2.1. Wastewater. Classification
Chemical and pharmaceutical enterprises consume a lot of clean water for their production cycles, for instance in manufacture of injections, at auxiliary sites. Water can be used as a medium for reactions, as a coolant for heat exchange equipment, for washing of devices, glass tubes, ampoules, for fire fighting, and for drinking (in canteen, bathroom, for cleaning).
Once contacted a chemical in a production process, water becomes wastewater.
Wastewater is the water used for production, domestic and other needs and contaminated with impurities that alter its initial composition and physical properties. In addition, wastewater is the water discharged from inhabited localities and industrial enterprises as a result of precipitations and watering.
There are three main types of wastewater, depending on their origin:
- production wastewater;
- residential wastewater;
- storm wastewater.
Production wastewater has extremely versatile composition. Depending on the enterprise type, it can contain acids, alkalis, oil products, arsenic, chlorides, sulfates, nitrates, nitrites, salts of heavy metals (Hg, Pb, Cd, Cu, Fe, Ag, etc.), phenols, natural and synthetic drugs, and products of their destruction.
Residential wastewater enters the drainage system from residential premises and utility spaces at various enterprises, from catering facilities and hospitals. The feature of residential wastewater is its relatively stable composition, resulting from the uniform human physiology and business operations.
Storm wastewater is a result of precipitations — atmospheric runoffs. This wastewater includes also melt water from snow and ice melting, and water used to wet territories (streets and industrial sites). Storm wastewater contains a lot of sand, rubbish, clay particles and oil products washed from streets and industrial sites.
Contamination of industrial sites causes impurities that are typical of a certain production and that enter storm wastewater. A distinctive feature of storm wastewater is its non-recurring nature and extreme irregularity of the quantity and composition of contamination.
There are two categories of production wastewater: partially clean water and wastewater treated to standard quality.
Partially clean wastewater means wastewater, discharge of which without treatment does not cause violations of the requirements to the wastewater quality.
Wastewater treated to standard quality is wastewater, discharge of which into water bodies (sewage system) after treatment does not cause violations of the requirements to the wastewater quality.