Te Puke Wastewater treatment Plant - Improvements to Gain Better Dissolved Oxygen Control

The Te Puke Wastewater Treatment Plant services the township of Te Puke in the Western Bay of Plenty (population of approximately 7,000 people). The plant uses an activated sludge process and has an inflow of approximately 1,800m3 of raw wastewater per day with little industrial effluent in the waste stream.

Wastewater effluent is firstly screened and is then split between two activated sludge aeration tanks where the wastewater is mixed with micro-organisms and oxygen. The micro-organisms effectively “eat” the organic matter in the wastewater. The solids and micro-organisms are then settled out of the water in a secondary clarifier. A large portion of the micro-organisms are then returned to the aeration tanks, while the treated wastewater is piped through a UV facility and wetlands before finally being discharged into the Waiari Stream. Sludge from the clarifier is dried mechanically onsite and then disposed to a vermicomposting farm.

The treatment plant was built in 1978, with an additional clarifier being added in 1998 due to the population growth of the town. Minor modifications to the treatment plant have also been undertaken to enhance the treatment operation.

Our roles as Trainee/Apprentice Treatment Plant Operators have provided exposure to a wide range of plant operational improvements. One of the most recent improvements has been to address the inadequate Dissolve Oxygen (DO) operational levels. The original plant design did not afford the ability to control the DO levels with any certainty.

This paper will present information and data showing the affects of inadequate DO controls and subsequently will present the improvements that have been implemented to achieve improved control and delivery. This project has allowed us to gain valuable insight into a common problem with a number of plants around the country.