Department of Biology
What can be disposed of down the sink?
- Aqueous chemical solutions can be disposed of down the sink provided:
- chemicals are dilute and below relevant hazardous waste threshold level(s)
- chemicals are not on the ‘Red List’ of chemicals that should never be disposed of down the sink through the sewerage system
- Dilution followed by disposal via the sink is not good practice and should therefore not normally be used as a means of disposing of hazardous liquids. However, it is recognised that biological research labs will generate small volumes (a few hundred millilitres) of relatively innocuous chemical solutions that would no longer be classed as hazardous following moderate dilution. As such, it is acceptable for solutions of small volumes (typically <500 mls) of non-toxic water soluble chemicals to be carefully washed down the sink with plenty of running water.
- The assessment of what is a 'small amount' relies on professional judgement, bearing in mind the concentration levels at which the substance(s) are toxic or otherwise harmful. Larger quantities or highly concentrated chemical substances must not be put down the drain but must be disposed of by an approved route.
- Examples of low hazard, water soluble waste includes:
- dilute acids, alkalis and alcohols
- harmless inorganic salts (including drying agents such as CaCl2, MgSO4, Na2SO4, P2O5)
- alcohols containing salts (e.g. from destroying sodium)
- all disinfectant solutions used to inactivate Hazard Groups 1 and 2 biological agents
- hypochlorite solutions (e.g. from destroying cyanids, phosphines)
- If you are in any doubt whether a solution can be put down the sink contact the Departmental H&S Advisor