Client: Central Hawkes Bay District Council
Date: September 2012 to November 2012
The Tukituki River that flows through the heartland of Hawkes Bay is noted as the best trout fishing river of the North Island.
This however is changing as periphyton growth is increasing on the riverbed due to elevated nutrient levels. Point source pollution such as sewage discharge is identified as obvious nutrient sources. Waterclean proved the treatment capacity at another location for the client so was engaged to design and build again at Waipawa.
The client is compliant 12 months before the 2014 date and is rewarded with very low operational expenditure compared to suggested land irrigation schemes that were considered prior to the Waterclean option. The Tukituki River will also benefit from the large reduction of nutrient entering the flow at the discharge point.
Wastewater influent and effluent quality
The discharge from the Waipawa WwTP is to river. This posed very tight parameter of discharge and the Floating Treatment Media would not meet the low limits in Dissolved Reactive Phosphorus DRP of 0.1mg/L.
The design has a low rate mechanical plant and UV treatment post the FTM. The mechanical treatment is a process of flocculent (alum), a primary clarifier and a moving sand bed filter which binds the phosphorus and this then is discharged through a filter bed and back into the head of works.
The final discharge is passed through UV treatment.
|Parameter||Infulent Median||Effluent from the FTM 2015 Median||Effluent from the Filter 2015 Median||FTM Removal Rates %|
|E Coli||6 – 7 log||2,000||< 3||99.99|
Note: all values are in mg/L except E Coli.