Heavy metals
Zinc compounds mainly enter sewage water through, for example, run-off from zinc gutters and from the wear and tear of galvanised steel in public areas, such as lampposts. Copper compounds enter sewage water from the wear and tear of copper water pipes in households and businesses, for instance. In addition, the traffic and transport sector is an important source of copper and zinc in surface water, including through the run-off into surface water of copper and zinc particles released from the wear of overhead wires, brake linings and tyres. Other traffic sources include the use of antifouling agents in recreational and commercial shipping and anti-rust agents used in locks and sluice gates.