Environmentally sustainable cement composition, its use for inerting dredging sediments/sludges, relative method and apparatus for inerting

Abstract

A cement composition based on a sulfoaluminate clinker is described, together with its use for agglomerating and inerting sediment/dredging sludge, and the relative inerting method and apparatus.

Claims

1. A method for inerting sediment/dredging sludge, which comprises the following steps: sucking/removing sediment from a bottom of a water basin forming dredging sludge; feeding the dredging sludge to a mixing and sedimentation chamber; feeding a cement composition to the mixing and sedimentation chamber, the cement composition comprising a sulfoaluminate clinker in a percentage ranging from 75 to 97.9% by weight with respect to the weight of the cement, ferrous sulfate (FeSO.sub.4nH.sub.2O) in a percentage ranging from 2 to 20% by weight with respect to the weight of the cement, and an accelerating agent of a hydration reaction in a percentage ranging from 0.1 to 5% by weight with respect to the weight of the cement, said accelerating agent of the hydration reaction being selected from the group consisting of alkaline metal carbonate, sulfate, or nitrate salts; mixing of the dredging sludge with the cement composition for a time ranging from 10 seconds to 5 minutes; sedimentation of the mixture thus obtained for a time ranging from 2 to 120 minutes; solidification of the sediment thus obtained for a time ranging from 1 to 24 hours; the entire method being carried out underwater.

2. The method for inerting sediment/dredging sludge according to claim 1, comprising the step of filtering and sieving the dredging sludge before feeding it to the mixing and sedimentation chamber.

3. The method for inerting sediment/dredging sludge according to claim 1, comprising the step of transferring the sedimented mixture to a maturation tank, before the solidification step.

4. The method for inerting sediment/dredging sludge according to claim 1, further comprising the following steps prior to the step of mixing: covering at least a portion of the bottom of a water basin with a hollow structure open below for defining the mixing and sedimentation chamber containing the sediment to be treated.

5. The method for inerting sediment/dredging sludge according to claim 4, wherein the step of covering at least a portion of the bottom of a water basin with the hollow structure comprises allowing the open end of the hollow structure to penetrate the bottom for at least a certain length.

6. The method for inerting sediment/dredging sludge according to claim 4, comprising the step of expelling the mixture of cement composition and sediment from the hollow structure through an expulsion opening of said hollow structure, before the sedimentation and solidification steps take place.

7. The method for inerting sediment/dredging sludge according to claim 6, comprising the step of gradually advancing the hollow structure in an advance direction and expelling the material treated in the opposite direction with respect to the advance direction.

8. The method for inerting sediment/dredging sludge according to claim 4, comprising the step of removing the hollow structure from the portion of the bottom once the sedimentation step has been completed.

Description

(1) Further characteristics and advantages of the present invention will appear evident from the following detailed description of some of its preferred embodiments, referring to the enclosed drawings. The various characteristics in the single configurations can be combined with each other as desired according to the above description, should advantage be taken of the benefits specifically deriving from a particular combination.

(2) In said drawings:

(3) FIG. 1 is a schematic representation of a first embodiment of a sediment inerting plant according to the present invention;

(4) FIG. 2 is a schematic representation of a second embodiment of a sediment inerting plant according to the present invention.

(5) In the following description, for illustrating the figures, identical reference numbers are used for indicating construction elements having the same function.

(6) With reference to FIG. 1, this shows a plant 100 for inerting sediment comprising a movable barge 101, in this case a dredger, on which a tank 102 of cement composition is positioned.

(7) The tank 102 is connected to an inlet opening 13 of an inerting apparatus 10.

(8) Said apparatus 10 comprises a hollow structure open below which, in the embodiment illustrated, is in the form of a bell-shaped body 11 having a cubic conformation which is positioned on the bottom 20 of a water basin for defining, with the portion of bottom 20 which it covers, a confined mixing chamber 12.

(9) The hollow structure 11 comprises mixing elements 14 which, in the preferred embodiment illustrated, are produced in the form of blade cylinders.

