IC14D User`s Manual and Exercise Guide
Contents
1. For this experience we are using flocculants produced by THE DOW CHEMICAL COMPANY a company that is present on the Italian market through UNIONE CHIMICA EUROPEA The polyelectrolytes selected for the tests are AP273 AP30 AP45 MG200 CP35 all of them with registered mark SEPARAN 2 A trademark of THE DOW CHEMICAL COMPANY Dissolution and solution preparation modalities IC 14D User s Manual 23 Exercises Prepare a 0 5 starting solution by adding the polyelectrolyte to the water in small quantities while stirring all along When the solution has become clear and homogeneous you can dilute it with water to the desired concentration 4 4 1 Execution of the test Perform experience no 1 up to point o then start adding flocculant and monitor settling velocity Perform the experience using all the types of polyelectrolytes available and listed above complete the table below with the analytical and the experimental data obtained Type of Settling time Dry concentration solid in polyelectrolyte of sludge suspension Without flocculant AP 273 AP 45 AP 30 MG 200 CP 35 Based on the values measured and entered in the table we can choose the most appropriate type of polyelectrolyte and then use it to perform another experience according to the same modalities and using in addition to the polyelectrolyte one litre of 0 35 ferric chloride solution in this manner we shall have2. In conclusion it is preferable to limit the pH value to lt 8 5 even if at higher values the process would be more effective Naturally this applies only if the difference in behaviour is not excessive 4 6 Experience no 6 Influence of the quantity of polyelectrolyte on flocculation Having identified through experiences 4 and 5 the best type of polyelectrolyte and the best pH value with this experience we shall assess the quantity of flocculant to be used leaving the other process parameters unaltered and namely e polyelectrolyte dilution 0 035 e add in rate 500 cc h and at all events a rate ensuring that the solution is added at an even pace over a time period corresponding to the passage of the 70 It of water to be treated e type of polyelectrolyte as identified in Experience no 4 e pH of the medium as identified in Experience no 5 Modalities of dissolution and preparation of the polyelectrolyte solution Prepare a 0 5 starting solution by adding the polyelectrolyte to the water in small quantities while stirring all along When the solution has become clear and homogeneous you can dilute it with water to the desired concentration Since the concentration of the polyelectrolyte solution used is kept constant the quantity of solution added will necessarily have to be changed in order to be able to vary the percentage of polyelectrolyte As a rule when the quantity of polyelectrolyte increases this achieves a
3. Synoptic view of system l Feed tank 13 Feed valve tank 4 2 Oxidising reducing agent tank 14 Feed valve tank 6 3 Acid base tank 15 Oxide reduction control valve 4 Oxide reduction tank 16 Acid base control valve 5 Settling tank 17 Discharge valve tank 4 6 Neutralisation tank 18 Discharge valve tank 5 7 Agitator tank 6 19 Discharge valve tank 6 6 Agitator tank 4 22 Filter tank 1 9 Agitator tank 5 23 Filter tank 2 10 Agitator tank 1 24 Filter tank 3 11 Acid base solenoid valve 78 pH meter 12 Oxide reduction solenoid valve 79 rH meter The water to be treated is prepared in tank 1 by adding the pollutants specified for the test By means of the control valves 13 the water is transferred into the oxide reduction tank 4 where the reactant is made to enter through the opening of valve 15 and solenoid valve 12 which in its turn is governed by the rH 79 control instrument After that the water is transferred to the neutralisation tank 6 to which the precipitating neutralising agent contained in tank 3 is added and whose quantity is controlled by valve 16 and by the pH control instrument 78 which works on solenoid valve 11 In the neutralisation tank 6 in order to activate the precipitation process it is possible to add a flocculant element This is dosed by means of a special graduated glass vessel equipped with a faucet Finally the water reaches the settler 5 which sep
4. the laboratory s water discharge system 3 Check the functionality of the pH and rH instruments Fig 3 1 Discharge manifold 3 1 1 pH instrument Set the selector ref 82 fig 2 3 on basification place a sample of acid liquid in a container add hydrochloric acid and introduce the pH probe set the instrument on set point 8 check whether indicator light ref 65 fig 2 3 lights up solenoid valve open add a small quantity of sodium hydroxide to make the liquid basic and wait until the indicator light ref 65 fig 2 3 goes out solenoid valve closed Always check with litmus paper the readings given by the instrument 3 1 2 rH instrument Set the selector ref 83 fig 2 3 on reduction place a sample of acid liquid in a container add hydrochloric acid potassium dichromate pH 3 and introduce probe rH check whether indicator light ref 68 fig 2 3 lights up solenoid valve open and IC14D User s Manual 13 Start up and maintenance check set point 100 mV add a small quantity of metabisulfite to reduce the chrome the colour changes from yellow to green and wait until the indicator light ref 68 fig 2 3 goes out solenoid valve closed The reading on the digital indicator changes from 400 mV to ca 100 mV Always check the values given by the instrument with sample solutions N B Before starting the system we recommend wearing protective clothing gloves and goggles in order to avoid contact with co
5. 3 Adjust the rH indicator controller transmitter instrument 79 on the control panel to a set point of 200 mV Adjust the pH indicator controller transmitter instrument 78 on the control panel to a set point of 7 0 Switch selector 55 on ON to start agitator 8 agitator activation is indicated by lighting of the corresponding telltale 56 Gradually open valve 15 In this manner the oxidant is transferred from tank 2 to tank 4 in the amount required by the rH instrument 79 its transfer is revealed by the lighting of the relative telltale 68 Switch selector 52 on ON to start agitator 7 whose activation is indicated by lighting of the corresponding telltale 53 Gradually open valve 16 when the liquid moves from tank 4 to tank 6 wait until the electrode is submerged in the solution In this manner the acid solution is transferred from tank 3 to tank 6 in the amount required by the pH instrument 78 its transfer is indicated by the lighting of the relative telltale 65 m Switch selector 58 on ON to start agitator 9 whose activation is indicated by n 0 t p lighting of the corresponding telltale 59 while the transfer of the turbid fluid from tank 5 to the settling tank is visible Monitor sludge settling and the outflow of clarified water Take a sample of clarified water and perform a chemical analysis on it to determine pH and check for the presence of cyanides Open valve 18 and dischar
