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Home / Issues / № 2, 2014

Phytotechnology inwastewater treatment of gold processing plants
S.S. Timofeeva, T.I. Shishilova

Phytotechnology is the application of plants to engineering and science problems. Phytotechnology uses ecosystem services to provide for a specifically engineered solution to a problem. Ecosystem services, broadly defined fall into 4 broad categories: provisioning (i.e. production of food and water), regulating (i.e. the control of climate and disease) supporting (i.e. nutrient cycles and crop pollination), and cultural (i.e. spiritual and recreational benefits). Many times only one of these ecosystem services is maximized in the design of the space. For instance a constructed wetland may attempt to maximize the cooling properties of the system to treat water from a wastewater treatment facility before introduction to a river. The designed benefit is a reduction of water temperature for the river system while the constructed wetland itself provides habitat and food for wildlife as well as walking trails for recreation. Most phytotechnology has been focused on the abilities of plants to remove pollutants from the environment. Other technologies such as  green roofs ,  green walls  and  bioswales  are generally considered phytotechnology. Taking a broad view: even parks and landscaping could be viewed as phytotechnology.

Asarule, atgoldprocessingplants local processing of cyanide containing waters with oxidizing materials is used: they are chloride, hypochlorite, ozone, hydrogen peroxide as well as sorption treatment at coal filters, electrochemical oxidation. Eachmethodhasitsadvantagesanddisadvantagesand in respect to specific conditions it is necessary to design treatment plan depending on technological regulations of gold extraction.

Recentlytherehavebeenmoreandmoreprojects to create new advanced reagentless methods of wastewaters treatment. Among such methods the most environmentally and economically efficient is plant technological advanced treatment.

S.S. Timofeevashowsthatalgae and water plants are resistant to cyanides by experiments. Concentration of cyanide of sodium 100 mg/ldoesn't influence on growth responsesof ElodeaCanadensis, Scenedesmusquadricauda. Onthecontraryatcyanideconcentrationof 1-50 mg/lone can observe intensive growth of plants and increase of protein concentration.

InhibitioneffectdependsonрН, atрН 8-10 itisconsiderablyweak, thenatрН 6, which is the consequence of destruction of cyanides in acidic media and cyanide utilizingability of microalgae and higher water plants.

Biochemicalanalysisprovesthefactthatwithin the experiment protein concentration in plants is constant or increases at high cyanide concentration (10-100 mg/l). Activityofoxidoreductaseinplantsatexposition on plants and solutionsof cyanides in concentration of 10 mg/l (plant mass  5g/l) is slightly changed, the difference is statistically inaccurate. Thoughitisknownthatcyanidesareinhibitorsofmetallic ferments, the observed phenomenon can be explained by the system of cyanide detoxication in plants. Summarizingtoxicometricexperimental data one can judge that algae and water plants possess high toxic resistance to cyanide. Thereisnoaccumulationofcyanidesinplants,they contain ferments, capable of the use of cyanide as a raw in biochemical transformations.

Cyanidesareverytoxicforanimalsbuttheyarenaturalmetabolites for plants. Inreferencestherearefactsofexistence of three possible ways of metabolism of cyanides in plants: reaction of replacement at b-cyanoalaninesynthase (КF 4.4.1.9), reaction of replacement at thiosulphitesulphidetransferase (rhodanese) (КF2.8.1.1.) and reaction of hydrolysis at cyanidehydrase (КF 4.2.1.66).

Themostwidelyspreadandstudiedindetailsisb-cyanoalaninesynthase, catalyzing hydrogen sulphide in the following chain

НSCH2CH(NH2)COOH + HCN - NCCH2(NH2)COOH + H2S

Itisstatedthat b- cyanoalaninesynthase is when a pyridoxaldependantlyase catalyzes reaction of replacement of cyanide byb -replacement. Productsofreactionarehydrogensulphideand b-cyanoalaine, which is transformed into cyanoalaninehydrase  (КF 4.2.1.65) inL-asparagine, which is the source of amine groups for synthesis of other aminoacids or modification of protein molecules.

Uptoourresearchitwasconsideredthatb-cyanoalaninesynthase is only in higher surface plants, in gramineous and legumes in particularhas a function of original ferment at one of the stages of biosynthesis ofasparagine (throughcyanoalanineas an intermediate product).  HendricksonH.R, ConnE.Eobtainrefined products ofcyanoalaninesynthasefrommitichondrites ofblue lupine and show that ferment isproteidepyridoxal -Рand catalyzes the following reactions:

L-cysteine +HCN ---   b - cyanoalanine + H2S

О-acetylserine + HCN --- - cyanoalanine = СН3СООН

L-cysteine + СH3SH ----S-methylcysteine +Н2S

We are the first to state that higher water plant Elodeacanadensis containscyanoalaninesynthase. Thisfermentunlikesurfaceplantsislocalizedincytoplasmwhich helps to utilize exogeneous cyanides and mercaptans of industrial origin coming into cell.

At capability to utilize cyanides and mercaptan compounds water plants and algae in the water bodies of the Asian part of Russia are studied.

Experimentalresearchisperformedatmodelecosystemswithintroductionofcyanides, mercaptans, rhodanides, butyl xhanthate, butyl thiophosphatein certain concentrations and placement of water plant mass into them.  According to classification of model ecosystems one can dividemicrocosm (less than 1 м3), mesocosm (between 1 and 10 m3) and macrocosm (over 10 m3) by the amount (Lalli, 1990).

Theplantsareselectedintheplacesoftheirgrowth, thoroughlysorted and conserved at the laboratories in dechlorinate water at temperature of -10-14 for psychrophilous and 20-25 С for thermophilic.

Inmicrocosmsolutionsofcyanideofsodiumormethylmercaptan of concentration from  0,1-100 mg/land weighed hydrophytes from 0,1 up to 50 g/lare put and through certain periods of time water samples are selected and residual concentration of cyanides and mercaptans are analyzed. To assess contribution of physical and chemical processes experiments are performed in closed and open systems and without plants.

Experimentsinmesocosmareperformedinconcretereservoir with the capacity of 1 m3 directly at wastewaters treatment plants of GPP. Asamacrocosmpondsofsludge pits of GPP are used.

Bioplatocomplexforwastewaterstreatmentconsists of the following structures:

  • structuresofmechanicaltreatment, for industrial wastewaters - structures of physical and chemical treatment;
  • filter units with vertical and horizontal water flow;
  • ground units

Forgoldprocessingplantsplanttechnologiesconsistingofthreestages in the following order are recommended:

  • 1stage - charophytes with coverage density of 2,5 kg/m2.
  • 2stage - ElodeaCanadensis with coverage density of 1,5 kg/m2;
  • 3stage - pondgrassand typha30-40 sample/m2.


Bibliographic reference

S.S. Timofeeva, T.I. Shishilova Phytotechnology inwastewater treatment of gold processing plants. International Journal Of Applied And Fundamental Research. – 2014. – № 2 –
URL: www.science-sd.com/457-24716 (20.08.2019).