Environmental Tech.
Environmental Tech.
Environmental Tech.
Environmental Report
DRAFT
Table of Contents
Preface Executive Summary 1. The Environmental Technology Programme for Industry
1.1 Demonstration Project
i 1 2
2
2.
3
3 3 3 3 3 3 4
6.1.1 Design Data 6.1.2 Assumptions 6.1.3 Components of the Plant 6.1.4 Land Requirements 6.1.5 Final Effluent Quality 6.1.6 Estimation of Capital and O&M Costs 6.2 Wastewater Treatment for Processing Raw Hides to Finished Leather 6.2.1 Design Data 6.2.2 Assumptions 6.2.3 Land Requirements 6.2.4 Components of the Treatment Plant 6.2.5 Final Effluent Quality 6.2.6 Estimation of Capital and O&M Costs
15 15 15 15 15 17 17 17 18 18 19 19 19
List of Tables
Table 2.1: Table 3.1: Table 3.2: Table 3.3: Table 3.4a: Table 3.4b: Table 3.5: Table 3.6: Table 3.7: Table 5.1: Table 5.2: Table 6.1: Table 6.2: Table 6.3: Table 6.4: Table 6.5: Table 6.6 Table 6.7: Table 6.8: Table 6.9: Table 6.10: Number of Tanneries in Different Cities of Pakistan Process-wise Water Consumption and Wastewater Generation of a Tannery Quantity of Wastewater Discharge from Tanneries Characteristics of Sludge Wastewater (Process-Wise) Characteristics of Composite Wastewater of a Tannery Characteristics of Composite Wastewater of a Tannery Characteristics of Sludge in Composite Wastewater of Tannery-A Estimated Quantities of Solid Waste and Disposal Practices Characteristics of Solid Waste A Brief Review of Cleaner Technologies Summary of Cost-Benefit Analysis for CRRP Estimated Daily Pollution Loads of Tannery A and B Load of Aeration Tank Land Requirement (m2) Final Effluent Quality Estimated Investment Cost of a Treatment Plant for (Wet) Finishing Tannery Process Daily Pollution Load Load of Aeration Tank Land Requirement (m2) Effluent Quality of Treatment Plant Estimated Capital Cost of a Treatment Plant with the Present Hydraulic Load of a Tannery
3.
Waste Generation
3.1 Wastewater 3.1.1 Source 3.1.2 Quantity 3.1.3 Characteristics 3.2 Solid Waste 3.2.1 Types of Solid Waste 3.2.2 Characteristics of Solid Waste 3.2.3 Disposal of Solid Waste 3.3 Air Emission 3.3.1Emissions from Generators and Boilers 3.3.2 Emissions from Process Activities
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5 5 5 5 6 8 8 8 9 9 9
4.
5.
Remedial Measures
5.1 General Measures 5.2 Environmentally Clean Technologies 5.2.1 Review of Cleaner Technologies 5.2.2 Reuse of Chrome 5.3 Wastewater Treatment Technologies 5.3.1 Primary Treatment 5.3.2 Secondary Treatment 5.3.3 Feasible Technology
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10 11 11 12 13 13 13 14
List of Figures
Figure 2.1: Figure 3.1: Figure 4.1: General Processes Flow Diagram Drying Characteristics of Sludge Environmental Input of a Tanner
6.
ii
List of Figures
Figure 5.1: Figure 6.1: Chrome Recovery and Reuse Plant Preliminary Layout of the Treatment Plant for a Medium Size Segmented Tannery with a Mechanical Dewatering System Preliminary Layout of the Treatment Plant with Mechanical Dewatering System Preliminary Layout of the Treatment Plant without Mechanical Dewatering System
Annexures
Annexure 1: List of Chemical Used in the Tanning Process Annexure 2: National Environmental Quality Standards (NEQS) Annexure 3A: Preliminary Design of a Treatment Plant Annexure 3B: Preliminary Design of a Treatment Plant
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Preface
This report has been prepared as part of the ETPI demonstration project component - collaborative efforts between the industry and FPCCI - and aims to address the environmental pollution problems in the leather manufacturing sector. This report has been prepared on the basis of the findings of environmental audits of four tanneries conducted by ETPI. The purpose of the environmental audits was to assess the nature and extent of the environmental problems and to develop solution for the tanning industry. Audits have established the basis of the demonstration project. Findings and recommendation of audits are being implemented in the selected unit and disseminated to the sector as a whole. Industrial unit level information remains confidential with ETPI. However, this program, at each stage shares the progress of the work with all its stakeholder. This report gives an overview about the environmental aspects of tanneries along with the possible investment required to abate these problems to meet the present and future environmental legislation. It is hoped that this effort will help to enable the local tanneries to initiate the efforts to combat the present and future environmental problems and to produce an environmentally clean product. Further, this study may contribute to the efforts which are being made by local research, education, policy making and monitoring institutions. The environmental audits of four tanneries were conducted jointly by two consulting firms of ETPI consortium, hired by Federation of Pakistan Chamber of Pakistan (FPCCI) to execute the program. These firms are National Environmental Consulting (NEC) Private Limited and HASKONING of the Netherlands. The general report has been prepared by the core team of ETPI. This report was first prepared in April 1997 on the basis of three audits and now it is being revised by adding more information obtained from the fourth audit conducted in this sector. Further, more details have been given on environmental technologies. We acknowledge the co-operation of Pakistan Tanners Association (PTA) and Tanneries who participated in the program and extended their co-operation in all the aspects of study.
