Spelling suggestions: "subject:"water - solar distillation"" "subject:"water - solar istillation""
1 |
Studies in Water Treatment : Defluoridation using Adsorption, Denitrification using a Microbial Fuel Cell, and Contaminant Removal using Solar DistillationSamrat, Maruvada Veera Venkata Naga January 2017 (has links) (PDF)
This thesis includes both experimental and modelling studies on the treatment of drinking water. Three aspects were studied: (i) removal of fluoride (F– ) by adsorption, (ii) removal of fluoride and other contaminants by solar distillation, (iii) denitrification by a microbial fuel cell.
The availability of potable water on earth is about 0.2% of the total available water. This very small quantity is polluted by anthropogenic and natural contaminants. Fluoride is a classic example of a natural contaminant, wherein the dissolution of F– bearing minerals causes the release of F– into the groundwater. Exposure to concentrations > 1 mg/L over ex-tended periods of time results in dental and skeletal fluorosis. Worldwide, about 220 million people are at risk. Nitrate is an example of anthropogenic contaminant, occurring because of addition of high quantities of fertilizers to the soil for better crop yields. The excess fertilizers penetrate the soil and mix with the groundwater, resulting in nitrate contamination. The major effect of nitrate contamination is met haemoglobin , which is caused because of the oxidation of ferrous ion in haemoglobin to ferric ion by the nitrite to form haemoglobin. The effects can be noticed by the change in colour of skin to bluish grey or brownish grey in infants. To counter the drastic effects of these anions, the World Health Organization (WHO) has prescribed permissible limits of 1.5 mg/L and 45 mg/L for F– and NO3 – , respectively.
For obtaining contaminant-free water, many methods have been used. Reverse osmosis (RO) is one of the widely-used methods. Even though this process removes most of the contaminants, about 50 - 70% of the inlet water is wasted as a reject stream with higher concentrations of the contaminants. This is a very unsustainable way of using water, particularly in drought-prone areas. So, in the thesis a conceptual strategy with three different methods is developed to treat reject water.
In the first part of the thesis, the removal of F– using adsorption was studied. Activated alumina (AA) and a hybrid anion exchange resin embedded with hydrous zirconium oxide nanoparticles (HAIX-Zr) (sample sent by Prof. Arup K SenGupta) were used as the adsorbents. The adsorbents were tested with synthetic water samples and reverse osmosis (RO) reject water. HAIX-Zr had a better adsorption capacity compared to AA when water containing only F– was used. The presence of high concentrations of co-ions affects the uptake of F– drastically, with a decrease of up to 34% and 79% for AA and HAIX-Zr, respectively. With AA, for a synthetic water sample with a small concentration of HCO3 – , there was a two-fold increase in the uptake of F– compared to a water sample containing only F– . There was no removal of NO3 – by AA. HAIX-Zr removes NO3 – , but to a lesser extent than F– . With AA, the pH of the inlet solution affected the adsorption capacity, because of the change in the surface charge of AA. Based on the type of water sample used, the cost of treated water varied from Re. 0.1 - 1.0/L ($ 0.0015 - 0.015/L) for AA and 0.2 - 11.5/L ($ 0.003 - 0.17/L) for HAIX-Zr. A community-level plant was set up to treat the RO reject water using AA. Due to challenges at the field level, the pilot plant had to be stopped after 80 bed volumes of water were treated.
From our observations and as also reported by many authors, the adsorption of F– is affected by the presence of many ions. When modelling the adsorption of F– , it is usually taken as a single entity getting adsorbed on the adsorbent. As this is not a proper assumption, a model was developed which takes into account all the speciation reactions that take place during adsorption, and all the species like H+, OH– , Na+, Cl– , and NO3 – present in the solution along with F– . Using the model, the equilibrium constants and rate constants for the reactions were obtained. For one initial concentration of F– , a good fit was obtained to the batch adsorption data, except at short times. Due to uncertainty about the amount of impurity present in the adsorbent, at higher initial concentrations of F– , there was a significant discrepancy between predictions and data. Considering column experiments, the breakthrough curve for F– was simulated using the developed model. For the special case of negligible mass transfer resistances, the predicted break-through volume was within 3% of the observed value.
