1,721,082 research outputs found
Fluoride tracer test for the performance analysis of a basin used as a lagooning pre-treatment facility in a WTP
No full textThe water treatment plant (WTP) of the city of Torino (NW Italy), which treats about 40•106 m3/y of raw water from Po river, has a 15-ha basin used as a lagooning pre-treatment facility. Since the efficiency of the lagooning process in the removal of pollutants from raw water depends on the internal hydrodynamics of the basin, the hydraulic performance of the basin was studied by combining the results of a stimulus-response tracer test with the monitoring of the tracer (fluoride) concentration throughout the basin at different times. The outcomes of the test demonstrated that the system was efficiently mixed and could be assimilated to a continuous stirred reactor presenting no flow anomalies, with an actual mean residence time (RT) of 12.7 days, compared with a nominal RT of 18 days. This assured that dissolved contaminants (such as fluoride) coming from the river were efficiently diluted before entering the WTP. The axial dispersion coefficient calculated from the RT distribution was of approximately 47,300 m2/d. Three of the most popular formulae developed for the calculation of the axial dispersion coefficient provided results spreading over three orders of magnitude, thus showing their limitations. Finally, because of the width extent of the basin and the characteristics of its inflow, the 1-D advection - dispersion model failed in predicting the tracer concentration values in time at the outlet channel. On the contrary, the analytical solution of the 2-D advection - dispersion model proved to be suitable to fit the tracer concentration data over time at the outlet channel but it failed in describing the tracer distribution throughout the basin on the monitoring date
Circular Water Resources Integrating Sustainability and Innovation in Wastewater and Water Management
Full text linkOzonation treatments for the abatement of ammonia and organic substances
No full textThis work was aimed to test the performances of ozone in the abatement of ammonia and organic carbon from on-purpose made wastewaters. In the first part of the work solutions containing ammonia (20 mg/l), bromide (0-20 mg/l), bicarbonate (200 mg/l) and free OH- ions were employed to investigate the efficacy of ozone in the abatement of ammonia and to understand the influence of the free OH- and bicarbonate species on the ammonia oxidation rate. The experimental findings pointed out that ozone was effective in the oxidation of ammonia and its reaction rate rose as the concentration of bromide increased, with kinetics different from zero-order. The reaction rate was also affected by the presence of free OH-. In the second part of the experimentation the oxidation of organic carbon (as H5C8O4K) with ozone or bromide/ozone was investigated. Bromide had no effect on the reaction rate of the ozonation of organic carbon, but it seemed to slow down the process because of the competition between the oxidation of the phthalate and the formation of HOBr. The results obtained in the lab tests may be useful for the full scale design of an oxidation treatment with ozone which has effect on both ammonia and organic carbo
Recycling of steel from grinding scraps: Reclamation plant design and cost analysis
No full textAbout 10,000 t of grinding scraps are produced in and around Turin each year.
Grinding scraps result fromhigh speed tool cutting processes in the automobile and aerospace industries
in which a fluid, called lubrorefrigerant oil, is used to cool the cutting tool.
At present, grinding scraps are landfilled with an involved cost of 60 D /t, because the oil content (equal
to 6.40% byweight, b.w.) does not permit recovery in secondary smelt furnaces. Secondary smelt foundries
in fact only accept turnings, borings, scraps and oily machinery waste with an oil content no higher than
1% b.w.
The lubrorefrigerant fluid and heavy metal content of some grinding scrap samples have been determined.
The characterized waste was then subjected to several laboratory tests in order to single out the most
convenient operating conditions; these resulted to be: solid–liquid ratio 1:20 b.w., one washing phase,
surfactant amount equal to 0.15% b.w. (of the washing water amount), solid–rinsing water ratio 1:20 b.w.,
employment of docusate sodium salt.
The obtained results allowed a wet treatment to be arranged aimed at removing the cooling/cutting
fluid from the waste and at a subsequent recovery or recycling the steel. The wet treatment involves a
washing phase in a stirred reactor in the presence of docusate sodium salt, a filtration in a plate and frame
filter for the solid separation and a final rinse in order to eliminate the residual surfactant amount. The
treated material is finally pressed to minimize the residual moisture content. The oil is separated from
the exhausted washing water using a cloth filter. The oily sludge is eventually landfilled.