Consulting Team: Mr. Mohammad Iqbal Mr. Izhar-ul-Haque Mr. J. A. S. Berns Co-ordinator Technology; ETPI National Environmental Consulting (Pvt.) Ltd. (NEC), Pakistan HASKONING, The Netherlands
April 1998
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Executive Summary
The Federation of Pakistan Chambers of Commerce & Industry (FPPCI) being the apex body representing all the business, trade and industrial organisations of the country, has launched a comprehensive five year program, called Environmental Technology Program for Industry (ETPI), with technical assistance from the Netherlands Government. The major objective of ETPI is to initiate measures to combat the existing and the expected industrial pollution problems which will also enable the industry to comply with the National Environmental Quality Standards (NEQS) and the forthcoming ISO 14000. The program is under implementation with the involvement of progressive industrial units. These units have willingly participated in the program for the implementation of the demonstration project. Pakistans leather and leather products industry is one of the major foreign exchange earners amongst the manufacturing goods sector. At present, about 90 % of the leather is exported in the finished form. There are presently over 595 tanneries in the formal sector and an equally large number of tanneries exist in the informal sector. The major cluster of tanneries are located in Karachi, Kasur, Lahore, Sheikhupura, Gujranwala, Multan, Sialkot and Jahangria. For leather production, locally available raw material ( hides and skins) and predominantly imported chemicals are used. In the leather sector a variety of finished leather is prepared which includes upper, lining, and garment etc., from salted raw skins/hides. The chrome tanning method is widely applied for preparation of finished leather. However, vegetable tanning method and a combination of chrome and vegetable tanning method is also used. Most of the chemicals are used to prepare the skins or hides for the tanning purpose. After performing their functions these chemicals find their way into the environment. The tanneries generate all the three categories of waste, i.e., liquid, air and solid wastes. The sources of air pollution in tannery are of two types; one is from the stack of generators and boiler and the other from the process. The emission here is below the NEQS standard. Hydrogen Sulphide and Ammonia generated from different sources such as washing of drums with ammonia, effluent of de-liming processes and mixing of tanning and de-liming effluent. Although, the emissions are intermittent they are nevertheless hazardous for the health of the workers. The major solid wastes generated are dusted curing salt, wet trimmings, dry trimmings, wet shavings, buffings, raw material packing, etc. Except dust salt other solid waste has a great attraction in local market. Poultry feed manufacturers due to the protein content of fleshing, raw trimmings, chrome shavings, dry trimmings, buffing dust, etc. collect this material from the tannery. The main problem associated with some of these wastes is their chrome content. End use of chrome containing solid waste varies in different parts of the country. In Punjab it is used for making leather board whereas in Karachi it is used for making poultry feed. During the process trivalent chromium (contained in the solid waste) is changed into hexavalent chromium (carcinogenic). Wet processes of the tannery are the main source for generating the wastewater. Water consumption per kg of raw hides varies from tannery to tannery. Consumption of water should not go beyond the normal requirement i.e., 50 litre/kg. However, it was found that tanneries are generally consuming more water as compared to the normal required quantity. During the peak season, the production and wastewater generation doubles. Despite the seasonal fluctuation, daily fluctuation in wastewater generation also exists due to variation in the quantity of raw material processed daily. The characteristics of wastewater shows that it is highly polluted with Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), suspended solids, settleable solids, total Kjedhal Nitrogen, Sulphate and Chromium, Chloride, etc. A considerable quantity of Sludge is also present in the wastewater. Values of these parameters vary from tannery to tannery due to different processes and raw material utilisation. Due to the high pollution level in wastewater, very severe environmental impacts are associated with its discharge into the environment without applying any measures. Recommended remedial measures for the various environmental problems are training of the workers, provision of safety items, improvement in the drainage system to avoid formation of hydrogen sulphide gas, installation of boards and notices about safety and health regulations at working places of the tannery and a proper arrangement to stop the use of tanned solid waste for the preparation of poultry feed. Implementation of cleaner technologies such as water conservation, use of environment friendly chemicals, green fleshing of hides, application of hair saving methods , recycling of sulphide liquor, Lime splitting and trimming and chrome recovery and reuse can provide economical benefits and will help the local tannery to combat the environmental problems. Approximately 30% discharge of the unused chrome compound is a financial loss for a tannery. This can easily be recovered from the spent tanning effluent and this can then be reused without compromising the quality of leather. Cost benefit analysis for chrome recovery and reuse plant has also been carried out which gives a payback period of 6-7 months. A wastewater treatment system is inevitable and different technologies are available in this regard. Two stage of treatment are suggested i.e., primary (physio-chemicals)
and secondary (biological). The characteristics of wastewater permit low loaded activated sludge system for biological treatment to bring down the level of BOD5, COD, suspended solids, chrome, sulphide and pH. For the removal of salt, in-house improvement is suggested. An estimated investment cost for such a treatment system for a tannery processing about 12000 kg of hides per day is approximately 44 million with a cost of about 7-9 million rupees for operation and maintenance.
The wastewater generated from tanneries involved in segmented production i.e., producing finished leather by using wet blue also contains significant pollution level which also needs to be treated before discharge into the local environment. The cost of a treatment system (primary and secondary) was estimated for two tanneries, the tannery processing 8000- 10,000 kg of wet blue per day would cost about Rs.10 million and for a tannery processing 600 - 1500 kg of wet blue per day, the cost would approximately be Rs.3 million.
National Environmental Consulting (NEC) (Pvt.). Ltd., Karachi-Pakistan; the lead consultant; HASKONING Royal Dutch Consulting Engineering and Architects, The Netherlands; KRACHWERKTUIGEN (KWT), The Netherlands; Management for Development Foundation (MDF), The Netherlands; and Hagler Baily, Pakistan.
This five-year project began in 1996 and works with Pakistani industries and their associations in identifying the most economical pollution prevention and abatement technologies and in implementing these solutions. The five components of the program include the development of a user-friendly database of relevant information, institutional networking within and between key industrial institutions of the country, dissemination and communication to promote cleaner industrial production, institutional support and training to create in-house environmental capacity within Chambers and Industrial Associations, and Demonstration Projects in 20 selected industrial sub sectors to demonstrate the economic feasibility and environmental efficacy of environmental technologies. Three representative industrial units were selected in each sub-sector for preliminary environmental audits to assess the extent and nature of the environmental problems. Based on the results of these audits, a general sub sector report is prepared in consultation with industry experts. The sub sector report highlights the key environmental issues in that industrial sector, lists possible solutions for major environmental problems in that sub sector, and recommends the technologies that are most economically
For the implementation of the demonstration project, a comprehensive procedure for the selection of industries in each sub sector has been developed. According to this procedure, three industries will be selected for an Environmental Audit from each sub sector. Subsequently one of these three will be selected for the demonstration project. In the sub sector of leather manufacturing, instead of three Environmental audits, 4 have been carried out. The findings of these audits have been compiled in the present report. During the environmental audit work, it was mentioned that the environmental audit report of the individual tannery will be a confidential document and that document must not be made accessible to every body.
It was therefore decided to prepare a general report by taking the inferences from these audits. However, it is difficult to generalize the information obtained from environmental audits for the whole sector. To overcome
this short coming help has been taken from secondary information. This report has been prepared with an aim that it will provide a general scenario about the environmental problems of local tanneries.
2.2.3 Water
An extensive quantity of water is used in the leather sector. The data shows that 50 -150 litre of water is used for the conversion of one kg of raw skin into leather. Tannery wet processes are the major consumers of water. The water in the wet processes and operations is used as a carrier to facilitate all chemical reactions involved in leather processing. After completion of the process and operation, the water leaves the system as wastewater in the same quantity as added to the system. Groundwater is used as a major source of the processing water in Leather sector.
widely used for the preparation of finished leather. However, vegetable tanning method and a combination of chrome and vegetable tanning method is also being applied. The three tanneries selected for the audit under the Environmental Technology Program for Industry
(ETPI) apply chrome tanning process for the production of finished leather. A series of processes and operations are involved for the production of leather. These are described as follows. The flow diagram of processes and operations is given in figure 2.1.
RAW MATERIAL (RAW SKINS/HIDES) PRE SOAK SOAKING SOAK WASH UNHAIRING & LIMING FLESHING DELIMING WASHINGS BATING DEGREASING PICKLING CHROME TANNING WET BLUE STORAGE *SPLITTING OF WET BLUE SORTING OF WET BLUE SHAVING OF WET BLUE WET BACK + NEUTRALIZATION + RETANNING
Hide processing
Wet Processes
items are provided by the tannery, workers do not pay much attention. The un-usage of these accessories during work may be due to the and ignorance and un-awareness of the workers. Information boards about safety and health regulations are not installed in the tanneries. Loading and unloading of the skins/hides during processing is normally carried out manually without using gloves and proper clothes for protection. Consequently the cloths of the workers become completely wet with the float of the different tanning processes.
3. Waste Generation
All the three categories of waste, i.e. liquid, air and solid, are generated by the tanneries. Following section describes the source, disposal, characterisation and quantification of these wastes. litre /Kg. However, it was found that the tanneries are generally consuming more water as compared to the normal required quantity. In some cases water consumption reaches to a level which is three time higher to the normal, i.e., 150 litre /kg of raw hides. Water consumption at each processing stage, for a tannery processing sheep and goat skins, has been summarised in Table 3.1. During peak season the processing of raw skins/hides doubles, which directly effects the quantity of wastewater generation. Despite the seasonal fluctuation, daily fluctuation in wastewater generation also exists due to the variation in quantity of raw skins/hides processed daily. The wastewater discharge is also intermittent and needs to be equalised before treatment. The quantity of wastewater discharged from different tanneries is given in Table 3.2.
3.1 Wastewater
3.1.1 Source
Wet processes of the tannery are the main source of the wastewater generation. Some mechanical operations also contribute small quantities of wastewater. Canteen, toilets, prayer hall or mosque also contribute a minor quantity of wastewater. Wet processes are highlighted in the flow diagram (Fig. 2.1). In the tannery processes, water is used as a chemical carrier to render the cleaning of raw hides and skins as well as to penetrate the chemicals facilitating reaction of chemical with collagen fibre of the skins. The process water, after completion of the process, is drained out as wastewater in the same quantity as it is added in the processes. The wastewater is disposed off without any treatment into the local environment.
