Years ago when I had to submit house plans to get a building authority the plans included a photographic darkroom. This attracted alarmed attention from the local waste water treatment facility. So I did some calculations for them about the silver challenge they faced:
Photographic materials, to a rough approximation, average 1 gram of silver per 1 square metre.
I process about 1000 sheets 8"x10" paper or film equivalent in a year. That about 50 square meters of area.
If half the silver stays in the finished pictures and half goes out with the fixer (a reasonable assumption) then I send about 25g (about an ounce) of silver down the drain every year.
My household water usage is about 100,000 litres per year or 100,000,000 grams of water per year.
Simple division shows the average annual silver concentration I deliver is 0.25mg/litre. And that's just me.
The community I live in has a population of about 55,000 and no commercial photographic processing facility. The one and only lab closed years ago.
Unity Water, the local community water company, supplies about 3 trillion litres of water a year some of which irrigates lawns or washes cars but most goes down the drain as bath water, washing machine water, and toilet flushes. This further dilutes my 25g of silver. I did get my darkroom approved; no further worries.
Photographic materials, to a rough approximation, average 1 gram of silver per 1 square metre.
I process about 1000 sheets 8"x10" paper or film equivalent in a year. That about 50 square meters of area.
If half the silver stays in the finished pictures and half goes out with the fixer (a reasonable assumption) then I send about 25g (about an ounce) of silver down the drain every year.
My household water usage is about 100,000 litres per year or 100,000,000 grams of water per year.
Simple division shows the average annual silver concentration I deliver is 0.25mg/litre. And that's just me.
The community I live in has a population of about 55,000 and no commercial photographic processing facility. The one and only lab closed years ago.
Unity Water, the local community water company, supplies about 3 trillion litres of water a year some of which irrigates lawns or washes cars but most goes down the drain as bath water, washing machine water, and toilet flushes. This further dilutes my 25g of silver. I did get my darkroom approved; no further worries.