The cost of disposal of the plant effluent to the drain is often overlooked. Under the Mogden formula the cost of wastewater disposal is not only based on the volume but also on the solids and BOD (Biological Oxygen Demand) sent to the sewer. Old treatment plant or none at all can see profits literally go down the drain.
Huber can look at removing the solids and BOD and if economically viable recycle some of your wastewater for yard wash down purposes.
When Erlenbacher Backwaren GmbH, who are part of the Nestle Group, looked at this they came to Huber to undertake the process equipment.
Erlenbacher’s wastewater contains high levels of sugar and fats and was originally sent to the local sewer via a collection tank.
Huber suggested converting the collection tank to a buffer tank and neutralising the acidic effluent, adding polymer and then pumping to a Dissolved air flotation (DAF) plant. The clarified water is then discharged to the local sewer at a much lower cost as the fats and suspended solids are flocculated and floated off and removed by a skimmer.
The Flotate sludge is collected in an integral hopper and pumped to a storage tank where it is dewatered using an automatic Huber Screwpress. The DAF plant achieves a 60-65% reduction in COD and a 92-95% reduction in Fats Oils and Greases (FOG) going to the sewer.
The Screwpress takes the 9-11% dry solids flotate and presses these to achieve a cake of ~35-45% dry solids. The filtrate is returned to the buffer tank and returned to the DAF plant.
The Screwpress is totally enclosed and completely automatic in operation, it rotates at 2-4 RPM and uses 14% of the power of other dewatering devices.