3.1.3 Characteristics
Tannery wastewater is highly polluted in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids, settleable solids, total kjeldhal nitrogen, conductivity, sulphate, sulphide and chromium. The values of these parameters are very high as compared to the values mentioned in the National Environmental Quality Standards (NEQS) set by the Government of Pakistan (see annexure 2). Pollutant values of different tanneries are given in Table 3.3 and 3.4.
3.1.2 Quantity
Water consumption per kilogram of raw hides varies from tannery to tannery. Generally water consumption should not go beyond the normal requirement i.e., 50
(A) Processes = Raw - Wet Blue: Pre-soak wash 500 60 Soaking 500 60 Soak wash 500 60 Liming & Un-hairing 500 60 De-liming 200 24 Washing-1 200 24 Washing-2 200 24 Bating 200 24 Degreasing 200 24 Washing -1 200 24 Washing -2 200 24 Washing -3 200 24 Washing -4 200 24 Pickling/Tannin 80 9.6 Water Consumption from raw to wet blue stage 465.6 (B) Processes = Wet Back - Finished Leather: Same weight ( 10,000 kg) of the wet blue skins is processed daily throughout the year for onward wet finishing processes Wet back 300 36 Neutralisation Re-tanning Washing 200 24 Fat liquoring / dying 200 24 Washing 200 24 Water Consumption in wet finishing 108 Total Water Consumption (A+B) 574 = Total Wastewater Generation
Source: ETPI Survey - calculated on the basis of water recipe provided by the tannery 5
Wastewater from each tannery process contains different types of pollutants. pH varies considerably from 3.3 to 12.6. Similarly, a large variation exists in parameters like BOD, COD, Chloride, Sulphate, TDS, TSS, settleable matter, etc. In addition to these parameters, results clearly show that the wastewater carries considerable quantities of chromium. The discharge of these chemicals into wastewater is not only hazardous but also a financial loss. A considerable quantity of sludge was also present in composite wastewater. The settleable matter is responsible for the sludge generation. This sludge content is presented in Table 3.5 and represented in figure 3.1
Tanneries
Series1
Series2
Parameters
pH BOD5 (Unfiltered) at 0 time settling BOD5 (Unfiltered) at 30 minutes settling BOD5 (Unfiltered) at 60 minutes settling COD ( Unfiltered) at 0 time settling COD (Unfiltered) at 30 minutes settling COD (Unfiltered) at 60 minutes settling Suspended Solid at 0 time settling Suspended Solids after 30 minutes settling Suspended Solids after 60 minutes settling Settleable matter after 30 min. settling Settleable matter after 60 min. settling T. Phosphate at 0 time settling Total Kjeldhal Nitrogen at 0 time settling Conductivity s/cm @ 0 time Sulphate as SO4 at 0 time settling Sulphide as (S) at 0 time settling Chromium (Cr) at 0 time settling *
* Estimated on the basis of chrome content in chrome tanning effluent (6132 mg/l.)
Parameters
pH BOD5 (Unfiltered) at 0 time settling BOD5 (Unfiltered) at 30 minutes settling BOD5 (Unfiltered) at 60 minutes settling COD ( Unfiltered) at 0 time settling COD (Unfiltered) at 30 minutes settling COD (Unfiltered) at 60 minutes settling Suspended Solid at 0 time settling Suspended Solids after 30 minutes settling Suspended Solids after 60 minutes settling Settleable matter after 30 min. settling Settleable matter after 60 min. settling T. Phosphate at 0 time settling Total Kjeldhal Nitrogen at 0 time settling Conductivity s/cm @ 0 time Sulphate as SO4 at 0 time settling Sulphide as (S) at 0 time settling Chromium (Cr) at 0 time settling *
Estimated on the basis of chrome content in chrome tanning effluent (6132 mg/l.)
Dry trimming 0.024 kg/skin 240 Dry shaving 0.034 kg/skin 340 Buffing dust 0.002 kg/skin 20 Total 5500 Cartons, bags, drums, No consistent quantity Miscellaneous refuse Source: Data supplied by Tannery. Note: These quantities are based on the average figures (10,000 kgs./day)
Sold
shaving and trimming, dry shaving, trimming and buffing. This exercise was conducted to determine the major constituents such as moisture, salt, lime, chromium, total and volatile solids, sulphide fats and proteins. Table 3.7 lists the characterisation of solid wastes of tannery processes.
Source: Laboratory Analysis. Note: All values are in gm /Kg. unless otherwise specified.
Recently, a study of solid waste management was carried out in Sector 7-A of Korangi Industrial Area under the PTA (Pakistan Tanners Association) Environmental Management Program. According to the study, poultry feed mixed tannery solid waste was collected and analysed. The results showed that the poultry feed, besides trivalent chromium, also contained hexavalent chromium. It seems that during the poultry feed preparation, trivalent chromium is being changed into its hexavalent form. The mixing of heavy metal in poultry feed in such a high quantity could produce severe health problems for human beings.
then two hours a day, on an average. Generators are usually diesel based. The boiler is kept operational for approximately 12 hours /day. Samples of emission from the boiler stack were collected and analysed.
of 3800 - 41300 mg/l. Whereas according to the NEQS, a value of 150 mg/l has been recommended for COD. Hence, tannery wastewater is carrying about 25 - 275 times more pollution load in terms of COD. Sewage water usually contains 1000 mg/l COD.
4.1.4 Sulphide
Due to sulphide discharged from the unhairing process, hydrogen sulphide is released at a pH value lower than 8.5. This gas has an unpleasant smell even in trace quantities and is highly toxic to many forms of life. In higher concentrations, fish mortality may occur at a sulphide concentration of 10 mg/l. Sulphide in public sewer can pose structural problems due to corrosion by sulphuric acid produced as a result of microbial action. Sewage contains sulphide in the range of 15-20 mg/l and composite tannery wastewater contains 290 mg/l, whereas, the NEQS recommends a value of 1.0 mg/l.
4.1.7 Salts
The sodium chloride used in the tannery produces no effect when discharged into estuaries or the sea, but effects fresh water life when its concentration in a stream or lake becomes too high. There is no economically viable way of removing salt from the effluent. A similar problem also exists for sulphate used as the chrome tanning salt. Sulphate in addition causes corrosion to concrete structures. The Chloride content of tanneries composite wastewater ranges from 5820 to 14160 and the sulphate content varies from 860 to 1814 mg/l.
4.1.5 Chromium
Trivalent chromium is released from the chrome tanning process. This is much less toxic than hexavalent chromium. For plant and animal life, the toxicity of chromium salts is variable. The toxicity is a function of the species itself. Algae have been shown to be particularly sensitive. Estuarine molluscs, although apparently unaffected in their own metabolism, accumulate trivalent chromium. At present, tanneries are discharging chromium (133 mg/l) in composite wastewater and in sludge (3 - 17.5 gm/kg). It can be seen that wastewater of chrome tanning process, which is about 2 % of the total wastewater of the tannery, contains 6000 - 7000 mg/l of chromium (Cr). The sewage of Karachi contains 0.1 to 0.5 mg/l of
WASTEWATER (600 M3/day) BOD5 = 13680 COD = 34200 Suspended Solids = 2790 Chromium = 80 Sulphide = 173 Sludge = 3280
SOLID WASTE AND BY- PRODUCTS UNTANNED Dusted Salt = 1000 Raw trimming = 240 Fleshing= 2500 TANNED Shaving = 1500 Trimming = 240 Buffing = 20 Total = 5500 All values are in Kg./day
LEATHER 1400 Kg
5. Remedial Measures
5.1 General Measures
As tanneries do not have an environmental management system, therefore, this system must be developed in tanneries, specially in the large and medium sized ones. Environmental management should be a responsibility of the personnel in addition to their routine duties. Short-term training on occupational health and safety aspects , modern practices for the handling of hazardous chemicals, etc. is required for the staff.
