fungi, enabling both nutrient and gaseous exchange to occur over as large a surface area as possible. In addition we will be growing our food crops in the swales to protect our system from drought, so all in all we will have no waste and create a low maintenance self watering and feeding system.