Graduation Project - Abraham Repaired)

8/8/2019 Graduation Project - Abraham Repaired)

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Defence University College of Engineering

Chemical Engineering Department

Assessment of Electroplating Waste Water atGafat Armament Engineering Complex

By

Group one Sub Group three



Content

Unit One

I. Introduction

1.1. Background

1.2. Company profile

1.3. Objective of the project

1.4. Significance of the project

1.5. Scope of the project

1.6. Method and Materials

I.6.1 Method

I.6.2 Materials

Unit Two

2. Literature Review

Unit Three

3. Result and Discussion

Unit Four

Conclusions and Recommendations

References



UNIT - ONE

I Introduction

1.1 Back ground

Electroplating is one of the varieties of several techniques of Metal Finishing. Itis a technique of deposition of a fine layer of one metal on another throughelectrolytic process to impart various properties and attributes, such as corrosion

protection, enhanced surface hardness, lustre, colour, aesthetics, value additionetc.

Electroplating is considered a major polluting industry because of the dischargeof toxic materials and heavy metals through wastewater (effluents), air emissionand solid wastes in to the recipient environment.

The chemicals used in various electroplating operations are numerous. Thesechemicals can be classified generally as (i) Acids and Alkalis for cleaning

purpose,( ii)inorganic chemicals, particularly heavy metals, which take part inreaction pertaining to plating and (iii)organic chemicals which help in achievingcertain properties or to enhance the process of plating. Throughout the process

of electroplating, there are a number of wastes discharged to the environmentwhich has diverse effect on human being as well as other living things.

The environmental effect are caused by several routs- (i) by directly reachingwith air water and soil, resulting in degradation of disintegration, (ii) byaccumulating as persistent chemicals - geo-accumulation (iii) by enteringenvironmental pathways and transcending from non-living to living beings,causing toxicity to living organisms and (iv) entering in to food chain- finallyaffecting humans and cattle. Some are carcinogenic, while others are mutagenic.Central and most important in this matter are health effects on workers, who areexposed routinely and persistently. Over a period of time such exposures, even

at a low level, have been known to cause diseases and various infirmities.

Liquid wastes obtained from industries generally much more polluted thandomestic or even commercial liquid wastes. It becomes necessary for theindustries to treat their liquid wastes in their industrial treatment plants beforedischarging their effluents either on land or lake or river or in municipal sewers.

Industrial liquid wastes usually contain several chemical pollutants and toxicsubstances in too large proportion. The characteristics of the liquid wastes willusually vary from industry to industry and also vary from process to process.

Therefore, this is a graduation project focused on Gafat Armament EngineeringComplex, one of the industry engaged in electroplating process, in order to



assess pollutants and degree of pollution caused by the discharges from thecompany, its impact on the environment and human beings and to recommend

possible solutions to minimize its adverse effect.

1.2 Company profile

Gafat Armament Engineering Complex is built by joint collaboration of Government of People Democratic Republic of Korea and Democratic Republicof Ethiopia by the name of Gafat Engineering Factory. The factory wasinaugurated on May 27, 1973 in Ethiopian Calendar by the then PresidentMengistu H/Mariyam. The factory is located 66 KM from Addis Ababa in thedirection of South East and 19 KM from Bishoftu town and stationed with in18,400,000 m2

The objective of the factory is to satisfy the military need of the country withadvanced technology through designing and production of appropriate war equipment that enhances the economic and industrial development of thecountry.

The factory is highly contributing for the industrial and technologicaladvancement of the country in producing efficient war tools with low cost andhigh quality that satisfies its customers needs.

Currently, five departments are operating in the factory such as simple tools

operation department, middle calibre production department, Rocket launcher production department, complex tools howitzers production department andarmy tools spare parts production department. And through these departmentsdifferent war tools like snipers, Shrapnel lawounchers, anti tank lawounchersetc... has been producing in the factory. In addition, different plastic materialsare also producing.

While engaging in production of such tools, the factory has been utilizingdifferent chemicals in order to electroplating and alkali colouring, which on

process changed in to hazardous wastes.

1.3 Objective of the project

The general objectives of this project are

• To indicate the degree of pollution caused by the effluencesdischarge

• To assess pollutants within the west water

The specific objective of the project

• To suggest liquid waste treatment mechanism with less cost



• To identify type and characteristics of pollutants that aredischarged during electroplating process

• To propose recycling methods and mechanisms• To evaluate the degree of pollution affecting the environment and

make them aware

1.4 Significant of the project

In Gafat Armament Engineering Industry waste treatment mechanism aretechnologically supported. However, the current treatment mechanism beingused is not as required due to several reasons. Therefore, it is necessary toidentifying the problem clearly through assessing the current mechanism bywhich the company been treating its waste water so that environmentally

friendly mechanisms should be recommended.