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Installation of information boards on safety and health regulations at the work places of the tannery are needed. Provision of safety gears like face protective shield for acid work specially in the pickling process, acid resistant gloves and aprons etc. Face masks to avoid inhalation of fumes of finishing chemicals, toxic gases, etc. The use of the safety gear should be implemented strictly. Proper arrangements to stop the use of tanned solid waste for the preparation of poultry feed. Simple disposal to the landfill site may not be a proper solution to stop this practice, as the poultry feed makers can get this material from these sites. Tanned solid waste materials can be used in leather board manufacturing, but in Karachi, a leather board factory does not exist. In the absence of a permanent solution to this problem at present, it is suggested that this material can be disposed off after mixing with other wastes, like circulation water of spray plant that caries unused finishing material. Other waste that can be mixed with tanned solid waste is
curing salt. After mixing with this waste, tanned solid waste will become contaminated and will not be useful for poultry feed makers. Improvement in drainage system in order to avoid formation of hydrogen sulphide gas inside the tannery.
Benefits
The use of pit or paddle for soaking operations results in a higher consumption of water, mainly for washing phase which are much less efficient than when using drums. Even for drums it is recommended to operate the sequential washing instead of continuous washing which leads to the savings of enormous amount of water at each stage. Low float technologies would also reduce the water quantity. Although such conservation do not reduce the pollution load, however, they can lead to the reduction in the size of the effluent treatment plant. Enzymatic product are considered to be less toxic and can be a good replacement of sulphide. Surfactants, if used, should be selected with respect to their biodegradability. Use of Penta Chloro Phenol (PCP) must be avoided. Replacement of ammonium sulphate with weak acids (organic). Degreasing with surfactants instead of organic solvent. Use of trivalent chromium for tanning purpose instead of hexavalent chromium (carcinogenic). Metal complex dyes, which contain restricted heavy metals and benzidine based dyes must be replaced. The chlorinated fatliquoring agents and retanning products should be replaced with the easily biodegradable products. Green fleshing just after deep soaking is a suitable procedure to obtain by-product at pH close to neutral, which can then easily be processed to recover fats and proteins with good marketing possibilities and to save liming and unhairing chemicals. Further green fleshing also improves the penetration of the chemicals and hence improves the quality of finished leather. Hair saving system use smaller quantities of sulphide as compared to hair destruction system, and allows easy separation of the protein constituted by the undissolved hair and hence imply less pollution than the hair dissolving process. The procedure results in a significant reduction of COD, BOD5 , nitrogen, sulphide, total and suspended solids in the wastewater, besides a decrease of sulphide consumption. The hair saving would decrease the organic load for treatment plant. Some of the liming unhairing techniques permit a direct reuse of the spent liquors after decantation and/or filtration. The procedure permits savings of water, sulphide, and lime. By reuse of un-hairing liquors after separation of insoluble substances by sedimentation important savings are claimed including 50 % sulphide, 40% lime and 60% of process water. Splitting and trimming is usually carried out after tanning which results in a by-product of low quality containing chromium in it. If these operations are carried out with the pelt, the produced by-product can be sold easily in the market than those resulting from splitting and trimming of wet blue (tanned hides/skins). The un-tanned solid waste will be a good raw material for manufacturing of gelatin or animal feed. This will also results in a reduction in the quantities of chemicals used for deliming, pickling, tanning and consequently the load of the pollutants in wastewater will be considerably reduced. Application of weak acids (organic) can eliminate the discharge of ammonium salt from deliming process. See Section 5.2.1.
Application of Weak Acids in Deliming Process Chrome Reuse in the Tanning Process
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5.2.2
Reuse of Chrome
Quite a few options are available for the reuse of the chrome discharged in the tanning effluent. These technologies do not completely eliminate the chromium being discharged through the effluent or sludge. However, it can be seen as apart of a general environmental plan of the tannery, since it reduces the necessary amount of chromium being discharged into the environment, thus facilitating the treatment and disposal of a small amounts of chromium containing sludge. Chrome reuse option also provides financial benefits. Direct Recycling of Chrome Tanning Float: This is the easiest method of chrome reuse. In this method after collection and sufficiently fine screening, the float is controlled and the chromium amounts used in the previous cycle are replaced by fresh chromium salts. Depending on the tanning technology in use, the degree of exhaustion reached for each cycle may vary. The recycling method may be repeated several times on the same float. However, it is limited by the occurrence of quality problems with delicate hides and by the need to control residual float. This technology is suitable for small tanneries. Recycling Of Chrome After Precipitation: This allows collection of the tanning float with the rinses, that sometimes occur at the end of the tanning and the effluent from various post-tanning stages (washing, dripping, sammying, etc). After collection, screening and storage, the floats are precipitated with different types of alkalies and bases including sodium hydroxide, sodium carbonate, magnesium oxide and even with lime. The reuse of sludge after simple settling and acidification has been experimented and practised. Schematic diagram of a typical chrome recovery and reuse plant is shown in figure 5.1. Large plants have operated under this scheme for many years in Germany, Itally, South America and France. In Pakistan four chrome recovery plants have been installed under the same process.
Cost-Benefit Analysis of a Chrome Recovery and Reuse Plant (CRRP): For the estimation of a total quantity of basic chromium sulphate (BCS) in the tanning effluent the maximum quantity of tanning effluent and minimum value of chrome quantity has been considered. Cost benefit analysis is given in the following table. These cost are approximate costs and given only for a general idea about the investment and pay back period of the chrome recovery project. Tanning Products that Improve the Exhaustion Rate: For the past few years, tanning and basification products have been available in the market which enable a tanning cycle to produce only small quantities of chromium waste. These products are developed with the aim of bringing about the complete fixation of the chrome onto the protein fibres so that the exhausted chrome tanning float contains little or no chrome. Chrome take up of over 90 % with exhaust of less that 1 gm per litre is possible. This reduces the initial chrome oxide offer to about 1.8 % on the fleshed weight and still obtains the same quantity of chrome fixed on the fibres.
Raw goat Skins Quantity of tanning float Total volume of float (a*b/100) Basic Chromium Sulphate (BCS) applied in tanning process Total BCS applied per day ( d*a/100) Chromium (Cr) in Tanning Effluent Total BCS in Tanning Effluent (c*f/170000) pH
3000 kg/day 80-100 % of a 2400 - 3000 litre 7-8 % of a 210 - 240 kg/day 7000 - 7500 mg/l 123.5 kilo/day 3.46 - 3.66
Amount 683,000 Unit Rs.
