Tài liệu Simultaneous Removal of Arsenic and Ammonia from Groundwater by Phytofiltration with Cattails (Typha SPP.) Cultivation

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TABLE OF CONTENTS TABLE OF CONTENTS 1 ABBREVIATIONS 3 LIST OF FIGURES 4 LIST OF TABLES 5 LIST OF DIAGRAMS / FLOWCHARTS 5 ACKNOWLEDMENTS 6 INTRODUCTION 7 CHAPTER 1- OVERVIEW 10 1.1. Water Sources and Quality Requirements for Drinking Purpose 10 1.1.1. Water sources: 10 1.1.2. Groundwater Quality Requirements for Drinking Purpose 10 1.2. Current Status of Ammonia and Arsenic Contamination of 11 Groundwater 1.2.1. Arsenic Contamination of Groundwater: 11 1.2.2. Ammonia Contamination of Groundwater: 16 1.3. Treatment Technologies 17 1.3.1. Arsenic Removal Treatment: 17 1.3.2. Ammonia Removal from Groundwater 19 1.4. Phytofiltration Systems 21 1.4.1. Characteristics of Phytofiltration Systems 21 1.4.2. Principles of Phytofiltration Systems 23 CHAPTER 2 - MATERIALS AND METHODS 28 2.1. Plant Selection: 28 2.2. Soil Selection for Rooting Media: 29 2.3. Setup and Operation of Phytofiltration Systems: 29 2.3.1. Plant Cultivation: 29 3 2.3.2. Operation: 29 2.3.3. Preparation of Ammonia and Arsenic Solutions 31 2.4. Sampling: 31 2.5. Chemical analysis of samples [APHS, 1970]: 31 2.5.1. pH-value measurement 31 2.5.2. Alkalinity determination 31 2.5.3. Ammonia-nitrogen analysis 32 2.5.4. Nitrite-nitrogen analysis 34 2.5.5. Nitrate-nitrogen analysis 36 2.5.6. Arsenic analysis 37 CHAPTER 3 - RESULTS AND DISCUSSIONS 40 3.1. Biomass Accretion of Cattails (Typha spp.) 40 3.2. Arsenic Removal Effectiveness 42 3.3. Ammonia Removal Effectiveness 44 3.3.1. Ammonium-Nitrogen: 44 3.3.2. Nitrite-Nitrogen: 48 3.3.3. Nitrate-Nitrogen: 49 CONCLUSIONS 51 RECOMMENDATION AND PROSPECT 53 REFERENCES 56 APPENDIX 61 4 ABBREVIATION APHA American Public Health Association ATSDR Agency for Toxic Substances and Disease Registry CETASD Center for Environmental Technology and Sustainable Development FAO Food and Agriculture Organization HUS Hanoi University of Science MCL Maximum Concentration Limit MONRE Ministry of Natural Resource and Environment NRC National Research Council TCVN The Vietnamese Standard US EPA The United Stated Environmental Protection Agency WEPA Water Environment Partnership in Asia WHO World Health Organization 5 LIST OF FIGURES Figure 1.1 Tentative risk map of arsenic concentrations in groundwater of 13 the Red River Delta Figure 1.2 Expressions of the black foot disease 15 Figure 1.3 Situation of ammonia contamination of groundwater in Hanoi City 16 Figure 1.4 Arsenic Removal Mechanisms in a Phytofiltration System 25 Figure 2.1 Cattails (Typha spp.) 28 Figure 2.2 Cross section of an phytofiltration system with cattails (Typha 30 spp.) cultivation. Figure 3.1 Biomass accretion of cattails after periods of transplanting time 40 Figure 3.2 Root accretion of cattails after periods of transplanting time 41 Figure 3.3 Loading rates on arsenic 42 Figure 3.4 [As] in outflows after periods of treatment time 43 Figure 3.5 Loading rates on ammonia (mg/d) 45 Figure 3.6 [NH4+-N] in inflows and outflows after periods of treatment time 47 Figure 3.7 [NO2--N] in outflows after periods of treatment time 49 Figure 3.8 [NO3--N] in outflows after periods of treatment time 50 Figure 5.1 Sequentially assembled phytofiltration systems with cattails 54 (Typha spp.) cultivation. Figure 8.1 Distribution of documented world problems with arsenic in 61 groundwater in major aquifers as well as water and environmental problems related to mining and geothermal sources. Figure 8.2 Evaluation of simultaneous removal of arsenic and ammonia via 64 hydroponically transplanted plants 6 LIST OF TABLES Table 1.1 MCL values for arsenic in drinking water 10 Table 1.2 Average arsenic concentrations and ranges in sample collected in rural districts in the Red River Delta in 2001 13 Table 1.3 Average arsenic concentrations and ranges in sample collected in the Mekong Delta on July, 2004 (n = 112) 14 Table 1.4 