FUNDAMENTOS DE CONTROL DE LA CALIDAD DEL AGUA TEBBUTT PDF

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Use of calcium sulphate dihydrate as an alternative to the conventional use of aluminium sulphate in the primary treatment of wastewater. The application of calcium sulphate dihydrate CaSO 4 '2H 2 O as a coagulant-flocculant alternative to the conventional use of aluminium sulphate in the primary treatment of wastewater was evaluated using a jar test apparatus.

Turbidity readings obtained for the doses of 4 g-f" 1 of aluminium sulphate varied from 3. The corresponding water pH was 3. Use of aluminium sulphate in the clarification of wastewater, thus, has financial and environmental implications due to the need to raise the pH of the treated water to 6. These findings suggest that the application of calcium sulphate di-hydrate CaSO 4 '2H 2 O as coagulant-flocculant, followed by the process of sedimentation, may be a suitable alternative for the clarification of wastewater.

However, the turbidity reported for the same doses was The effect of gypsum on turbidity warrants further research. Keywords: coagulation-flocculation, jar test, wastewater clarification, turbidity of water. Wastewater treatment systems are pre-emptive systems used to control water pollution reaching surface water bodies such as lakes, rivers and seas Perez et al.

Water quality is augmented through adequate wastewater treatment, thus having beneficial effects on both the environment and public health, as well as enhancing the potential for re-use Silva et al.

Water reuse and recycling is a necessary strategy for the sustainability of all of the economic activities which water supports Dominguez et al. However, appropriate treatment is necessary to ensure high efficiency, low cost and protection of the environment in the use of recycled water Arreguin and Mejia, Turbidity is considered an important parameter for evaluating the quality of a water body.

It indicates quality in terms of concentration of colloidal particles Arboleda, ; Harris, The higher the particle count, the more turbid the water is Yan et al.

These colloidal particles have, in most cases, a negative surface charge, causing repulsion between them Chen, This phenomenon is known as the diffuse double layer and it prevents the agglomeration of these particles Haydar and Anwar, Therefore, it is important to promote the destabilisation of the particles by adding cationic coagulants Simina et al. The later stages of water treatment depend largely on the success of the coagulation-flocculation-sedimentation process Diaz et al. Aluminium sulphate is conventionally used for the coag-ulation-flocculation process in primary treatment of waste-water.

Aluminium is considered a toxic element for plants and animals. Therefore, its presence in soils and aquatic systems can cause negative effects Delhaize and Ryan, ; Rapp and Bishop, Increased acidity in soils is associated with toxic levels of aluminium in plants Lidon and Barreiro, ; Mossor-Pietraszewska, ; Pacala, et al.

Therefore, there is interest in developing the use of alternative, new coagulants without this impact, since the benefits outweigh, in many cases, the costs of using them Murrillo, ; Qui, et al. It is, therefore, necessary to evaluate the performance of other coagulants in the clarification of wastewater. This study evaluated the use of calcium sulphate dihydrate CaSO 4 '2H 2 O gypsum as an alternative to aluminium sulphate in wastewater clarification, with the option to provide treated reused water for agricultural purposes, amongst other options.

It is important to emphasize that there are no antecedents for the use of calcium sulphate as a coagulant-flocculant. Hence, this study aimed to demonstrate the possibilities of its application as such, without changing the original characteristics of the sample waters and taking into account the variables which directly influence the success of the primary treatment process, i. Materials and methods. Sample collection and processing. Water samples were collected in 19 l plastic bottles.

The samples were collected at a single point with 4 replications. Origin of calcium sulphate dihydrate gypsum and its characteristics.

The product is known commercially as 'maximum agricultural gypsum' and comes in a powder form. The technical specifications are presented in Table 1. Variables for the characterisation of sample water. The study employed 3 response variables:. These 3 variables were measured in the raw wastewater before treatment was applied. Hydrogen ion concentration is an important parameter for both natural and sewage waters because it has an influence on the effluent conditions, which could affect both the flora and fauna of the receiving water body.

The final value of this parameter is governed by regulation of the maximum allowable discharges for wastewater going into sewers or receiving bodies. Electrical conductivity is also of great importance as it indicates the degree of mineralisation present in the wastewater. Turbidity is useful as an indicator of water quality and plays an important role in the performance of wastewater treatment plants; turbidity is an important consideration in water for human consumption and for use in food processing and beverage industries, amongst others.

Turbidity values are used to determine the degree of treatment required by a raw water source, its filterability and, consequently, the most suitable filtration rate, and the effectiveness of the processes of coagulation-flocculation, sedimentation and final filtration. EC and pH were measured with the Horiba D potentiometer. Turbidity was measured using a Hach U spectrophotometer Program A sub-sample of 5 m 3 was taken from the upper part of the sample in order to avoid sampling solids that had already settled.

The coagulants-flocculants used in this experiments were: calcium sulphate dihydrate Ca SO 4 2 H 2 O , a divalent compound, and aluminium sulphate with 18 molecules of water Al 2 SO 4 3 18 H 2 O , a trivalent compound. The doses of the 2 coagulant-flocculants for the treatment were 0. These doses were established after performing an initial test to determine the dose at which coagulation started. The sedimentation equipment jar test apparatus; Fig.

