LECTURE NOTES ON INDUSTRIAL WASTEWATER TREATMENT Course Code: (A) IV kaz-news.info Civil - I Semester SRINIVAS ANGADI Asst. Professor in. 4 days ago PDF | Treatment of chemical industrial wastewater from building and construction chemicals factory and plastic shoes manufacturing factory. PDF | On Jan 1, , Derin Orhon and others published Industrial Wastewater Treatment by Activated Sludge.
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edge to explain how different treatment processes work, how they can be optimized and how . Treatment Evaluation Process: Industrial Wastewater. Citation: Maulin PS, Borasiya H. Industrial. Waste Water Treatment. J Appl Microbiol. Biochem. , The phrase “vanguard therapy " can. Environment Control & Measures for Industrial Wastewater Treatment. 2. Considering Aspects on Wastewater Treatment Plant Design. 3. Wastewater Treatment.
Each pollution problem calls for specific optimal and cost-effective solution; if one technology proves less or ineffective, the other takes its place. It is indispensable to treat industrial wastewaters for their subsequent use for irrigation, drinking, and other purposes.
In addition, due to an increased scarcity of clean water, there is a need for appropriate management of available water resources [ 3 ].
The factors like profound demographic, economic changes and global energy crisis are compelling the implementation of low-cost natural treatment systems for the domestic and industrial wastewaters [ 1 ].
In the recent years, the wastewater treatment strategies have been shifted to one of the most promising methods, that is, biological anaerobic treatment with the adoption of high rate anaerobic systems like upflow anaerobic sludge blanket UASB and other related treatment systems. The outstanding characteristics of high rate ABR include the anaerobic microorganisms capable of aggregation, low operational and maintenance costs, energy recovery in the form of biogas, low energy consumption, and low production of digested sludge [ 4 — 7 ].
In developing countries like India, Brazil, and Colombia, where financial resources are generally scarce due to high energy costs, the process is familiar as one of the most feasible methods for the wastewater treatment.
Despite several modifications, the quality of ABR treated effluent hardly ever meets the discharge standards [ 6 , 8 ]. Since its inception, wider hype has been gained by this process [ 16 , 17 ]. The ABR treated effluents can be employed for irrigation of various crops. However, such type of effluent may be high in chemical oxygen demand COD , biochemical oxygen demand BOD , and coliforms [ 18 ].
Thus, additional posttreatment strategy is mandatory for the ABR treated effluents if further use is desired [ 19 — 21 ]. CW wastewater treatment systems are engineered structures specifically designed for treating wastewater by optimizing the physical, chemical, and biological processes that occur in natural wetland ecosystems [ 1 , 18 , 22 — 24 ].
CW is known as green technology which uses plants for the removal of contaminants from a specified area, and process is known as phytoremediation [ 25 ].
CW is a low-cost or economical on-site wastewater treatment technology which is not only effective but also aesthetically pleasing. These include vegetable or chrome tanning, shaving and finishing. The finishing operation includes bleaching, stiffing and fat liquoring and coloring. Protective treatment administrated soon after the hides and skines are flayed is called curing.
Curing involves dehydration of the hide by drying it with salt or air in order to stop proteolytic enzyme degradation. Curing creates an envionment for the hides and skins in which the protein destroying organism cannot function. Its sole purpose is to ensure that the hides and the skins are protected during transit from slaughter house to the tanneries which are generally located some good distance away. It also facilitates storing. Fleshing removes the fatty tissues from the skin by mechanical means.
Cured hydes and skins arriving at tannary are trimmed to remove long shanks and other unwanted areas. Washing and soaking remove the dirt, salts, blood, manure and nonfibrous proteins and restore the moisture lost during preservation and storage. Unhairing is accomplished by the use of lime, with or without sodium sulfide, this makes the skin more attractive and more amenable to the removal of trace protein impurities.
Lime splitting separates the skin into two layers, one is more valuable grain layer the other the lower or flesh side is called the split. Bating prepares the hide fir tanning by reducing the pH, reducing the swelling, peptizing the fibres and removing the protein degradation products.
Bating is generally accomplished with ammonium salts and a mixture of commercially prepared enzymes, the bathing bath renders the grain sticky, slippery, smoother and more porous increases its width and decreases its wrinkles. Pickling generally precedes chrome tanning and involves treatment of the skin with salt and acid to prevent precipitation of the chromium salts on the skin fibers.
