DD229887B5 - Process for the purification of heavy metal contaminated water - Google Patents

Description

The invention relates to a process for the purification of heavy metal contaminated water and is applicable to industrial waters with low heavy metal contents, for which a metal recovery is ineffective. Furthermore, it is applicable for the purification of acidic, iron-containing open pit waters and heavy metal contaminated groundwater underground.

The method is also useful for preventing the spread of substances, in particular heavy metals, which have penetrated into the ground by punctiform or areal entry of such contaminated waters. This is due to improper storage of industrial waste products, defective storage tanks, leachate from landfills and mining by weathering of heavy metal sulfides, which are present to a considerable extent in the underground, possible.

The method can be used at sites with suitable hydrogeological conditions.

For the purification of waters containing heavy metals, treatment processes of all kinds are available.

Known is an ion exchange method described by VERMEULEN, KLEIN and HIESLER in "Adsorption and ion exchange" in Chemical Engineers Handbook, Now York, McGrow-Hill, 1973 and by KÜMMEL, WINKLER and BECK in "Elimination and recovery of metal ions from wastewater Overview ", Acta hydrochim. hydrobiol. Issue 12 1984, 2227-237. Here, heavy metal cations are bound to a resin matrix and thus enriched in the solid phase.

This treatment process is expensive and requires large quantities of elution chemicals, depending on the heavy metal content of the water.

Furthermore, according to WASSILEW and ZLATEW "cadmium and zinc production from wastewater from lead production", published in Neue Hütte 26 (1981), 112-113, after LÖSCHER and HEIL "A new method for the precipitation of heavy metals from wastewater based on polysulfide" and after BHATTACHARYYA, JUMAWAN, GRIEVES "Separation of toxic heavy metals by sulfide precipitation", published in Separation Science and Technology 14, 5 (1979), 441-452, method for the precipitation and sedimentation of heavy metals as hydroxides or oxide hydrates by the use of There are also methods for underground de-ironing and demanganization, such as

- REISSIG, FISCHER and REIMANN

Laboratory investigations on the underground de-ironing of groundwater Acta hydrochim. hydrobiol. 10.5 (1982), 487-496

- HALLBERG

Method for de-ironing and de-mangling groundwater in the soil IFO-AB Vyredox, 29500 Bromölla Sweden

- HARTMANN

Contribution to the de-ironing and demanganization of groundwater in the aquifer Final Report Faching.-Studium "Groundwater" TU Dresden, 1978

- ROTT, BOOCHS and BAROVIC

Underground groundwater treatment by discharging oxygenated water into the ground

Water and Soil 8 (1978), 206-211 can be read.

Here, iron and manganese are converted into a depositable form by infiltration of oxygenated water. The Oxydations- and hydrolysis products are deposited in the underground. Both of these methods require a high investment and operating costs to carry out and are therefore expensive.

The aim of the invention is to achieve high efficiency in the purification of heavy metal polluted water without additional use of chemicals, with low construction costs and low running costs.

The invention has for its object to provide a method for underground water treatment for only slightly contaminated with organic and heavy metals water, especially for those with iron, which prevents premature clogging of a filter bed and forms a heavy metal barrier to prevent groundwater contamination in another embodiment.

According to the invention, this is done by setting hardened granulated Kraftwerksasche or Kraftwerksasche is deposited with a carrier in a pit or a trench, in which continuously heavy metal contaminated water is introduced, it due to the alkaline buffer level and the mechanical filtering effect of Kraftwerksasche to a precipitate and after a Coagulation of the flakes to fix all excreted heavy metals in the filter bed comes. Subsequently, the purified water is taken with the help of wells and the use or the Vorflut supplied, tn a further embodiment of the method according to the invention, an ash layer is introduced perpendicular to the flow direction of the heavy metal contaminated water in the form of a backfilled slot in the soil, the mechanism of heavy metal retardation as well as when purifying water in a pit or ditch.

embodiment

With reference to an embodiment, the invention will be described in more detail.

If heavy metals (preferably iron) are to be removed from industrial and mining waters, the alkalization agent Kraftwerksasche is mixed in pure form or with a carrier substance, for example sand, and applied in a previously applied and the flow rate of the water adapted pit or in a trench. A mixture with sand as a carrier serves to increase the hydraulic permeability coefficient. The required mixing ratio Kraft ash sand depends strongly on the acidity, the heavy metal content and the throughput. With high acidity, high heavy metal content and low throughput, it is also possible to completely dispense with the sand. Normally, the mixing ratio of power plant ash sand should be in the order of 1: 1 to 3: 1. This results in kf values of about 5 · E - 6 to 0.25 · E - 6 m / s. If the above conditions are met, cleaning effects in the order of 85-100% can be achieved. In a continuous process, heavy metal-containing water is introduced.

In the underground passage, due to the alkaline buffer level of power plant ash, precipitation of the heavy metals as hydroxides, oxide hydrates or carbonates occurs depending on the solubility dependent on the ionic strength and fixation on the ash-soil matrix.

For microcomponents in which the solubility product of the carbonates and hydroxides is not exceeded, iron (III) oxide hydrate flocs may cause coprecipitation and / or sorption on their surfaces. Occurs in mine waters iron as the main heavy metal component, other heavy metals are removed in this way from the water when using the method according to the invention.

After coagulation of the flakes occurs due to the mechanical filtering action of the ash to fix the precipitated heavy metals in the filter bed.

The purified water is collected with the help of wells and fed to the use or discharge into the receiving water. By a suitable choice of mine site, z. B. beyond a watershed, the version of the water can be omitted.

The life of such a pit or trench depends on the amount or buffer capacity of the power plant ash used and, to a significant extent, on the quality parameters of the water to be treated.

If the alkaline capacity of the power plant ash is exhausted, the ash-soil mixture is renewed. However, the pits can also be covered with soil and re-dug elsewhere. Outsourced sand-ash-iron oxide hydrate material may be left in the dump or in the treatment room without concern from the point of view of environmental protection.

Another possibility of using Kraftwerksasche serves to produce a heavy metal barrier. This may be necessary if in the underground flow processes have a constantly spreading heavy metal contamination result. For this purpose, a Erdschlitz is produced perpendicular to the flow direction of heavy metal contaminated water, which is filled with an ash layer or an ash-sand mixture. The strength of the ash barrage depends in turn on the quality and quantity of the water.

The same processes take place as with water purification in a ditch or pit. The ash-sand mixture acts as a precipitation zone.

The use of an ash-sand mixture as a barrier for migrating species is possible for all substances that form solid, precipitable precipitation products or gel-like substances in the alkaline medium, which are retained in the grain structure of the aquifer during the flow process.

Claims (2)

1. A method for purifying heavy metal contaminated water for the purification of industrial wastewater with low heavy metal contents and acidic iron-containing opencast waters and heavy metal contaminated groundwater in the underground, characterized in that hardened granulated Kraftwerksasche or Kraftwerksasche mixed with a carrier substance is deposited in a pit or a ditch, in which continuously heavy metal contaminated water is introduced, the alkaline buffer level and the mechanical filtering effect of Kraftwerksasche lead to precipitation and coagulation of the flakes to fix all the precipitated heavy metals in the filter bed, then the purified water is taken in wells or fed to the receiving water. 2. A method for purifying heavy metal contaminated water according to claim 1, characterized in that an ash layer of pure Kraftwerksasche or mixed with a carrier perpendicular to the flow direction heavy metal contaminated water in the form of a filled, previously brought down in the soil slot is introduced, the mechanism of heavy metal retardation as well expires, as in the case of water purification in a pit or ditch.