Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/20—Heavy metals or heavy metal compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/20—Heavy metals or heavy metal compounds
  • C02F2101/203—Iron or iron compound
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/20—Heavy metals or heavy metal compounds
  • C02F2101/206—Manganese or manganese compounds

Definitions

• This invention relates to the treatment of waste water in order to reduce the level of contaminants therein and to produce environmentally acceptable products. It is of particular value in the treatment of acidic mine waste water.
• a multi-step process including certain steps which are novel per se.
• the process may include for example a multi-step process including a first step in which zinc, copper and/or cadmium may be extracted from the mine waste water as saleable products, while iron and aluminium may be extracted to be discarded as chemically neutral slurries or dried solids.
• Step 2 may include removal of the remaining heavy elements, calcium, magnesium and most of the sodium.
• Step 3 provides for the removal of sulphate and chloride, and step 4 may prepare or "polish" the water prior to on-site usage or off-site discharge.
• economic advantages are maximised by recycle of reagents, whereby consumption of reagents is significantly reduced, as well as by production of saleable products.
• topographical surface e.g. tailings, dams and dumps, waste rock dumps and shallow mine workings and open pits. These techniques include barrier methods that isolate the
• sulphides mainly pyrite
• chemical additives to inhibit the growth or development of iron-oxidising bacteria.
• Recent procedures have included the incorporation of large amounts of alkalinity and/or phosphate within the sulphides, the use of surface geophysics to identify potential problem areas, the sealing of fractured stream beds using polythene or silicate based grout and the use of anionic surfactants and bacteriocides to inhibit the activity of iron oxidising bacteria.
• the approach detailed below aims to treat the acidic mine water, once formed, in a chemically efficient and cost effective manner to produce high quality dischargeable water and marketable extracted base metals and salts in an environmentally acceptable package.
• a first reaction and settling vessel where calcium carbonate is added along with an oxidation medium such as air which also functions to stir the stored waste water.
• an oxidation medium such as air which also functions to stir the stored waste water.
• Sufficient calcium carbonate is added to bring the pH of the solution to a level of about 5 and at the same time react with the heavy metals present such as lead, copper or zinc.
• Calcium sulfate and respective heavy metal carbonates precipitate and settle to the bottom of the treatment zone where they may be readily removed.
• calcium hydroxide along with enough calcium carbonate to maintain an excess of carbonate ion are added to complete separation of the heavy metals. Final removal of precipitate from the solution is
• US patent 5,013,453 discloses a method which can be used to remove dissolved heavy metals and/or iron from nearly any aqueous stream.
• the invention is particularly useful in removing the large concentrations of copper, nickel, zinc, gold, silver, cadmium, tin, chromium and lead from pickling acid wastes and other acidic waste streams formed in the metal finishing industries.
• a selected carrier precipitate is created within an aqueous waste solution which is contaminated with heavy metals and/or iron. The contaminants are thereby caused to coprecipitate with the carrier precipitate and are thus removed from the aqueous solution.
• JP 80049555 discloses treatment of waste water containing heavy metals and organic matter involving biological oxidation to decompose the organic matter. Heavy metals are converted to their carbonates and the pH is
• US patent 3,725,266 discloses a process for removing one or more metal compound contaminants from contaminated
• the preferred precipitating agents as hydroxides and carbonates, such as, sodium hydroxide, calcium hydroxide and sodium carbonate, which produce the insoluble metal hydroxides and carbonates, respectively.
• AMISTRY OF ACIDIC MINE WATER FORMATION AND CONTROL Prevention and/or control of acidic mine water (AMW) formation depends upon an understanding of the chemical, biological and geological characteristics of base metal sulphides.
• a series of chemical reactions describe AMW formation which results from the exposure and weathering of pyritic material (FeS 2 ) normally present in base metal mine and coal wastes to the combined effects of atmospheric oxygen, water and iron and sulphur oxidising bacteria such as
• Thiobacillus ferrooxidans (T. ferrooxidans),
• Ferrobacillus ferrooxidans F. ferrooxidans
• Thiobacillus thiooxidans T. thiooxidans
• Fe 3+ +3H 2 O Fe (OH) 3 (s) + 3H + - - - - - - (3 )
• reaction (1) is oxidised into Fe 3+ and
• the rate of acid production is high and is limited by the concentration of ferric ions.
• Fe 3+ activity becomes significant at a pH of approximately 2.5; a vicious cycle of pyrite oxidation and bacterial oxidation of Fe 2+ results from the combined effects of reactions 2 and 4.
• the rate of reaction 2 exerts primary control on. the cycle by limiting the availability of Fe 3+ which is the major oxidant of pyrite.
• sulphides e.g. Mo, Sn, Ag, Hg, Sb, Bi.
• the high sulphate levels will result in Pb being precipitated as an insoluble sulphate following the decomposition of Pb ore (galena).
• a further disadvantage was the inability to handle organic non-ionic contamination and the difficulty of obtaining elemental separations without very careful reagent elution control.
• stage 2 successively with CaCO 3 in stage 1 to a pH about 5, and a residue separated containing Fe and Al.
• treatment with Na 2 CO 3 raised the pH to 8 to 8.2, and a residue separated containing Zn as a basic carbonate, as well as Cu, Cd, Co and Ni.
• stage 3 lime was added to increase t ⁇ e pH to 10 to 10.5 to precipitate Mg and Mn, and in stage 4 NaOH was added to increase the pH to 11 to 12, thus precipitating Ca and more Mn.