Degreasing removes natural grease, thus preventing formation of metallic soaps and allowing the skin to be more evenly penetrated by tanning liquors.
Chrome tanning is used primarily for light leathers while vegetable tanning is preferred for most heavy leather products. The process of chrome tanning is of shorter duration and produces more resistant leather.
In chrome tanning process the tanning is done in the same vat after one day of pickling by adding a solution of chromium sulphate. After 4 hours of tanning, the leather is bleached with a dilute solution sodium thiosulphate and sodium carbonate in the same bath. The third stage of finishing consists of stuffing and fat liquoring followed by dyeing. In the former process the tanned leather incorporates oil and grease and thus becomes soft and resistant to tearing.
Dying can be done using synthentic dye stuffs. Depending on the type of product, either vegatable substances containing natural tanning eg. Vegetable tanning produces leathers which are fuller, plumper, more easily tooled and embossed and less effected by body perspiration or changes in humidity. Dyeing to produce the final colored leather product is usually done with basic dyestuffs. Sources of waste water and their characteristics: The waste may be classified as continuous flow waste and intermittent flow waste.
Continuous flow waste consists of wash wastes after various processes and comprise of a large portion of the total waste, and are relatively less polluted than the other one.
Spent liquors belonging to soaking, liming, bating, pickling, tanning and finishing operations are discharged intermittently. Although these are relatively small in volume, they are highly polluted and contain varieties of soluble organic and inorganic substances.
The waste water from beam house process viz. The spent soak liquor contains soluble proteins of the hides, dirt and a large amount of common salt when salted hides are processed. The spent liquor undergoes putrefaction very rapidly as it offers a good amount of nutriants and favourable environments for bacterial growth.
The spent bate liquor contains high amount of organic and amonia-nitrogen due to the presence of soluble skin proteins and amonia salts. The vegetable tan extract contains tannins and also non tannins and high organic matter. The waste water from tanyard process viz. The spent lime liquor contains disolved and suspended lime and colloidal proteins and their degradation products, sulphides, emulsified fatty matters and also carry a sludge composed of unreacted lime, calcium sulphide and calcium carbonate.
The spent liquor has a high alkalinity, moderate BOD and a high ammonia-nithogen content. Effects of waste on receiving water and sewers: Tannery wastes are characterized by high BOD, high-suspended solids and strong color. These wastes when discharge as such deplete the dissolved oxygen of the stream very rapidly, due to both chemical and biological oxidation of sulfur and organic compounds. A secondary pollution of the stream may occur due to the deposition of the solids near the discharge point and its subsequent putrefication.
Presence of tannins in the raw water renders it unsuitable for use in certain industries. The tannery waste when discharged into a sewer only chokes the sewer due to the deposition of solids, but also reduces the cross- section of the sewer arising out of the lime encrustation.
Treatment of waste: The method of treatment of waste may be classified as physical, chemical, and biological. The physical treatment includes mainly screening and primary sedimentation. Screens are required to remove fleshings, hairs and other floating substances. Chemical coagulation, with or without prior neutralization followed by biological treatment is necessary for better quality of the effluent.
Ferrous sulfate is reported to be the best coagulant for the removal of the sulfides and may be used for the effective removal of color, chromium, sulfides, BOD and suspended solids from chrome tan wastes.
Both oxidation pond and anaerobic lagoons are recommended for small and isolated tanners. For further improvement of the effluent quality the anaerobic lagoons may be followed by an aerated lagoon.
Composition of composite waste water pH 9. Cotton textile mill waste: An integrated cotton textile mill produces its own yarn from the raw cotton.
Production of yarn from raw cotton includes steps like opening and cleaning, picking, carding, drawing, spinning, winding and warping. All these sequences are dry operations and as such do not contribute to the liquid waste of the mill.
It is a process in the manufacture of spun yarns whereby the staple is opened, cleaned, aligned and formed into a continuous untwisted strand called sliver. It is the process of increasing the length per unit weight of sliver.
A method to remove short fibers, foreign matter from cotton stock by pressing it through a series of needles or combs. It is a process by which a long strand of fibres is drawn out to a short strand and converted into a yarn. After drawing out, it is subjected to twisting and the resulting yarn is wound into a bobbin. It is the process of transfer of a yarn or threadfrom one type of package to another. It is the process of interlocking two yarns of similar materials so that they cross each other at right angles to produce a woven fabric.