In the second part of the thesis, nitrate removal was investigated using microbial fuel cell (MFC). In a MFC, power is generated by the activity of the microorganisms present in the cell. The organisms present in the anode side release electrons (e– ) by the use of substances that can be oxidized, namely, glucose, acetate, etc. On the cathode side, the organisms have the potential to take in e– and reducible substances, and release reduced products like nitrogen, hydrogen, etc. In the present case, nitrates added to the cathode side were reduced to nitrogen gas by the use of a consortium of micro-organisms taken from seawater. A similar consortium was used in the anode chamber
Here, the study was focused on improving the efficiency of MFC for removal of NO3 – , by changing the buffering medium used in the cells. Commonly, phosphate buffer is used, but when using a MFC for treatment, the presence of PO43 – causes water contamination and is not suitable for drinking. There-fore, PO43 – was replaced with HCO3 – on the cathode side of the cell. This resulted in a higher removal of NO3 – and power production compared to the PO43 – buffered solution
In the third part of the thesis, contaminant removal using solar distillation was investigated. For this as inclined basin still was used. Investigations were based on the evaporation rate of contaminated water, and the odour and concentrations of ions in the distillate. In order to improve the evaporation rates, different radiation absorbing materials like sand, activated charcoal, and carbon nanoparticles encapsulated in polymer sheets (PCNP) were investigated. It was observed that the evaporation rates were higher with activated carbon than the other materials. Using this technique there was about 99% removal of NO3 – , F– , SO42 – and the concentrations of ions in the distillate were well below the acceptable limits. When sand or PCNP was used as an absorbing/wicking medium, the distillate had an objectionable odour. With the use of AC, the odour could be eliminated because of the adsorption of odour-causing compounds.
|
2 |
Desenvolvimento de um destilador solar para tratamento de ?guas de produ??o de petr?leo com vistas a sua utiliza??o na agricultura e gera??o de vapor / Development of a solar distillator for treatment of produced water of oil with aims its use in the agriculture and vapor generationSousa, Magna Ang?lica dos Santos Bezerra 02 September 2004 (has links)
Made available in DSpace on 2014-12-17T15:01:15Z (GMT). No. of bitstreams: 1
MagnaASB.pdf: 1635517 bytes, checksum: df420c88397a6cd630a5381fcef348b7 (MD5)
Previous issue date: 2004-09-02 / The production of petroleum is frequently accomplished with great volumes of water, that it is carried of the underground with the oil. It is a challenge of the present century the development of technologies that allow the use of waste water for purposes that consume great amounts of water and don't demand as rigid as the one of the drinking water requirements. The solar distillation has been configuring as an alternative of clean technology for desalination of brine and saline. Besides causing the minimum possible damage to the environment, it takes advantage of an abundant and free energy source: the solar energy. That study aims to develop a Solar Distillator for treatment of the produced water of the oil wells, to obtain an efluent to use in agriculture and vapor generation. The methodology for collection, conservation and analysis of the physical-chemical parameters obeyed the norms in APHA (1995). The sampling was of the composed type. Experiments were accomplished in the solar distillation pilot and simulation in thermostatic bathing. The operation was in batch system and for periods of 4, 6 and 12 h. The developed Distillator is of the type simple effect of two waters. It was still tested two inclination angles for covering; 20? and 45?. The Distillator presented minimum of 2,85 L/m2d revenues and maximum of 7,14 L/m2d. The removals of salts were great than 98%. The removal of TOC in the simulation was great than 90%. In agreement with the data of energy and mass balance, it was verified that the developed solar Distillator presented compatible revenues with those found in literature for similar types. It can be inferred that the obtained distilled water assists to the requirements CONAMA in almost all the points and could be used for irrigation of cultures such as cotton and mamona. As the distilled water has characteristics of fresh water it can be used in the generation of vapor / A produ??o de petr?leo ? realizada freq?entemente com grandes volumes de ?gua, que ? carreada do subsolo junto com o ?leo. ? desafio do presente s?culo o desenvolvimento de tecnologias que possibilitem ou uso ou reuso de efluentes para outros fins. A destila??o solar ? uma alternativa de tecnologia limpa para dessaliniza??o de ?guas salobras e salinas. Esse estudo visa desenvolver um Destilador Solar para tratamento da ?gua de produ??o de petr?leo, com vistas a se obter um efluente pass?vel de utiliza??o na agricultura e gera??o de vapor. A metodologia para conserva??o e an?lise dos par?metros f?sico-qu?micos obedeceu preconiza??o do APHA (1995). A amostragem foi do tipo composta. Foram realizados experimentos no destilador solar piloto e simula??o em banho termost?tico. A opera??o foi em sistema de batelada e por per?odos de 4, 6 e 12 h. O destilador desenvolvido ? do tipo simples efeito de duas ?guas. Testou-se ainda dois ?ngulos de inclina??o para cobertura; 20? e 45?. O destilador apresentou rendimentos m?nimo de 2,50 L/m2d e m?ximo de 7,5 L/m2d. As remo??es de sais foram superiores a 98%. A remo??o de TOC na simula??o foi superior a 90%. De acordo com os dados dos balan?os energ?tico e de massa, verificou-se que o destilador solar desenvolvido apresentou rendimentos compat?veis com os encontrados na literatura para seus similares. Enfatiza-se que o isolamento utilizado n?o estava nas condi??es de otimiza??o, logo, esse rendimento pode ser melhorado. Pode-se inferir que a ?gua destilada obtida atende aos requisitos CONAMA em quase todos os pontos, podendo ser utilizada, com ressalvas, na irriga??o de culturas n?o comest?veis como o algod?o e a mamona. Como a ?gua destilada tem caracter?sticas de ?gua doce pode ser utilizada na gera??o de vapor
|
Page generated in 0.0952 seconds