The Reduction of Water Irrigation Salinity by Solar Distillation for the STEP of Ouargla

The Reduction of Water Irrigation Salinity by Solar Distillation for the STEP of Ouargla

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Procedia Engineering 00 92 (2012) Procedia Engineering 33 (2012) – 97000–000

Procedia Engineering www.elsevier.com/locate/procedia

ISWEE’11

The Reduction of Water Irrigation Salinity by Solar Distillation for the STEP of Ouargla Zahia.Tigrinea, Zoubir.Belgrouna, Brahim.Abbada, Halima.Dalia , Hanane.Aburideha*, a

Solar Equipement Develpement Unit ,UDES,National road N°11,P.O.Box386 ,Bou-Ismail, 42415, Tipaza, Algéria.

Abstract With the aim of mitigating the problem of salinity of purified waste water of the STEP (waste water treatment plant) of Ouargla, one proposed to study the possibility of integration of solar energy to solve the problem of this water intended for the irrigation of the agricultural surfaces and in particular the palm trees, which underwent major damage because of the salinity of this water. A physicochemical and biological study was carried out on a sample of 20 L, whose pH is of 8.03, a salinity of 5.2g/l, and a conductivity of 9170

µ S/cm, we

note that distillation was spread out over 5 days.

The results thus carried out, do not present any danger to the animal species or vegetable, since, this water is close to the recommended standards.

© 2012 Published by Elsevier Ltd. Selection and peer-review under responsibility of ISWEE’11 Keywords: solar energy, pH, conductivity, distillate, salination, irrigation.

Nomenclature

γ

conductivity ( µS/cm).

BOD

Biochemical Oxygen Demand

COD

Chemical oxygen demand

* Corresponding author. Tel.: +0-213-24-410-298; fax: +0-213-24-410-333. E-mail address: [email protected] 1877-7058 © 2012 Published by Elsevier Ltd. doi:10.1016/j.proeng.2012.01.1180

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1. Introduction Sea water and brackish water desalination is a promising technique for some countries mainly in the arid regions. It permits to achieve two objectives: drinking water supply and irrigation of agricultural surfaces. The problems encountered at the level of the purification station of Ouargla concerning the salinity of the purified waste water. The solar distillation is an interesting technique as it can be easily adapted in the arid regions, it has many advantage as it is simple, it can be easily carried out, not expensive and it is of rustic design. This is why our team of research has chosen this technique. Our study consists of using a solar still prototype of Chapel type as a desalination technique of the purified waste water; the experimental results are very satisfactory concerning the various physico-chemicals parameters. The developement realized in the solar energy field since 1872, indicates that the solar distillation is economically the most suitable technique mainly if the water quantity is not big. Many types of solar still configurations have been designed and used all over the world. At the same time many of researchers proposed mathematical models to describe the heat transfers and material transfers in the still solar [1-2].

In 1870, the first American patent on solar distillation was granted to wheeler and Evans. This work is based on an experimental study concerning the solar still and corrosion problems related to it. The researchers described greenhouse effect, analyzed in detail condensation and evaporation, moreover, they have discussed the black surface absorption, the still must be oriented in a manner to obtain the maximum incident solar radiation and so a high operating temperature [3]. Two years later, the Swedish engineer Charles Wilson has constructed the first industrial solar still. The installation was planned for the mining city of Las Salinas in the north of Chile. The still used basin of wood on a surface of 4.700 m2 to produce 23.000 liters pure water per day, is 4,9 liters per solar square meter of distiller. The structure functioned during 40 years [4-6]. In July 2005, a group of researchers of the faculty of Nancy have built concrete solar still on the Mauritanian littoral to satisfy the need for the population, this project has been carried out in partnership with the faculty of Nouakchott. The still is a greenhouse built out of cement, coating for the basin and the plexiglass or glass for the covered. Distilled water streams then towards a gutter of PVC. Now, the water pyramid technology is the most developed and used technique. its concept was installed in several tropical regions, in rural areas and the islands (Island, Gamby 2005, Inde2009 and Indonisia2009).It allows the transformation of salted water , worn water into water quality (drinking water, distilled water, water of irrigation), the production exceeds the 1250L water distilled per day for a surface of 600 m2 . It is a hybrid system; This concept is based on the principle of solar distillation, It is also used to collect rainwater during the winter season, the obtained water is tested and controlled regularly until it becomes drinkable through the disinfection and filtering technique[7]. Our work consists of testing in the first time the solar still of chapel type that exist in our center to analyze the distilled water obtained from purified worn water of the step of Ouargla. The studies will allow on the one hand to reduce the salinity of this water which is characterized by a conductivity of 9170 µS/cm, a salinity of 5.2 g/l and a pH of 7.38. on the other hand, some physico-chemicals parameters which have affect on this water to be studied.

