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A Report of theOffice of Environment and Natural Resources

Bureau for Global ProgramsUnited States Agency for International Development

POLLUTION PREVENTION DIAGNOSTIC CANE SUGAR MILL

FINAL REPORT

Prepared for:

Hagler Bailly Consulting, Inc.1530 Wilson Blvd., Suite 900

Arlington, VA 22209-2406

Environmental Pollution Prevention Project (EP3)Project Number 936-5559

Contract Number PCE-5559-Q-00-3022-00

1998

Environmental Pollution Prevention Project (EP3) CONFIDENTIAL INFORMATION ii

ACKNOWLEDGMENT

This publication was made possible through support provided by the Office of Environment and NaturalResources, Global Programs Bureau, U.S. Agency for International Development, under the terms of ContractNo. PCE-5559-Q-00-3022-00. The opinions expressed herein are those of the author(s) and do not necessarilyreflect the views of the U.S. Agency for International Development.

The pollution prevention audit/assessment reported on herein was conducted by a team of EP3 and industryrepresentatives. The primary purpose was to assist industry or facility management in creating a sustainablepollution prevention and waste minimization program.

This report was prepared for Hagler Bailly Consulting, Inc. by Patricio Gonzalez Morel, environmental engineerat EP3/Washington. Other members of the assessment team and contributors to this report include:

Donal Day, sugar processing expertParticipant X, program director for EP3Participant Y, chemical engineerParticipant Z

Environmental Pollution Prevention Project (EP3) CONFIDENTIAL INFORMATION iii

TABLE OF CONTENTS

CHAPTER 1: Executive Summary

CHAPTER 2: Objectives

CHAPTER 3: Background Information

3.1 Plant and process description3.2 Water supply to the sugar mill and alcohol plant3.3 Water consumption of the sugar mill, alcohol plant and spray pond3.4 Wastewater3.5 Wastes

CHAPTER 4: Analysis and Recommendations

4.1 Eliminate the discharge of lead from the facility=s laboratories

4.2 Improve the quality of the wastewater discharged to the lagoons4.2.1 Separate sanitary wastes from the mixed plant effluent4.2.2 Pretreat the plant=s mixed effluent4.2.3 Maximize the recovery of NaOH from the evaporators4.2.4 Improve the use of boiler wash water4.2.5 Improve housekeeping practices

4.3 Reduce Mill X=s water consumption4.3.1 Reduce the use of water for the spray pond4.3.2 Minimize water use and losses in plant operations4.3.3 Reduce the amount of water used in cooling down the evaporators

4.4 Reduce the volume of dilution water added to the product

CHAPTER 5: Concluding Remarks

APPENDICES

Appendix A: Processes for wastewater pre-treatment

Environmental Pollution Prevention Project (EP3) CONFIDENTIAL INFORMATION 1

CHAPTER 1EXECUTIVE SUMMARY

The assessment conducted by EP3 focused only on the Group’s sugar mill and distillery, located close to TownX. The total area of the plant is around 30 acres, having its own wells. Electricity is both generated by the mill,using bagasse, and bought from the city.

Mill X has a capacity to process 5,500 tons of sugar cane per day and expects to increase up to 6,000 in the nextfew years. This facility had an annual production of 58,000 tons of sugar and 7,140 m3

of alcohol in 1997, expecting to reach an annual production of 92,000 tons of sugar and 11,200 m3 of alcohol,in 1998.

The pollution prevention assessment of these two plants was conducted during the week of July 6th, 1998 by ateam composed by EP3 engineers and an industry specialist. The collaborative effort between the EP3 team andMill X’s staff led to the identification of the twelve pollution prevention opportunities that are summarized in Table1. If fully implemented, the proposed measures will:

• Eliminate the discharge of lead from laboratories;

• Lower the plant’s water consumption at least in 40% ;

• Reduce the purchase and discharge of NaOH;

• Improve the quality of the effluents discharged to the treatment lagoons;

• Increase the efficiency of the treatment lagoons;

• Generate a trend to “zero discharge”.


