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On-site Disposal System
- Our Service
We offer effective solutions to recycle "used-water" back into your environment, using a range of site specific, passive natural systems that are applicable to households, community facilities, farms and commercial operations.
We offer a complete service to the property owner, through resource consents, design, installation, planting and maintenance. We excel at providing solutions for "difficult" sites where there are constraints due to soil types, steep slopes, limited area, and/or perched water tables.
- An Introduction to our Solutions
- Following is a list of the main components that may be used in our systems. This is not a complete list. In each case the components, and their configuration, will depend on specific needs of the client and site requirements.
Primary Treatment (Solids Removal)
- Septic Tank
- Standard tanks fitted with Autoflow EF series screen filters.
Designed output of fluids, Total Suspended Solids (TSS)<50mg/l, Biological Oxygen Demand (BOD)<60mg/l
The septic tank receives and contains the solid material, and decomposes it utilising anaerobic bacteria. Septic tanks can be effective in the proper circumstance, however where larger amounts of waste are expected or site area is limited the more efficient aerobic action Vermicomposter (below) is usually a better alternative.
- Vermicomposter
- A Vermicomposter provides aerobic composting of the solid content without any odours. This primary treatment chamber receives and processes all organic wastes and used waters. It is arranged to provide an aerobic environment for a living ecosystem of decomposer organisms (worms, slaters etc.). The solid wastes from toilets, kitchen scraps, paper and grease land on the surface of the base media where the decomposition processes take place. The ability of the Vermicomposter to deal with greasy kitchen waste avoids the need for messy and expensive grease traps. This is a significant cost saving for commercial premises such as cafes, hotels, and large residential complexes. Once the process is established (about two years) a proportion of the castings are removed at intervals via an extraction tube, and dug into the ground for soil improvement. Primary treated effluent is dispersed into the soil for tertiary treatment through a carefully designed and planted soakage field. For more details please read the section on Tertiary Treatment.
Designed output of fluids, TSS<50mg/l, BOD<50mg/l. Click here for more information
Secondary Treatment Options
Secondary treatment is usually only necessary on difficult sites where there are limitations on tertiary treatment capacity.
- Sub-surface Flow Wetland Containments
- 600mm deep containments filled with pea gravel (6-10mm) and capped with peat, surface planted with emergent reeds to enhance aeration, 3-day retention of liquid.
Designed output of fluids, TSS<10mg/l, BOD<10mg/l
- Vertical Flow Wetland Containments (Trickle Filter)
- 1 metre deep containments filled with several layers of graded media (sand/ pea gravel/gravel). Layers are infiltrated by aeration pipes to ensure the contained environment remains aerobic. The effluent is dose loaded 4 times per day at 100mm/day. The surface is planted with emergent reeds to enhance aeration and maintain high percolation rates.
Designed output of fluids, TSS<10mg/l, BOD<10mg/l
(As a comparison most aeration treatment plants claim an output of 20/20,TSS/BOD, and this level of performance is achieved mechanically by screening through a 120-micron filter.)
Tertiary Treatment - Options
Tertiary treatment is accomplished in soakage fields using the KISS principle (keep infiltration systems shallow). Generally areal loading is applied at a maximum rate of 5mm per day to a well-planted field. The method used depends on the characteristics of the soil, terrain and available area, therefore each site requires specific analysis. In most cases, an LPP distribution system (ARC Environment Technical Publication No 58) is used. Difficult sites may necessitate RAAM drip irrigators with the precondition of wetland secondary treatment.
A properly designed pipe distribution network controls discharge so that even dispersal is achieved. By dose loading the field periodically through each day (say <5 times a day), over-saturation is avoided. Our preferred passive dose loading system uses the Vortech Dosing Siphon. By applying low loading rates (usually 5mm/m2/day) the soils maintain their ability to remove pathogens by natural bacterial processes in the soil, (as little as 300mm of unsaturated soils is all that is required to do this). Much of the water is taken up by the plants and transpired into the atmosphere, and soakage to ground water is minimised. Planting of the soakage field with appropriate plants is essential for sustainable operation. Inadequate or unsuitable planting causes system failures, and proper standards are rarely achieved by contractors who lack understanding of this aspect of the system. We also ensure that the planting adds to the aesthetic appeal of the landscape.
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