(10) The rotation of the cylinders 14 therefore causes a mixing of the cement composition 22 at the inlet with the sediments 21 present in the bottom portion 20 covered by the hollow structure 11.

(11) The mixing elements 14 also envisage at least one vortex breaker (not illustrated).

(12) The hollow structure 11 of the embodiment of FIG. 1 comprises an expulsion opening 15 of the mixture composed of sediment and cement composition.

(13) In this way, it is possible to operate in continuous as the sedimentation phase takes place on the open bottom of the water basin after the mixture has been expelled from the mixing chamber.

(14) Motorized forward advancing means of the inerting apparatus are also envisaged, which can also be of the automatic type. In this case, at least one turbidity sensor is envisaged, which provides a signal on the basis of which the motorized means are driven.

(15) FIG. 2 illustrates an embodiment variant of the inerting plant 100 of the present invention which differs from the embodiment of FIG. 1 in particular for the production of the inerting apparatus 10.

(16) The inerting apparatus 10 illustrated in FIG. 2 has no expulsion openings as the sedimentation of the mixture of sediments and cement composition also takes place in the mixing chamber.

(17) Once the sedimentation phase has been completed, the hollow structure 11 is removed from the treated portion of bottom 20, to be positioned in correspondence with a new portion of bottom 20 to be treated.

(18) In particular, according to the present invention, the cement composition in the inerting plant is the composition previously described and exemplified hereunder.

(19) The inerting method implemented by the plant of FIG. 1 is as follows.

(20) At least a portion of a bottom 20 of a water basin is initially covered by the bell-shaped body 11 of the inerting apparatus 10 so as to define a confined mixing chamber 12 containing sediments 21 to be treated.

(21) In particular, the open end 11a of the hollow structure 11 is caused to penetrate the bottom 20 for at least a length.

(22) The cement composition is introduced into the mixing chamber 12, and contemporaneously, the fluid present in the mixing chamber 12 is stirred in order to lift at least part of the sediments 21 covered by the bell-shaped body 11.

(23) There is therefore a mixing phase of sediments with the cement composition.

(24) In the plant 100 of FIG. 1, the mixture is then expelled from the mixing chamber 12 so that the subsequent sedimentation and solidification phases take place outside the inerting apparatus 10, on the bottom 20 of the water basin.

(25) The bell-shaped body 11 is caused to advance along a certain advance direction A, contemporaneously with the expulsion of the mixture from the mixing chamber 12.

(26) Unlike the plant 100 of FIG. 1, the embodiment of FIG. 2 envisages that the sedimentation be carried out in the mixing chamber 12 and the bell-shaped body 11 is subsequently removed. Consequently only the complete solidification takes place outside the inerting apparatus 10.

(27) Other characteristics and advantages of the invention will appear evident from the following illustrative and non-limiting examples.

(28) The objective of the examples provided hereunder is to demonstrate the efficiency of cement compositions according to the present invention in the agglomeration and inerting of sediment/dredging sludge.

(29) In particular, sediment/sludge and water were used with the characteristics indicated hereunder.

(30) Harbour sludge, cement compositions and water were used in various combinations for each test, so that these example reflect, as closely as possible, the actual situation that exists on the bottom of the water basin to be treated.

(31) The test marine sediments used in the following examples consist of sediment/sludge removed by pumping from the port of Genoa and are representative of various types of marine sediment/harbour sludge.

(32) The sediment/sludge was characterized from the point of view of particle-size and chemical composition.

(33) The particle-size of the sludge was evaluated wet by sieving on standardized net sieves with the characteristics indicated in Table 1.

(34) TABLE-US-00001 TABLE 1 Standardized sieves used for sieving the sludge ASTM - E11 Net span (mesh) (μm) Sieve 1 100 150 Sieve 2 140 106 Sieve 3 270 53

(35) Table 2 hereunder indicates the particle-size distribution of the three examples of harbour sludge used in the experimental tests, object of the following examples.

