The nursery industry is under increasing pressure to demonstrate responsible and efficient use of diminishing water resources. The overall aim of this Project was to find the optimum peat-based biofilter design to allow run-off from nurseries to be collected and re-used without causing problems with either disease or nutrient overload.
The principal focus was on establishing and then characterising the ideal blend of BiogreenTM humic and/or fibrous peat with other ingredients to form a biofilter matrix. The ultimate ambition of this project was to produce and validate a system that would enable commercial and retail nurseries to recycle and reuse their water economically. This has the potential to save over 1000 megalitres of water per annum in Melbourne alone.
A full-scale test and demonstration biofilter has been installed and trialled at the Olinda Nurseries site.
Water is pumped from the dam by a high-output electric pump to either (or both) of the header tanks. In normal operation, the pump is activated by a pressure-differential switch set to supply power to the pump whenever the water in the tanks falls below a pre-determined level. (However, for many of the experiments conducted here, the pump was activated manually with the tanks at less than full capacity.) The tanks are also fitted with an overflow line that connects to the outfall drain from the outfall sump.
The collected dam water is drained or pumped from either (or both) of the header tanks into either or both of the biofilter modules. The distribution pipework at the top of each module spreads the water evenly over the surface of the biofilter matrix, through which the water percolates under gravity. Drainage from the tanks delivers water to the biofilters at up to 95 litres per minute, while pumping increases the delivery rate to nearly 180 litres per minute.
Filtered water is then collected by the lower distribution pipework, from which it drains to the outfall sump. In the test and demonstration unit, the filtered water is returned to the dam, but in a typical installation the water would be drained or pumped to a storage tank, and then re-used in the nursery.
This project demonstrated the effectiveness of the system, particularly for attributes of the biofilter matrix that were not previously known. Of particular value has been the project’s ability to demonstrate that very high flows can be achieved through these biofilters, using a proprietary blend of Biogreen™ peats as the biofilter matrix. Much has also been learned about how to operate and manage these biofilters, both in general and in the specific context of reclaiming nursery run-off. In particular, the biofilter matrix has been confirmed to remove key plant pathogens, particularly the major plant pathogenic fungus of concern to Victorian nurseries, Phytophthora cinnamomi.
The system as built at Olinda can handle in excess of 250,000 litres of run-off per day on a continuous basis. Given that this system has a physical footprint of less than 50 square metres, this in turn indicates that the biofilter technology should be applicable to essentially any nursery in Victoria. Specifically, the data allow us to provide a detailed and specific system plan and specification to any nursery that should enquire, and have allowed us to develop a simple check-list for scoping and pricing proposed systems.