Renovation of a wetland for filtering both grey and black water at Protea Eco

Renovation of a wetland for filtering both grey and black water at Protea Eco

 The wetland was originally designed to accommodate one house with a bathroom and a kitchen.  Waste water from the house first enters a septic tank where solids are removed.  The partially filtered water leaves the septic tank and enters the wetland pond which is filled with bog plants.  Water entering the wetland is made up of soaps and organic waste which provide a food source for millions of naturally occurring micro-organisms.  The micro-organisms convert this food source into plant food such as nitrates and phosphates which in turn provide a food source for the bog plants.  Once filtered, the water flows out of the wetland and is stored in a tank for irrigation purposes.

 The original wetland pond was lined with bentonite, a clay based product which offers excellent water-proofing properties.  The product did not work as expected and over a period of two months the bentonite settled to the bottom of the pond leaving the upper areas not waterproofed.  Once full, water entering the wetland area leaked out of the pond into the surrounding soil.

 The decision was made to waterproof the pond with ultra violet resistant plastic pond liner.  The pond was drained and the rock-gravel-compost contents or aggregate removed. All stones and roots where removed to prevent tearing of the new lining.

The length and width of the existing pond was carefully measured taking into account some overlap around the edges.  The new liner which measured 8m x 9m, was carefully unfolded so as not to damage any of the welded seams and dragged into the old pond area.  Once the liner was in place, large concrete blocks where placed around the pond to secure from wind damage.

 Installing the liner

 All the necessary plumbing was installed and sealed.  The existing bentonite certainly helped to seal the plumbed inserts as the soils underneath where constantly wet.

 Inserting the plumbing

 Sealing the plumbing

 Topsoil was placed directly on top of the liner followed by a rocky aggregate to approximately half a meter using buckets and hand packed so as not to damage the liner

 Filling rock aggregate

 A gravel aggregate was layered above the rock layer and finally compost was added to provide a planting medium for the wetland plants.

 Crushed stone aggregate layer

Compost planting medium

 The wetland is working well and water is flowing efficiently throughout the aggregate without leaking into the surrounding soil.

 Wetland ready for planting of bog plants

 Wetland with bog plants