(36) TABLE-US-00002 TABLE 2 Particle-size distribution of the harbour sludge used Sludge 1 Sludge 2 Sludge 3 Fraction, Fraction, Fraction, Size weight % weight % weight %  <50 μm 29 38 36  50 μm-100 μm 15 35 30 100 μm-150 μm 7 19 12 >150 μm 49 8 22

(37) The sediment consisted of a higher fraction (>150 μm) composed of sand and grit with an extremely heterogeneous particle-size, two fractions (with a particle-size ranging from 100 μm to 150 μm and from 50 μm to 100 μm) composed of fine and very fine sand and a lower fraction (<50 μm) corresponding to lime. The lower fraction is that which is mainly responsible for the turbidity of the water for considerable times during the dredging operations and moving of the sediment.

(38) The sludge was analyzed to determine the main components and typical pollutants. Table 3 indicates the composition of the three examples of harbour sludge used in the experimental tests, object of the following examples.

(39) TABLE-US-00003 TABLE 3 Main polluting components present in the harbour sludge used Sludge 1 Sludge 2 Sludge 3 Contaminant Concentration Concentration Concentration Heavy metals (mg/Kg ss) (mg/Kg ss) (mg/Kg ss) Al 15888 25000 18000 Fe 30978 15000 7670 Pb 1125 227 212 Cu 1382 110 112 Zn 14473 363 372 As 20 10 6 Cr 75 450 100 Cd 15.8 <1 <1 Hg 3.9 1.4 2.8 Ni 34 45 55 V 27 54 44 Organic carbon 50300 31000 42500 Light and heavy 3046 1200 1520 hydrocarbons Aromatic 0.158 1.621 2000 polycyclic hydrocarbons (IPA) Polychloro- 1.54 0.110 0.120 biphenyls (PCB) ss means dry solid

(40) The sludge used in the following examples is under reducing conditions. In general, as previously indicated, a sludge can contain variable concentrations, also high, of numerous heavy metals with toxic characteristics (for example Cr, Cu, Pb), polluting organic compounds such as aromatic polycyclic hydrocarbons and polychlorobiphenyls, pesticides and dioxins.

(41) In particular, the sludge pumped and used in the present examples contains a quantity of water equal to about 70% by weight.

(42) Table 4 below indicates the composition of three samples of seawater used in the experimental tests, object of the following examples.

(43) TABLE-US-00004 TABLE 4 Analysis of seawater Composition A Composition B Composition C (supernatant) (supernatant) (supernatant) Compound sludge 1) sludge 2) sludge 3) Chlorides (Cl.sup.−) (mg/l) 21.200 18.980 20800 Sodium (Na.sup.+) (mg/l) 11.800 10.556 11900 Sulfates (SO.sub.4.sup.2−) (mg/l) 2.950 2.649 3060 Magnesium (Mg.sup.2+) 1.403 1.262 1360 (mg/l) Calcium (Ca.sup.2+) (mg/l) 423 400 355 Potassium (K.sup.+) (mg/l) 463 380 663 Bicarbonates (HCO.sub.3.sup.−) — 140 3 (mg/l) Strontium (Sr.sup.2+) (mg/l) — 13 7.69 Bromides (Br.sup.−) (mg/l) 155 65 <100 Borates (BO.sub.3.sup.3−) (mg/l) 72 26 18 Fluorides (F.sup.−) (mg/l) — 1 1 Silicates (SiO.sub.3.sup.2−) — 1 1 (mg/l) Iodide (I.sup.−) (mg/l) 2 <1 <1 Total dissolved solids 38600 34483 38040 (mg/l) aluminium μg/l <5 <5 <5 arsenic μg/l < 1 4 4 cadmium μg/l <0.1 <0.1 <0.1 chromium μg/l <1 24000 176 iron μg/l <5 <5 <5 copper μg/l <1 3 3 zinc μg/l <1 3 3 total hydrocarbons <10 <10 50 μg/l aromatic polycyclic <0.01 <0.01 35.6 hydrocarbons μg/l

(44) The compositions described above refer to the analysis of the water pumped together with the sludge previously described.