1.5 Scope of the project

To assess the source of industrial liquid wastesTo evaluate the effect of industrial wastes disposed to the environmentTo propose how to mange the liquid waste of the industry

1.6 Method and Materials1.6.1 Methods

In order to undertake the project, the group will visit GAEC /Gafat ArmamentEngineering Complex/ for first hand information and also review differentliteratures and internet for 2 nd hand information. In addition, the group willundertake experiment in laboratory in order to come up with tangible results.

The methods used to achieve the project objectives are:-

• Observation :- observing the type of chemicals that are used for plating purpose in Gafat Armament Engineering complex; identify the effect of liquid west discharged to the environment

• Consultation :- consulting at all stage and activities of the project withthe advisor, Laboratory technicians, and other relevant persons ( thefactory workers)

• Secondary data collection :- collect secondary data which is relevant tothe study from various sources

• Samplingo Primary data collection with appropriate type and quantityo Site visit and liquid waste sample collection at different times

from the site



o Proper and careful transportation of the collected sample to thelaboratory

• Laboratory work /experiment

Determine the degree of pollution and PH value of the liquid wastes, so as tocharacterize it.

• Data analysis and interpretation of the results obtained

The data collected has to be analyzed thoroughly by adopting analyticaltechnique and by identifying the similarities and differences with thesecondary data

• Evaluate the data based on the analysis

1.6.2 Materials

Some of the materials required for laboratory work and sample collections are:-

• Laboratory equipments such aso conical flask,o Beaker -100mlo Buretteo Hot plateo Measuring cylinder

• Personal safety equipmentso Gloveo Mask (mouth and nose)o Goggleo Eye glass

• Reagents that facilitates the experimento Sulphuric Acido Phenolphthaleino Iron sulphateo Potassium permanganate



UNIT-TWO

II. REVIEW OF RELATED LITERATURE

2.1 Electroplating waste

Electroplating is considered a major polluting industry because of the discharge of toxic materials and heavy metals through wastewater (effluents), air emission andsolid wastes in to the recipient environment,( Newsweek 2008, Central PollutionControl Board, DELHI)

In electroplating, a wide variety of chemicals and substances are used, depending upon the surface properties of the object to be electroplated, plating and finishingrequirements as well as the technology / facility offered by platters /. Among themetals used in platting, chrome platting is the most widely used one.

2.1.1 Chromium

Chromium is bluish- white and lustrous metal that is resistant to corrosion in mostatmospheres. Chromium plating, therefore, is extensively used as a final finishingoperation.

Chromium is naturally found in rocks, animals, plants, soil and in volcanic dust andgases. It is one of the high priority persistent, bio-accumulative and toxic (PBT)chemicals that do not readily break down in the environment, are not easilymetabolized, may accumulate in human or ecological food chains throughconsumption or up take and may be hazardous to human health or environment. PBTchemicals, once released to the environment, may present increasing long term toxiceffects to human health and the environment, even if the release was of a smallamount.

Chromium is present in the environment in several different forms. The mostcommon forms are chromium (O), trivalent (III), and hexavalent (VI). Chromiumoccurs naturally in the environment and is an essential nutrient required by thehuman body . Chromium enters the environment mostly in the Chromium (III) and(VI) forms as a result of natural processes and human activities. It cycles betweenthe soil, the atmosphere, surface and ground waters. Electroplating is one of theseveral industrial activities (like stainless steel welding, chemical manufacturing,tanning, textile process & dyeing and coal ash from power plants), that discharge

both Cr(III) and Cr(VI) in to water and soil. Chromium (III) is considered safe andis an essential nutrient.

Cr (Vl) is a strong oxidant and is reduced in the presence of electron donors.Electron donors commonly found in soils include aqueous Fe (l I), ferrous iron



minerals, reduced sulfur, and soil organic matter. The reduction of Cr(Vl) by ferrousiron can be written as HCrO~ + 31% + 7H+ + Cr3+ + 3F23+ + 4H 0 This reaction isvery fast on the time scales of interest for most environmental problems with thereaction going to completion in less than 5 minutes even in the presence of dissolvedoxygen (Eary and Rai, 1988). Only when the pH is greater than 10 or when PO~