Average NH4+-N and NO2--N concentrations and ranges in samples collected in 2004 in the Mekong River Delta 17 Table 1.5 The seven states of oxidation in which nitrogen can exist 19 Table 2.1 Initial concentrations of ammonia and arsenic in inflows 31 Table 2.2 Daily-taken volumes of outflow samples 31 Table 3.1 Front accretion of cattails after periods of transplanting time (n=6) 41 Table 8.1 Classification of nitrogen compounds pollution levels in groundwater in general 61 Table 8.2 Major arsenic minerals occurring in nature 62 Table 8.3 Ammonium-Nitrogen Concentrations in several rivers in the North of Vietnam (in 2004) 33 Table 8.4 Values of Ka (Ionization constant in the ammonia and ammonium equilibrium) dependent on Temperature 33 Table 8.5 Loading rates on arsenic and ammonia of some plants transplanted hydroponically in arsenic- and ammoniacontaminated water 64 Table 8.6 Experimental Results 65 LIST OF DIAGRAMS / FLOWCHARTS Flowchart 5.1 Potential applications of phytofiltration for arseniccontaminated soil and water 7 55 INTRODUCTION Groundwater in Vietnam is abundant; however, it is often polluted by different contaminants, especially by arsenic and ammonia [WB, 2002]. The frequency of ammonia-contaminated groundwater demonstration in the Red River Delta areas is approximately 80% - 90% with average ammonia concentrations ranging from 10 mg/L – 30 mg/L [Le Van Cat, Tran Mai Phuong, 2005]. In the Mekong River Delta, ammonia contamination of groundwater is also alarming with average ammonia concentrations ranging from 0.1 - 35 mg/L [M. Berg, 2006]. Ammonia does not directly cause poisoning, but unfortunately, its transformed products (such as nitrite NO2-, nitrate NO3-...) can cause health risks to human beings [US EPA, 2000]. Besides, groundwater in Vietnam is significantly polluted by arsenic [WB, 2002]. The levels of arsenic contamination were examined and varied from 1 µg/L to 3050 µg/L (48% above 50 µg/L and 20% above 150 µg/L) in groundwater samples from domestic shallow tube-wells in rural areas in the Red River Delta. Particularly, of which, the groundwater used directly as drinking water source had an average concentration of 430 µg/L in several highly affected rural areas [Tran Hong Con, 2006]. In the Mekong River Delta, arsenic concentrations in groundwater are also high in range from 1 µg/L to 845 µg/L [M. Berg et al., 2006] Actually, such high arsenic- and ammonia-contaminated groundwater indicates that millions of people, especially who are living in the Red River Delta and in the Mekong River Delta daily consuming untreated groundwater, might be at high considerable health risks of poisoning caused by such contaminated groundwater. Treatment technologies for arsenic and/or ammonia removal from contaminated groundwater have been paid much attention and concern. There are several current treatment technologies for ammonia removal from groundwater such as Breakpoint Chlorination, Ion Exchange by Clinoptilolite, Air-stripping... [Le Van Cat, 2007]. Main methodologies for arsenic removal include Precipitation, Adsorption, Ion 9 Exchange by Activated γ-Al2O3...[US EPA, 2000]. However, selection of an optimal treatment technology depends on both objective and subjective factors, for example, contaminant contents, economic conditions, treatment scales, availability...While precipitation is the most common among such methods, the disadvantage is that it only reduces the dissolved metal concentration to the solubility product level, which is frequently out of compliance with rigorous discharge permit standards and thus requires additional cleaning stages. These aforementioned techniques are all generally expensive and might possibly generate by-products dangerous to human health [US EPA, 2000]. Regarding to rural areas conditions, the priority factors which should be much taken into account are costs and treatment scales. Applications of these technologies for small-scale treatments are certainly more difficult in comparison