(45) As already mentioned, the objective of the examples provided hereunder is to demonstrate the efficiency of various cement compositions according to the present invention in the agglomeration and inerting of sediment/dredging sludge.

(46) In particular, the sedimentation, clarification and setting steps were carried out and evaluated, using the following methods and equipment.

(47) Jar Tester Apparatus

(48) A jar tester is a commercially available apparatus (for example flocculators produced by Velp Scientifica (http://www.velp.com/it/prodotti/linea/2/famiglia/32/fl occulatori) or by Phipps and Bird (http:/www.phippsbird.com/)) which allows the behaviour in sedimentation and clarification of water or a turbid product to be simultaneously compared, following the contemporaneous addition of various substances or the addition of the same substance in different quantities.

(49) A jar tester is an instrument consisting of various mechanical stirrers that operate contemporaneously, and is widely used for simulating mixing, sedimentation and clarification conditions in water purification plants.

(50) The apparatus consists of a plurality of transparent containers, all having the same dimension, in which the samples are introduced and mixed at the same adjustable rate for the times established for each experiment, by means of stirring/rotating blades all having the same dimensions, that can be regulated in height and velocity.

(51) Clarification Evaluation

(52) The clarification efficiency, i.e. the efficiency in abating the turbidity, was evaluated by means of absorbance measurements with a UV/Vis spectrophotometer according to the method APAT-IRSA-CNR 2110—Turbidity Ed. 2003. When the absorbance value was higher than 40 NTU, the sample was diluted, taking this into account in the expression of the result.

(53) The abatement percentage of the turbidity at generic time t, following the addition of the cement, was calculated with respect to the turbidity of the sample of sediment at the same time t, as follows:

(54) $\left[\mathrm{Turbidity}\mathrm{abatement}\mathrm{efficiency}\right]\%=\frac{\left(\mathrm{Turbidity}\mathrm{of}\mathrm{sludge}\mathrm{sample}\right)-\left(\mathrm{Turbidity}\mathrm{of}\mathrm{treated}\mathrm{sample}\right)}{\left(\mathrm{Turbidity}\mathrm{of}\mathrm{sludge}\mathrm{sample}\right)}\times 100$
Setting evaluation with a Vicat-type apparatus

(55) The apparatus used is analogous to that described in the reference standard UNI EN 196-3, consisting of a sliding rod that has, at the lower end, a needle or conical tip, on which one or two cylinders having a known mass (150 g) act.

(56) Cement and water pastes were prepared for effecting the setting test, in a weight ratio of 1:2 and pastes of water, cement and sludge with a solid/water weight ratio of 1:2.

(57) The pastes thus composed were positioned in small jars and placed under the sliding rod. At this point, the needle or tip was positioned so as to touch the upper surface of the paste and was left to descend under its own weight (150 g): the first measurement is effected when the needle or tip is on the surface of the paste and then the subsequent measurement when the needle or tip reaches the run-end with its own weight: the penetration is given by the delta between these two measurement data: the start of the setting is defined as the moment in which the needle or tip stops at 3 mm from the bottom and the end of the setting is the moment in which the needle penetrates the paste for not more than 0.5 mm.

(58) In the following examples, this test allowed the setting efficiency of the cement compositions of the present invention described in the examples, to be evaluated.

(59) The tests carried out with this apparatus directly under the treatment conditions described in the examples were effected with the following rods:

(60) 1) diameter 6 mm, weight 87 g;

(61) 2) diameter 3 mm, weight 6 g.

EXAMPLE 1

(62) Preparation of the Cement Compositions.