concentrations exceed 0.1 molar does the rate of oxidation of F&+ by dissolvedoxygen exceed the rate of oxidation by Cr(Vl) (Eary and Rai, 1988). When the pH of the groundwater is greater than 4, Cr(lll) precipitates with the Fe(lll) in a solidsolution with the general composition CrXFel..JOH), (Sass and Rai, 1987; Amonetteand Rai, 1990). If the reduction of Cr(Vl) by Fe(n) is the only source of Fe(lll) andCr(lll), a solid solution with the composition CrO,z~FeO,JOH), forms via thereaction HCrO~ + 3F62+ + 3H20 + 50H+ + 8~0 + Fe2+ where the ions in the

brackets denote ions within the crystal structure of biotite. To maintain charge balance, K is released to solution as the iron in the crystal structure is oxidized. TheCr(Vl) in solution is then reduced by the Fez+. The Fes+ resulting from thisreduction reaction is then adsorbed to the surface of the biotite where it is againreduced to F&+, thus setting up a cycle that ultimately results in the reduction of more Cr(Vl) than is stoichiometricaliy possible for the amount of iron that is insolution.

There are some key experimental difficulties in studying groundwater/mineralinteractions such as those just described that have some bearing on the transfer of knowledge to the field. Although the processes can in some cases be interpretedfrom the data on mineral reactions, the rates themselves may be quite useless. A keydifficulty in studying mineral reactions in the laboratory is that the rate of thereaction depends on how the solid phase was prepared. For example, if the samplesare ground and simply washed before use, microparticles can adhere to the larger grain surfaces. These microparticles have greater specific surface area and can reactat a much faster rate than the larger size particles. Such experimental artifacts wereobserved in weathering studies of pyroxenes (Schott et al., 1981). Another importantreductant in soils is organic matter. In fact, bichromate reduction has been used as awet combustion method for the determination of soil organic carbon (Walkley andBlack, 1934). Bichromate can react with soil organic carbon according to 2Cr20~- +3C + 16H+ --+ 4Cr3+ + 3C0 (Eary and Rai, 1988; Sass and Rai, 1987). Thevolubility of CrXFe,-X(OH)~ decreases as the mole fraction of Fe(lll) in the solidincreases. Therefore, if the pH is between 5 and 12, the concentration of Cr(lli) isexpected to be less than 10+ molar.

Numerous minerals in geologic materials contain ferrous iron that is potentiallyavailable for the reduction of hexavalent chromium. These iron-containing mineralsmay be silicates, oxides, or sulfides. Common ferrous iron-containing silicatesinclude olivine; pyroxenes such as augite and hedenbergite; the amphiboleshornblende, cummingtonite, and grunerite; micas such as biotite, phlogopite, andglauconite; chlorites, and the smectite nontronite. Iron oxides such as magnetite(Fe2+Fe~+OJ contain iron as a major constituent, however, hematite (Fe~+03) cancontain small amounts of (FeO). In sulfide minerals such as pyrite (FeS2), both theferrous iron and the sulfide are active in reducing hexavalent chromium. Lancy(1966) suggested that pyrite could be used for treating spent cooling waters that

contain Cr(Vl) as a corrosion inhibitor. He stated that the reduction of Cr(Vl) occursat the pyrite surface rather than in solution. Lancy (1966) found that reduction by



pyrite occurred even in slightly alkaline solutions; however, the pyrite had to becontinuously abraded to remove surface coatings. Blowes and Ptacek (1992)conducted batch tests in continuously agitated reaction vessels containing a solutionof 18 mg/L Cr(Vl) and pyrite both in the presence and in the absence of calcite. Inthe experiments that used both pyrite and calcite, 509!. Of the Cr was removed in

less than 6.5 hours. Concentrations were <0.05 mg/L after 20 hours. Experimentsconducted without the calcite attained 50% removal in 1 hour and concentrationswere c 0.05 mg/L in less than 4 hours. Cr( Vl) reduction in the presence of ironoxides has been observed in several experiments. White and Hochella (1989) foundthat magnetite and ilmenite reduced Cr(Vl) to Cr(lli). The reduction of Cr(Vl) in the

presence of hematite (Fe20J was demonstrated by Eary and Rai (1989). Theyattribute the reduction to the presence of a small amount of an FeO component in thehematite. They suggest that reduction occurs in solution after the FeO componenthas been solubilized.

