Different chemical compounds from chemical and biological laboratories, a d
ry cleaning laundry, car services and a medical centre are discharged into
sewers and simultaneously interfere with waste water from household activit
ies, some of which may pass through a treatment plant and create an adverse
impact. Some of these chemicals are toxic, others are known to produce tox
ic and carcinogenic products. It is recommended that their disposal in a mu
nicipal wastewater treatment plant is prevented by recycling these chemical
s, establishing a special pretreatment programme or by separate disposal.