6. converter of the display to the output stage in current for conversion to 0 4 to 20 mA and to the controllers stage where the signal is compared with the thresholds so as to obtain the conditions of the output relay A solenoid valve for the dosage of the corrective solution is connected to this relay see fig 2 6 IC 14D User s Manual 7 System components and description Characteristics Measuring range 0 to 1000 mV or 500 to 500 mV Input from redox electrode Accuracy 0 3 96 f s Repeatability 0 2 96 f s Output in current 0 20 4 20 mA on max load of 700 2 ON OFF controllers Two mutually independent relays with exchange contact max capacity 3A at 220V AC resistive Timing of relay K1 From one to 15 minutes in one minute steps set by means of a dip switch on panel front Calibrating the thresholds Press the reading button of relay 1 and read the setting on the display to change it work on the relative trimmer turn it clockwise to increase it counter clockwise to reduce it 2 Press the reading button of relay 2 and work on the relative trimmer to change the setting 3 When the two buttons are released the values reappear on the display The threshold exceeded and relay energised conditions are indicated by the relative LEDs on the front panel If no timing has been set the THRESHOLD LED and the K1 RELAY LED light up and go out at the same time Fig 2 6 Detail of neut
7. cyanides it is achieved through oxidation in the alkali field Similar pollution phenomena are due among others to effluents from tanning plants oil refineries chemical and food processing plants wine makers 2 Didacta Italia Chapter 2 2 System components and description If your system differs from the one described below see Annex 1 to this manual 2 Composition Fig 2 1 Overall view of the system L IC14D User s Manual 170 lt mixture preparation tank in polished clear polymethacrylate with graduation for volumetric filling with electrically operated agitator 23 It tank for oxidising or reducing agent in polished clear polymethacrylate with graduation for volumetric filling 23 It tank for acids or bases in polished clear polymethacrylate with graduation for volumetric filling 23 litre oxidation or reduction tank in polished clear polymethacrylate with electrically operated agitator 70 It settling tank with DORR sludge conveyor in polished clear polymethacrylate 23 It neutralisation tank polished clear polymethacrylate with electrically operated agitator Wheeled stainless steel frame for easy handling in the laboratory Control and monitoring electric panel with protections fuses indicator lights main switch and control buttons System components and description 2 2 Description 1 10 2 3 P 8 12 15 23 omz1 O2dm a 24 16 11 T Fig 2 2
8. oa 25 4 5 1 Execution ef The ToS ore ee te OR RARO RE B D Ed 25 4 6 Experience no 6 Influence of the quantity of polyelectrolyte OM MOCCUIAUON sais icici P 26 4 6 Execution of the Test cie eet eee ridere d ed rra 26 IC14D User s Manual V table of contents 4 7 Experience no 7 Influence of the degree of dilution of the polyelectrolyte on the flocculation process oe 27 47 4 Execution Ofthe Test diia ce a Ore i a ae aa vad ve Dr aa e ru re x f Fa x 27 4 8 Experience no 8 Influence of the simultaneous variation of type of polyelectrolyte and ph of the medium on the flocculation efec 28 4 9 Experience no 9 Chemical evaluation of pollutants contained in the water before and after the treatment plant sse 29 4 10 Experience no 10 Dosing hexavalent and trivalent chrome 3 4 11 Experience no 11 Crystallisation studies seee 35 vi Didacta Italia Chapter 1 1 General As its immediate consequence technological progress has brought about an unbalance in the chemical biological composition of natural waters The need to discharge industrial effluents in fact represents a very severe ecological problem since such effluents contain in greater or lesser quantities substances that are harmful to man animals and plants These pollutants affect the people that use natural water courses for drin
9. pH instrument 78 its transfer is indicated by the lighting of the relative telltale 65 Switch selector 58 on ON to start agitator 9 whose activation is indicated by lighting of the corresponding telltale 59 while the transfer of the turbid fluid from tank 5 to the settling tank is visible Monitor sludge settling and the outflow of clarified water Take a sample of clarified water and perform a chemical analysis on it to determine pH and check for the presence of chrome Open valve 18 and discharge the sludge Didacta Italia Chapter 4 r Take a sample and perform a chemical analysis to determine the percentage of dry matter in the sludge 4 2 Experience no 2 Cyanide removal galvanising plants Of all the pollutants contained in galvanising plant effluents we have selected those generating the worst forms of contamination i e hexavalent chrome exp no 2 and alkaline cyanides Cyanides are present in an alkaline solution and are subjected to an oxidising treatment by means of hypochlorite in a markedly basic environment Reaction time varies depending on pH and in order to keep it within technically acceptable limits it is necessary to work at pH gt 12 Active chlorine which is contained in the hypochlorite solution reacts with the cyanides according to the following reaction CN Cl 2CN Cl c cl The cyanogen chloride that is formed initially is converted into cyanate CN CI OH CNO H
10. samples taken from the known titre solution being for instance 0 cc no load test 0 1 0 2 0 4 0 6 0 8 1 adjust the volume of each sample taken plus the different reactants added to the same value by adding 10 9 9 9 8 9 6 9 4 9 2 9 cc of bidistilled water respectively The iron content in the starting solution being 0 1 the percentage of this metal contained in each sample will be 0 0 1 0 2 0 4 0 6 0 8 and 1 mg lt respectively Let the test tubes prepared in this manner rest for 30 and read them under a spectrophotometer or spectrocolorimeter under a light with 51 Ohm wave length Plot the calibration curve from the values obtained IC 14D User s Manual 33 Exercises Now take a 10 cc sample of the water to analysed add 1 cc of HC1 N and bring to a boil let it cool restore the volume to the initial 10 cc add 0 5 cc of the sodium acetate solution 0 3 cc of the ascorbic acid solution and 1 cc if the orthophenanthroline solution In this case too prepare a no load test starting with 10 cc of bidistilled water and as usual use it to reset the instrument The result is expressed in mg It of iron Settling substances Settling substances are the solids suspended in the effluents at the time of discharge that can settle over a time period of up to two hours The result is expressed in terms of cc of substances settled per litre of water The equipment u