(63) The cement compositions indicated in Table 5 below were prepared:

(64) TABLE-US-00005 TABLE 5 Cement compositions Clinker FeSO.sub.4 (%) LiCO.sub.3 (%) NaCO.sub.3 (%) Mixture 1 Alipre ® 5 1 — Invention Mixture 2 Alipre ® 5 2 — Invention Mixture 3 Alipre ® 5 — — Comparison Mixture 4 Alipre ® — — — Comparison Mixture 5 Portland 52.5 — — — Comparison R Mixture 6 Alipre ® 10 2 — Invention Mixture 7 Alipre ® 10 — 5 Invention
Clinker Alipre® is a commercial product having the following composition:
Chemical Constituents (% XRF Analysis)
CaO 42; SiO.sub.2 6; Al.sub.2O.sub.3 32; Fe.sub.2O.sub.3 1; SO.sub.3 14+minor oxides
Mineralogical Composition
C4A3$58%, C2S 20%+minor phases
The volume mass and average fineness of Alipre® are:
Blaine specific surface 4,500 cm.sup.2/g;
Volume mass 2.8 g/cm.sup.3.

EXAMPLE 2

(65) Sedimented Volume/Abatement Efficiency, Setting Time

(66) 800 ml of seawater (Table 4, Composition A) were added to 90 g of sediment/harbour sludge (Tables 2 and 3, Sludge 1) in a beaker having a volume of 1 l. The sediment and seawater were mixed at a rate of about 200 rpm using the Jar Tester equipment described above.

(67) 100 g of each cement composition listed in Table 5 were then added to all the containers and the stirring was interrupted after about 1 minute.

(68) Two containers were prepared for the comparative tests, the first containing only sludge 1 (90 g) and seawater (composition A, 800 ml) and the second containing sludge 1 (90 g), seawater (composition A, 800 ml) FeSO.sub.4 (5 g) and LiCO.sub.3 (2 g).

(69) After about 15 minutes, the quality of the clarification was evaluated by measuring the turbidity of each sample, following the method indicated above. After about 30 minutes, the volume of the sediment was measured and after about 120 minutes the tendency to consolidate was measured with the Vicat-type equipment described above, with a rod weighing 85 g.

(70) The maximum turbidity abatement that can be obtained is that in which the seawater overlying the sediment is under calm conditions and corresponds to 95%.

(71) TABLE-US-00006 TABLE 6 Turbidity abatement Sediment efficiency after 15 Penetration depth Sludge 1 + volume after minutes of (85 g) after 120 Water + 30 minutes, ml sedimentation, % minutes, cm Mixture 1 290 85 0.1 Mixture 2 300 89 0.1 Mixture 3 300 82 Complete as far as the bottom of the container Mixture 4 470 88 Complete as far as the bottom of the container Mixture 5 350 94 Complete as far as the bottom of the container Mixture 6 350 82 0.1 Mixture 7 350 84 0.3 FeSO.sub.4 and Not 51 Complete as far as LiCO.sub.3 observable the bottom of the container

(72) The addition of the cement compositions according to the present invention allows an interface to be observed between solids that settle and clarified water and enables the assessment of the volume of the solid material that has settled on the bottom of the container with values ranging from 290 to 390 ml. If the values are higher, due to the dredging times and volumes involved, the process is considered to be ineffective.

(73) In particular, as far as the clarification capacity of the cement compositions according to the present invention is concerned, the turbidity abatement data indicated in Table 6 show that the mixtures allow turbidity abatement values to be obtained, within 15 minutes, with values ranging from 80 to 94%.

(74) The sole addition of ferrous sulfate and lithium carbonate to the sludge in concentrations comparable to those present in the cement mixtures according to the present invention, does not lead to a marked improvement in the sedimentation and clarification.

(75) With respect to the setting capacity, it should be noted that not all the cement compositions tested are capable of starting the consolidation process in the presence of sludge and seawater. Mixture 1, Mixture 2 and Mixture 6 (cement compositions according to the present invention) were the only ones capable of consolidating so as to prevent the penetration of the rod of the penetrometer.

