Despite the manifest environmental benefits of public transit, the daily or periodic maintenance operations of an urban bus transport fleet in a large city such as Valencia can itself be damaging in terms of the effluents released. For bodywork, the washing water, containing low quantities of oils and fats with low COD (Chemical Oxygen Demand) values - the amount of oxygen in mg/l required to oxidise both organic and oxidisable inorganic compounds)is 125 mg/l. However colour and odour emissions do not permit its reuse. The motor washing water has similar characteristics, as well as solvents. Their emulsified oil content is higher and its COD is around 2,500 mg/l. Glycol refrigeration fluids are filled with radiator and distribution conduit dirt. Their COD is 500,000 mg/l. If cleaning takes place after draining, the COD of radiatorcleaning water is around 10,000 mg/l. Without prior draining, its COD is between 80,000 and 100,000 mg/l. Flat-battery acids contain 15-20% sulphuric acid and dissolved lead in a colloidal state, accumulated during the running down process. Brake fluids have very high COD levels (1,500,000 mg/l). Their degradation is the consequence of an accumulation of substances in suspension, metals and waters. Despite the multifarious above concerns, recycling practices to prolong the life-cycle of the effluents generated are unheard of in the public transport sector.