Routing general chemical waste

Purpose

To get every spent solution into the container for its own stream, labelled and logged, without two streams meeting and without anything reaching a drain that should not.

When to use it

Whenever a spent solution leaves a tray, a tank or a bottle: spent developer, spent stop bath, the later washes, and the solid waste a session produces.

It does not cover the silver-bearing streams — spent fixer, the first wash after fixing, and anything that has touched silver nitrate. Those have their own procedure, because they are the valuable ones and the ones that must not be diluted into the rest.

Before you start

You should already have read waste, silver and the drain and the disposal caveat, and looked up what your own local authority actually accepts, with the date you looked.

On the bench: one labelled container per stream, standing in a tray, each with room for what this session will produce; one funnel per family; the waste log; gloves and eye protection.

Procedure

1. Name the liquid before you pour it: what it is, which stream it belongs to, and whether it is silver-bearing. If it is silver-bearing, stop here and use the other procedure.
2. Ask whether it is acid. Spent stop bath, and anything else acid, goes to the acid container and to nothing else — acid liberates sulfur dioxide from sulfite and from thiosulfate at once, and thiosulfate also throws down sulfur.
3. Pour it through that family’s funnel into that stream’s own container. One container per stream: a mixed container has the disposal constraints of the worst of its contents and the value of none of them.
4. Leave headspace. A container filled to the neck has nowhere to put the gas from a slow reaction and no room for the next session.
5. Cap it, wipe the outside, and stand it back in its tray.
6. Top up the running-volume line on the label, and add today’s date.
7. Put solids in their own bag or tub — packaging, contaminated wipes and gloves, spent absorbent, film and paper offcuts. They are not liquid and they do not go into a liquid stream.
8. When a container is full, close it, date it, and take it by the route you looked up. If the route field on the label is blank, fill it in before the container moves anywhere.
9. Write the log line.

How you know it worked

• Every container holds exactly one stream, and its label says which.
• No acid has gone into a container holding sulfite or thiosulfate, and none ever will, because they are different bottles in different places.
• Every container has headspace, a cap, a tray under it and a current volume figure.
• The waste log has a line per container carrying the volume, the route and the date you checked that route.
• Nothing was diluted in order to make it acceptable, and nothing was neutralised and then treated as disposed of.

If a step fails

Step 1, you cannot identify the liquid. Give it its own container, labelled with the date, the process and the word unidentified, and settle it before it moves. Never pour an unknown into a labelled stream: it makes the whole bottle unknown.

Step 2, an acid has already gone into a container holding fixer or developer waste. No source in this course’s corpus gives a remedial procedure for that, so what follows is reasoning from the chemistry rather than a cited instruction. Do not seal the container and do not lean over it. Move it to where the air is moving, leave it open, leave the room, and come back when the smell has gone, in eye protection. Then treat the whole container as one mixed waste of the worse kind, write on the label what happened, and route it accordingly.

Step 3, the container for a stream is missing or full. Close and date the full one and start a fresh one. Do not use whichever bottle happens to have room; that is how a stream loses its identity.

Step 8, you do not know your local route. A sealed, labelled container standing in a tray is a solved problem for weeks, so the answer is not to hurry. Write on the label the date by which you will find out, and use the checklist on the disposal caveat to find out.

Somebody tells you the drain is the answer. Two sentences settle it. Dilution changes a waste’s concentration and not its quantity, so the same mass arrives at the same treatment works in more water — water that goes down the same drain. Neutralisation changes pH and leaves every other property exactly where it was.

What to record

One line per container in the waste log: the date it was opened, the stream, the container and its size, the date it was closed, the running volume, the route taken, and the date you last checked that route. A year of those lines tells you something no general page can — how much of each stream your own practice actually produces — and that number is what decides container sizes, collection frequency and, later, whether recovery is worth the equipment.