11. sulphide deposits dark colouring are eliminated with an appropriate detergent Ingold 9892 or equivalent 3 2 2 Calibrating the pH probe The equipment must be calibrated periodically and whenever an electrode is replaced this is indispensable because the characteristics of sensitivity and the 0 point of the electrodes vary as a function of type use and time This operation must be repeated at a greater or lesser frequency in relation to the accuracy required Proceed as follows 1 Rinse the electrode and remove any encrustation 2 To reactivate the membrane 2 this is necessary especially after a prolonged period of inactivity by submerging the electrode first in a 1 2 solution of HF Ingold 9895 or equivalent for 30 seconds and immediately afterwards in distilled water for at least 12 hours 3 Remove and fit back the plug of the lateral filling hole 1 to equilibrate the inner pressure with the outside pressure 4 Eliminate any air bubbles from inside the membrane 2 5 Pour the buffer solutions pH 7 and pH 4 or 9 into two plastic cups with capacity of ca 10 ml each this is done not to waste an excess quantity of the buffer solutions which must not be salvaged 6 Rinse the electrode with distilled water and submerge it in the pH 7 solution until the porous membrane is covered 7 Stir for 5 seconds wait at least 10 seconds and work on the ZERO adjustment until the reading corresponds to
12. the pH of the butter at that temperature buffer solutions are supplied with a table listing the pH values at different temperatures IC 14D User s Manual 15 Start up and maintenance 8 Remove the electrode from the solution rinse it with distilled water and submerge it into the pH 4 or pH 9 solution and observing the times described above work on the GAIN trimmer until the reading corresponds to the pH value assumed by the buffer solution at that temperature 9 Repeat these steps at least a couple of times always rinsing the electrode in distilled water before passing from one solution to another 3 2 3 pH rH electrode regeneration When an electrode has crystal particle at the tip it has to be regenerated also make sure that the electrode is also filled with liquid Prepare a saturate solution of potassium chloride distilled water KCl H20 submerge the electrode in distilled water to dissolve the salts empty out the solution from the electrode wash the electrode with distilled water and fill it up with the KCl H20 solution 16 Didacta Italia Chapter 4 4 4 1 Exercises Experience no 1 Chromate removal galvanising plants Of all the pollutants contained in galvanising plant effluents we have selected those generating the worst forms of contamination i e hexavalent chrome and alkali cyanides Hexavalent chrome is contained in the effluents of galvanising plants in an acid environment a
13. Didacta Italia ICI4D Water Conditioning Plant User s Manual and Exercise Guide gitalia Didacta Italia ICI4D Water Conditioning Plant User s Manual and Exercise Guide This manual illustrates the technical characteristics and operating instructions of the system Didacta IC14D Water Conditioning Plant giving the instructor or the student a specific knowledge of the unit and its applications Besides the manual contains a choice of exercises ready to be performed in the laboratory Didacta Italia Srl Strada del Cascinotto 139 30 10156 Torino Tel 39 011 273 17 08 273 18 23 Fax 39 011 273 30 88 http www didacta it e mail info didacta it The information contained in this manual has been selected and verified with the greatest care However no responsibility stemming from its use can be ascribed to the Authors or to Didacta Italia or any person or company involved in its preparation The information contained in this manual can be modified at any time and without warning on account of technical or educational needs Copyright Didacta Italia 2010 Reproduction by any means including photocopying of this test or parts thereof or the figures contained therein is strictly prohibited Printed in Italy 15 11 10 Code 01903E1202 Edition 01 Revision 01 table of contents Table of Contents EE CIO EeePC 2 System Components and Description 3 2V CO
14. MPSON E C e oes uate TE PATE TE EEE rescore 3 V MPI egencaem mE 4 2 2 COMMON patrielis rrt cbe Per te eta deseo da FL Ee tans CAELESTIA ERA ERRAT d 5 2 2 2 AgITOTOIS A15 tci er llt t lei i ie f ad e PER ER DR ta E EE TR d nd ERE RT TR lade 9 AT FOW GONI Oliana rr 10 3 Start Up and Maintenance eeeeeeeeeeeeeeeen 13 3 1 Starting Ie SVST Ts dosis rdo bee edet to eia etie buc beide eos 13 3 1 1 pH instr rnenT ice erc eerte rer er eR ER EXER FERE XR TE Le Y 13 31 2 TH Instr rnenfsso a a eA eese AT ied aded ei erii 13 3 2 MGIRTENONG MT TT C OT TODO T 14 3 24 DELDIODO o et ere ED rr sands dence braun deine me P ashes lea Pe P RENE ERR 14 3 2 2 Calibrating the pH probe ssseeeene eene nnns 15 3 2 3 pH rH Electrode regeneration ssseeeee eene nene 16 4 EXGICISQS o o dee tede Eet la o ne seo det eua certs 17 4 Experience no 1 Chromate removal galvanising plants 17 4 2 Experience no 2 Cyanide removal galvanising plants 19 4 3 Experience no 3 Trivalent chromate removal tanning plants 21 4 4 Experience no 4 Influence of the nature of the polyelectrolyte in the MOECUIATION DrIOGCOSS 1 et eden obe eee brevet gru b cost etd doce Sa 22 4 4 1 EXECUTION of the Test erecti hace de Dre T d eH Lei darin 24 4 5 Experience no 4 Influence of the pH of the medium on the flocculation Proc ESS emu tec Pa E am E mca a wp REPRE rer ta
15. added 3500 mg of salt to the 70 litres of H2O to be treated with a concentration of 50 ppm mg l The checks to be performed at the end of this test include settling velocity dry concentration of the sludge percentage of solids in suspension The results obtained must be compared in order to assess the influence if any of the addition of a flocculant consisting of a trivalent metallic ion 24 Didacta Italia Chapter 4 4 5 Experience no 4 Influence of the pH of the medium on the flocculation process Having identified in Experience no 5 the most effective type of polyelectrolyte with this experience we shall assess the influence of the pH of the medium on the effectiveness of the flocculation process leaving the other process parameters unaltered ie e quantity of flocculant 5 ppm corresponding to 350 mg for 70 litres of water e degree of dilution 0 035 it takes one litre of solution e add in rate 500 cc h and at all events a rate ensuring that the solution is added at an even pace over a time period corresponding to the passage of the 70 It of water to be treated e type of polyelectrolyte the one identified in Experience no 4 Modalities of dissolution and preparation of the polyelectrolyte solution e prepare a 0 5 starting solution by adding the polyelectrolyte to the water in small quantities while stirring all along When the solution has become clear and homogeneous you can dilute it with water to th