to those for large-scales in point of views of financial problems, operation and maintenance conditions. In Vietnam, several studies on removal of arsenic and ammonia from contaminated groundwater have been researched and implemented in recent years. However, applications of the above-mentioned technologies often faces difficulties and disadvantages such as high costs, complicated operation and maintenance skills... In addition, each of these treatment technologies can be compatible for partially removing one contaminant. Thus, simultaneous removal of contaminants requires a series of sophisticatedly combined treatment systems. An optimal treatment technology which can be broadly applied in rural areas must be considered in terms of low cost, small-scale treatment, simple operation and maintenance...Moreover, requirements of simultaneous removal of both arsenic and ammonia should necessarily be taken into account. Phytofiltration system, a plant-based technology for the removal of toxic contaminants from soil and water, has been receiving renewed attention. A great deal of research in decades that plants have the genetic potential to remove many toxic contaminants from water and soil [R.L. Chaney et al., 2000]. Plants can 10 uptake nutrients for their biomass development and growth. Moreover, plants can transport oxygen from the air through their leaves, their shoots and finally to their root-zones for aerobic microorganisms to carry out nitrification and denitrification, with presence of ammonia as a preferable nutrient source. Ammonia will be transformed to gaseous nitrogen (non-toxic) and to escape to the air. In addition, plants have metals-accumulating ability to build their own cellular matters via uptake process. Consequently, arsenic and ammonia will be removed from groundwater after periods of time. Phytofiltration has been proposed as a cost-effective, environmental-friendly alternative technology. A number of plants have been identified for the phytofiltration, and some have been used in practical applications. In this study, cattails (Typha spp.) were chosen as a model plant for the phytofiltration systems because of its high arsenic-accumulating ability coupled with its rapid growth and generation of high biomass yields. This finding may open a door for phytofiltration of ammonia and arsenic-contaminated groundwater in Vietnam. This study aims at: 1. Examining simultaneous removal ability of ammonia and arsenic from contaminated water by three pilot phytofiltration systems with cattails (Typha spp.) cultivation; 2. Constructing and developing an optimal treatment technology for simultaneous removal of ammonia and arsenic (and other contaminants) from groundwater for drinking uses. 11 CHAPTER 1 - OVERVIEW 1.1. Water Sources and Quality Requirements for Drinking Purpose 1.1.1. Water sources: In Vietnam, the water sources exploited and used for domestic purposes are mainly from surface water and groundwater. Surface water source is abundant, mainly from rivers, lakes, ponds... It is commonly recharged with rainwater, shallow-level groundwater, and wastewater. Moreover, surface water quality is often affected by human life activities such as agriculture, industries. Nowadays, surface water does gradually not meet basic requirements for domestic purposes if it is not treated before use. Besides, groundwater quality is somewhat better than that of surface water in general. However, groundwater sources are also gradually polluted by both natural and anthropogenic contamination sources. 