Reduction of Cr(Vl) by ferrous iron-containing silicates has been reported. Eary andRai (1989) suggest that the reduction of Cr(Vl) in the presence of biotite occurs insolution rather than at the mineral surface. They observed an increase in the rate of reduction when their suspensions were spiked with Fe&. They explain their resultswith the mechanism proposed by White and Yee (1985) in which Fe3+ is reduced atthe mineral surface by the reaction [Fe(n), K+]~iOtit~ + Fe3+ ~

Persistent, bio accumulative and toxic (PBT) chemicals do not readily break down inthe environment, are not easily metabolized, may accumulate in human or ecologicalfood-chains through consumption or uptake and may be hazardous to human healthor the environment. A PBT chemical, once released to the environment, may presentincreasing long-term toxic effects to human health and the environment, even if therelease was of a small amount. Chromium is a high priority PBT chemical.Hexavalent chromium or chromium(VI) is a recognized carcinogen. Exposure tochromium(VI) in dust is associated with increased incidence of lung cancer and isknown to cause inflammation of the skin (dermatitis). In contrast, trivalentchromium or chromium(III) is considered relatively safe. It is an essential nutrientthat helps the human body utilize sugar, protein and fat. It is not known if exposureto chromium will result in birth defects or other developmental effects in people.

body. Chromium(VI) and chromium(0) are generally produced by industrial processes. The metal chromium, or chromium(0), is a steel-gray solid with a highmelting point. It is used mainly for making steel and other alloys. The naturally

occurring mineral chromite in the chromium(III) form is used as brick lining for high-temperature industrial furnaces, for making metals, alloys and chemicalcompounds. Chromium compounds, mostly in chromium(III) or chromium(VI)forms produced by the chemical industry, are used for chrome plating, themanufacture of dyes and pigments, leather tanning and wood preserving. Smaller amounts are used in drilling muds, rust and corrosion inhibitors, textiles and toner for copying machines. Chromium enters the environment mostly in the Chromium(III) and Chromium (VI) forms as a result of natural processes and human activities.Emissions from burning coal and oil and producing steel can increase Chromium(III) levels in air. Birth defects have been observed in animals exposed to Chromium(VI). Studies with mice have shown that chromium crosses the placenta and

concentrates in fetal tissue. Therefore, pregnant women who are exposed tochromium in the workplace or by living near chromium waste sites may transfer



chromium from their blood into the baby where it may build up at levels greater thanin the mother. There is some evidence that chromium can be transferred from thehuman mother to infant through breast milk.

Today, both hexavalent chromium [chrome (VI)] and trivalent chromium [chrome(III)] electroplating processes are commercially available for decorative chrome

plating operations. Because electroplating with (V1) has historically been easier thanchrome (III), chrome (V1) was essentially the only decorative chromium processused for almost 70 years.

Electroplating with chrome (VI), however, is more toxic than chrome(III) And presents a real threat to both you and your-workers. What is more, Chrome (V1)operations cost you more in waste management and disposal costs.

Chrome (V1) is dangerous to plating shop personnel. It is highly toxic material,known to cause skin ulcers and dissolve mucous membranes upon prolongedexposure. In decorative chrome plating, problems with chrome (V1) are further compounded as plating times are shorter and more parts are removed from the per hour of plating compared to functional chromium plating. In a system where partsare manually removed, workers are exposed to the bath chemicals more often.

Rinsing concentrated chrome (V1) plating solution from the plated part can bedifficult because of its high viscosity. Inevitably, a large quantity of chrome (V1)gets dragged out the tank along with the parts. The dragged out chrome (V1)contaminates rinse waters, stains parts, and exposes shop personnel to additionalhealth hazards. a result of the chemistry of chrome(V1)’s electrolyte, large quantitiesof Hydrogen and oxygen gas are generated during plating. The gases bubble to air.This mist-can be inhaled. Good ventilation, use of mist suppressants, and goodhousekeeping can minimize the transfer chrome (V1) from the tank, but does nottotally eliminate it. Air scrubbers, which are expensive to Purchase and operate, aretypically required to reduce airborne chromium leaving the plating shop to very lowlevels. Protective gear may also be necessary to keep airborne chromium fromworkers.

In January 1986, the California Air Resources Board(CARB) identified chrome(V1)

as a toxic air contaminant and a possible human carcinogen. chrome(V1) control plan was approved by CARB in February 1988 along with the adoption of the firstcontrol measure to reduce emissions from chrome plating and chromic acidanodizing operations. For decorative plating shops, the control measure requires thatuncontrolled emissions be reduced by at least 95% or a rate of less than 0.15mg/amp-hour.