In slashing, to give it the tensile strength and smoothness necessary fot subsequent weaving the yarn is strengthened by loading it with starch or other sizing substances. After slashing the yarn goes for weaving. Enzymes are usually used in India to hydrolyze the starch ; acids may also be used for this purpose.
To remove the natural impurities such as greases waxes, fats and other impurities, the desized cloth is subjected to kier boiling i. After boiling the spent liquor is discharged as waste. This is a strong waste, dark brown in colour, and highly alkaline. Temperature of the effulient is high. Replacement of soap used in scouring by low B. D detergents may reduce B. Bleaching operations use oxidizing chemicals like peroxides and hypochlorites to remove natural colouring materials and to render the clothes white.
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The bleaching process is necessary where fabrics are to be given a full white or where they are to be dyed in specific shades. In this process the natural colouring matter in the textile material is removed by the use of oxidising chemicals like peroxides and hypochlorites.
The process improves the strength, elasticity , lustre and dye affinity. Waste from this section is recycled after sodium hydroxide recovery. Dyeing may be done in various ways, using different types of dyes and auxiliary chemicals. Classes of dyes used include vat dyes, developing dyes, napthol dyes, sulfur dyes, basic dyes, direct dyes etc. Direct Dyes Neutral Dyes are used as they are easy to apply and no auxillary chemicals are needed.
Basic Dyes: This class of dyes give bright colours. They are applied along with week organic acids. Sulphur Dyes: For dark colours, these dyes employed. These are sulphur compounds applied usually with sodium sulphide followed oxidation with chromate.
Vat dyes require caustic soda and sodium hydrosulfite to reduce the dye into a soluble form. Sulfur dyes are reduced by sodium sulfide and oxidized by chromate. Indigo dyes are also similar to vat dyes, but require only air oxidation.
Colour from the dyes vary widely and although those are not usually toxic, they are esthetically objectional when they impart colour in the drinking water supplies.
After fixation of the prints, the fabric is given a thorough wash to remove unfixed dyes. The finishing section of the mill imparts various finishes to the fabrics.
Various types of chemicals are used for various objectives. Composition of composite cotton textile mill waste pH 9.
Wool wastes originate from scouring , carbonizing , bleaching , dyeing , oiling , fulling and finishing operations. Impurities of raw wool, consisting mainly of wool grease and other foreign matter are removed by scouring the wool in hot detergent alkali solution.
Some wool are scoured by organic solvents. Wool grease may be recovered from the scouring waste by centrifuging , coagulation or floating and may be processed further for the production of lanoline and potash. Carbonizing is a process in which hot concentrated acids are used to convert vegetable matter in the wool into loose charred particles, followed by mechanical dusting of the same. Wool may be dyed at any stage, either as raw stock, or after spinning and weaving.
Normally hot dye solutions are circulated through the wool, packed in a metal container. In oiling, usually olive oil or a barg-oil-mineral-oil mixture is sprayed over the wool to aid in the spinning. Fulling is an operation where the loosely woven wool from the loom is shrunk into a tight closely woven cloth.
To aid this process, chemicals like soda ash, soap etc are used. Excess fulling chemicals , all of the oil etc are washed out of the fabric in a finishing process. Waste from a dyeing and finishing process are contributed by the spent liquors and by subsequent washing of wool after bleaching , dyeing and finishing. Characteristics of a typical wool waste: The crude waste, if discharged into the streams, causes rapid depletion of the dissolved oxygen of the streams. The condition aggravates due to the settlement of the suspended substances and subsequent decomposition of the deposited sludges in anaerobic condition.
The alkalinity and the toxic substances like sulphides and chromium affect the aquatic life; and also interfere with the biological treatment process; some of the dyes are also found toxic.
The pollution load of the waste is dealt with in the operations like segregation , equalization , neutralization, chemical precipitation , chemical oxidation and biological oxidation. Several chemicals are used to reduce the BOD by chemical coagulation.
Industrial wastewater treatment by means of membrane techniques
These are alum, ferrous sulfate , ferric sulfate, ferric chloride etc. Calcium chloride is found to be effective in treating wool-scouring waste. The dye wastes may be treated economically by biological methods, with prior equalization , neutralization and chemical oxidation for certain wastes.
A composite waste, when free from toxic substances may be treated as efficiently as domestic sewage, as most of the textile mill wastes contain sufficient nutrients like nitrogen and phosphorus. Trickling filters, Activated Sludge Process , Waste Stabilization ponds, all these types of biological treatment have been tried for the treatment of textile mill wastes and all of them are found to be very effective. Excellent results were also obtained with Extended Aeration in treating a strong waste , even without any equalization and pre-treatment; this method eliminates the necessity of sludge digestion as well.