1.1.2. Groundwater Quality Requirements for Drinking Purpose a/ Arsenic MCL Standard for Drinking Water: The MCL for arsenic in drinking water according to several standards are shown in Table 1.1: Table 1.1 - MCL values for arsenic in drinking water [J. Matschullat, 2000] Standard WHO* EU NL TVO-D DVGW TCVN [As] (µg/L) 10 50 10 - 60 10 10 - 30 10 ▪ WHO: World Health Organization, drinking water guidelines for arsenic; ▪ EU: European Union; ▪ NL: Dutch drinking water guidelines for arsenic (the first numbers refer to reference values, the second to maximum permissible levels); ▪ TVO-D: German drinking water standards for arsenic; 12 ▪ DVGW: German surface water (raw water) guidelines (for ranges see NL); ▪ TCVN: Vietnamese Standards b/ Ammonia MCL Standard for Drinking Water: Ammonia MCL standards for drinking water in somewhere around the world are different. The WHO and EU standards for ammonia MCL in drinking water is of 0.5 mg/L. Whereas, Vietnamese standard has set a limit for ammonia-nitrogen MCL in drinking water is 3 mg/L according to new TCVN 5520-2003 [TCVN, 2003]. 1.2. Current Status of Ammonia and Arsenic Contamination of Groundwater 1.2.1. Arsenic Contamination of Groundwater: a/ Arsenic Contamination: Arsenic, a significant contaminant of groundwater, has been found in many regions around the world [P.L. Smedley and D.G. Kinniburgh, 2002]. Arsenic is widely known for its adverse effects on human health, affecting millions of people. High concentrations of arsenic (above 50 g/L) in groundwater used as drinking water source have been reported in several countries such as Bangladesh, India, China, Mexico, Nepal, Taiwan, Vietnam… In some Asian countries, arsenic in groundwater is a major health concern and the risks from using shallow tube-wells (STWs) for drinking water are well-known. As part of the green revolution, millions of STWs have been installed throughout Asia over the last three decades. This has resulted in a sharp increase of groundwater extraction for irrigation. The direct consumption of groundwater through tube-wells in an attempt to replace polluted surface water supplies has resulted in widespread arsenic poisoning. a1/ Sources of arsenic contamination: Arsenic is one of the most toxic elements encountered in the environment. Arsenic can enter groundwater through both natural geologic processes (geogenic) and 13 anthropogenic activities. The primary anthropogenic contributions of arsenic to groundwater are from application of arsenical pesticides, irrigation, mining and smelting of arsenic-containing ores, combustion of fossil fuels (especially coal), land filling of industrial wastes, release or disposal of chemical warfare agents [K.H. Goh and T.T. Lim, 2005], manufacturing of metals and alloys, petroleum refining, and pharmaceutical manufacturing [R.Y. Ning, 2002]... Another potential contributing source of arsenic in groundwater is the current use of chromated copper arsenate (CCA) as wood preservative. Organic arsenic is also a constituent of feed additives for poultry and swine for the control of coccidian intestinal parasites and to improve feed efficiency, and appears to concentrate in the resultant animal wastes. There is a significant use of arsenic in the production of lead-acid batteries, while small amounts of very pure arsenic are used to produce gallium arsenide, which is a semi-conductor used in computers and other electronic applications [R.Y. Ning, 2002]. Even though industrial use of arsenic has decreased in recent years, it remains a significant arsenic contamination source of groundwater for some human health problems [M. Karim, 2000]. a2/ Arsenic contamination of groundwater in Vietnam: Groundwater in the two large alluvial deltas of Mekong River and Red River has been exploited for domestic uses by private tube-wells [M. Berg et al., 2006]. M. Berg et al., (2006) found that the arsenic concentrations in groundwater somewhere in the Mekong River Delta and Red River Delta range from 1 to 845 µg/L and from 1 to 3050 µg/L, respectively. Whereas, Trang et al., (2006) found elevated arsenic concentrations in areas of the Mekong Delta, where 405 (40%) of the tube-wells had arsenic levels higher than 100 µg/L. A tentative risk map of arsenic being higher than 50 µg/L in groundwater of the Red River Delta is presented in Figure 1.1. This map was established from geological raster information, climate and land use. 14 Figure 