These simulate the mixing and settling conditions in a clarification plant. When the experiment is conducted in the laboratory, there is the advantage of being able to make 4 runs simultaneously with the help of the jar test apparatus. The engine has an electronic speed control from 0 to rmin -1 and the tachometer is mechanical. It operates on V and includes a fluorescent lamp base and 4 Armfield brand 1 l cups. After the characterisation of raw water, the standard doses of coagulants-flocculants were applied using the jar test apparatus, with the aim of defining the following parameters: raw water quality, rates of coagulation and flocculation, retention times, and pH adjustment.

The procedure used was as follows:. It was applied in the centre of the pallet where the vortex is formed, to ensure maximum dissemination and allowing the process to continue for another 60 s at the maximum speed. It is at this point that coagulation occurs. It is at this point that flocculation occurs. Each of the blades was carefully removed and the samples left to sit for 15 min - the settling time for this experiment. Statistical analysis. The results of the jar test with the respective doses for each of the treatments are shown in Table 2 and graphically presented in Figs.

Potential of hydrogen. Table 2 shows the variation of pH with respect to the incremental doses of coagulants used Fig. For the 1 gT -1 dose, a maximum value of 7. For addition of aluminium sulphate, the higher the dose of Al 2 SO 4 3 , the lower the pH becomes. It is important to note the effect of aluminium on pH. This implies a considerable reduction in the pH of the raw treated water when aluminium sulphate is used. The minimum dose also gave an acidic character to the water.

The raw water had the highest pH and the treated water that received a dose of 2. The likely chemical process involved is as follows: The raw water had a neutral pH; by adding aluminium sulphate it was hydrolysed to form a colloidal aluminium hydroxide and an equivalent amount of sulphuric acid in accordance with the following chemical equation:.

When using commercial aluminium sulphate, it is found that 1 gl -1 of aluminium sulphate destroys 0. Therefore, the pH variation with addition of this coagulant was minimal, and within the regulated range for treated effluent in Mexico.

The resulting neutral pH of the treated water is an advantage for reuse of the water. The ranges were within the values established by the regulations. It is important to note from Tables 2 and 3 that for both floccu-lant-coagulants the pH does not differ significantly between the different doses tested.

Electrical conductivity. Table 2 shows that increasing the dose of both coagulants results in an increase in electrical conductivity Fig. Martinez found that at pH values below 5.

The values of EC for both treatments are below 0. With respect to turbidity removal, the results for all doses of calcium sulphate di-hydrate CaSO 4 '2H 2 O tested were not encouraging.

From Table 2 , the original turbidity of the raw water was Use of aluminium sulphate, by contrast, resulted in a clearance rate of The turbidity results achieved for the different doses of the two coagulants studied were significantly different in most cases Table 2.

Table 3 presents the coefficients of variation around the mean of the results for all doses of each coagulant. The coefficients of variation for turbidity were Gypsum retails at a price of USD0. This study was a first step in assessing the suitability of calcium sulphate di-hydrate as coagulant-flocculant in the primary treatment of wastewater. Due to the complexity of the coagulation-flocculation process, further investigation and the refinement of various elements is required.

The alternative use of calcium sulphate di-hydrate CaSO 4 '2H 2 O as a coagulant-flocculant in the primary treatment of wastewater may be economically and environmentally beneficial. However, it is well known that an 'at-source' waste-water treatment plant represents a complex system.

Therefore, more research is needed to understand the coagulation-flocculation phenomena, and to establish the specific isoelectric point for calcium sulphate di-hydrate CaSO 4 '2H 2 O , i. This project was carried out by the Ph. Water Resources Development and Management. Plant Physiol. Water Air Soil Pollut. Water Sci.

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Fundamentos de control de la calidad del agua

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FUNDAMENTOS DE CONTROL DE LA CALIDAD DEL AGUA TEBBUTT PDF

Fundamentos de control de la calidad del agua has 1 rating and 0 reviews. Get this from a library! Fundamentos de control de la calidad del agua. Fundamentos de control de la calidad del agua by T. Tebbutt, January , Editorial Limusa S. Increased acidity in soils is associated with toxic levels of aluminium in plants Lidon and Barreiro, ; Mossor-Pietraszewska, ; Pacala, et al. These colloidal particles have, in most cases, a negative surface charge, causing repulsion between them Chen, Turbidity values are used to determine the degree of treatment required by a raw water source, fundamfntos filterability and, consequently, the most suitable filtration rate, and the effectiveness of the processes of coagulation-flocculation, sedimentation and final filtration.

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Use of calcium sulphate dihydrate as an alternative to the conventional use of aluminium sulphate in the primary treatment of wastewater. The application of calcium sulphate dihydrate CaSO 4 '2H 2 O as a coagulant-flocculant alternative to the conventional use of aluminium sulphate in the primary treatment of wastewater was evaluated using a jar test apparatus. Turbidity readings obtained for the doses of 4 g-f" 1 of aluminium sulphate varied from 3. The corresponding water pH was 3.

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