Advanced Pond Systems

28 February 2007

Advanced Pond Systems - from research to eco-technology

For more than 30 years, oxidation ponds have been used to treat wastewater in most small and medium-sized communities and intensive agricultural ventures. The conventional ponds do pretty well at removing suspended solids and biochemical oxygen demand. They’re also cost-effective and require little maintenance, but when it comes to removing pathogens and nutrients, conventional ponds are highly inconsistent, so they discharge poor quality effluent into waterways.

The problem: to upgrade or replace ponds by using mechanical treatment systems is costly.

The solution: New Zealand already has considerable investment in pond technology, so redesign the ponds to make best use of natural processes, like sunlight, to treat the effluent.

Advanced Pond Systems (APS) are a quantum leap over conventional oxidation ponds. They take up about the same amount of land area, but virtually eliminate sludge disposal, produce less odour, and are capable of consistently providing a higher degree of nutrient and pathogen removal and disinfection. For example, conventional oxidation ponds treating domestic sewage produce median values for E. coli 400 times higher than for APS. APS are also much easier to operate, more energy efficient, and more economical than mechanical treatment systems.

Typically, a series of four separate ponds is used to get the best sequence of physical, chemical, and microbiological processes. The ‘engine room’ of the system is the High Rate Pond, which promotes the growth of algae to produce huge quantities of oxygen, which breaks down dissolved organic matter. It also raises the pH of the pond, which helps remove nutrients, and enhances the rate at which sunlight disinfects the wastewater.

NIWA offers a complete scientific, engineering, and project management service for APS, including design, construction, commissioning, and monitoring. We can design and build a system, either from scratch or by upgrading conventional ponds, to meet particular effluent specifications and/or reuse requirements.

NIWA Advanced Pond Systems™

  • consistently higher effluent quality than conventional ponds
  • minimal odour compared with conventional methods of treatment
  • simple operation and maintenance
  • construction and operating costs typically less than half those of mechanical treatment plants
  • environmentally sustainable, with significant potential for energy and nutrient recovery.