1.1 - Tentative risk map of arsenic concentrations in groundwater of the Red River Delta [FAO, 2007] Table 1.2 - Average arsenic concentrations and ranges in sample collected in rural districts in the Red River Delta in 2001 [M. Berg et al., 2006] Rural Districts n Average (µg/L) Range (µg/L) A 48 32 1 – 220 B 48 67 1 – 230 C 55 140 2 – 3050 D 45 430 2 – 3010 SUMMARY 196 159 1 – 3050 15 Table 1.3 - Average arsenic concentrations and ranges in sample collected in the Mekong Delta on July, 2004 (n = 112) [M. Berg et al., 2006] Arsenic concentratioin (µg/L) in the Mekong Delta Average Median Range 39 <1 1 – 845 In Vietnam, the aquifers under the large deltas of Mekong River and Red River are now widely exploited for drinking water and for agricultural uses. These abovepresented data are demonstrating that people living in the two deltas are chronically exposed to elevated arsenic levels in groundwater used as their drinking water source via broadly-distributed tube-well system and at high risk of arsenic contamination. The total number of tube-wells in the two regions is unknown but could be over one million [P.L. Smedley and D.G. Kinniburgh, 2002]. It means that millions of people in Vietnam are likely to be affected by using contaminated groundwater from tube-wells and through consumption of contaminated foods. Unfortunately, symptoms of chronic arsenic poisoning usually take more time than ten years to develop and appear, the number of future arsenic related ailments in Vietnam, therefore, is likely to increase. Urgently, early mitigation measures should be a high priority. b/ Arsenic Toxicity b1/ Arsenic speciation: Arsenic can be present in groundwater as chemical compounds of both inorganic and organic forms, which include elemental arsenic, arsenide, sulphide, oxides, arsenates and arsenite [E. Miteva et al., 2005]. A list of some of the most common arsenic compounds is given in Table 8.2. Among them, arsenate As(V) and arsenite As (III) are the most abundant [M.B. Hossain, 2005]. 16 b2/ Arsenicosis: Arsenic contamination of water supplies poses serious risks to human health because inorganic arsenic is a known carcinogen and mutagen, and is detrimental to the human immune system [NRC, 2001]. Drinking water and/or obtaining foods rich in arsenic over a long period lead to arsenicosis. Chronic levels of 50 µg/L of arsenic can cause health problems after 10 to 15 years of exposure. The development of symptoms of arsenicosis is strongly dependent on exposure time and the resulting accumulation in the body. The various stages of arsenicosis are characterized by skin pigmentation, keratosis, skin cancer, effects on the cardiovascular and nervous system, and increased risk of lung, kidney and bladder cancer [H.M. Anawar et al., 2002]. In China, exposure to arsenic via drinking-water has been shown to cause a severe disease of the blood vessels known as “black foot disease” [M.M. Wu, 1989]. Figure 1.2 - Expressions of the black foot disease (WHO 00229, 2007) b3/ Arsenicosis causes: Arsenicosis is caused by the chemical arsenic, especially inorganic arsenic. Arsenic is a toxic element that has no apparent beneficial health effects for humans. Arsenicosis is caused by exposure over a period of time to high arsenic 17 concentrations in drinking water. Besides, it may also be due to intake of arsenic via food or air. The multiple routes of arsenic exposure contribute to chronic poisoning [WHO, 2001]. 