Description 2. Capital Cost 3. Operation and Maintenance Cost: A: Annual Operating Cost - Manpower - Electricity - Chemicals - Maintenance ( @ 5% of Capital Cost ) - Miscellaneous( @ 5% of Capital Cost) B: Depreciation Cost (@ 5% of Capital Cost) TOTAL O & M Cost 4. Benefits: - Total Recovered Chromium/day* - Total Recovered Chromium/annum (300 days) - Value of Recovered Chromium @ Rs. 36/kg Net Profit = 3-2 5. Pay Back Period
60,000 9,600 160,000 17,000 34,000 34,000 314,600 124 37200 1,339,200 1,024,600 7-8
Rs./year Rs./ year Rs./ year Rs./ year Rs./ year Rs. Year Rs./ year kg/day. Kg/year. Rs/year. Rs/year months
12
introduced into a tank aerated by mechanical stirring or by compressed air. Here it mixes with the mass of bacterial floc maintained constantly in suspension. After sufficient contact time, the mixture is clarified in a settling pond and sludge is recycled in the aeration tank. The excess sludge from the system is treated with primary sludge. This is a proven technology for the treatment of tannery wastewater and widely used all over the world. Modified forms of this technology are available. Aerated Lagoons: An aerated lagoon is an earthen basin in which the oxygen required by the process is supplied by surface aerators. In an aerobic lagoon, all the solids are maintained as suspension. To meet the secondary treatment standards, this technology can safely be used for the treatment of tannery effluent. However, it requires a large area of land as compared to other technologies. For the present study, this technology is not being considered due to insufficient area of land available. Facultative Ponds: Ponds in which the stabilization of waste is brought about by a combination of aerobic, anaerobic and facultative bacteria, are known as Facultative (anaerobic-aerobic) Stabilization Ponds. Three zones exist in a Facultative Pond: a surface zone where aerobic bacteria and algae exist in a symbiotic relationship; an anaerobic bottom zone in which accumulated solids are decomposed by anaerobic bacteria; and an intermediate zone that is partly anaerobic, in which the decomposition of organic waste is carried out by facultative bacteria. Conventional facultative ponds are earthen basins filled with wastewater. In this pond, large solids settle out to form an anaerobic sludge layer. Soluble and colloidal organic materials are oxidized by aerobic and facultative bacteria, using bacteria produced by algae growing near the surface. Carbon dioxide produced in organic oxidation serves as carbon source for the algae. Anaerobic breakdown of the solids in the sludge layer results in the production of dissolved organic compounds and gases such as carbon dioxide, hydrogen sulphide and methane, which are either oxidized by the aerobic bacteria or vented to the atmosphere. In practice, oxygen is maintained in the upper layer of the facultative lagoon by the presence of algae and by surface aeration. In some cases, surface aerators have also been used. If a surface aerator is used, algae is not required. Like an aerobic lagoon, this type of lagoon also requires a large area of land. In addition, odour is also a problem. Therefore, this technology also does not look feasible for the treatment of wastewater for the tanneries under study. Anaerobic Lagoon: Typically, an anaerobic lagoon is a deep earthen pond with appropriate inlet and outlet piping to conserve heat energy and to maintain an anaerobic condition. Anaerobic lagoons are constructed with depths of up to 30 ft. The waste that is added in the lagoon settles down at the bottom. The partially clarified effluent is usually discharged to another process for further treatment. Usually, these ponds are anaerobic throughout the depth, except for an extremely shallow surface zone. Stabilization is brought about by the combination of
The selection of the technology depends on many factors like capital cost, availability of land, operation and maintenance cost, efficiency of the process etc. In the following sections, technical viability as per the available tannery data, along with a brief process description of these technologies has been discussed. Activated Sludge: During a biological treatment by activated sludge, the wastewater to be treated is
13
precipitation and the anaerobic conversion of organic waste into carbon dioxide, methane, other gaseous end products, organic acids and cell tissues. Conversion efficiencies of BOD up to 70% can be achieved. High sulphate concentration in the tanneries would cause the production of hydrogen sulphide gas and which can adversely effect the surrounding areas. This technology also requires a large land area, therefore, it is also not feasible for treatment of wastewater of the tanneries under study. Trickling Filter: The working principle of the trickling filter is by percolating the water to be treated through a mass of porous or cavernous material, which serves as support for micro-organisms. The necessary oxygen required for maintaining an aerobic state for fixing the biomass to the support is generally supplied by natural ventilation. Due to natural ventilation, aeration cost is not required. This technology is being used in Pakistan for the treatment of domestic wastewater. This has not been tested for treatment of tannery wastewater on a large-scale. Due to a heavy load of pollution in tannery wastewater, its performance is doubtful. Tanneries are discharging wastewater containing 40 times more BOD value as compared to domestic wastewater. Nitrification is possible in this type of technology whereas denitrification of wastewater is not possible. Therefore, it is not possible to apply this technology for the treatment of wastewater of tanneries. However, it is a very simple technology and operation and maintenance cost is also very low as compared to the activated sludge technology. A small land area is required for this technology. Upflow Anaerobic Sludge Blanket (UASB) Technology: As it is evident from its name, this is an anaerobic process based technology. This treatment system is based on the upward flow of wastewater through a sludge layer of active anaerobic microorganisms. The wastewater is evenly distributed at the bottom of the reactor, and after a suitable hydraulic retention time in the reactor it leaves from the system from top of the reactor. The contact between the microorganisms of the wastewater is enhanced by the production of biogas, due to the rising bubbles which provide gentle mixing. There is no need for mechanical mixing. This simplifies the design of the reactor. After
passing through the sludge bed, a mixture of biogas, sludge and water enters a three phase separator. The biogas is separated in a gas collector, whilst the sludgewater mixture enters a settling compartment, thus providing effective sludge retention in the reactor. The effluent is discharged from the top of the reactor via an overflow weir. The excess sludge is discharged from the bottom of the reactor at the regular intervals onto a drying bed. This technology has been successfully applied for the treatment of tannery wastewater diluted with domestic wastewater in India. On the basis of the same principle, a UASB treatment plant is also being installed in Karachi, for the treatment of tannery wastewater for a cluster of more than 160 tanneries, situated in sector 7 - A of Korangi Industrial Area. Besides other toxic waste present in the tannery wastewater for anaerobic process, sulphate concentration is one of the more important factors. In the presence of sulphate, an anaerobic process starts the generation of hydrogen sulphide gas and at the same time the production of Methane gas is badly effected. Wastewater of tanneries under study contains sulphate (SO4) in the range of 860 - 3,146 mg/l. To overcome the problems of this technology, the tannery wastewater is treated after dilution with domestic wastewater in a ratio of 1:3. Due to this large quantities of domestic wastewater would be required. The tanneries under study cannot arrange this large quantity of domestic wastewater, therefore, this technology cannot be considered for the treatment of wastewater for individual tanneries
14
The suggested treatment plant comprises of a primary and secondary level treatment system.
Output of Primary Treatment* (kg/d) 153 206 52 Nil Output of Primary Treatment* (kg/d) 35 17 10 0.016
Sludge (kg/d)
309
Sludg e (kg/d)
25
* Considered loads to the aeration tank for design of volume and capacity.
Description
PH BOD5 (20 C) total BOD5 (20 C) settleable solid COD (total) COD settleable solid Tot. suspended solids Tot. Kj Nitrogen Sulphate Sulphide Phosphate
Note: BOD suspended solids are based on the difference of BOD at 0 time and BOD after 60 minutes settling. Source: Laboratory Analysis.
Sludge Handling Primary sludge pumps (for pumping of primary sludge from the sedimentation tank to the sludge thickener); Excess sludge pumps (for pumping of excess sludge from the return sludge pit to the sludge thickener); Sludge thickener (to increase dry sludge concentration i.e reduction of the sludge volume);and Drying beds and belt filter press.
6.1.2 Assumptions
The following assumptions have been made for the preliminary design: Wastewater quantity of the peak season has been taken into consideration, maximum flow which means a higher capacity, especially in aeration tanks and hydraulic capacity; The liquid effluent will be lifted (pumped) only once for the required water level in the plant; The removal efficiencies of the primary sedimentation tank are summarized in Table 6.2; The design of the aeration tank is based on a low loaded activated sludge system (including sludge stabilization); and Mechanical dewatering is taken into consideration as relatively high amounts of sludge are generated daily.
