WASTE WATER TREATMENT

Long time ago in ancient Egypt charcoal was used for “absolution of the body and soul from sin”.

A charcoal-based purification method was described by Hippocrates in his works in 40 BC.

Activated charcoal made of birchwood was used in medicine in Ancient Russia.

Ancient Romans used charcoal to purify drinking water, beer and wine.

Since the 18^th century activated charcoal has been used as a powerful antidote which effectively binds poisons penetrating the gastrointestinal tract.

At the end of the 18^th century scientists already knew that carbolene effectively adsorbs various gases, vapours and dissolved substances. People noticed that several charcoals placed into a pot in which they cooked their dinner adsorbed flavours and odours which remained after cooking.

In 1773 a German chemist Carl Scheele reported effectiveness of charcoal for adsorption gases. Later scientists found that charcoal also can discolour liquids.

In 1785 a pharmacist T.E. Lovits from Saint-Petersburg, who later became an academician, was the first to notice the ability of charcoal to purify alcohols. On the basis of findings he got in the process of multiple experiments, he explained that mere shaking of wine with charcoal powder added to it makes the wine much purer and improves its quality.

In 1794 charcoal was first used at a sugar refinery in England.

In 1808 in France charcoal was first used for clarification of sugar syrup.

In 1811 workers involved manufacturing black shoe polish found out the ability of bone char to discolor substances.

In 1830 a pharmacist who did a self-experiment took one gram of strychnine and survived as he took 15 grams of activated charcoal at the same time, which adsorbed the deadly poison.

In 1915 a Russian scientist Nikolay Zelinsky invented the first ever filtering carbon gas mask. In 1916 this invention was put to use by military forces of the Entente. Activated charcoal was used in the gas masks as the major adsorbing material.

Commercial enterprises started producing activated charcoal at the beginning of the 20th century.

The first lot of activated charcoal powder was produced in Europe in 1909.

Waste Water Treatment at Electric Power Stations

Removal of petroleum products (boiler oil and other oils) from water at state-managed district electric power stations, heat power stations and nuclear power plants is one of the most complex issues in maintenance of water chemical systems. Petroleum product concentrations in some waste waters can reach 1000 mg/L, while it increases drastically in case of emergencies and unit discharges. High volatility of such substances in the process of vaporization causes pollution of distillate products in which these substances may accumulate in concentrations of up to 10 mg/L.

Furthermore, as a rule, boiler oil and other petroleum products are poorly dissolvable in water and resistant to biochemical oxidation. Such properties increase the risk of pollution of natural waters with such products. Thus, during 2-7 days petroleum product concentrations in water decrease just by 15% at temperatures up to 50°C, and by 40-50 at temperatures up to 200°C.

Hydromechanical systems including grit catchers, oil separators, settling ponds, and filters, are one of the most widely known and used waste water treatment systems.

Such filters are filled with various materials, including activated charcoal. Adsorption capacity of various filtering materials is given below (kg/kg):

Filtering material	Adsorption capacity (kg/kg)
BAU activated charcoal	0.89
Expanded-clay aggregate	0.33
Boiler slag	0.21
Burnt rock	0.26
Anthracite	0.2
Sulfonated coal	0.22
Petroleum coke	0.23
Silica sand	0.11

Supply of hot water steam under pressure of 0.03-0.04 MPa through the upper dispenser rather than washing provides the best results for regeneration of sorption filters. Steam heats petroleum products caught by the filter and displaces the products from the filtering layer. At the same time, steam is condensing. Steam flow required for regeneration (on a condensate basis) does not exceed 1-2 volumes of the filtering layer. Duration of the regeneration process depends on petroleum products removed and the degree of pollution of the filter. The process normally takes 2-3 hours. Displacement of petroleum products from the filter is accompanied by increase in concentration of the products in condensate, which is followed by decrease in such concentrations.

Condensate can be discharged through the inlet to oil separator. Such technique prevents increase in water flow through the waste water treatment facilities. Physical and chemical methods (e.g. adsorption) provide for removal of emulsified and suspended particles (of less than 100 μm) and dissolved impurities.