16. alibrated 50 cc volumetric flasks according to the following table Sample solution of conc 1 0 10 25 0 50 0775 1 2 5 5 75 10 mg l in ml Bidistilled water in m1 50 49 75 49 50 49 25 49 47 5 45 42 5 40 Diphenylcarbazidesolution 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 2 5 in ml Chrome content in mg l 0 0 005 0 010 0 015 0 02 0 05 0 1 0 15 0 20 Let the reactants rest for 10 to enable the colouring to develop fully then measure with a colorimeter or a spectrophotometer with 540 mm wave length With the data obtained we plot the Cr cnc extinction curve Through the same modalities repeat the reading with the water being examined and work out the chrome content directly from the curve Total chrome dosage is performed by oxidising Cr and Cr and then performing the determination process as in the previous case This gives the sum of Cr Cr subtract from this value the one obtained before for Cr alone to obtain the value of Cr IC14D User s Manual 31 Exercises The oxidation of Cr requires the following reactants freshly made e sulphuric acid 1 2 e sodium sulphite solution sulphite solution analytically pure gr 1 26 Mbidistilled water ml 100 e potassium permanganate solution potassium permanganate gr 0 632 Mbidistilled water ml 100 e sodium azide solution sodium azide gr 0 5 distilled wat
17. ange contact max capacity 3A at 220V AC resistive Timing of relay K1 From one to 15 minutes in one minute steps set by means of a dip switch on panel front 6 Didacta Italia Chapter 2 Calibrating the thresholds 1 Press the reading button of relay 1 and read the setting on the display to change it work on the relative trimmer turn it clockwise to increase it counter clockwise to reduce it 2 Press the reading button of relay 2 and work on the relative trimmer to change the setting 3 When the two buttons are released the values reappear on the display The threshold exceeded and relay energised conditions are indicated by the relative LEDs on the front panel If no timing has been set the THRESHOLD LED and the K1 RELAY LED light up and go out at the same time 2 2 1 2 rH meter ref 79 fig 2 3 Fig 2 5 rH controller Panel mounted instrument for the measurement and control of the redox with 3 4 digit LCD The standard version has a 0 4 20 mA output for signal transmission to remote units and two ON OFF control outputs one of which is timed In addition to the input from the pH electrode there is a thermocompensation input The very high impedance signal in mV generated by the electrode is amplified and converted into a 0 2V signal Amplification involves asymmetry control by means of the ZERO trimmer and gain control GAIN trimmer The 0 2V signal is then transmitted to the A D
18. arameters unaltered and namely e add in rate a rate ensuring that the solution is added at an even pace over a time period corresponding to the passage of the 70 It of water to be treated e type of polyelectrolyte as identified in Experience no 4 e pH of the medium as identified in Experience no 5 e quantity of flocculant as identified in Experience no 6 Modalities of dissolution and preparation of the polyelectrolyte solution It is good practice to prepare a 0 5 starting solution and from this produce the solutions to be used so as to have a series of solutions from 0 01 to 0 05 with concentration intervals of 0 005 4 7 1 Execution of the test Since the amount of flocculant employed is kept constant in order to assess the degree of dilution we shall vary the quantity of solution added First of all perform Experience no 6 in its entirety at step o add the flocculant solutions at different concentrations but make sure that the dosage is the same in each test Plot the results obtained in the charts according to the following schemes e the interpretation of the two charts will make it possible to identify the optimal concentration e the degree of dilution fosters the finest possible dispersion in the water to be treated increasing the contact surface IC 14D User s Manual 27 Exercises 4 8 Experience no 8 Influence of the simultaneous variation of type of polyelectrolyte and ph of the mediu
19. arates the water from the sludge the clarified water going to the discharge pipes comes out from the top of the settler while the sludge comes out from the bottom via a ball valve 18 A by pass valve 14 makes it possible to transfer the water directly from the feed tank 1 to the neutralisation tank 6 when the water to be treated only contains trivalent chrome as is generally the case in effluents from tanning plants 4 Didacta Italia Chapter 2 2 2 1 Control panel Fig 2 3 Control panel 7 8 9 10 11 12 51 52 53 55 56 Tank 6 agitator control Tank 4 agitator control Tank 5 agitator control Tank 5 agitator control Tank 1 agitator control pH solenoid valve control Emergency button Agitator 7 magnetothermal switch Agitator 7 indicator light Agitator 8 magnetothermal switch Agitator 8 indicator light IC14D User s Manual If your electrical control panel differs from the one described below see Annex 1 to this manual 58 59 61 62 64 Agitator 9 magnetothermal switch Agitator 9 indicator light Agitator 10 magnetothermal switch Agitator 10 indicator light pH solenoid valve test button 65 pH solenoid valve indicator
20. cl Then cyanate reacts with the hypochlorite ions according to the following reaction H0 2 CNO 3cl 0 52CO N 3 cl 2H The treatment process includes several steps e checking the pH of the water to be treated e oxidising the cyanides with hypochlorite e neutralising the water e sedimentation of any noxious substances contained in the water e discharging the clarified water e discharging the sludge if any The operations to be performed on the system are a Fill tank 1 to about circa 70 1 add ca 300 cc 10 sodium hydroxide solution and with the aid of litmus paper make sure that pH value is about 12 add 9 gr of potassium cyanide so as to obtain a concentration of 50 ppm in the 70 litres of water poured into the tank IC 14D User s Manual 19 20 b c d e g h s j k Exercises Switch selector 61 on ON to start agitator 10 agitator activation 1s indicated by lighting of the corresponding telltale 62 Analyse the water to determine the titre of cyanide Open valve 13 to direct the flow into tank 4 Prepare the oxidant solution to be transferred into tank 2 keep in mind that it takes ca 50 gr of sodium hypochlorite to oxidise the 9 gr of potassium cyanide employed we recommend preparing 10 1 of a 1 solution it is always a good idea to have an excess quantity of reactant Prepare the neutraliser solution to consist of 10 1 of 1 H2SO solution and transfer it into tank