• stage 4 NaOH was added to increase the pH to 11 to 12, thus precipitating Ca and more Mn.
• the liquid phase product of stage 4 was treated by reverse osmosis to produce high quality clean discharge water and the concentrate was crystallised to produce a marketable sodium sulphate.
• Other products were zinc carbonate, zinc oxide and zinc metal and a Cu, Cd, Co, Ni fraction which was readily converted to a Cu cementate.
• the process is similar to 2. (above) but the concentrate from the RO is directed to an evaporation dam. The cost is reduced, but with a potential rehabilitation problem occuring in terms of the long term operation of the evaporation dam.
• a pretreatment filtration or settling system may be required.
• AMW (pH 2.5 - 3.3) is treated with crushed limestone in an agitated tank. A slight excess of limestone is required.
• the pH of the water rises to 4.9 - 5.0 and results in the precipitation of 90 - 95% of the Al and Fe. Oxidising conditions are maintained using air sparging. This precipitate settles quickly and can be removed by thickening, it also acts as a feed water particulate removal stage with a significant reduction in organic content due to adsorption on the bulky Fe/Al hydroxides.
• the partially neutralised water from Stage 1. (pH 4.9 - 5.0) is then treated with sodium carbonate (Na 2 CO 3 ) in an agitated tank.
• the pH of the water rises to 8.0 to 8.2 and results in the precipitation of Zn, Cu, Co, Ni and Cd and the remaining Al and Fe.
• the precipitate is processed to produce marketable products.
• Zn is converted to zinc oxide or zinc metal and Cu is
• the Al from Stage 1. together with Al from the Stage 2. precipitate can be extracted to market a chemically purified Al product such as aluminium sulphate.
• the metal fatty acid salts can be removed by filtration or flotation and on acidification (pH1-2) with hydrochloric acid the fatty acids are regenerated and the cations solubilised for treatment as a concentrated solution.
• fatty acids allowed the simple removal of Ca and Mg and also reduced the remaining heavy metals to levels suitable for discharge. Also the application of ultra filtration (UF) and microfiltration (MF) techniques using ceramic filters or filter pads is promising for the rapid, continuous and efficient removal of the fatty acid metal salts.
• UF ultra filtration
• MF microfiltration
• Organic bases such as amines (primary, secondary and tertiary), amides, diamines and quaternary ammonium
• Chloride salts formed with the organic bases tend to be more soluble but some co-removal of chloride with the sulphate
• composition of the feed water e.g. pH, Eh, ionic content, organic content.
• the ability to recycle the reagents e.g. treat anion precipitate with Na 2 CO 3 /NaOH at pH 10-11 to reform the amine.
• benzidine is not to be recommended, from a safety viewpoint.
• the surfactants used were -
• ABS Alkyl benzene sulphonate
• Dodecylamine in about 2% solution was dispersed in 1% (v/v) HCl and added in slight excess to the sulphate test solutions. These were then stirred for 30 minutes. the dispersions were treated with 0.2 ml 0.1% surfactant and stirred for a further 2 minutes.
• Solid/liquid separation was achieved using an 0.45 micron micro filtration assembly.
• the "biobed” system uses living biological systems to absorb the remaining heavy metal pollutants.
• the water is allowed to pass through a series of weir structures, constructed to allow adequate contact with the biological absorbers.
• Systems using bacteria, algae, moss and simple plants have been used with considerable success.
• Another technique utilises the percolation of water through columns of mineral absorbers such as marble chips, clays or zeolites and soils. These materials act in both an
• Acid mine water A at a pH of 2.5 to 3.3, is treated with crushed limestone 1.1 in an agitated tank 1.
• the pH of the water rises to 5.0 and results in the precipitation of 90 to 95% of the Al and Fe. Oxidising conditions are
• the product of this stage is separated into a solid phase 1.2 and a liquid phase 1.3.
• the solid phase containing the Al, Fe residue is removed at 1.4.
• stage 1 liquid phase
• stage 2 liquid phase
• the precipitate (solid phase) is treated via 2.4 to remove for marketing Zn as metal and/or oxide and Cu with Co, Ni, Cd as a cementate. It may also be possible to extract the Al and market a chemically purified Al product.
• stage 3 soluble fatty acid salts 3.1 are added to the treated water 2.3 at pH 8 to 8.3 to precipitate Ca, Mg, Mn, some of the Na and to scavenge the remaining heavy metals.
• the precipitate 3.2 is removed either by flotation or filtering via 3.4 and treated to recover the fatty acids for
• the liquid phase 3.3 is treated in stage 4 with fatty acid amines 4.1 to precipitate the anions, sulphate and
• stage 4 is separated into a solid phase 4.2 and a liquid phase 4.3 by
• Removed amine sulphate 4.4 is subjected to alkali treatment in 4.5 to separate the amine, with production of sulphate salts or sulphuric acid removed via 4.8.
• the amine is purified in 4.6 and solubilized in 4.7 and recycled to 4.1.
• Clean water is discharged via 5.1 and an algal-plant residue removed at 5.2.
• the solid phase 3.2 recovered from stage 3 via 3.4 contains Ca, Mg, Mn, (Na) and traces of other heavy metals as fatty acid salts, and is treated in the following manner.
• the said solid phase is acidified in 3.5, producing a solution of cations in acid 3.6, from which products 3.7 are

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Removal Of Specific Substances (AREA)

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• 1992
  • 1992-06-10 EP EP19920911885 patent/EP0589953A4/en not_active Withdrawn
  • 1992-06-10 WO PCT/AU1992/000272 patent/WO1992022504A1/en not_active Application Discontinuation
  • 1992-06-10 BR BR9206149A patent/BR9206149A/pt not_active Application Discontinuation
  • 1992-06-10 JP JP4511011A patent/JPH06508060A/ja active Pending
  • 1992-06-10 CA CA002103247A patent/CA2103247A1/en not_active Abandoned
  • 1992-06-11 ZA ZA924275A patent/ZA924275B/xx unknown

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