Tannery B
With Mechanical Dewatering 160 Without Mechanical Dewatering 212
15
Figure 6.1: Preliminary Layout of the Treatment Plant for a medium size segmented tannery with a Mechanical DeWatering System
Table 6.5: Estimated Investment Cost of Treatment Plant for (Wet) Finishing Tannery Process
Description A: Civil Works Grit chamber Equalization tank Primary sedimentation tank. Aeration tank Final settling tank Complete sludge thickner Sludge drying bed Control/Service room Sub Total B: Mechanical Equipments Mixer Pumps Scraper, skimmer, bridge etc Surface aerator Belt filter press Sub Total Total A + B 1. Electrical/ mechanical work ( 20 % total A+B) 2. Contingencies (20% of total A+B) Total Cost of Treatment Plant (million Rs) Estimated Annual Operation and Maintenance Cost 1520% of the total (million Rs)
Land Area Requirement (m2)
Tannery -A
Tannery B
PH BOD5 (20 C) total COD (total) Tot. suspended solids Tot. Kj Nitrogen Sulphate
42000 490000 70000 2275000 105000 392000 228200 100000 3702200 100000 700000 50000 150000 2500000 3500000 7202200 1440440 1440440 10.1 1.5-2
4000 210000 21000 560000 35000 392000 158000 50000 1430000 50000 350000 --------200000 ---------600000 2030000 406000 406000 2.85 0.4-0.6
1753 -2777
160 -212
16
As peak season is only two months per year, the design capacity will be based on the average flow, a design for a maximum flow means a high capacity, especially aeration tanks and hydraulic capacity;
The liquids effluent will be lifted (pumped) only once for the required water level in the plant; The removal efficiencies of the primary sedimentation tank are summarized in Table 6.7; The design of the aeration tank is based on a low loaded activated sludge system (including sludge stabilization); and
Due to the availability of the land, drying bed has been suggested.
1705
Considered loads to the aeration tank for design of volume and capacity.
BOD5 (20 C) total BOD5 (20 C) settleable solid Tot. suspended solids Tot. Kj Nitrogen Sulphate
6.2.3 Land Requirements Preliminary layout of the treatment plant is presented in Figure 6.2 & 6.3. Land requirement with and without a mechanical dewatering system is shown in Table 6.8 below: Table 6.8: Land Requirement (m2)
With Mechanical Dewatering 7838 Without Mechanical Dewatering 13834
Note: BOD5 suspended solids are based on the difference of BOD5 at O time and BOD5 after 60 minutes settling.
6.2.2 Assumptions
The following assumptions have been applied for the preliminary design:
17
Figure 6.2: Preliminary Layout of the Treatment Plant with Mechanical Dewatering System
Figure 6.3: Preliminary Layout of the Treatment Plant without Mechanical Dewatering System
18
Table 6.10: Estimated Capital Cost of Treatment Plant with the Present Hydraulic load of Tannery
Description A: CIVIL WORKS 1. Grit chamber 2. Equalization tank 3. Primary sedimentation tank. 4. Aeration tank 5. Final settling tank 6. Complete sludge thickner 7. Sludge drying bed 8. Control/Service room Sub Total B: MECHANICAL EQUIPMENTS 1. Mixer 2. Pumps 3. Scraper, skimmer, bridge etc. 4. Surface aerator 5. Belt filter press Sub Total Total A + B 1. Electrical/ mechanical work ( 20 % total A+B) 2. Contingencies (20% of total A+B) Total Cost of Treatment Plant Annual Operation and Maintenance Cost per year (15-20% of total cost) Land Area Requirement ( m2) Note: Land cost is not inculded. Estimated Cost (Rs.) 157,500 3,500,000 535,500 17,787,000 766,500 1,218,000 868,000 100,000 24.9 million 1,200,000 400,000 200,000 2,000,000 30,000,000 6.8 million 31.7 million 6.34 million 6.34 million 44.38 million 7 - 9 million 11,351- 13,834
19
Annexure 1:
List of Chemicals Used in the Tanning Process
S. No. I. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 II. 1 2 III 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 NAME PRE-TANNING CHEMICALS LIME POWDER CHINA CLAY AMONIUM SULPHATE SODIUM META BI SULPHATE KEROSENE OIL SEA SALT SULPHURIC ACID SODIUM BI CARBONATE CAUSTIC SODA OROPON SODIUM FORMATE SODIUM SULPHIDE BUSAN 30 FORMIC ACID MAGNISIUM OXIDE CHRMEND BASE FN/MD MERLO 89 ARACITAK SELLANTAN CF/LIG. TANNING MATERIAL PAK CHROME CHROMOSOL BF (WET) FINISHING CHEMICALS BASINTAN DLN/LE/LV TANIGAN AN RETIGAN R7 TANIGAN BN TANIGAN PAK-N MAGNOPAL STD 4 FBW CUTISAN SL SUTISAN IK TETRAPOL SAF CHROPIPOL L.LSAF(B.A.S.F). OMBRELLON WR TENSECO/SELLASOL HH TINO FIX CARTON O POWDER MIMOSA POWDER LIQUOR AMMONIA OXALIC ACID RELUGAN BTW BASINTAN FC BABRACHO ALUMINUM SULPHATE BASYNTAN WL S. No. 25 26 27 28 29 30 31 32 IV 1 2 3 4 5 6 7 8 9 10 11 12 13 14 V 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 NAME BASANTAN J-Z/J-Z IRGAPADOL PN-NEW IRGAPADOL FF4 BELLASOL -NG LIQ BOREX DERMAGEN DM TANIGAN QF HESLINIOUS DYES DERMA CARBON GS DERMA BROWN 1288/1289 DERMA BROWN 2G DERMA BROWN 2RM DERMA BROWN 2490 DERMA RED 2201 DERMA RED BA DERMA GREY 2411 DERMA DEIGE 2401 DERMA BLUE 2222 DERMA OLIVE 2402 DERMA BORDEX 2430 DERMA BEIGE Z DERMA BROWN HGP FINISHING CHEMICALS MICRO BINDER AM BINDER IF BINDER ON E.M. FINISH G/PANAMOL WAX EG LURAN LUSTER E BINDER LUSTER E BINDER U KONZ/PO EUKESOL OIL P BAYSIN LUSTER K PU BI GULF BINDER 001 GULF WAX 50 GULF GROUND 72 BAYDERM FINISH 80 UD EUE DESPERSION 92 A AQUALAN AKU K.S.3121 FROMAL-DE-HYDE ETHYLENEGLYCOL ACITIC ACID UNI WAX ST DP 5151 GULF WAX BR S. No. 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 NAME GULF OIL 44 MESLINIOUS GULF PUK 99 GULF TUCH 45 NEOSON DOUBLE WHITE NEOSON BLACK/D NEOSON BEIGE NEOSON BROWN NEOSON YELLOW NEOSON ORANGE NEOSON VIOLET NEOSON BLUE T BAYFEROX - 915 EUKANOL RED-D EUK. BLUE/NEO.BLUE -M EUKANOL RUBIN N EUKANOL BRILLIANT BLACK IRIODIN 100 (SILVER POWDER) IRIODIN 300 (GOLD POWDER) LEVADERM LEMON LIQ.N LEVADERM YELLOW LIQ.N LEVADERM ORANGE LIQ.N LEVADERM RED LIQ.N LEVADERM BORDEX LIQ.N LEVADERM BLUE LIQ.N LEVADERM NAVY BLUE LIQ.N LEVADERM OLIVE GREEN LIQ IRGADERM ORANGE M IRGADERM BLACK N EULASOLAR RED GL LIQ LEVADERM ORANGE LIQ.N LEVADERM RED LIQ.N LEVADERM BORDEX LIQ.N LEVADERM BLUE LIQ.N LEVADERM NAVY BLUE LIQ.N LEVADERM OLIVE GREEN LIQ IRGADERM ORANGE M IRGADERM BLACK N EULASOLAR RED GL LIQ EUK. BLUE/NEO.BLUE -M EUKANOL RUBIN N EUKANOL BRILLIANT BLACK IRIODIN 100 (SILVER POWDER) IRIODIN 300 (GOLD POWDER) LEVADERM LEMON LIQ.N LEVADERM YELLOW LIQ.N LEVADERM ORANGE LIQ.N LEVADERM RED LIQ.N
20
Annexure 2:
National Environmental Quality Standards (NEQS)
Air Emissions
(mg/Nm3 unless otherwise specified)
Parameter
1. 2. Smoke Particulate matter Boilers & furnaces: Using oil Using coal Cement kilns Grinding, crushing clinker coders, & related processes, metallurgical processes, convertors, blast furnaces and cupolas Hydrogen chloride Chlorine Hydrogen fluoride Hydrogen sulphide Sulphur oxides Carbon monoxide Lead Mercury Cadmium Arsenic Copper Antimony Zinc Oxides of nitrogen (NOX)
Standards
40% or 2 (Ringlemann Scale)
300 500 200 500 400 150 150 10 400 800 50 10 20 20 50 20 200 400
Noise Pollution
Nos
1. Noise level
Parameter
Standard
80 db
Liquid Effluents
(mg/litres unless otherwise defined)
Nos
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32.