21. e desired concentration 4 5 1 Execution of the test Perform all the steps described under experience no 1 up to point h then calibrate the pH instrument Do this several times starting from a pH value of 7 5 and ending with pH 12 in 0 5 increments Initially do not make any other changes to Experience no 1 then repeat it with the same pH increments but adding the polyelectrolyte as described in Experience no 4 Enter the results obtained into the chart using the following schemes Each of the two diagrams will show two curves one corresponding to the tests without polyelectrolyte and another with the polyelectrolyte Thus we shall be able to assess the effectiveness of the flocculant if the test has been performed with care the dotted line must be above the solid line at least from pH 8 upwards and we shall be able to identify the most appropriate pH To this end it is necessary to keep in mind that according to the current regulations on water pollution the pH of effluents must be comprised between 6 5 and 8 5 so that if it proves necessary to work at pH 8 5 it will then be necessary to subject the clarified water to a further process of neutralisation This suggests that if there is no appreciable difference in behaviour it is more advisable to work at a pH that will remain within the legal limits so as to avoid a further process and the ensuing increase in system costs IC 14D User s Manual 25 Exercises
22. ed it will not be necessary to perform all the checks but only those relating to the elements that may be a cause of pollution The aspects to be checked include the following e pH in order to determine the functionality of the pH meter instrument 78 e settling substances to asses the functionality of the settling tank 5 e substances in suspension to assess the validity of the flocculation process limited to Experiences nos 1 3 4 5 6 7 Hexavalent chrome Trivalent chrome Cyanides limited to Experience no 2 ron if ferric chloride is used as a flocculant agent Settling substances Settling substances are the solids suspended in the effluents at the time of discharge that can settle over a time period of up to two hours The result is expressed in terms of cc of substances settled per litre of water The equipment used is Ihmoff s cone option which is a 1 litre capacity glass vessel with a graduated scale in millilitres The water to be treated is homogenised by energetic stirring and then is introduced into Imhoff s cone option To have an idea of settling velocity it is good practice to take readings of the volume of substances sedimented after 45 1h 1h and 30 and then take a final reading after 2h Substances in suspension IC 14D User s Manual 29 30 Exercises These are the solid substances that are found in suspension in the water and do not settle of their own accord during a 2 h
23. er ml 100 The procedure consists of reducing Cr to Cr oxidising all the Cr and Cr and then determining it colorimetrically Place 25 cc of the water to be analysed in a 250 cc flask then add 5 cc of 1 2 sulphuric acid and 1 cc of the sodium sulphite solution Heat to ca 90 C for 5 minutes and dilute with 20 cc of bidistilled H20 then bring to a boil add the solution of KmnO in drops until a persistent pink colouring is obtained boil for 10 minutes Eliminate excess KmnO with the sodium azide solution paying attention not to add too much then boil for another 2 minutes Cool and place 50 cc in a calibrated volumetric flask Determine the quantity of Cr through the calorimetric method Determination of cyanides Cyanides are determined volumetrically after distilling them in the presence of H2SO and collected in the form of alkaline cyanides in a KOH solution This initial operation is performed in a type Kjeldahl device by pouring into the flask 250 cc of the water to be examined and adding in drops 25 cc of concentrated H2SOx Distil for one hour by bubbling the distillate in 50 cc of KOHN the cyanide acid is then collected as NaCN At this point the alkaline cyanide solution is tritrated with AgNO 0 1 N using dimethylaminobenzalrhodamine as an indicator 0 02 solution in acetone In lieu of dimethylaminobenzalrhodamine it is possible to use KI in 10 solution 32 Didacta Italia Chapter 4 The Ag ions added i
24. examine the phenomenon of crystallisation by cooling starting from a hot saturate solution This experiment can be performed on a solution of any salt we shall exemplify the procedure with a saturate solution of copper sulphate The solubility curve can be worked out from the following table Temperature Crystallised copper sulphate dissolved in 100 cc of H2O gr 0 31 6 10 36 9 20 42 3 30 48 8 40 56 9 50 65 8 60 77 3 70 94 0 80 118 0 90 156 4 100 203 3 In the tank used to prepare the solutions of the water to be treated prepare a salt solution at a temperature of between 50 C and 70 C Transfer the solution to the the tank equipped with a coil in which the coolant is circulated This will cause a crystallisation process and the water containing the crystals will be transferred to the settling tank At this point settling velocity can be determined as a function of crystal size which in its turn depend on cooling rate Several experiments can be performed at this point by varying the following parameters either singly or in combination a temperature at the inlet of the coolant IC 14D User s Manual 35 36 b coolant flow rate c flow at the settling tank Exercises Didacta Italia
25. ge the sludge if any Take a sample and perform a chemical analysis to determine the percentage of dry matter in the sludge Didacta Italia Chapter 4 4 3 Experience no 3 Trivalent chromate removal tanning plants Tanning plants discharge huge volumes of water containing different pollutants of both organic and inorganic nature Among these we have selected the chrome coming from mineral tanning baths which is present in the form of trivalent chrome in a markedly acid environment The treatment process includes several steps checking the pH of the water to be treated neutralising the water precipitation of Cr in a mildly alkali environment sedimentation of Cr OH 3 discharging the clarified water discharging the sludge The operations to be performed on the system are a b c d e g h i Fill tank 1 with waters to about three quarters of its capacity ca 70 litres add ca 200 cc of sulphuric acid in a 20 solution and by means of litmus paper make sure that pH value is approx 2 add 35 gr of chrome alum so as to obtain a concentration of ca 50 ppm of Cr in the 70 litres of water poured into the tank Switch selector 61 on ON to start agitator 10 agitator activation is indicated by lighting of the corresponding telltale 62 Analyse the water to determine the titre of trivalent chrome Open valve 14 to direct the flow into tank 6 Prepare the neutraliser solution to consis
