Land treatment or discharge of municipal, industrial and other waste water streams is becoming increasingly common. There is increasing pressure to remove the discharges from our rivers and lakes, whether that be for environment, cultural or amenity reasons. Invariably the land discharge is through spray irrigation and use of a cut and carry pasture land use.
Site selection is key to effective and sustainable waste water irrigation; e.g.
- Size sufficient to accommodate the current and future waste water volume – future proofing
- Soils that have sufficient topsoil to support a healthy pasture and free draining to infiltrate the irrigated waste water
- Deep free draining sub-soil with no pans or shallow groundwater
- Location to minimise effects (odour, wind drift and the like)
HydroServices has had a key involvement in a number of successful waste water irrigation designs:
- Clandboye Dairy Factory (when it was Alpine Dairy Company)
- Municipal waste water irrigation at Oxford, Rakaia and Rolleston in Canterbury
- Proposed municipal waste water irrigation for Te Anau and Feilding.
Any waste water irrigation scheme requires a detailed design process to be followed;
- A feasibility assessment carried out in the vicinity for a suitable site;
- Waste stream flow and chemistry characterised;
- A suitable site identified following a screening process;
- Detailed soil and soil hydraulic investigations carried out at the selected site; and
- A proposed irrigation design and land use management plan for the site developed.