I had left half way the topic of wastewater carring high quantities of pollutin dissolved in it (Nitrates and phosphates).
I would like to pick it up again showing new data, more precise and useful in catering a rough idea on how to dimension the beds that dispose of this water rather than let it penetrate the water table.
Watts Bridge is a far away little community in Queensland, Australia, in there, a small avio field manages their wastewater in a reed bed vegetated with vetiver. Instead of pollute the soil, they produce biomasses.
The Vetiver Network International has helped designing the work.
Here are some numbers: the daily average inlet is 1670 liters the total length of the rows sums up to 80 meters for a total of 400 plants in 100 sq. meters.
The total Nitrogen measured at the inlet is 68 mg/l while at the end of the beds measures 0,095 mg/l
Phosphorus goes from 10,6 mg/l to 0,138 mg/l.
Dispersion wells, full tricameral tanks, careless empting of wastewaters, generate pollution in the watertable that in one way or another re enters the food chain.
Solving this problem does not necessarily have to be a cost; it can be transformed in a resource and generate income: I can't help thinking of bovine stables: they can reuse the wastewaters and lower the costs of their forage using the biomasses produced from vetiver reed beds into a feed base for their cattle, saving money used for producing equivalent weight of more costly forages.
A careful management with frequent cuts will also improve the strong taste that this forage has.
Looks like a clever idea to me.....
To see the work, have a look at this....