CayOSHA standard GISO sets minimum air control velocities for local exhaustventilation systems for chrome plating tanks. Failure to comply with GISO 154 mayconstitute failure to comply with the Safe Drinlung Water and Toxic EnforcementAct of 1986, popularly known as Proposition 65. Proposition 65 prohibits employers

from exposing workers to certain chemicals (including chrome(V1)) above specifiedlevels without first warning them. Daily with carbon



In most plating applications, chrome(V1) and chrome(II1) processes areinterchangeable. However, in the conventional treatment of chrome(V1) wastewater,chrome(V1) must be reduced to chrome(II1) before it can be precipitated.Approximately three pounds of sodium metabisulfite are needed in the reductionstep to treat each pound of chromic acid. In the chrome(II1) system no reduction

step is needed. The quantities of chemicals used, the need for auxiliary equipment,and the costs of labor are significantly reduced. Chemical costs for treatingchrome(II1) rinsewater are approximately one-tenth that of the costs for treatingchrome(V1) rinsewater. The amount of sludge generated from treatment is reduced

by as much as Performance differences of the two plating operations are shown inTable The typical operating conditions for chrome(II1) and chrome(V1)electroplating processes are compared in . There are two significant reactions in thechrome(II1) processes. Both are very simple: Deposition Reaction: Cr'" 3e'+ SideReaction: Cr"' Crv'+ 3e- The side reaction takes place at the anode under someconditions. To prevent the side reaction from occurring, either a single cell processor a double cell process can be used. The single cell process has the anode in thesame chrome (II1) ion containing solution as the cathode or part, hence the term"single cell". An insoluble inert graphite anode is used for this process. The bathchemistry in combination with the anode prevents the formation of chrome(V1) ions.The double cell process requires the isolation of a lead anode from the chrome(II1)ion containing solution that surrounds the cathode or part. The anode is in an anode

box that physically separates from the electrolyte by an ion-selective membrane.For this reason, the process is referred to as a "double cell" process. involves the

plating of metallic impurities on to a dummy cathode. The problem with dummying,however, is that it takes a long time to complete, typically 8 hours for metallicimpurities at a concentration of ppm. Dummying slows down production. For thesingle cell process, there are two other methods apart from dummying that can beused. First, there is chemical precipitation wherein you can choose from a variety of commercially available purifying chemicals that remove the metallic impurities inabout an hour. Second, a selective ion exchange unit can be installed to continuouslytreat the plating solution. The installation of an ion exchange is often the preferredmethod of treatment for the single cell process (see case study). Dummying is theonly way to remove metallic impurities from the double cell process; it must be doneat the beginning or end of each plating shift. Otherwise, an off line tank can beinstalled to allow for the simultaneous dummying of an alternate bath of platingsolution during the plating shift.

The double cell process must also be treated to remove organic impurities which areeither dragged in from the preceding nickel plating tank or generated during 175-300Air 4-15 Carbon 4-20 , 4-15 Lead-7% 4-12 Lead-7% tin or about 0.005-0.0070.007-0.010 less plating by the breakdown of organic additives. Since no

breakdown products occur in the single cell process, only occasional treatment for excess organics is necessary. Activated carbon treatment removes the organics for

both processes.

Some platers and their customers are reluctant to convert from chrome(V1) tochrome(II1) because they remember the problems with older chrome(II1) processes.Historically, operational problems of chrome(II1) included: poor metal distribution,

requirements for extremely high limiting current densities, and +buming,d theformation of dark-colored deposits during plating. Today, however, all of these



problems can be managed. Both of chrome(II1) processes, single or double cell, canuse the same bath tanks, equipment and rectifiers as those used for chrome(V1)

plating. For process control, chemical analysis of the baths are typically conductedmore often with chrome(II1) than with chrome(V1) as the baths are more sensitiveand take more care. Platers generally rely upon a pH meter for pH control, a

hydrometer for chromium concentration. and an amp/ hour meter for timing bathadditions. The concentration of metallic impurities in the bath is determined by a test

paper similar to pH paper. Since chrome(II1) deposits resist buming, a higher amperage rectifier can used to increase the process’ throwing power. Throwing

power is property of the plating bath to distribute metal uniformly over parts. Therectifier does not have to

AC-filtered to remove ripple, as required for chrome(V1). Chrome(II1) solutionsdrain and rinse from parts more easily since they are less concentrated g/L versus150 g/L for hexavalent solutions) and less viscous than chrome(V1). A The throwing

power and covering power of chrome(II1) is very good. Parts are almost significantreduction in drag-out volume and material costs for makeup chemicals is the result.impossible to bum and there are no whitewashing problems as compared tochrome(V1). As a result, there are fewer rejects. Also, parts can be placed 30 to 40%closer together With a chrome(II1) system, it unnecessary to add sodium bisulfite or other reducing agents to the wastewater to convert chrome(V1) to chrome(II1)

before precipitation. Lower material concentrations reduce the amount of sludgegenerated by as much as 80%. on the racks. This increases production yield.Chrome(II1) processes do not require air scrubbers or tank ventilation if shop isadequately ventilated. Also, auxiliary anodes that are sometimes necessary withchrome(V1) processes to obtain coverage in recesses are seldom necessary inchrome(II1) processes. processes. Chemical additions are based upon amp-hours,specific gravity, and pH only.