26. king purposes terrestrial animals that find in rivers and lakes their natural sources of drinking water as well as the river and lake fauna and flora that may be poisoned whether directly or indirectly by such by industrial products As a first approximation industrial effluents can be subdivided into two major groups e effluents basically consisting of organic products e effluents containing substances of inorganic origin The former reduce the quantity of oxygen dissolved in the water which results in the fauna dying for lack of air while the others have toxic effects and represent veritable poisons in the traditional understanding of the term Many pollutants belong to both groups some organic substances in fact consume the oxygen contained in the water and are also toxic inorganic substances erode the oxygen because of their reducing action Other forms of pollution are due to settling and suspended compounds Aside from an accessory toxic effect the former tend to settle on the bottom of water courses and damage the local flora thereby hampering the regular formation of plankton the latter make the water turbid thereby preventing the penetration of sunlight and slowing down chlorophyll photosynthesis The best way to prevent the severe consequences of pollution obviously consists of preventing all types of contaminants from being discharged into natural water courses This can be obtained by processing all effluents with t
27. light 67 68 rH solenoid valve test button rH solenoid valve indicator light 78 pH control instrument 79 82 83 rH control instrument Basification acidification selector Oxidation reduction selector System components and description 2 2 1 1 pH meter ref 78 fig 2 3 Fig 2 4 pH controller Panel mounted instrument for the measurement and control of pH with 3 digit LCD The standard version has a 0 4 20 mA output for signal transmission to remote units and two ON OFF control outputs one of which is timed In addition to the input from the pH electrode there is a thermocompensation input The very high impedance signal in mV generated by the electrode is amplified and converted into a 0 2V signal Amplification involves asymmetry control by means of the ZERO trimmer and gain control GAIN trimmer The 0 2V signal is then transmitted to the A D converter of the display to the output stage in current for conversion to 0 4 to 20 mA and to the controllers stage where the signal is compared with the thresholds so as to obtain the conditions of the output relay A solenoid valve for the dosage of the corrective solution is connected to this relay see fig 2 6 Characteristics Measuring range 0 14 pH Input from pH electrode Accuracy 0 3 96 f s Repeatability 0 2 96 f s Output in current 0 20 4 20 mA on max load of 700 ON OFF controllers Two mutually independent relays with exch
28. m on the flocculation process As a rule polyelectrolytes display a behaviour that varies to a significant extent depending on the pH of the medium actually in some cases they will be totally inactive at a given pH even if the latter remains within the limits of validity for the type of polyelectrolyte employed whereas with a variation of but 0 5 in pH the activity of the electrolyte may be appreciably enhanced Accordingly it was deemed worthwhile to test out the action of different polyelectrolytes of anionic type in this particular case as a function of pH by repeating Experience no 5 in its entirety for each polyelectrolyte tested and entering the results in the two tables reproduced below pH Type of flocculant Settling velocity pH Type of flocculant dry of sludge 28 Didacta Italia Chapter 4 4 9 Experience no 9 Chemical evaluation of pollutants contained in the water before and after the treatment plant Having identified the most effective flocculation method it is important to determine the effectiveness of the entire treatment Accordingly we shall perform a number of analytical determinations in order to assess the degree of effluent clarification achieved For the sake of clarity we have produced a table showing the limits of acceptability of the effluents as provided for by most local bodies insert table Naturally for the various experiences suggest
29. n improvement in the flocculation process or even beyond certain values its stabilisation however the curve reflecting process efficiency will rarely undergo a decrease hence the aim of this experience to determine the minimum quantity of flocculant We want to know this because the price of polyelectrolytes commonly used is rather high and hence we want to use the minimum quantity the cost of polyelectrolytes being approx 2500 lire kg it is obvious that even one ppm more than is technically necessary will give rise to an increase in costs of 2 5 lire per m of water to be clarified 4 6 1 Execution of the test Perform Experience no 4 in its entirety but at point o vary the quantity of flocculant solution employed to carry out a series of experiences with polyelectrolyte quantities ranging from 1 to 6 ppm change the quantity in 0 5 ppm steps Plot the results in the charts using the schemes given below The interpretation of the two charts will make it possible to identify the minimum quantity needed 26 Didacta Italia Chapter 4 4 7 Experience no 7 Influence of the degree of dilution of the polyelectrolyte on the flocculation process Having identified through Experiences 4 5 and 6 the best type of polyelectrolyte the appropriate quantity of polyelectrolyte and the ideal pH of the medium with this experience we want to assess the degree of dilution of the polyelectrolyte solution while leaving the other process p
30. n the previous step combine with the CN to form a soluble complex when all the CN have reacted the addition of a small excess quantity of AG causes the dimethylaminobenzalrhodamine to turn salmon pink or the AgI precipitate to turn light yellow Denoting with A the quantity of AgNO 0 1N in cc used in 250 cc of water the CN content in mg It is given by the following relationship A 5 2 1000 250 Determination of iron The determination of iron is performed through the colorimetric method based on the reddish colour taken on by ferrous salts in the presence of orthophenanthroline The reactants to be used dissolved in bidistilled water without any trace of iron are as follows e HCI N solution e saturate solution of sodium acetate e 1 ascorbic acid solution freshly made e freshly made solution of orthophenanthroline e starting solution of 1 gr lt of iron weigh exactly 100 mg of iron filings pure and washed with ether dissolve in flasks with 10 cc of HNO conc 40 cc of water In a volumetric flask adjust volume to 100 cc e 0 1 iron solution this is produced by diluting to 1 10 the previous solution To perform the calibration curve take various samples from 0 1 to 1 cc of the known titre iron solution containing 0 1 iron add 1 cc of the NCI N solution 0 5 cc of the saturate sodium acetate solution 0 3 cc of the 196 ascorbic acid solution and 1 cc of the 0 196 orthophenanthroline solution The
