The Harding’s Rd Industrial wastewater ponds system is operated at full treatment capacity between mid-February to mid-June.
When Vintage proceeds and grape processing at the wineries contained within Riverlands Industrial Estate & Cloudy Bay Business Park is a 24hr operation, loading expressed as kg/BOD/day increases ten-fold in a very short period.
The treatment system relies on two fully mixed aeration lagoons with over 2000kW of aeration power available.
The aerated lagoons are like a bio reactor and operate well when the biomass is maintained at an optimum level for the loading (food). This is called the Food-To-Mass Ratio.
A good indication of how well the ponds are performing is the level of Dissolved Oxygen (DO) expressed as ppm or mg/l.
If a pond is overloaded the DO value can quicky drop to zero and if maintained at this level will become anoxic, eventually the pond will crash and become very odorous and difficult to reverse back to operational condition.
The optimum level for the ponds system is 2.0ppm, although the DO can be as low as 0.5ppm for 50% of the time if the loading is variable to allow periods of increased DO levels.
The treatment plant’s primary role is to treat wastewater from the reticulation in the two industrial estates. However, there is capacity to treat tankered winery waste, if this is managed, and loading isn’t excessive.
In previous years loading to ponds from tankered waste was disproportionate to the volumes and loadings from the reticulated network. As an example, one of the wineries transporting liquid waste via a tanker became the second highest loading contributor despite the comparatively low volume of waste discharged.
Therefore, limits for Total
Biological Oxygen Demand 5-Day (TBOD5) and Total Suspended Solids (TSS) like those that are acceptable from the reticulated network are now applied to tankered waste.
Industrial Ponds acceptable characteristics are:
- TBOD5 less than 15,000 gm/m3
- TSS less than 10,000 gm/m3
- Accumulative Max Vol of 100 m3 per day.
During
the Vintage processing period (typically Feb-June, dependant on expected start
of fruit processing) consideration will be given to tankered waste to be discharged at the ponds under the above conditions if all other alternatives have been explored. Outside
of this period we have no capacity to treat waste of this nature and parameters
for acceptance are much lower.
Other alternatives can include disposal to Bluegums landfill, remembering the landfill is for solid waste and can only accept very small quantities of liquid waste on daily basis, acceptance to landfill will be considered under the following characteristics:
Bluegums Landfill acceptable characteristics are:
- 50% Total Dry Solids
- Max volume 100 m3/day.
Historically, RDV cake in good solid form has not created a problem. However, material coming from high solids cross flow filters has proven to be very difficult to manage and was creating odour.
We are happy to continue to accept RDV cake in the form that has been common if this has been delivered in previous years and processes haven't changed. Providing it is of the same consistency as in previous years it can be taken to the landfill without a solids test being carried out. However, wineries may want to satisfy themselves that is meets the solids threshold. In these scenarios we will focus on measuring the solid composition (50%) as it arrives. If any solid waste arrives that consequently tests below 50%, we will push back on future deliveries from that source.
Waste from high solids cross flow filters will have to be tested for solids content before delivery is made. Once there is a history and understanding of what the cake with a solids content of 50% or greater from these filters “looks like” from each winery we will begin to accept this also without a solids content test.
Meeting these parameters is more than has been required in the past but we are looking to protect the landfill against the problems caused by the very liquid material received last year. Council’s consent to operate the landfill requires that there are no objectionable odours beyond the boundary. This was experienced last year during harvest.
The performance of the Industrial ponds system is key to the continued acceptance of tankered waste.