Parameter
Temperature pH Value (acidity/basicity) 5-day biochemical oxygen at 20oC Chemical Oxygen demand (COD) Total suspended solids Total dissolved solids Grease and oil Phenolic compounds (as phenol) Chloride (as Cl) Fluoride (as F) Cyanide (as Cn) Anionic detergents (as MBAS) Sulphate (SO4) Sulphide (S) Ammonia (NH3) Pesticides, herbicides fungicides and insecticides Cadminum Chromium Copper Lead Mercury Selenium Nickel Silver Total toxic metals Zinc Arsenic Barium Iron Manganese Boron Chlorine
Standard
40oC 6-10 pH 80 150 150 3500 10 0.1 1000 20 2 20 600 1.0 40 0.15 0.1 1.0 1.0 0.5 0.01 0.5 1.0 1.0 2.0 5.0 1.0 1.5 2.0 1.5 6.0 1.0
21
Annexure 3:
Preliminary Process Design of a Treatment Plant for Segmented Tanneries {8000-10000 Skins (Wet Blue) / Day}
Average Flow
Characteristics (Average Value BOD (TOTAL) S.S Kj-N SULFIDE FLOW PER DAY TIME OF FLOW (12 7 PM) GRIT CHAMBER HYDRAULIC LOAD HYDRAULIC SURFACE LOAD SURFACE AREA EQUALIZATION TANK RENTENTION TIME FLOW DISCHARGE FLOW PRIMARY SEDIMENATION TANK NUMBER OF TANKS FLOW TO EACH TANK HYDR. SURFACE LOAD SURFACE DIA METER DEPTH VOLUME OF EACH TANK TOTAL VOLUME OF TANKS RETENTION TIME EFFICIENCY OF PST BOD5 SS Kj-N SULFIDE SLUDGE REMOVED FROM PST PRIMARY SLUDGE PRODUCTION SLUDGE CONC. SLUDGE VOLUME PUMPING TIME REQUIRED CAPACITY AERATION TANK SLUDGE CONCENTRATION ORG SLUDGE LOAD VOLUME NET DEPTH SURFACE AREA RETENTION TIME OF WATER BOD REMOVAL OXYGEN REQ. BOD REMOVAL OXYGEN REQD. Endog.resp ODYGEN REQ. RES NITRIFICATION OXYG.REQD. Kg/d Kg/d Kg/d Kg/d 40% 50% 10% 0% LOAD TO AERATION TANK 1190.4 1718 434/7 0 142.848 206.16 52.164 0 Kg/day Kg/day Kg/day Kg/day
M3/d
Mg/l Mg/l Mg/l Mg/l M3/d Hrs
120
1984 4295 483 0 1200 7 Load/per Day Kg/d 238.08 Kg/d 515.4 Kg/d 58 Kg/d 0
M3/HR M/H M2 M M M3 M3 Hr
22
DENITRIFICATION OXY.PRODUCTION SULFIDE OXIDATION OXY.REQD. TOTAL OXYGEN REQUIRED TOTAL OXYGEN REQUIRED AERATION PEAK FACTOR OXYGEN DEFICIT ALPHA FACTOR OXYGEN INPUT OXYGEN INPUT POWER REQD. EXCESS SLUDGE (RATE) BOD REMOVAL EXCESS SLUDGE PRODUCED EXCESS SLUDGE CONC EXCESS SLLUDGE PRODUCED DISCHARGE HR (Pumping Time) REQUIRED CAPACITY RETURN SLUDGE CAPACITY
60 Note: Max denitrification = 62% 136 100 0 301 13 1.2 1.24 0.9 21 1.2 17.3 x 24 x 365 = 151548 Kw/year 0.6 95 81 10 8 8 1.0 5
Kg/hr Kg O/Kw Kw Kg d.s./Kg % Kg d.s./d Kg/d/s/M3 M3/D hrs M3/hr M3/hr FINAL SETTLING TANK
NUMBER OF TANKS FLOW TO EACH TANK HYDRAULIC SURFACE LOAD SURFACE AREA OF EACH TA DIAMETER OF EACH TANK AVERAGE DEPTH VOLUME OF EACH TANK TOTAL VOLUME OF TANKS RETENTION TIME TOTAL SLUDGE PRODUCTION PRIMARY SLUDGE (PST) EXTRA SLUDGE (FST) TOTAL SLUDGE PRIMARY SLUDGE EXTRA SLUDGE TOTAL SLUDGE SLUDGE THICKNER SLUDGE LOAD SURFACE AREA DIAMETER AVE.DEPTH VOLUME SLUDGE CONCENTRATION SLUDGE VOLUME MECHANICAL DEWATERING DEWATERING TIME CAPACITY OF DEWATERING DRY SOLID CONCENTRATION SLUDGE VOLUME SLUDGE DRYING BEDS SLUDGE LOAD SURFACE AREA DRY SLUDGE CONC TOTAL VOLUME OF SLUDGE
M3/hr M/hr M2 M M M3 M3 Hr
Kg d.s./da M2 M M M3 % M3/d
30 15 4.4 3.5 53 3 15 Note: Mechanical Dewatering will not be used in this case
16 1 20 2
Kg/M2.d M2 % M3/d
1.2 378 20 2
23
Annexure 4:
Preliminary Process Design of Treatment Plant for Segmented Tanneries {600-1500 Kg Skins (Wet Blue) / Day
Average Flow
CHARACTERISTICS (Average Value) BOD (TOTAL) S.S Kj-N SULFIDE FLOW PER DAY TIME OF FLOW (6 AM 7 PM) GRIT CHAMBER HYDRAULIC LOAD HYDRAULIC SURFACE LOAD SURFACE AREA EQUALIZATION TANK RENTENTION TIME FLOW DISCHARGE FLOW
M3/d
mg/l mg/l mg/l mg/l M3/d Hrs M3/hr M/hr M2 M3 Hr hr/d M3/h PRIMARY SEDIMENATION TANK
40
Load/per Day 1468 1042 459 0.6 40 12 3 7 0.5 30 18.0 24 1.7 Kg/d Kg/d Kg/d Kg/d 58.72 41.68 18 0.02
NUMBER OF TANKS FLOW TO EACH TANK HYDR. SURFACE LOAD SURFACE DIA METER DEPTH VOLUME OF EACH TANK TOTAL VOLUME OF TANKS RETENTION TIME EFFICIENCY OF PST BOD5 SS Kj-N SULFIDE PRIMARY SLUDGE PRODUCT SLUDGE CONC. SLUDGE VOLUME PUMPING TIME REQUIRED CAPACITY AERATION TANK SLUDGE CONCENTRATION ORG SLUDGE LOAD VOLUME NET DEPTH SURFACE AREA RETENTION TIME OF WATER BOD REMOVAL OXYGEN REQ. BOD REMOVAL OXYGEN REQD. Endog.resp OXYGEN REQ. RES NITRIFICATION OXYG.REQD. DENITRIFICATION OXY.PRODUCTION
