Waste water processing - England

[Simon L]

Hi all

First post on here (and a dull one) but I've found this forum super useful over a past four years or so - thanks!

We've already planted 100 M25 trees of various traditional UK cider apple varieties. Whilst we wait for them to bear, we're planning our set up in a barn. It's not connected to mains drainage and our house, 50 or so metres away, shares a STP with a neighbour, who I'm sure shouldn't receive our cider waste water.  The barn is low-lying, bounded by a pasture field, a stream and our back garden. There's space to dig or space to store. There's water and power. I guess max production in the next few years is 10,000 litres. What are our (economical) waste water options?

Thanks for reading

Simon