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2.The waste-water of Ouargla step After cleaning, worn water is regarded as a second hand resource. It is used in many fields: irrigation, industry (industrial washing and transport of materials, industrial cooling,etc) and for municipal use (watering of parks and public gardens, roads cleaning, fights against fires,..etc). Waste-waters of Ouargla step comes from the various domestic used of water. It contains essentially an organic pollution. This waste water comes from bathrooms, kitchens they contain generally lot of grease, solvent and water valves; the treatment of this waste-water is done in lagoon by tertiary treatment. 3. Why the choice of a greenhouse solar distillation? Actually, there are many desalination systems which have been developed and uses in industry. The principal techniques are classified into two categories depending on the applied principal. The thermal process using a phase shift (water-vapor) like distillation and freezing and, membrane processes which use membranes like opposite osmosis. In fact, these two processes are the most commercialized in the desalination world market. But the major problem in a project of desalination by opposite osmosis is the excessively expensive cost of technique, on the contrary, the solar distillation by greenhouse is cheap, this is why, we have chosen this technique. 4. The greenhouse solar stiller process composition The structure is composed of a basin covered with an absorbing black layer and from a transparent covering out of glass or plastic. The lower part is isolated by a layer of wool glass or polystyrene Fig (a). The process consists of heating water directly by the solar radiation in a closed .enclosure covered with glazing. The water is heated until evaporation, the produced vapor which condenses is collected in the form of condensed in gutters inclined on the glazing. The principle is very simple and reliable Fig (b).

Fig .1 (a) concept of solar still; (b) The operating principle of solar still.

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5. Water physicochemical parameters determination The evaluation of the water quality requires many analyses, including the proportioning of multiple physicochemical parameters. These analyses are carried out by methods whose protocols are well defined. The water of the process comes from a water of lagoon of the STEP of Ouargla. The basin is filled with a water blade of 2,5cm, that is to say a volume of 20 liter of waste water purified for a surface of 1.17 m2 . Significant measurements of characterization of distilled water (salinity, electric conductivity, pH) were made with the help of a conductivimeter of the type Inolab (Cond level1). 6 . Results and discussions The purified waste water of the step of Ouargla distilled on the level of the UDES was analyzed. The experimental results illustrated in table N° 01 show a very important reduction in conductivity, this is explained by the solid deposit of the materials dissolved which existed in water of the process including salts at the bottom of the vat, these values do not cause any problem according to the organization FAO (Food and Agriculture Organization) The values of pH generally observed in natural environment go from 6 to 8,5; the pH measurement respects the standards required by world office of health OMS (see table 2), these values coincide, after GAUJOUS, 1995, with the normal pH of sea water and fresh water in calm zones [08] . Salinity is completely null; it is a positive point because the desired quantity of salts necessary for the irrigation can be introduced by an exact way in distilled water by means of demineralization. The values obtained and mentioned in table N° 03 show that they are in conformity with the standards of all the physicochemical parameters for the chemical demand for oxygen (COD) and the Biochemical Oxygen Demand (BOD). a water is polluted when, the dissolved oxygen concentration is located below a certain limiting value; because consumption oxygenate in water is mainly due to polluting substances which are biologically degradable[09-10] . Some inorganic substances belong to this category, but majority of made up which uses oxygen are of nature organic. Beside oxygen dissolves are given, the content NH4, of NO2 and PO4 [11-12]. Table1. Results of the physicochemical analyses