A cost analysis, carried out on the proposed reclamation plant, highlighted the economic advantage of
the treatment (total annual plant operating costs are equal to about 40 D /t of treated grinding scrap) in
comparison to the landfilling operation
Recovery of exhaust magnesium sands: Reclamation plant design and cost analysis
No full textAt present about 1200 t/year (the 45% b.w. of the solid waste production) of exhaust sands utilized for moulds and cores in the magnesium casting operations of a foundry plant in Northern Italy are landfilled. In fact, these sands cannot be subjected to the usual process of thermal regeneration because of the presence of potassium fluoborate, a salt which becomes plastic at high temperature values and binds silica grains in close heaps. A dissolution process was tested as a possible solution aimed at recovering both silica sands and potassium fluoborate. Some laboratory tests were performed in order to single out the best operative conditions (dissolution temperature, contact time and solid-liquid ratio) to obtain high quality products and raw water saving. On the ground of the obtained results a full scale plant for the sands reclamation was designed: for this plant the equipments design, the streams evaluation and the costs assessing were performed
Process design and economic evaluation for the recycling of exhaust sands from a magnesium foundry plant
No full text
Experimental study on the abatement of ammonia and organic carbon with ozone
No full textAmmonia and organic carbon are commonly widespread substances both in municipal and in industrial wastewaters and are usually treated having recourse to biological processes. This work presents some preliminary results useful for the design of an oxidation treatment using ozone which has effect on both ammonia and organic carbon. In the first part of the paper the oxidation of relatively low concentrations of ammonia (20 mg/l) by means of ozone and halides (chloride, bromide) was investigated with the aid of on-purpose made solutions. The experimental findings pointed out that the reaction rate of an oxidation process involving ammonia and ozone (or ozone and halides) is different from a zero-order kinetics and is affected by the presence of free OH- ions. In fact high pH values promote both the ozone (O3) decomposition in HO• radicals and the displacement of the ammonia equilibrium (NH3/NH4+) toward NH3. Chloride was found to have no effect on the ammonia oxidation, on the other hand, the joined effect of ozone and bromide results in a more effective and faster reaction, which generates lower amounts of nitrate in comparison with the oxidation due to the only ozone and/or HO• radicals. In the second part of the work the oxidation of organic carbon (as potassium hydrogen phthalate) with ozone or bromide/ozone was investigated. In the process of the ozonation of organic carbon, bromide has no effect on the reaction rate, but it seems to slow down the process because of the competition between the oxidation of the potassium hydrogen phthalate and the formation of HOBr. The obtained results show that the oxidation stops when the residual concentration of organic carbon reaches a value equal to about 50% of the initial valu
The role of boundary conditions in the bromide-enhanced ozonation process for ammonia nitrogen removal and nitrate minimization
Full text linkIn this study we investigated the effect of some operating conditions, such as the ratio between ammonia nitrogen
(AN), ozone and bromide, the initial value of water pH, the amount of bicarbonate used as a buffering
substance and the possible interference of organic matter, in a bromide-enhanced ozonation process for the
removal of AN. One of the peculiarities of this process is that the oxidation of AN proceeds through the generation
of reaction intermediates (bromoamines) and ends with molecular nitrogen (N2) with none or limited
generation of nitrate. The results of the ozonation tests carried out at a lab scale demonstrated that nitrate
generation could be lowered to less than 10% of the theoretical value when three conditions coexist. Firstly, all
the AN was present in the form of ammonium ion (NH4
+); this happened when the pH of the system was lower
than 8. Secondly, the ratio between bromide and ozone species was optimized, so as to avoid the presence of free
ozone and the consequent direct reaction with AN. Finally, the acidification induced by the oxidation of AN was
controlled with a buffering substance (bicarbonate). The generation of inorganic bromoamines from the reaction
between AN and bromide inhibits the oxidation of bromide to bromate. In fact, in the tests carried out in this
study the formation of bromate was limited to values of less than 0.2% of the molar bromate yield.
Organic substances in the form of glucose or potassium hydrogen phthalate (KHP) did not affect the removal
rate of AN. Conversely, the presence of substances such as phenol and hydroquinone, that had a higher reactivity
towards ozone and HOBr, determined a reduced AN removal rate and a bromate generation of one order of
magnitude higher than that observed with KHP and glucose. Finally, all the organic substances employed in the
study seemed to have a positive effect in reducing the nitrate generation (-30% of the value obtained with sole
AN)
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