1.2.2. Ammonia Contamination of Groundwater: a/ Ammonia Contamination: Researches on ammonia contamination of groundwater, especially in the Red River Delta, have been paid much attention [WB, 2002]. A few initial results have been achieved to evidently demonstrate and alarm such high ammonia contamination of groundwater in Vietnam. As shown in Figure 1.3 it is the situation of ammonia contamination of groundwater in several sites of Hanoi City: Figure 1.3 - Situation of ammonia contamination of groundwater in Hanoi City [CETASD, 2004] Investigated sites: MD: Mai Dich PV: Phap Van HD: Ha Dinh NSL Ngo Sy Lien TM: Tuong Mai LY: Luong Yen NH: Ngoc Ha YP: Yen Phu 18 As presented, groundwater in several sites of Hanoi City is strongly affected with high ammonia concentrations, especially in Ha Dinh and Phap Van areas with ammonia concentrations of higher 10 mg/L (shown in red color). In the Mekong River Delta, ammonia contamination of groundwater is also alarming. M. Berg et al., 2006 researched and found demonstrations of ammonia contaminations of groundwater as shown in Table 1.4 below: Table 1.4 - Average NH4+-N and NO2--N concentrations and ranges in samples collected in 2004 in the Mekong River Delta [M. Berg et al., 2006] Average Range NH4+-N concentration (mg/L) 5.0 0.1 - 35 NO2--N concentratioin (mg/L) 0.25 0.25 – 4.4 */ Ammonia contamination sources of groundwater can be from both natural and anthropogenic sources. Natural sources include biological fixation of atmospheric nitrogen which serves as a significant source of natural nitrogen input to water. Anthropogenic sources include uses of chemical fertilizers, pesticides, run-off, industrial discharges, etc. [ATSDR, 2004]. b/ Ammonia Toxicity: There has no scientific report told that ammonia affects directly to human health but transformed products made from ammonia like nitrite, nitrate via nitrification and denitrification are very dangerous [ATSDR, 2004]. Nitrite can combine with secondary amines in the digestive tract to produce N-nitrosamine which is carcinogenic. And, nitrate is agent created bluish coloration of the skin NH4+ → NO2- 1.3. Treatment Technologies 1.3.1. Arsenic Removal Treatment: 19 → NO3- (a) The most common water treatment technologies for arsenic-contaminated water include the following: a/ Coagulation/Filtration: Coagulation/filtration removes arsenic by co-precipitation with iron oxide [US EPA, 2002]. Coagulation/filtration using alum is already used by some utilities to remove suspended solids, and may be adjusted to remove arsenic. Iron oxide adsorption filters the water through a granular medium containing ferric oxide. Ferric oxide has a high affinity for adsorbing dissolved metals such as arsenic [US EPA, 2002]. The iron oxide medium eventually becomes saturated, and must be replaced. This treatment method is effective for removal of As(V) according to lab- and pilotplant tests. However, it is generally unable to successfully remove arsenic in largescale system to lower levels due to the affinity and solubility limitation of the resultant products [US EPA, 2002]. The procedures are also time-consuming and expensive, and not cost-effective. And another disadvantage of this method is the generation of large volumes of arsenic-contaminated coagulation sludge [US EPA, 2002]. The disposal of such contaminant wastes may be a concern, especially if nearby landfills are unwilling to accept such sludge. b/ Lime Softening: This method for removing dissolved arsenic from groundwater is comprised of the following steps [US EPA, 2002]: 1. Adding lime to the aqueous medium, wherein the step of adding lime increases the pH of the aqueous medium to at most approximately 10; and 2. Adding one or more sources of divalent metal ions other than calcium and magnesium to the aqueous medium wherein said metal ions comprise one or more sources of copper ions or zinc ions; 20 3. Wherein substantially no ferric ions are added to the aqueous medium; and whereby dissolved arsenic in the aqueous medium is reduced to a lower level than possible if only the step of adding lime were performed. 