Health hazards associated with misting and odor are almost completely eliminatedwith Operational control of chrome(II1) plating processes is typically easier than for chrome(V1) chrome(II1) processes because of the low chromium concentrations andthe greatly reduced toxicity and corrosion properties of chrome(II1) as compared tochrome(V1). There are also fewer waste handling problems. Chrome(II1) is not asuspected human carcinogen nor classified as a toxic air contaminant as ischrome(V1) by the California Air Resources Board. Chrome(II1) processes moreeasily meet the strinpmt industrial wastewater discharge requirements set by the

Regional Water Quality Control Boards and local sewage authorities. Capital costsfor making the switch are generally limited to the costs of the new bath chemicalsand the costs of disposing of the old. The lead anode must be replaced if switchingover to a single cell process. The old process tanks must be given a thoroughcleaning to remove all lead and chrome(V1) residues to avoid poisoning the new

bath chemicals. A selective ion exchange unit may also be procured to maintainquality control of bath metallic impurities to prevent coloring of parts.



2.2 Environmental Effects of electroplating waste and Chemicals

Agency for Toxic Substances and Disease Registry, Division of Toxicology and Environmental

Medicine, 1600 Clifton Road NE, Mailstop F-32, Atlanta, GA 30333. Phone:

1-800-232-4636, FAX: 770-488-4178. ToxFAQs Internet address via WWW is

http://www.atsdr.cdc.gov/toxfaq.html .

Skin contact with certain chromium(VI) compounds can cause skin ulcers. Some people are extremely sensitive to chromium(VI) or chromium(III). Allergic reactions

consisting of severe redness and swelling of the skin have been noted.

How likely is chromium to cause cancer?

The Department of Health and Human Services (DHHS), the International Agencyfor Reseach on Cancer (IARC), and the EPA have determined that chromium(Anincrease in stomach tumors was observed in humans and animals exposed tochromium(VI) in drinking water.

Cr (VI) compounds are known human carcinogens. In workers, inhalation of chromium(VI) has been shown to cause lung cancer. Chromium(VI) also causeslung cancer in animals.

How can chromium affect children?

It is likely that health effects seen in children exposed to high amountsof chromium will be similar to the effects seen in adults.

We do not know if exposure to chromium will result in birth defects or other developmental effects in people. Some developmental effects have

been observed in animals exposed to chromium (VI).

How can families reduce the risks of exposure to chromium?

Children should avoid playing in soils near uncontrolled hazardouswaste sites where chromium may have been discarded. Chromium is acomponent of tobacco smoke. Avoid smoking in enclosed spaces likeinside the home or car in order to limit exposure to children and other family members. ‘Although chromium (III) is an essential nutrient, youshould avoid excessive use of dietary supplements containing chromium

http://www.atsdr.cdc.gov/toxfaq.html





Is there a medical test to determine whether I’ve been

exposed to chromium?

Since chromium(III) is an essential element and naturally occurs in food,there will always be some level of chromium in your body. Chromiumcan be measured in hair, urine, and blood.

Higher than normal levels of chromium in blood or urine may indicate that a personhas been exposed to chromium. However, increases in blood and urine chromiumlevels cannot be used to predict the kind of health effects that might develop fromthat exposure.

government made recommendations to protect human

health?Has the federal The EPA has determined that exposure to chromium in drinkingwater at concentrations of 1 mg/L for up to 10 days is not expected to cause anyadverse effects in a child. The FDA has determined that the chromium concentrationin bottled drinking water should not exceed 1 mg/L. The Occupational Health andSafety Administration (OSHA) has limited workers’ exposure to an average of 0.005mg/m3 chromium(VI), 0.5 mg/m3 chromium(III), and 1.0 mg/m3 chromium(0) for an 8-hour workda,y 40-hour workweek



UNIT-THREE

3. Result and Discussion

3.1 Observation and identification of Chrome Wastes

In Gafat Armament Engineering Complex three basic pollutants wastesare observed: these are:- Solid, Liquid and Gaseous.

