Veschetti ENGL

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Water treatment technologies for the reduction of chemical contaminants: 

Water treatment technologies for the reduction of chemical contaminants E. Veschetti Istituto Superiore di Sanità - Rome, Italy Umowa Twinningowa PL2005/IB/EN/03 - Komponent 1, Działanie 1.3 International Workshop Warsaw, 18 – 19 April 2007

Slide2: 

Systemathic parameters not conforming ti values set in Legislative Decree 31/2001

Slide3: 

Arsenic

Arsenic : toxicity: 

Arsenic : toxicity Acute poisoning: Mortal dosis: 70 ÷ 300 mg As2O3 Chronic poisoning: Hyperpigmentation, cutaneous lesions, xerosis, hepathomegalia, circulation disorders, viscle, skin, kidney, liver tumors. Classified as Group I by the International Agency for Research on Cancer (cancerogenic substances to humans)

Arsenic: basic chemical compounds : 

Arsenic: basic chemical compounds Not ogrganic: Arsenic anhydride As2O3 (white arsenic), solid, from arsenic metallurgy (in the process of ore sulphorate calcination) Arsenic anhydride As2O5 , solid, from dehydration of arsenic acid H3AsO4 Arsine AsH3, gas of acute poisoning properties Organic significant to environment and metabolism Monomethlarsenic acid CH3AsO(OH)2 Dimethylarsenic acid (CH3)2AsOOH Arsenic betine (CH3)3AsCH2COOH

Arsenic: Circulation in groud waters: 

Arsenic: Circulation in groud waters AsS FeAsS As2S3 AsO3- Fe2O3 Al2O3 Fe2O3 ···· AsO3- Al2O3 ···· AsO3- AsO2- Fe2+

Arsenic: presence in water: 

Arsenic: presence in water Usually 1 ÷ 2 μg/L Up to 12 mg/L in vulcanic areas close to sulphorate ores (average 0,5 mg/L).

Arsenic: elimination: 

Arsenic: elimination

Arsenic: phyto-filtration: 

Arsenic: phyto-filtration Pteris Vittata is a Chinese fern able to accumulate significant quantities of As (2,3% of leave mass, 22 g / kg of tissue) from polluted soil or water of hydroponic cultivation (experimental technique used in small installations).

Arsenic: flocculation: 

Arsenic: flocculation The most widespread mathod is flocculation by means of FeCl3, following oxidation with As(III) to As(V) through NaClO or ClO2. In the case of As(V) effectivness of elimination is higher. The process consists in co-precipitaiton and adsorbtion of AsO3- on the layer of iron hydroxide.

Arsenic: flocculation: 

Arsenic: flocculation Variants: Biological oxidation (to eliminate Fe, Mn, NH3), next comes floccilation; FeCl3 can be also applied in the beginning of the process of biological treatment without impact on its effectiveness (single-phase process). Biological oxidation and Arsenic elimination as one step Iron dosing through anode digestion

Arsenic: adsorbtion: 

Arsenic: adsorbtion Adsorbtion in a system with stationary packing with the use of the following fillings: Filler on the basis of iron – iron oxides (GFH) Sand covered with iron oxides (better surface binding) Activated alluminium oxide Pyrolusite In all cases, the effectivensess of the elemination process is higher if it is followed by oxidation of As(III) to As(V).

Arsenic: ion exchange: 

Arsenic: ion exchange Anion exchange rasins have high efficiency in elimination of As(V). In order to eliminate As(III) it is indispensable to apply oxidation before ion exchange. Efficiency of elimination is marked (> 85 %), but decreases with the concentration increase of SO42-

Arsenic: inverted osmosis: 

Arsenic: inverted osmosis The following reduction is obtained : 85 ÷ 90 % for As (V) 60 ÷ 70 % for As (III) The effectivness can be additionally boosted through a multi-phase process.

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Boron

Boron: toxicity: 

Boron: toxicity Acute poisoning Mortal dosis: 15-20 g (total) and 3-6 g for adults and children respectively. Chronic poisoning Cutaneous lesions, gastrointestinal disorders, convulsions. It can also influence metabolism and several substances regulating life process (Ca, Cu, Mg, N, O2 – reactive, glucose, triglycerides, estrogens). In small doses can be potentially important in nutrition.

Boron: presence in water: 

Boron: presence in water Usually 0,1 ÷ 0,3 mg/L In Italy and Spain average concentration is between 0,5 to 1,5 mg/L due to rocks and soils containing borates and borosilicate.