Synthetic Textile Mill Waste: The most prominant man made synthetic fibers are Rayon, nylon and polyster. These fabrics require no processing for the removal of natural impurities as they are man made.
Manufacture of synthetic fabrics involve two steps: Wastes from the manufacture of the synthetic fibre resembles chemical manufacturing wastes, and depends entirely on the raw materials used and the process adopted. A typical synthetic fibre Nylon-6 is obtained through polymerization of caprolactum and subsequent pelletization , drying , remelting in extruders , spinning and twisting.
The wastes from this manufacture are usually characterized by a colloidal type turbidity , a typical colour , a low alkalinity pH around 7. The waste usually contains a large amount of nitrogen, entirely of organic origin. Dairy Wastes Units Operation in a Dairy: Receiving Stations The receiving station serves as a collection point for raw milk from the farmers.
When milk is delivered to the dairy in cans and these cans are emptied, rinsed and washed and in some cases sterilized before returning. Bottling Raw milk received is weighed and classified generally based on the fat content , it is preheated, pasteurized, cooled and then filled into bottles, polythene bags, cardboard packets etc. Product Making Dry milk, milk powder, cheese, butter and other products as ice cream, condensed milk are prepared out of milk.
Sources of wastes: Waste producing operations are washing of bottles, cases, cans, tanks, cooling equipment, Processing equipment and floors. Dripping, leaks, spillages and overflows due to improper equipment or inefficient operation.
Discharges from evaporators. Spoiled raw or treated products. Classification of Waste: Water used for condensing and free from milk solids. These are easily disposed off. Whey and buttermilk have high BOD.
Characteristics of wastes: Heavy black sludge and strong butyric acid odors because of decomposition of casein are common. Also, these wastes contain nitrogen and phosphorous which are excellent nutrients for algae and other aquatic plants, which on death add to the taste and odour of the waste water.
Combined Industrial Wastewater Treatment in Anaerobic Bioreactor Posttreated in Constructed Wetland
Parameter Value pH 7. Reduction of volume and strength of the wastes by: Prevention of spills, leakages and dropping of milk from cans. By reducing the amount of water for washes iii. By segregating the uncontaminated cooling water and recycling the same. Due to the intermittent nature of the waste discharge, it is desirable to provide, Equalization tank with or without aeration before the same is sent for biological treatment. A provision of grease trap is also necessary as a pretreatment to remove fat and other greasy substances from the waste.
Both high rate trickling filters and activated sludge plants can be employed very effectively for a complete treatment of the dairy waste. On the other hand the low cost treatment methods like oxidation ditch, aerated lagoon, waste stabilization pond etc can be employed with simpler type of equipments and less maintenance.
Breweries Wineries Distilleries Introduction: While Breweries and Wineries produce beer and wine respectively, a large number of products of varying origin are obtained in Distilleries. The range of products from distilleries includes industrial alcohols, rectified spirit, silent spirit, absolute alcohol, beverage alcohol etc. But two things are common all the products: All the products are obtained through the bio-chemical process of fermentation by yeast, using carbo-hydrates as raw materials 2.
All the products contain ethyl alcohol in different proportions.
Origin and Characteristics of Breweries Wastes Making of beer essentially consists of two stages: Preparation of malt from grains like barley and 2. Brewing boiling and fermentation the Barely. In malt making, the barely grains are steeped soaked in liquid to bleach out colour, and then made to sprout appear or begin to grow under aerobic conditions. The grain malt is then dried and stored after screening the sprouts out. The wort is then filtered and cooled.
The filtered wort is then inoculated with a prepared suspension of yeast, which ferments the sugar to alcohol. When the fermentation is complete the yeast and malt residue is filtered out and finally the beer is carbonated before packing for sale. Brewery Wastes Originate in both these stages.
One being the spent water from the steeping process from the malt house. The waste includes the water soluble substances of the grain that are diffused into it. Characteristically it contains a large amount of organic soluble solids indicated by a high B.
In the brewing plant, the major potential pollutant is the fermentation residue or the spent grains. Wastes also originate in the preparation of yeast suspension, from washing of containers, equipments and floors. Large volume of almost on polluted water also comes out as waste cooling water. The waste from the brewing plant contains high-suspended solids and also a high B. The beverage alcohol industries utilize different grains, malted barley and molasses as raw materials.