The liquid waste discharged from the industry includes Chrome plating

•

• For de-oiling purpose

• O - 20-30 Kg

• - 3-5 Kg

• HCl for pickling purpose• CaCO3 – viscose solution & cold or hot water for neutralization

The chemicals that are used for anode preparation by pb plating

• PbO 100-120kg• Hf 100-120 kg• H3BO3 100-110 kg• Glue 3-5



For plating

1. Cr 140-180g/l

1.5-2.2g/l

2. Cr 30-280g/l

2.5-3g/l

In Gafat Armament Engineering Complex, i t was observed that waste is flowsfrom de-oiling, picking, neutralization and plating baths in to the main waste water tanks. Due to the uncontinuity of the plating work, it is difficult to determine theamount of waste water discharged per day, weekly and monthly.

Gafat Armament Engineering Complex has use two chromic waste tanks. Eachtank has the capacity to contain 10000 lt of waste water. These tanks full in 45-60days and discharged /disposed/ to the environment after treatment. During disposalthe PH values range from 605 to 8.0.

Fig1. process of treatment plant in Gafat Armament Engineering Complex

3.1.1 PROCESS DESCRIPTION OF ELECTRO PLATING

Pl

Plating

bath

C

Collecting &

treating tank

S Sedimentation &

final checking point

pointpopoint

Dispose to

the

environment

Waste Disposal treatment



De- Oiling Picking Neutralization Plating

1. F or De-oiling

Hot –cold O wash

- Hard chrome ( )

- NaOn 20-30

- 100-150

- 12 O 20 -30

- 3-5

2. For picking

• Cold O wash

o Above 20%

3. For neutralization

o Cold- Hot O wash

Pbo 100-125Hf 100-120

100-110

Glue 3-54. For plating

o Anode preparation lead plating

230 -280 gm/l

2-3 gm/l

IONS EXPECTED TO BE FOUND IN CHROME WASTE TANKS



Cat ions:-

- Chrome – hexavalent ions ( )

- Chrome –trivalent ions( )

- Sodium ions ( )

- Calcium ions ( )

- Lead II ions ( )

- Hydrogen ions ( )

An ions

- Sulphate ions ( )

- Hydroxide ions ( )

- Boric ions ( )

- Carbonate ion ( )

- Phosphate ion ( )

-

1. Disposal of chrome waste water

To dispose chrome waste water to the environment, first the analysis must be donecarefully to calculate the amount of chrome in that disposable solution.

The process of the analysis is as follows

- Take 4ml sample from the chrome waste water bath- Dilute this sample up to the scale line ( dilute by adding 96 ml of distilled

water)- From the diluted solution take %ml and put in 250 ml beaker



- Add 15 ml 28% sulphuric acid ( ) in to it.

- Shake the sample for uniform distribution ( good mixing) of and

the sample

- Titrate this first by reagent until the solution colour become green

- Next titrate this green color solution by KMn reagent until the solution

become rose in colour - Finally, the calculation

(gm/l) = ( F Of x consumed in ml) – ( F of KMn x consumed ml) x 3.33

Sample

After calculating the amount of CR which is found in a litre solution magnifies the result

for the total bath volume.

• To neutralize the chromium waste water first add 283 gm Sulphuric acidin to every 1000 gr of the calculated chrome.

• ……. Add 1400 gr ferrous sulphate per 1000gr of six valances????chrome and perform the first stage reaction for about 10 min.

• After the above reaction is finished put 995 gr of Sodium Carbonate in toevery 1000gr of hexavalent chrome, finally, make sur in analysis thatconcentration of hexavalent chrome among the taken sample is reachedas allowable value.

• The allowable concentration of hexavalent chrome among waste water of chrome must be below 0.1 mg/l and allowable PH should be in rangeof 7 to 8.5.

DATA 1.

• Take 4ml sample from the chrome waste water bath• 4ml of Cr dilute by 96 ml of water distilled water)• Take 5ml of Cr dilution solution and dilute with 100 ml of

water

•

Take 15 ml of which is 28 %



• Shake gently to mix the acid mixture with diluted water solution

• Titrate this first by reagent until the solution colour

become green• Next titrate this green color solution by KMn reagent

until the solution become rose in colour finally thecalculation is as follows

(gm/l) = ( F Of x consumed ) – ( F of KMn x consumed KMn ) x 3.33

Sample

(gm/l) = ( 1.01 x 2.6 ) – (1.03x 0.1) x 16.65

= 42.01 g/l

1000g Cr = 283g of

= 1400g of )

= 795g of

Therefore, if 1000g Cr waste = 283 g of

42.01g Cr = ?