Water alimentation (purified waste water) Distilled water 30/10/2010 01/10/2010 02/10/2010 03/10/2010 04/10/2010

Amount

pH

Salinity g/l

Conductivity µS/cm

20L

8.03

5.2

9170

output (L) 4.5 3 3 2.5 3.5

pH 7.43 6.93 6.77 6.35 5.86

Salinity g/l 00 00 00 00 00

Conductivity µS/cm 167 240 112.5 49.9 38.6

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Table2.Standards according to FAO and OMS According to standards( FAO) Parameters

Conductivity ds/m Salinity mg/l

no problem

Used problems Low to be moderated

severe

<0.75 <450

0.75-2 450-2000

>3 >2000

According to standard (OMS) Parameters

Rang

pH

6.5-8.4 30-60 10-20 16-33

COD BOD MO

(mg/l) (mg/l) (mg/l)

Table3.Physic-chemicals parameters for the day of the 04/10/2010 Parameters

Unit

Results

COD BOD MO NH4 Oxygen dissolves NO2 PO4

mg d’O2/l mg d’O2/l mg d’O2/l mg/l mg/l mg/l mg/l

35.2 15.7 22,2 2 2.92 1 0.8

We also noticed that the percentage of production was of 80% for a surface of 1,17 m2. 7. Conclusion The purified waste water can involve economic repercussions for the farmers, because the high salinity of this water, affects the cultures of the palm trees. Solar still, if it is well adapted, it makes it possible to reduce salinity considerably. In this work, we are interested in purified waste water produced by the STEP of Ouargla, of which the aim to be to develop at agricultural ends. The reduction of salinity is the purpose of different physic-chemical parameters COD, BOD, pH, ect . This makes it possible to qualify this water, since the results obtained agreed with the standards of FAO and OMS. In prospect, we intend to carry out in a forthcoming stage a field of still of concrete effect on the level of the STEP of Ouargla on large scale in order to regulate the problem of salinity definitively.

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8. References [1] Malik M.A.S., Tiwari G.N., Kumar A and M.S. Sodha, Solar distillation. Pergamon press,New york, 1982. [2] Cooper P.I., Appleyard. The construction and performance of a three effect, wicktype, tilted solar still, Sun at work, 1967; 12-4. [3] Goff P. RUSTQUES ;1986. [4] Gravilish P. Parents of inventions.1783; Pat N°226; 9-7. [5] Harding J. paratus for solar distillation. pp. 284- 288, London;1883. [6] Pages J., Chaboub C., Laloë, P. Sagna, Sow I, A Fresh water Point in the Islands of Saloum, Examination of the Possibilities of the Solar still. Sénégalaise review of Agricultural Research and Halieutics. 1989 ; 2 ;34. [7] www.aaws.nl/home.htm; Aqua-Aero WaterSystems (AAWS) [8] Gaujous D. The pollution of the aquatic environments: memory, 2nd edition, Technique and documentation, Paris ; 1995; 220. [9] Gondard B , F. the cleansing of waste water, Thechnicité, 2003. [10] Grosclaude G, dir. The water, tome 1 : Natural environment and control And tome 2 : Uses and pollutants. Versailles, National institute of the agronomic research (Coll. « Un point sur… ») ;1999; 204 - 210 .

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[11] Aminot A,Chaussepied,M. handbook of the chemical analyses in seamen circle;1983, 395. [12] Gerard Miquel M. The water quality and of the cleansing in France. Report/ratio of the parliamentary office of evaluation of the scientific and technological choices ; 2002-2003; (ROPECST) ;215 .

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