Introduction to Wastewater Treatment Processes
In beverage alcohol industry, the preparation of mash consists of: Preparation of green malt 2. Preparation of cooked slurries of the grains 3. Mixing of the above two followed by ph adjustment and nutrient ammonium salts and phosphates supplementation. On the other hand in molasses distilleries, the preparation of mash consists of: Nutrient addition.
The yeast suspension is prepared separately in the laboratory with art of the diluted molasses and then inoculated into the mash for fermentation under controlled conditions. The same is then degasified, and then the alcohol is stripped leaving a spent wash. The crude alcohol is then redistilled and stored in vats. The spent wash is the major polluting component of the distilleries and it is reported to be ten to fifteen times the final product in volume.
The other pollutants include yeast sludge, which deposits at the bottom of fermentation vats. Malt house wastes also contribute towards pollution in beverage alcohol distilleries. In addition to these major B. D and solids contributing wastes, floor washes, waste cooling water, and wastes from the operations of yeast recovery or by-products recovery process also contribute to the volume of these wastes.
The wineries utilize the fruit juices as the raw materials. So the first operation in any winery is the pressing of fermentable juice from the fruits like grape etc. The second stage in any winery consists of fermentation of this juice employing the method described earlier. The wine attains its final form at this stage and requires only decantation, blending and bottling for sale. The waste from this stage comes from fermentation, decanting spillages, floor washes etc Characteristics of Combined Wastes from Brewery, Winery and Food Processing Units: Parameter Value pH 4.
Treatment of the Wastes: Brewery wastes being comparatively less strong can be treated by aerobic biological treatment,after screening and neutralization. D reductions. D and is rich in proteins, carbo hydrates, vitamins may be treated separately for by product recovery. The raw spent wash with low pH, high dissolved solids, high temperature, high sulphates, and high B. D is not amenable to aerobic biological; treatment.
Two-stage biological methods of treatment consisting of an aerobic treatment have been widely accepted as the only methods of treatment of the wastes from the distilleries. A single stage digester is usually adopted for the anaerobic treatment when land available is limited. Anaerobic lagooning is a low cost alternative to the digesters when land is available in plenty.
The only disadvantage of anaerobic lagoons is the evolution of volatile gases and obnoxious odour from the ponds. Effluent of the digesters an the anaerobic lagoons still contain a high B.
D, which cannot be discharged into the receiving streams. These effluents can successfully be treated either in aerated lagoons, or in oxidation ponds. The yeast sludge from the distilleries contains the degradation product of the dead yeasts and organic debris from the malt s like proteins, fats, vitamins and carbo-hydrates. On the other hand the spent wash contains al, the above nutrients plus unfermented sugars, amino acids, ammonium phosphates etc. So two types of by products viz.
The segregation of yeast sludge for processing for animal feed is practiced in some distilleries, which in turn reduces the insoluble B. D load of the waste. Meat Packing Wastes Meat Processing Meat is the dressed flesh derived from cattle, buffalo, sheep, goat, pigs and poultry.
Meat being a highly perishable product, can be kept in a fresh condition only through proper processing and storage. When meat gets spoiled it becomes slimy or sticky, turns dark brown and develops an unpleasant smell and taste. Meat is preserved in a number of ways such as freezing, curing, smoking, dehydration and canning. Processed meat: Almost all the meat produced in India is consumed as fresh meat, only pork and a very small quantity of mutton and beef is preserved and processed into different products.
Stockyards 2. Slaughter House and 3. Packing House The Stockyard wastes consists primarily of animal manure with urine, straw and unconsumed food along with dirt and water used for cleaning. The stockyard waste are strong and posses a very high BOD. Killing, dressing and some by product processing are carried out in the slaughter house. The animals are stuck and bled on the killing floor. Flushing of killing floors contribute significant volumes of strong waste waters. Then hides and are skins are removed, salted and piled in separate place.
In Packing house meat is further processed by cooking, curing, smoking and pickling. The other processes carried out in Packing house are meat canning, sausage manufacture, rendering of edible and inedible fats to edible and inedible tallon respectively. The effluent from killing floor is deep reddish brown in colour, a high BOD and suspended matter.
Origin and Characteristics of Meat Packing Wastes: Stockyard wastes contain excreta, both liquid and solid. The amount and strength of the waste vary widely, depending on the presence or absence of cattle beams horns , how thoroughly or how often manure is removed, frequency of washing etc.