31. nd hence the chromate dichromate balance 2 Crog 2H Cr O07 HO fosters the formation of dichromates The treatment process includes several steps checking the pH of the water to be treated reducing Cr to Cr with bisulphite according to the following reactions Cr 07 3HSO 5H 22Cr 3507 4H20 neutralising the water precipitation of Cr in a slightly alkaline environment through the addition of a flocculant agent to make the flocs bigger sedimentation of Cr OH discharging the clarified water discharging the sludge The operations to be performed on the system are a Fill tank 1 to about three quarters ca 70 litres add ca 200 cc of sulphuric acid in a 20 solution and by means of litmus paper make sure that pH value is approx 2 add 10 gr of potassium dichromate so as to obtain a concentration of 50 ppm of Cr in the 70 litres of water poured into the tank b Switch selector 61 on ON to start agitator 10 agitator activation is indicated by lighting of the corresponding telltale 62 c Analyse the water to determine the titre of hexavalent chrome IC 14D User s Manual 17 d e g h j k Exercises Open valve 13 to direct the flow into tank 4 Prepare the reducing solution to be transferred into tank 2 keep in mind that for stoichiometric purposes 100 gr of potassium dichromate require 105 g of sodium bisulphite and the latter is originated by dis
32. our time period To measure them we have to collect them on a filter and weigh them the result is expressed in mg per litre of water The working procedure is as follows Wash a cellulose filter of appropriate porosity dry it in an oven at 105 C and after cooling it in a drier weigh it Pass through a calibrated filter a volume V of the water in question after homogenising it by rapid stirring Dry the filter in an oven at 105 C until its weight is stabilised cool it in a drier and weigh it Let us denote with P the weight obtained with Po the weight of the filter and with V the volume of water filtered in ml the substances in suspension in mg lt are obtained through the following formula AT P Po 1000 substances in suspension in mg lt E Didacta Italia Chapter 4 4 10 Experience no 10 Dosing hexavalent and trivalent chrome Cr is dosed through the calorimetric method using diphenylcarbazide as an indicator we get a red purple colouring Reactants needed freshly made e Bidistilled water e Diphenylcarbazide solution diphenylcarbazide analytically pure g 0 2 ethylic alcohol at 95 ml 100 sulphuric acid 1 10 ml 400 e Sample solution of hexavalent chrome 1 mg l To perform the test it is necessary first of all to plot the calibration curve with known titre solutions of Cr The samples are prepared by placing increasing quantities of the sample chrome solution in c
33. ralisation tank solenoid valve 11 8 Didacta Italia Chapter 2 2 2 2 Agitators a SOWA Fig 2 7 Agitator 10 with impeller in stainless steel 100 rpm Nw AA n Wwe Fig 2 8 Agitator 8 with impeller in stainless steel 100 rpm IC 14D User s Manual System components and description Fig 2 10 Agitator 9 in stainless steel with DOOR type rake blades 2 rpm 2 2 3 Flow control The system is not equipped with instruments for the direct reading of flow rate To control flow work on the valves shown in figure 2 8 Flow can be adjusted as necessary by means of a chronometer not supplied and the graduated scales applied to the tanks Didacta Italia Chapter 2 Fig 2 11 Flow control detail 13 Valve for flow control from tank 1 to tank 4 14 Valve for flow control from tank 1 to tank 6 15 Valve for oxidant reducer flow control 16 Valve for acid base flow control Product flow to the settling tank ref 5 fig 2 1 depends on the sum of the flow rates from the feed tank ref 1 fig 2 1 the oxide reduction tank ref 2 fig 2 1 and acid base tank ref 3 fig 2 1 IC14D User s Manual 11 System components and description Didacta Italia Chapter 3 3 Start up and maintenance 3 1 Starting the system System start up is very simple just follow the steps listed below 1 Conned the system to the power mains as shown on the control panel 2 Connect the discharge pipe fig 3 1
34. rameters affecting the flocculation process and hence be able to identify detect optional conditions Limited to addition of polyelectrolyte flocculation is a function of e nature of the polyelectrolyte e pH of the medium e quantity of polyelectrolyte e degree of dilution e add in rate accordingly it is advisable to perform a number of tests changing the afore mentioned parameters one at a time and then in combination according to logical and reasonable criteria The effectiveness of the flocculation process can be assessed by determining settling velocity and or from the dry concentration of sludge Therefore it is possible to construct a number of charts in which we can plot one of these values as a function of the parameter that we intend to vary The polyelectrolytes commonly employed as flocculation adjuvants can be grouped into three basic types e cationic e anionic 22 Didacta Italia Chapter 4 e non ionic Cationic polyelectrolytes are active in a field with acid or neutral pH those in the second group in an alkaline pH field those in the third group will work in either field provided that pH it is not too far from neutrality Sometimes polyelectrolytes act alone but they often work as an adjuvant of other flocculants of inorganic nature normally metal salts The reason for this lies in the fact that metal ions form a floc which gests bigger with the addition of polyelectrolytes which react with
35. reatment plants designed to bring the composition of the effluents into line with applicable standards Obviously it is not possible to design a single treatment plant that will handle all types of effluent Process selection is a decision of the utmost importance requiring a preliminary study that takes into account all the factors involved case by case It is impossible to identify beforehand all the pollutant factors associated with each single effluent because each case is a unique instance and therefore cannot be viewed as a standard of universal validity IC 14D User s Manual General However the effluents to be treated can be assigned to major categories as a function of their origin Since treatment plants represent a major cost for manufacturing plants these systems should be studied in detail so as to enable future technicians to familiarise with their working principles and be able in future to select the most appropriate systems case by case This knowledge is necessary to the people responsible for designing operating or maintaining the water treatment plants To this end DIDACTA ITALIA has designed and created IC14D as an indispensable teaching and testing aid for the problems to do with the clarification of industrial service waters The most dangerous effluents from galvanising plants basically consist of cyanides and chromates In the latter case toxicity is eliminated through reduction in the acid field for