(76) It can therefore be seen from the data that the best compromise in terms of final volume of sediment produced, quality of the clarified product and setting capacity is represented by Mixture 1, Mixture 2 and Mixture 6, said mixtures falling within the qualitative and quantitative ranges according to the claims of the present patent application.

EXAMPLE 3

(77) Chromium Abatement Tests

(78) 800 ml of seawater having Composition B (Table 4) were added to 90 g of harbour sludge 2 (tables 2 and 3) in a beaker as described in Example 2. The sediment and seawater were mixed at a rate of about 200 rpm using the Jar Tester equipment described above.

(79) 100 g of each cement composition listed in Table 5, prepared according to Example 1 were then added to all the containers, and the stirring was interrupted after about 1 minute.

(80) The concentration of chromium was then measured in the liquid overlying the volume of sediment, after 24 hours, and the chromium abatement efficiency was determined as follows:

(81) $\left[\mathrm{Efficiency}\mathrm{of}\mathrm{chromium}\mathrm{abatement}\right]\%=\frac{\begin{array}{c}\left[\mathrm{Starting}\mathrm{chromium}\mathrm{concentration}\right]-\\ \left[\mathrm{Chromium}\mathrm{concentration}\mathrm{after}24\mathrm{hours}\right]\end{array}}{\left[\mathrm{Starting}\mathrm{chromium}\mathrm{concentration}\right]}\times 100$
Obtaining the results indicated in Table 7

(82) TABLE-US-00007 TABLE 7 Chromium abatement Chromium abatement efficiency in seawater 2, % Mixture 1 99.5 Mixture 2 99.5 Mixture 3 81 Mixture 4 0 Mixture 5 0 Mixture 6 99.5 Mixture 7 99.5

(83) It can be observed that Mixture 6 (containing Portland alone) does not allow the abatement of chromium in the seawater overlying the sediment consisting of sludge and the cement mixture. The best results were obtained with Mixture 1, Mixture 2 and Mixture 6 which allow chromium abatement efficiencies higher than 95%. The best behaviour was obtained with Mixture 1, Mixture 2 and Mixture 6.

(84) On comparing the data obtained in the previous Example 2 with the data of the present Example 3, it can be seen that the presence of ferrous sulfate, supported by the presence of lithium carbonate, optimizes the capturing of the chromium precipitate in the structure of the sediment volume, completely removing it from the water.

EXAMPLE 4

(85) Release Tests of Organic Contaminants

(86) About 200 g of Mixture 1 were added, under stirring at 200 rpm, to 200 g of Sludge 1 with 2 l of seawater having composition A as supernatant. After about 1 minute, the stirring was interrupted to allow the sedimentation, clarification and setting as described in Example 2. A sample of clarified water was then collected to verify the presence of total Hydrocarbons, Aromatic Polycyclic Hydrocarbons (APH) and Polychlorobiphenyls (PCB). Table 8 summarizes the data obtained.

(87) TABLE-US-00008 TABLE 8 Analysis of the release of organic contaminants on the part of the sludge after treatment with Mixture 1 Concentration of contaminants Contaminants Analysis method after treatment with Mixture 1 Total hydrocarbons ISO 9377-2: 2002   <10 μg/l Aromatic polycyclic EPA 3510C 1996 + benzo(a)anthracene hydrocarbons EPA 8270D 200 benzo(b)fluoranthene chrysene indene(1,2,3-c,d)pyrene  <0.01 μg/l benzo(a)pyrene benzo(g,h,i)perylene dibenzo(a,h)anthracene total (31, 32, 33, 36) <0.001 μg/l benzo(k)fluoranthene pyrene <0.005 μg/l Polychlorobiphenyls EPA 3510C 1996 + Each PCB < 0.005 μg/l EPA 8270D 2007

(88) Starting from Sludge 1 with a content of about 3,050 mg/Kg ss of total Hydrocarbons, about 158 mg/Kg ss of Aromatic Polycyclic Hydrocarbons and 1.54 mg/Kg ss of Polychlorobiphenyls, the treatment with the cement compositions according to the present invention does not cause the rapid release into water of organic contaminants present in the sludge following the same treatment.