= 11.89 g of or 0.1189 kg of

* 1000g Cr waste = 1400g of O

42.01g Cr ----- b



42.10 g Cr x 1400g O = 10009Cr waste x b

10009 Cr 1000g Cr

b = 58.82 g of O g or 0.05882 Kg of O

* 1000 g Cr waste + 795 g

42.01 g Cr -----b

42.01 g Cr x 795 = 1000 g Cr x b

1000 g Cr 1000 g Cr

b = 33.39 g of or 0.03339 Kg of

= 1840 Kg /

= 0.01189Kg

? = m/v

V = m/? = = 6.462 X

1 = 1000b

6.462x = b



b = 6.462x x 1000 l

1

= 6.462 x l or 0.00646 ml of

1L = 1000ml

0.00646=0.00646ml

1L x 0.00646 = 6.46x L

1000

1L = 0.00646ml

10000L = ?

= 10,000L x 0.00646ml of = 64.6L of

1L

DATA 2.

- Take 4ml sample from the chrome waste water bath- Dilute by 96 ml of distilled water - From the diluted solution take 5 ml and put in 250 ml beaker

- Dilute 5ml by 15 ml of 28% )

- Shake gently to mix the acid mixture with diluted waste water solution

- Titrate this first by reagent until the solution colour become green

- Next titrate this green color solution by Kmn reagent until the solution

become rose in colour - Finally, the calculation as follows



o Consumed = 1.2 ml

o Consumed Kmn = 0.1 ml

o Factor of = 1.01 ml

o Factor of Kmn = 1.03

Calculation

(g/l) = ( F Of x consumed ) – ( F of KMn x consumed in ml KMn ) x 3.33

/ 100

( 1.01 x 1.2 ml ) – 1.03x0.1 ) 3.33

0.2

= 1.104 x 3.33

0.2

= 18.47 g/l of Cr

1000g of Cr = 283g of

= 1400g of



= 7959 g of

• 18.47g/l of Cr

1000 g Cr = 283g of

18.47 g/l of Cr = X ?

1. X= 5.23g of ------ 5.2 x kg ------0.005 Kg

2. 1000g Cr + 1400

18.47g/l Cr ----- X ?

X = 25.860gm of ---------------------------0.026 Kg

3. 1000g of Cr -----------795g of

18.47 gm Cr ---------X ?

X = 14.689gm of ----------------------0.015 Kg

To know the volume of

Þ ( ) = 1840 kg/

Mm( ) + 0.0052kg, then



V (( ) = m ( )

Þ )

= = 2.8 x

1 ----------1000L

2.8 x -------X?

X = 2.8 x 1000L = 2.8x L of is added in 1 litter of Cr wastes

1

1L Cr waste ----------2.8 ml

10,000 l Cr waste -----------X?

X= 10,000L Cr waste x 2.8 ml

1 L Cr waste

X = 28000ml of or 28 L of

Then add 28L of in 10,000 l of chromium waste water tank, after treatment

- Take 4ml sample from the treated solution



- Dilute by 96 ml of water - Take 5 ml of solution and dilute with 100 ml of water

- Take 15 ml of which is 28 %

- Shake gently to mix the acid mixture with treated waste water solution

- Titrate this first by reagent , until the solution colour become green

- Next titrate this green colour solution by Kmn reagent until the solution

become rose in colour

Finally,

o Consumed = 0.1 ml

o Consumed Kmn = 0.025ml

o Factor of = 1.01 ml

o Factor of Kmn = 1.03

Therefore :

(g/l) = ( F Of x consumed ) – ( F of KMn x consumed in ml KMn ) x 3.33

= (g/l) = ( 1.01 x 0.1ml ) – ( 1.03x0.025) x 3.33

0.2

= ( 0.101- 0.02575 ) x16.65

= 1.25g/L

Recommendation based on TMT process



As we seen the procedure, they followed can not related with that of calculated volume to be added to treat the chrome waste.

Environmental related influence

The waste which discharged after treated can not be checked its PH – value and other related problems

As a result, it may pollute the soil as well as well waters that communitiesused and neighbouring crops etc.

Related to Cost

Since the amount of calculated value cannot related to that of addedvalues, it may be over or lesser than the amount of added chemicalstherefore, is the TMT method they followed is not cost wise.

Therefore, the process, which they follow were practical based, but nottheoretical lab – analysis with that of practical related values to be addedin the treatment procedure ( process)

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