1.3.2. Ammonia Removal from Groundwater a/ Biological-nitrogen species: In nature, nitrogen-compounds can be existed in many states of oxidation, ranging from reduced ammonia – nitrogen (NH3-N)/ammonium – nitrogen (NH4+-N) to highly oxidized nitrates-nitrogen (NO3--N). In all, nitrogen can exist in seven states of oxidation, as shown in Table 1.5: Table 1.5 – The seven states of oxidation in which nitrogen can exist [Le Van Cat, 2007) Compound Formula Valence Ammonia – nitrogen / Ammonium – nitrogen NH3-N / NH4+-N -3 Nitrogen gas N2 0 Nitrous oxide N2 O +1 Nitric oxide NO +2 Nitrite – nitrogen NO2--N +3 Nitrogen dioxide NO2- +4 Nitrate – nitrogen NO3--N +5 b/ Ammonia Removal from Groundwater: In water, ammonia/ammonium and nitrate are more abundant than nitrite and other organic nitrogen-compounds. At aim of an achievement of the most effective ammonia removal technology from groundwater, such technology should be a 21 complete transformation of the nitrogen-compounds finally into gaseous nitrogen, which is inert and does not pollute environment. Based on this principle, physiochemical and/or biological treatments can be applied for removal of nitrogen-compounds from groundwater as follows: b1/ Transformation of the nitrogen-compounds finally into gaseous nitrogen which then releases to the air. This method is due to the following processes:  Biological processes (Nitrification and Denitrification); o Nitrification: Ammonium is converted into nitrite, and finally to nitrate. The bacteria involved are autotrophic and use oxygen as their electron acceptor, whereas ammonium is used as their substrate. The conversion to nitrite is performed by Nitrosomonas sp; and the conversion to nitrate by Nitrobacter sp. These bacteria are obligate aerobes, meaning that they can grow only in the environment in which dissolved oxygen (DO) is present. If the absence of DO for prolonged periods, however, is not lethal to those microorganisms [H.A. Painter, 1970]. o Denitrification: In the absence of dissolved oxygen, bacteria will use nitrate as a terminal electron acceptor and convert nitrate to nitrogen gas.  Anamox process (Oxidation/Reduction of ammonia via microorganism activities);  Direct oxidation of ammonia to form gaseous nitrogen; b2/ Transformation of the nitrogen-compounds into cellular components (biomass of plants and microorganisms)  These transformations are involved in biochemical reactions occurring in plant cells (via photosynthesis reactions) and microorganism cells (via assimilation reactions). These processes exist in nature. b3/ Volatilization of ammonia into the air. 22 Treatment cost-effectiveness these methods are certainly different. An optimal selection of treatment technology should be based on cost-effectiveness (low operation and maintenance cost, simple handling...) and treatability (long-life, maximum elimination of not only ammonia but other contaminants...) 1.4. Phytofiltration Systems 1.4.1. Characteristics of Phytofiltration Systems a/ Phytofiltration: Phytofiltration, the use of plant with extensive root systems and high accumulation capacity for contaminants, to absorb and adsorb pollutants from water and streams, is gaining a lot of importance in recent times since it is a cost-effective, promising and environmentally-friendly technology [D.E. Salt et al., 1995]. b/ Main Components of Phytofiltration Systems: The three main components of a phytofiltration system are hydrology, soils/sediments, and vegetation. The interactions of these components dictate the overall contaminant removal efficiency of the phytofiltration systems. 1. Hydrology: Hydrologic regime is the major regulating factor of all phytofiltration systems used for water treatment. Hydrologic characteristics depend on configuration or geometry of phytofiltration systems, water loading rate, and water depth. 2. Soil substrate for rooting media: The type and textile of soil affect physical, chemical, and biological mechanisms regulating the removal of contaminants from water. Soil characteristics which should be taken into account are soil pH, soil penetrability, and soil thickness... Of which, soil penetrability, soil thickness are important factors in soil selection. Soil vertical penetrability is dependent on the type and textile of soil. Sandy soil has high spongy textile which is supportive for penetration. 23
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