M3/hr M/h M2 M M M3 M3 hr
Kg/d 40% Kg/d 60% Kg/d 10% Kg/d 0% SLUDGE REMOVED FROM PST Kg/d % M3 hrs m3/hr
LOAD TO AERATION TANK 880.8 35.232 416.8 16.672 413.1 16.524 0.6 0.024 25 3 0.8 0.5 1.7
Kg/M3 Kg BOD/D M3 M M2 days % Kg/Kg Kg/d KgO/Kg ds.day Kg/d % Kg/d % Kg/d
4 0.11 80 4 20.0 2.00 95 0.5 17 0.11 35.232 95 71.7 60 43 Note: Max denirification =62%
24
SULFIDE OXIDATION OXY.REQD. TOTAL OXYGEN REQUIRED TOTAL OXYGEN REQUIRED AERATION PEAK FACTOR OXYGEN DEFICIT ALPHA FACTOR OXYGEN INPUT OXYGEN INPUT POWER REQD. EXCESS SLUDGE (RATE) BOD REMOVAL EXCESS SLUDGE PRODUCED EXCESS SLUDGE CONC. EXCESS SLLUDGE PRODUCED DISCHARGE HR (Pumping Time) REQUIRED CAPACITY RETURN SLUDGE CAPACITY
Kg/hr Kg O/Kw Kw Kg d.s./Kg % Kg d.s./d Kg/d/s/M3 M3/D Hrs M3/hr M3/hr FINAL SETTLING TANK
40589 Kw/Year
NUMBER OF TANKS FLOW TO EACH TANK HYDRAULIC SURFACE LOAD SURFACE AREA OF EACH TANK DIAMETER OF EACH TANK AVERAGE DEPTH VOLUME OF EACH TANK TOTAL VOLUME OF TANKS RETENTION TIME TOTAL SLUDGE PRODUCTION PRIMARY SLUDGE (PST) EXTRA SLUDGE (FST) TOTAL SLUDGE PRIMARY SLUDGE EXTRA SLUDGE TOTAL SLUDGE SLUDGE THICKNER SLUDGE LOAD SURFACE AREA DIAMETER AVE.DEPTH VOLUME SLUDGE CONCENTRATION SLUDGE VOLUME MECHANICAL DEWATERING DEWATERING TIME CAPACITY OF DEWATERING DRY SOLID CONCENTRATION SLUDGE VOLUME SLUDGE DRYING BEDS SLUDGE LOAD SURFACE AREA DRY SLUDGE CONC TOTAL VOLUME OF SLUDGE
M3/hr M/hr M2 M M M3 M3 hr
25.008 20.1 45 1 2 3
Kg d.s./da M2 M M M3 % M3/d
30 2 1.4 3.5 5 3 2 Note: mechanical dewatering will not be used in this case
16 0 20 0
Kg/M2.d M2 % M3/d
1.2 38 20 0
25
Annexure 5:
Preliminary Process Design of a Treatment Plant for Tanneries Processing Hides to Finished Leather (Appox. 2000 Kg/Day)
Average Flow
CHARACTERISTICS BOD (TOTAL) S.S Kj-N SULFIDE FLOW PER DAY TIME OF FLOW (6 AM 7 PM) GRIT CHAMBER HYDRAULIC LOAD HYDRAULIC SURFACE LOAD SURFACE AREA EQUALIZAION TANK RENTENTION TIME FLOW DISCHARGE FLOW
M3/d
mg/l mg/l mg/l mg/l mg/l Hrs m3/hr m/hr m2 M3 hr hr/d M3/h PRIMARY SEDIMENATION TANK
1836
Load/per Day 1740 1327 25 2 1836 13 141 30 4.7 1000 13.1 24 76.5 kg/d kg/d kg/d kg/d 238.08 515.4 58 0
NUMBER OF TANKS FLOW TO EACH TANK HYDR. SURFACE LOAD SURFACE DIA METER DEPTH VOLUME OF EACH TANK TOTAL VOLUME OF TANKS RETENTION TIME EFFICIENCY OF PST BOD5 SS Kj-N SULFIDE PRIMARY SLUDGE PRODUCT SLUDGE CONC. SLUDGE VOLUME PUMPING TIME REQUIRED CAPACITY AERATION TANK SLUDGE CONCENTRATION ORG SLUDGE LOAD VOLUME NET DEPTH SURFACE AREA RETENTION TIME OF WATER BOD REMOVAL OXYGEN REQ. BOD REMOVAL OXYGEN REQD. Endog.resp OXYGEN REQ. RES NITRIFICATION OXYG.REQD. DENITRIFICATION
M3/hr M/h M2 M M M3 M3 hr
LOAD TO AERATION TANK Kg/d 30% 1218 2236 Kg/d 70% 398.1 731 Kg/d 10% 22.5 41 Kg/d 0% 0 4 SLUDGE REMOVED FROM PST Kg/d 1705 % 5 Note: Lab results M3 ss12 hrs 8 m3/hr 1.6 Note: Excluding Spare Pumps Kg/M3 Kg BOD/D M3 M M2 days % Kg/Kg Kg/d KgO/Kg ds.day Kg/d % Kg/d % 4 0.11 5082 4 1270.6 2.77 95 0.5 1062 0.11 2236.248 95 179.3 60
26
OXY.PRODUCTION SULFIDE OXIDATION OXY.REQD. TOTAL OXYGEN REQUIRED TOTAL OXYGEN REQUIRED AERATION PEAK FACTOR OXYGEN DEFICIT ALPHA FACTOR OXYGEN INPUT OXYGEN INPUT POWER REQD. EXCESS SLUDGE (RATE) BOD REMOVAL EXCESS SLUDGE PRODUCED EXCESS SLUDGE CONC. EXCESS SLLUDGE PRODUCED DISCHARGE HR (Pumping Time) REQUIRED CAPACITY RETURN SLUDGE CAPACITY
108 100 7 3378 141 1.2 1.24 0.9 233 1.2 193.9 0.6 95 1275 10 127 8 1.0 Note: Excluding Spare Pumps 77
Kg/hr Kg O/Kw Kw Kg d.s./Kg % Kg d.s./d Kg/d/s/M3 M3/D Hrs M3/hr M3/hr FINAL SETTLING TANK
NUMBER OF TANKS FLOW TO EACH TANK HYDRAULIC SURFACE LOAD SURFACE AREA OF EACH TANK DIAMETER OF EACH TANK AVERAGE DEPTH VOLUME OF EACH TANK TOTAL VOLUME OF TANKS RETENTION TIME TOTAL SLUDGE PRODUCTION PRIMARY SLUDGE (PST) EXTRA SLUDGE (FST) TOTAL SLUDGE PRIMARY SLUDGE EXTRA SLUDGE TOTAL SLUDGE SLUDGE THICKNER SLUDGE LOAD SURFACE AREA DIAMETER AVE.DEPTH VOLUME SLUDGE CONCENTRATION SLUDGE VOLUME MECHANICAL DEWATERING DEWATERING TIME CAPACITY OF DEWATERING DRY SOLID CONCENTRATION SLUDGE VOLUME SLUDGE DRYING BEDS SLUDGE LOAD SURFACE AREA DRY SLUDGE CONC TOTAL VOLUME OF SLUDGE
M3/hr M/hr M2 M M M3 M3 hr
Kg d.s./da M2 M M M3 % M3/d
16 6 20 15
Kg/M2.d M2 % M3/d
1.2 2483 20 15
27