EXAMPLE 5

(89) Capture Tests of Organic Contaminants

(90) About 200 g of Mixture 1 were added, under stirring at 200 rpm, to 200 g of Sludge 3 with 2 l of seawater having composition C as supernatant. After about 1 minute, the stirring was interrupted to allow the sedimentation, clarification and setting as described in Example 2. Samples of clarified water were collected to verify the presence of Aromatic Polycyclic Hydrocarbons (APH) after 1 hour and after 24 hours (Table 10) (according to the method EPA 3510C 1996+EPA 8270D 2007).

(91) TABLE-US-00009 TABLE 9 Analysis of the release of organic contaminants on the part of the sludge after treatment with Mixture 1 APH concentration APH concentration APH concentration in sea water in the clarified in the clarified (composition C) water 1 hour after water 24 hours after before treatment with treatment with treatment with Mixture 1, μg/l Mixture 1, μg/l Mixture 1, μg/l acenaphthene <0.01 <0.01 <0.01 acenaphthylene 0.82 0.5 0.39 anthracene 0.83 0.65 0.33 benzo(e)pyrene 1.967 0.298 0.329 benzo(j)fluoranthene 1.029 0.155 0.255 dibenzo(a,e)pyrene 1.959 0.005 0.005 phenanthrene 2.4 2.25 0.91 fluoranthene 3.2 0.96 0.75 fluorene 0.33 0.24 0.25 benzo(a)anthracene 3.58 0.85 0.63 benzo(a)pyrene 2.821 0.413 0.454 benzo(b)fluoranthene 1.42 0.21 0.26 benzo(k)fluoranthene 1.485 0.217 0.268 benzo(g,h,i)perylene 1.486 0.184 0.242 chrysene 3 0.58 0.61 dibenzo(a,h)anthracene 0.643 0.001 0.073 indeno(1,2,3-c,d)pyrene 1.47 0.18 0.21 pyrene 2.17 0.589 0.476 Total (31, 32, 33, 36) 5.861 0.791 0.98
After treatment with Mixture 1, the organic contaminants initially present in the seawater were mostly removed from the water matrix with an overall removal efficiency from 75% after 1 hour to 80% after 24 hours.

EXAMPLE 6

(92) Simulation of the Setting Process in a Tank Under Conditions Similar to Real Conditions.

(93) A layer of sludge 1 having an overall height of 10 cm and seawater having composition A as supernatant for an overall height of about 1 m, are present on the bottom of a container having a volume of about 2.5 m.sup.3 with a base of about 1 m×2 m. The supernatant water was clarified before proceeding with the simulation.

(94) Plastic pipes having the following diameters: 7 cm, 10 cm, 20 cm, were inserted on the bottom of the container, for almost the whole depth of the sludge, without moving the same.

(95) A stirrer was inserted in each pipe for the mixing operation. The mixing conditions applied were the same as those described in Example 2. During the mixing phase, Mixture 2 was added to the pipes having different diameters, in the quantities indicated in Table 10, which approximately correspond to a sludge/cement ratio of 1/1. The mixing/stirring was maintained for about 2 minutes.

(96) During the mixing operations inside the pipes, no turbidity phenomena of the sea water outside the pipes was observed. With reference to the setting capacity, the values found are in compliance with the data indicated in Example 2, again referring to Mixture 2.

(97) After about 120 minutes, the plastic pipes were extracted so that their content remained inside the tank. No consistent turbidity phenomena were observed. When the pipes were extracted from the container, their content, remaining inside the tank, proved to consist of blocks having their own form and hardness, in the setting phase.

(98) After about 24 hours the end-products, completely consolidated, were extracted from the tank and the turbidity phenomena were negligible.

(99) TABLE-US-00010 TABLE 10 Pipe diameter, cm Quantity of Mixture 2, kg 7 0.67 10 1.37 20 5.47