Stockyard Waste Parameter Value B. In plant recovery practices, screening, floatation and biological treatment are the major methods used to treat meat plant wastes.
The most common methods used for treatment of meat plant wastes are fine screening, sedimentation, chemical precipitation, trickling filters and activated sludge process. Rice Milling Waste: In the preparation of edible rice, large volumes of wastes are produced in the soaking ,cooking and washing processes. Since most of the B. D reduction has been obtained by using ppm of lime as a coagulant ;digestion can yield a B.
Characteristics of composite rice water: Manufacturing Process: The Process of manufacturing of paper may be divided into two phases - Pulp making and then making of final product of paper. The major portion of the pollution from papermaking originates in the pulping processes.
Raw materials are reduced to a fibrous pulp by either mechanical or chemical means. The bark is mechanically or hydraulically removed from wood before it is reduced to chips for cooking.
Mechanically prepared groundwood pulp is made by grinding the wood on large emery very hard mineral or sand stone wheels and then carrying it by water through screens.
The screened bark effluent contains fine particles of bark and wood and some dissolved solids. Chemically prepared pulps, as compared with mechanically prepared ones, are made by the soda, sulfate Kraft or sulfite process. In all these methods the wood is prepared, as in the making of groundwood, by reduction to chips and screening to remove dust. The chemical processes differ from one another only in the chemical used to digest the chips. Pulping is the process in which wood or other cellulosic raw materials are digested with chemicals under high temperature and pressure so that cellulosic fibres of wood are relieved from its binders such as lignin, resin etc To a digester holding about four cords cft of chips, a mixture of soda ash Na2CO3 and Lime Ca OH 2 alkali process is added and the total contents are boiled under steam pressure for about ten hours.
This digestion decomposes or separates the binding , non cellulosic materials , such as lignins and resins from the fiber. During digestion most of the lignins are hydrolysed to alcohol and acids. The spent liquor produces by the above process of digestion is known as black liquor. Black liquor very rich in lignin content but also cintains a large amount of unutilised chemicals. The black liquor of the Kraft process is concentrated by evaporation, and then incinerated with the addition of sodium sulphate.
The organics like lignin, resin etc are burnt out, and the spelt is dissolved in water. The resulting liquid is known as green liquor. Lime is added to this liquor, resulting in the formation of white liquor and lime mud containing chiefly calcium carbonate. White liquor contains desired cooking digestion chemicals and is sent for use in digester. The sulfate process calls for a shorter digestion period of about five or six hours , with a mixture of sodium sulfide, hydroxide , sulfate and carbonate.
The lignin and non cellulosic materials are dissolved , leaving a stronger fiber for paper formation. After digestion, chemically prepared wood pulps are blown into a closed blow pit, where the black liquor is allowed to drain to the sewer or to the recovery processes. These wash waters may then be wasted, reused or sent through recovery operations while the washed pulp is passed through some type of refining machine to remove knots and other non disintegrated matter.
A cylindrical screen, called a Decker , revolving across the path of the pulp partially dewaters it, after which it is passed to bleach tanks, where it is mixed in a warm, dilute solution of calcium hypochlorite or hydrogen peroxide.
The dried , bleached pulp is then ready for sale or delivery to the paper mill. The washed cellulosic fibres are sent for the bleaching in 3 stages, where chlorine, caustic and hypochlorite are used in successive stages.
Waste waters from first and last stages are light yellow in colour, while that from caustic highly coloured. In the paper mill, the pulp mixture is disintegrated and mixed in a Beater to which are added various fillers like alum, talc etc and dyes, to improve the quality of the final paper product, and sizing to fill the pores of the paper.
The Beater is essentially an oblong tank equipped with a rotating cylinder, to which are attached dull knives to break up the knotted or bunched fibers and cause a through mixing of the entire contents of the tank.
Sometimes the pulps are washed in the 'breaker beater ' prior to the addition of chemicals. After beating, the pulp is usually refined in a Jordan, machine that consists of a stationary hollow cone with projecting knives on its interior surface, fitted over a rapidly rotating adjustable cone having similar knives on its outside surface. This machine cuts the fibers to the final size desired. The pulp then passes to stuffing boxes, where it is stored, mixed and adjusted to the proper uniform consistency for papermaking.
Finally the pulp is screened to remove lumps or slime spots, which would lower the quality of the final paper. The pulp is evenly distributed from a head box over a travelling belt of fine wire screening , known as fourdrivein weir , and carried to rolls. A small portion of the water contained in the pulp passed through the screen while the longer fibers are laid down as a mat on the wire.
