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Hampton Downs Landfill Leachate Treatment Plant

Category : Water Treatment

The Client

The North Waikato Regional Landfill at Hampton Downs is New Zealand’s largest landfill. Situated between Auckland and Hamilton it receives 500,000 Tonnes per annum of municipal waste from Auckland.

Their Issue

The landfill needs to dispose of 150kL to 300kL of leachate each day. This was being transported offsite and discharged into the Auckland sewer 70 km away.

How Much it was Costing Them

To transport and discharge the leachate cost $22 /kL, or between $3,300 – $6,600 a day. The continued tankering of leachate offsite for the landfill’s anticipated life of  35+ years was quite literally throwing atleast a million dollars a year down the drain.

The owner and operator of the landfill, EnviroWaste Services, projected that as the size of the landfill grows this cost will increase by a further one million dollars every five years. By 2020 the transport and treatment costs alone will be $2.5M. Add to this the capital costs of more storage tanks and tanker trucks, price increases by the waste water treatment plant and the ever present risk they could change their acceptance criteria.

What needed to change

The ability to treat and dispose of the leachate onsite was desired. To achieve this the processes considered included:

  • evaporation
  • biological and chemical treatment
  • reverse osmosis

Evaporation was dismissed as nonviable. Evaporation to air is not possible due to Auckland’s average relative humidity in the range of 70% – 85%.

The landfill generates and harvest its own landfill gas, which it uses to generate electricity that it can on-sell. Using this gas to power an evaporator was investigated but the cost in lost revenue from electricity sales would be $38 per kL of leachate treated.

If the leachate is not vaporised and released into the air then any liquid or solid effluent/by-product of the treatment process would need to be disposed of to land or a waterway. Solid or sludge by-products could be returned to the landfill but any liquid effluent that could not be reused on site would need to be irrigated or released into a waterway. Their consent to irrigate to land only permits this when there is a soil moisture deficiency and only allows 150 kL per hectare per three days, and only from October to March. The Waikato River runs just east of the landfill and a consent to discharge into the river was granted, but with strict water quality criteria, particularly regarding Boron and Ammonia, and an allowable conductivity of only 20 μS/cm.

Reverse osmosis was going to be needed in order to achieve the strict environmental consent quality requirements. Traditional spiral wound reverse osmosis membranes would require pre-treatment, using either a biological system or otherwise a series of micro and ultrafiltration membranes, in order to prevent them from fouling and constantly needing cleaning.

The Solution

Alternatively a single pass through a vibrating membrane was proven in a series of pilot tests to adequately clean the leachate without fouling the membrane. The principle behind the vibrating membrane is that the vibration prevents the membrane from fouling.

Syngineering designed and constructed a treatment plant capable of treating 300 kL/day.  The system uses six VSEP systems to reduce the feed water with a Total Dissolved Solids (TDS) of 5,ooo ppm down to 550 ppm.


VSEPs at Hampton Downs Leachate Treatment Facility

The permeate from the first stage is then treated through four stages of spiral RO.

Spiral ROs for polishing

Spiralwound ROs for polishing

Through this process it is possible to achieve a final permeate that is well below the required levels:

  • TDS of 0.1 ppm, down from 5,500 ppm
  • COD of 0.002 mg/L, down form 4,100 mg/L
  • Ammonium of 0.08 mg/L, down from 930 mg/L
  • Boron of 0.18 mg/L, down from 26 mg/L

Feed Water into the VSEP, resulting Concentrate and treated Permeate.

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Hampton Downs Commissioning

Category : Construction

With the design and construction of the facility now complete it is time to install the equipment and commission the plant.

Following our factory acceptance testing at the manufacturers in the USA the pre-assembled skids arrived ready to be installed.

Spiral RO skid

Spiral RO skid

The well planned project came together like clockwork ensuring the project was delivered on schedule.


VSEPs at Hampton Downs Leachate Treatment Facility

Spiral ROs for polishing

Spiral ROs for polishing


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Hampton Down Landfill Leachate Construction

Category : Construction

Syngineering has been given the green light to proceed to constructing the Hampton Downs landfill leachate plant.

Construction of the leachate treatment plant we designed  to treat 300 kL/day of landfill leachate is well underway.

The site of the Hampton Downs Water Treatment Plant

The site of the Hampton Downs Water Treatment Plant

Starting with what was quite literally a greenfield site, the bulk earthworks and slab were completed without delay once the contract was awarded and it was not long before the shed was up.


Hampton Downs slab for the shed and tank bund


Shed frame erection

Hamption Downs Shed and Tanks

Hampton Downs Shed and Tanks

Inside, the installation of the crane and the electrical switch room needed to be completed and ready for the arrival of the equipment.



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Hampton Downs Treatment Process Design

Category : Process Engineering

Syngineering have completed the process engineering design for the proposed landfill leachate treatment facility at Hampton Downs.

At a conceptual level, the system utilises VSEP followed by four stages of spiral RO, illustrated in this Process Flow Diagram.

After gaining approval for the concept, the detailed design was undertaken. This involved not only the process engineering, but drawing on Syngineering’s multi-disciplinary engineering capability to design the entire balance of plant, from the building to house the equipment though to the power supply to run it.

Waste water treatment plant design for

Waste water treatment plant design for Hampton Downs

Syngineering’s Design and Construct team have used our experience in advanced 3D modelling to capture every detail.  The ability to visualise the design in such detail also provides reassurance to the client that nothing has been missed.  Modeling the plant in 3D also assists us in providing a very competitive price to deliver the project, with confidence that there will be no costly surprises leading to price variations during the construction.

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