Boron: elimination: 

Boron: elimination Elimination methods Ion exchange Flocculation Inverted osmosis Adsorbtion

Bor: flocculation: 

Bor: flocculation Traditional treatement methods based on coagulation, flocculation and sedimentation provide moderate efficiency (< 28 %), which is addittionaly strongly connected with water turbidity and its pH.

Boron: adsorbtion: 

Boron: adsorbtion Application of granulated active carbon (GAC) provides efficciency of 90%. The method does not require large quantities of the adsorbent agent. Adsorbent agents on the basis of Fe(OH)3 – Fe2O3 have limited pollution reduction capacity (30 ÷ 50 %), depending on the pH. Similar results are obtained through adsorbtion/coagulation caused by Fe3+ at the of pH 8,5 on inert filters. Disadvantages: partial hardness reduction; gradual filter stoppage.

Boron: ion exchange: 

Boron: ion exchange Anion exchange resins proved efficient (i.e. żywice styrene resins with Amine (III) subsitituted by z carbohydret). Highly efficient method (> 95 %). Also possible to increase its selectivity throug water saturation with CO2.

Boron: inverted osmosis: 

Boron: inverted osmosis The following reduction is obtained : > 50 % for pH = 8,5 ÷ 9,5 ~ 80 % for pH > 10 Efficiency of the method can be increased throug a multi-phase process

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Fluoride

Fluoride: toxicity: 

Fluoride: toxicity Acute poisoning Insignificant as it caused by concentrations > 30 mg/L: cardiorespiratory arrest , impact on central nervous system. Chronic poisoning Neurotoxic impact on fetous, fluorosis, osteoporosis, inhibits the activity of several enzymes important for growth and cellular processes. Concentrations about 1 mg/L are associated with low caries incidence.

Fluoride: presence in water: 

Fluoride: presence in water Usually << 10 mg/L. Concentration in ground waters is limited by solubility of fluorite (3,1 mg/L in the presence of Ca2+ and concentration of 40 mg/L ). Concentration decreases in waters in contact with ores containing fluoride and poor with Ca2+ (max. concentration 2,8 g/L).

Fluoride: elimination: 

Fluoride: elimination Elimination methods Flocculation Inverted osmosis Adsorbtion

Fluoride: flocculation: 

Fluoride: flocculation Precipitation through salts Ca2+, Fe2+ or Al3+ in basic environment (low solubility of given fluorides and densyfying effect of hydroxides). As adjuvant agent in flocculation polyacrylamide is applied. Efficiency, about 75 ÷ 95 %.

Fluoride: adsorbtion: 

Fluoride: adsorbtion Adsorbtion on activated alluminium oxide at pH = 5,0 ÷ 6,0 (efficiency: > 90 %). Adsorbtion on animal carbon (efficency: 40 ÷ 60 %). Adsorbtion results from the presence of hydroxyapatite Ca10(PO4)6(OH)2 in which hydroxyle group is substituted by fluoride.

Slide29: 

Nickel

Nickel: toxicity: 

Nickel: toxicity Acute poisoning Nausea, emesis, headaches, diarrhea, respiratory problems. Chronic poisoning Alergic dermatitis caused by contact or ingestion, cancerogenicty (through inhalation). Ni compounds are classified by International Agency for Research on Cancer as Group 1 (cancerogenic to humans) in case of inhalation; Metallic Nickel as Group 2B (possibly cancerogenic to humas).

Nickel: presence in water: 

Nickel: presence in water Usually < 10 μg/L Up to 0,5 mg/L in case of nocturnal release by chrome Up to 2,5 mg/L in the presence of anthropogenic pollution or natural deposits

Nickel: elimination: 

Nickel: elimination Elimination methods Adsorbtion Flocculation Ion exchange

Nickel: flocculation: 

Nickel: flocculation Traditional treatement methods based on coagulation, flocculation and sedimentation provide moderate efficiency (< 28 %), which is addittionaly strongly connected with water turbidity and its pH. As adjuvant agent in flocculation also powdery active carbon (PAC) is applied.

Nickel: adsorbtionn: 

Nickel: adsorbtionn Application of granulated active carbon (GAC) does not give good resutls. Adsorbent agents based on Fe(OH)3 – Fe2O3 have limited capacites in terms of elimination of pollution (30 ÷ 50 %), which depends on pH. Similar results are obtained through adsorbtion/coagulation caused by Fe3+ at pH 8,5 on inert filters. Disadvantages: partial hardness reduction; gradual filter stoppage.

Nickel: ion exchange: 

Nickel: ion exchange Skuteczne okazały się (> 90%) żywice jonowymienne o działaniu chelatującym. Ni ion exchange give analogous effects to Ca and Mg ion exchnge (concomitant water softening).

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