A considerable portion of the fine fibers and some fillers also pass through the screen wire with the water.
Because of its colour, this waste water is called white water. Characteristics of pulp and paper mill wastes: The volume depends mainly on the manufacturing procedure, and the water economy adopted in the plant.
It has been observed that a well operated and well managed integrated pulp and paper mill employing Kraft process for pulping , produces a waste volume in the range of to m3 per tone of paper manufactured. The mills manufacturing special quality of paper produce larger amount of water for washing and beleaching.
Like the volume of waste, the chemical composition of the waste will also depend on the size of the plant, manufacturing process. In most of the small paper mills in India, the chemical recovery is not practiced due to economical reasons. Crude pulp and paper mill wastes, or insufficiently treated wastes cause very serious pollution problems, when discharged into the streams.
A toxic effect may also be induced upon the flora and fauna of the stream due to sulfites and phenols in the waste. The bottom deposit of Lignin - Cellulosic materials near the point of the discharge of the waste in a stream undergo slow decomposition and may lead to the dissolved oxygen depletion followed by the creation of anaerobic condition and destruction of the aquatic life.
The treatment of the waste may consist of all or a combination of some of the following processes: The recovery of the process chemicals and the fibres reduces the pollution load to a great extent. Where the economy permits the colour bearing black liquor is treated for the chemical recovery. In this process the lignin is destroyed. The same may also be recovered from the black liquor, by precipitation by acidulation with either carbon dioxide or sulphuric acid.
The fibres in the white water from the paper mills are recovered either by sedimentation or by floatation using dissolved air in the tank. Chemical treatment for colour removal: In this process, entire quantity of lime, normally required for the recaustisation of green liquor into white liquor, is taken and allowed to react first with the coloured waste effluent.
The colour is absorbed by lime and the sludge after settling is used in recaustisting the green liquor. Activated carbon for colour removal: Biological treatment of the waste: Considerable reduction of BOD from the waste can be accomplished in both conventional and low cost biological treatment processes.
If sufficient area is available, the waste stabilization ponds offer the cheapest means for treatment. Aerated lagoons are the improved forms of the stabilization ponds. P ratio of Activated sludge process is the most satisfactory and sophisticated system for the effluent treatment. The algae numbers are unsustainable and eventually most of them die.
The decomposition of the algae by bacteria uses up so much of the oxygen in the water that most or all of the animals die, which creates more organic matter for the bacteria to decompose. In addition to causing deoxygenation, some algal species produce toxins that contaminate drinking water supplies. Different treatment processes are required to remove nitrogen and phosphorus. Nitrogen removal[ edit ] Nitrogen is removed through the biological oxidation of nitrogen from ammonia to nitrate nitrification , followed by denitrification , the reduction of nitrate to nitrogen gas.
Nitrogen gas is released to the atmosphere and thus removed from the water. Nitrification itself is a two-step aerobic process, each step facilitated by a different type of bacteria. Denitrification requires anoxic conditions to encourage the appropriate biological communities to form.
It is facilitated by a wide diversity of bacteria. Sand filters, lagooning and reed beds can all be used to reduce nitrogen, but the activated sludge process if designed well can do the job the most easily.
This can be, depending on the waste water, organic matter from feces , sulfide , or an added donor like methanol.
The sludge in the anoxic tanks denitrification tanks must be mixed well mixture of recirculated mixed liquor, return activated sludge [RAS], and raw influent e. Sometimes the conversion of toxic ammonia to nitrate alone is referred to as tertiary treatment. Over time, different treatment configurations have evolved as denitrification has become more sophisticated.
An initial scheme, the Ludzack—Ettinger Process, placed an anoxic treatment zone before the aeration tank and clarifier, using the return activated sludge RAS from the clarifier as a nitrate source. Influent wastewater either raw or as effluent from primary clarification serves as the electron source for the facultative bacteria to metabolize carbon, using the inorganic nitrate as a source of oxygen instead of dissolved molecular oxygen.
This denitrification scheme was naturally limited to the amount of soluble nitrate present in the RAS. Nitrate reduction was limited because RAS rate is limited by the performance of the clarifier.
The "Modified Ludzak—Ettinger Process" MLE is an improvement on the original concept, for it recycles mixed liquor from the discharge end of the aeration tank to the head of the anoxic tank to provide a consistent source of soluble nitrate for the facultative bacteria.