36. rrosive substances Always comply with local regulations on the use and handling of corrosive substances Before discharging any substance into the laboratory s discharge system make sure that the substance has been neutralised Comply with the applicable regulations on the disposal of chemical substances 3 2 Maintenance At the end of each exercise empty out and clean the tanks The pH and rH probes must be treated as described below 3 2 1 pH probe Fig 3 2 pH probe Protect the plug and cable splices against humidity The electrodes must be kept scrupulously clean and free of grease when they are not used they must be kept under distilled water or preferably in a KCl 3M solution 14 Didacta Italia Chapter 3 During transport and storage they must be protected with a special rubber cap 5 filled with the same solution remove the cap to take the measurements The level of the electrolyte 4 must not drop below 20 mm from the feed hole 1 Electrodes mounted on an armature without reserve must not be submerged by more than 200 mm A summary cleaning of the sensitive part of the electrode must be performed at least once a week by rubbing it gently with a paste consisting of water and a slightly abrasive degreasing factor and then rinsing it thoroughly Alkaline encrustations can be readily eliminated by submerging the part in a standard strong acid solution Obstructions in the porous membrane 3 due to silver
37. sed is Ihmoff s cone option which is a 1 litre capacity glass vessel with a graduated scale in millilitres The water to be treated is homogenised by energetic stirring and then introduced into Imhoff s cone option To have an idea of settling velocity it is good practice to take readings of the volume of substances sedimented after 45 1h 1h and 30 and then take a final reading after 2h Substances in suspension These are the solid substances that are found in suspension in the water and do not settle of their own accord during a 2 hour time period To measure them we have to collect them on a filter and weigh them the result is expressed in mg per litre of water The working procedure is as follows e Wash a cellulose filter of appropriate porosity dry it in an oven at 105 C and after cooling it in a drier weigh it e Pass through a calibrated filter a volume V of the water in question after homogenising it by rapid stirring e Dry the filter in an oven at 105 C until its weight is stabilised cool it in a drier and weigh it e Let us denote with P the weight obtained with Po the weight of the filter and with V the volume of water filtered in ml the substances in suspension in mg lt are obtained through the following formula P Po 1000 V substances in suspension in mg lt 34 Didacta Italia Chapter 4 4 11 Experience no 11 Crystallisation studies In this experience we shall
38. solving metabisulphite in water according to the following reaction Na38205 H20 2NaHS0 to reduce all the dichromate added to the initial 70 litres of water it takes 10 5 g of bisulphite corresponding to 9 5 g of metabisulphite Accordingly for tank 2 we may prepare 10 litres of 0 296 solution of metabisulphite it is always a good idea to have an excess quantity of reactant on hand Prepare the neutralising solution with 10 litres of 1 sodium hydroxide solution and transfer it into tank 3 Adjust the rH indicator controller transmitter instrument 79 on the control panel to a set point of 110 mV Adjust the pH indicator controller transmitter instrument 78 on the control panel to a set point of 8 5 Switch selector 55 on ON to start agitator 8 agitator activation is indicated by lighting of the corresponding telltale 56 Gradually open valve 15 In this manner the reducing agent is transferred from tank 2 to tank 4 in the amount required by the rH instrument 79 its transfer is revealed by the lighting of the relative telltale 68 Switch selector 52 on ON to start agitator 7 agitator activation is indicated by lighting of the corresponding telltale 53 m Gradually open valve 16 when the liquid moves from tank 4 to tank 6 wait until n 0 p q the pH electrode is submerged in the solution In this manner the alkaline solution is transferred from tank 3 to tank 6 in the amount required by the
39. t of 10 1 of 1 sodium hydroxide solution and transfer it into tank 3 Adjust the pH indicator controller transmitter instrument 78 on the control panel to a set point of 8 5 Switch selector 52 on ON to start agitator 7 agitator activation is indicated by lighting of the corresponding telltale 53 Gradually open valve 16 Wait until the pH electrode is submerged in the solution In this manner the alkalising solution is transferred from tank 3 to tank 6 in the amount required by the pH instrument 78 its transfer is indicated by the lighting of the relative telltale 65 IC14D User s Manual 21 Exercises j Switch selector 58 on ON to start agitator 9 whose activation is indicated by lighting of the corresponding telltale 59 while the transfer of the turbid fluid from tank 5 to the settling tank is visible k Monitor sludge settling and the outflow of clarified water Take a sample of clarified water and perform a chemical analysis on it to determine pH and check for the presence of chrome m Open valve 18 and discharge the sludge n Take a sample and perform a chemical analysis to determine the percentage of dry matter in the sludge 4 4 Experience no 4 Influence of the nature of the polyelectrolyte in the flocculation process Repeat Experience no 1 up to the precipitation step at that point add a polyelectrolyte solution to tank 6 This is done manually to be able to modify as desired the pa
40. the zeta potential see theory and as they settle drag along lighter or colloidal particles which otherwise might remain dispersed in the liquid phase above In the specific case in question since the solution already contains trivalent metal ions i e Cr we may presume that it is not indispensable to add any metal flocculant However it is interesting to assess the influence of this addition to the flocculation process and therefore the experience will involve a number of tests concerning both the identification of the most effective type of polyelectrolyte and the influence of added metal ions in addition to those already contained in the water to be treated In this experience which is only designed to determine the type of flocculant to be added the other parameters are maintained unaltered with the following values e quantity of flocculant 5 ppm corresponding to 350 mg for our 70 It of water e pH of the medium 8 5 e degree of dilution 0 035 it takes one litre of solution e add in rate 500 cc h and at all events a rate ensuring that the solution is added at an even pace over a time period corresponding to the passage of the 70 It of water to be treated In view of the basic nature of the solution to be treated we must proceed with anionic or non ionic polyelectrolytes At all events a number of tests will also be performed with a cationic flocculant in order to assess the applicability of these adjuvants
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