Simple, chemical-free algae and DO management in wastewater
Tucked away in a hidden enclave on Sydney’s North Shore is a private golf course — a golf course with a water issue that needed to be tackled. A long narrow dam of theirs in the base of a gorge suffered from low dissolved oxygen (DO) and destratification. The low DO was causing unwanted odours and poor water quality for use on the course. Wanting to tackle the problem the right way, they employed the services of a specialist consultancy firm, who specialise in assisting their clients with investigation, procurement, operation and maintenance of water and wastewater infrastructure.
The consultancy firm suggested the use of Venturi-Aerators from Hydro Innovations. These aerators are mounted on the banks of dams or lagoons, making access easy for maintenance. They require a pump to deliver flow to the inlet nozzle (under pressure), where an increase in velocity uses the Venturi Principle to draw in atmospheric air, mix it with the water, and discharge it saturated with DO into the dam. Venturi-Aerators are very efficient at delivering DO, but because the suction and discharge of the system can be located at any depth within the dam, destratification issues could also be dealt with.
The consultancy firm enlisted the help of a local specialist pump installer, who was given the task of installing the equipment at the bottom of a steep gorge. Two pumps were installed to deliver flow to two 4″ Venturi-Aerators, which were set up to deliver 11.8 kg of DO per hour per unit.
After running the units for a few weeks, Oxidation Reduction Potential (ORP) and DO readings were taken. The ORP measured >125 mV at all depths from 1.0 to 4.0 m below the surface. This compared to measurements that were taken after a rain event earlier in the year, which showed ORP to be less than 60 mV through the same depths.
The DO measurement showed 6.0 mg/L at the surface, and 7.3 mg/L at a depth of 4.75 m. This compared to previous measurements of <0.3 mg/L also taken earlier in the year. This led the Managing Director of the consultancy firm to comment, “In short, results look fantastic! A positive ORP and higher pH will reduce dissolved metals and take load off the other components of the water treatment system.”
Hydro Innovations will generally pair Venturi-Aerators up with Gorman-Rupp self-priming pumps to allow installation of the systems on the banks of dams and lagoons, making them safer and more cost effective to maintain. When the right pumps are selected, oxygen transfer rates can be as high as 1.86 kg O2/kWh, making good use of available power.
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