In this instance, raw wastewater continues to provide the electron source, and sub-surface mixing maintains the bacteria in contact with both electron source and soluble nitrate in the absence of dissolved oxygen. Many sewage treatment plants use centrifugal pumps to transfer the nitrified mixed liquor from the aeration zone to the anoxic zone for denitrification.
At times, the raw or primary effluent wastewater must be carbon-supplemented by the addition of methanol, acetate, or simple food waste molasses, whey, plant starch to improve the treatment efficiency. These carbon additions should be accounted for in the design of a treatment facility's organic loading. Use of an anaerobic tank following the initial anoxic process allows for luxury uptake of phosphorus by bacteria, thereby biologically reducing orthophosphate ion in the treated wastewater.
Even newer improvements, such as Anammox Process, interrupt the formation of nitrate at the nitrite stage of nitrification, shunting nitrite-rich mixed liquor activated sludge to treatment where nitrite is then converted to molecular nitrogen gas, saving energy, alkalinity, and secondary carbon sourcing.
Phosphorus removal is important as it is a limiting nutrient for algae growth in many fresh water systems. For a description of the negative effects of algae, see Nutrient removal. It is also particularly important for water reuse systems where high phosphorus concentrations may lead to fouling of downstream equipment such as reverse osmosis. Phosphorus can be removed biologically in a process called enhanced biological phosphorus removal.
In this process, specific bacteria, called polyphosphate-accumulating organisms PAOs , are selectively enriched and accumulate large quantities of phosphorus within their cells up to 20 percent of their mass. When the biomass enriched in these bacteria is separated from the treated water, these biosolids have a high fertilizer value.
Phosphorus removal can also be achieved by chemical precipitation , usually with salts of iron e. Chemical phosphorus removal requires significantly smaller equipment footprint than biological removal, is easier to operate and is often more reliable than biological phosphorus removal.
Some systems use both biological phosphorus removal and chemical phosphorus removal. The chemical phosphorus removal in those systems may be used as a backup system, for use when the biological phosphorus removal is not removing enough phosphorus, or may be used continuously. In either case, using both biological and chemical phosphorus removal has the advantage of not increasing sludge production as much as chemical phosphorus removal on its own, with the disadvantage of the increased initial cost associated with installing two different systems.
Once removed, phosphorus, in the form of a phosphate-rich sewage sludge , may be dumped in a landfill or used as fertilizer. In the latter case, the treated sewage sludge is also sometimes referred to as biosolids. Further information: Advanced oxidation process The purpose of disinfection in the treatment of waste water is to substantially reduce the number of microorganisms in the water to be discharged back into the environment for the later use of drinking, bathing, irrigation, etc.
The effectiveness of disinfection depends on the quality of the water being treated e. Cloudy water will be treated less successfully, since solid matter can shield organisms, especially from ultraviolet light or if contact times are low.
Generally, short contact times, low doses and high flows all militate against effective disinfection. Common methods of disinfection include ozone , chlorine , ultraviolet light , or sodium hypochlorite. After multiple steps of disinfection, the treated water is ready to be released back into the water cycle by means of the nearest body of water or agriculture.
Afterwards, the water can be transferred to reserves for everyday human uses. Chlorination remains the most common form of waste water disinfection in North America due to its low cost and long-term history of effectiveness.
One disadvantage is that chlorination of residual organic material can generate chlorinated-organic compounds that may be carcinogenic or harmful to the environment. Residual chlorine or chloramines may also be capable of chlorinating organic material in the natural aquatic environment.
Further, because residual chlorine is toxic to aquatic species, the treated effluent must also be chemically dechlorinated, adding to the complexity and cost of treatment.Similarly, iron oxide tailings were found to be effective for phosphorus removal from both pure solutions and liquid hog manure Biological Treatment Assimilation Phosphorus removal from wastewater has long been achieved through biological assimilation — incorporation of the P as an essential element in biomass, particularly through growth of photosynthetic organisms plants, algae, and some bacteria, such ascyanobacteria.
The rolls also get heated during the process and are cooled with liberal supply of water. The usual unit capacity requirements may be reduced, provided the operations are controlled and carried out as follows: The direct disposal of the waste into the streams without any treatment.
The tannery waste when discharged into a sewer only chokes the sewer due to the deposition of solids, but also reduces the cross- section of the sewer arising out of the lime encrustation. Mixing of the above two followed by ph adjustment and nutrient ammonium salts and phosphates supplementation. Fertilizer intermediates 3.