SUMMARY OF POLLUTION PREVENTION OPTIONS

Section Pollution prevention recommendations Benefits

4.1. Eliminate the discharge of lead from the facility’slaboratories

• Eliminate the discharge of 44 kg of lead/harvest to the lagoons

4.2. Improve the quality of the wastewaterdischarged to the lagoons

• Improve performance of the lagoon’s and quality of the treatedeffluent

• Facilitate the use of the treated effluent for agricultural purpose

4.2.1. Separate sanitary wastes from the mixed planteffluent

• Reduce risks in the reuse of the treated effluent in the spray pondand for agricultural purpose

4.2.2. Pretreat the plant’s mixed effluent beforedischarging it to the lagoons

• Reduce the amount of solids in the discharges and theaccumulation of sludge in the lagoons

• Improve the quality of the treated effluents

4.2.3. Maximize the recovery of NaOH from theevaporators after cleaning operations

• Reduce the consumption of NaOH in the plant

• Reduce the shock loadings of high pH wastewaters to thelagoons

4.2.4. Improve the use of boiler wash water • Reduce the suspended solids load to and the accumulation ofsludge in the lagoons

• Reduce the amount of vegetal condensates consumed in boilersauxiliary operations

4.2.5. Improve housekeeping practices • Reduce COD load in the effluents and in the lagoons

• Reduce the amount of grease/lubricants in the effluents

4.3. Reduce water consumption • Minimize water shortage problems during droughts

• Reduce the volume of the effluent to the lagoons and increase theretention time in the lagoons, improving their performance

• Eliminate the discharges of treated water to the river

• Increase the service life of wells and pumps

• Reduce the amount of energy consumed in pumping operations

• Reduce water use at the spray pond

• Reduce the amount of water used to cool the evaporators

4.3.1. Reduce the use of water for the spray pond • Reduce 44% of the plant’s total water use

4.3.2. Minimize water use and losses in plantoperations

• Reduce water consumption in a Percentage to be determined

4.3.3. Reduce the amount of water used in coolingdown the evaporators

• Increase the amount of heat absorbed by each unit of water in thecooling operation

4.4. Reduce the volume of dilution water added to • Reduce the consumption of water


the product • Reduce the energy needed to remove water by evaporation


CHAPTER 2OBJECTIVES

The EP3 Project

The Agency for International Development (AID) is implementing an environmental pollution preventionproject (EP3) worldwide. EP3 is designed to operate directly with industry groups to provide technicalassistance in pollution prevention, waste minimization and clean technologies. Technical assistance isdelivered in the form of: 1) diagnostic studies of selected industries conducted by US and local experts, 2)recommendations on measures to minimize pollution through the use of clean technologies, 3) training andinformation on EP3 practices, 4) tours by local experts to the US to meet with their industrial counterpartsthat have successfully pollution prevention measures, and 5) dissemination of effective experiences in theprogram.

The EP3 project is being implemented worldwide through the services of a contractor, Hagler BaillyConsulting, Inc., in addition to 16 sub-contractors. The EP3 Project uses the services of paid or pro-bonoexperts and environmental and regulatory experts from the US Environmental Protection Agency (EPA).

The EP3 Assessment

The objective of the EP3 assessments is to identify cleaner production options which (1) reduce the quantityof raw materials, chemicals and water used in the manufacturing process, and thereby reduce industrialpollution and worker exposure to toxic substances; (2) demonstrate the environmental and economic valueof cleaner production practices; and (3) improve manufacturing competitiveness and product quality.

The assessment focuses on the technical aspects of pollution prevention and is not intended to be acomprehensive evaluation of the safety and health impacts or considerations of the plant's operation. Theassessment also does not address general business and management practices such as accountingprocedures, data gathering, and data analysis. This report provides information on how to achieve andmaintain pollution prevention changes at the facility and serves as a first step in developing a sustainablepollution prevention program at the facility.


CHAPTER 3BACKGROUND INFORMATION

3.1. Plant and process description

3.1.1. Sugar Production

Sugar harvesting in this part of the country usually begins in later April, and it lasts until October.

Mill X was constructed in 1974 and started operations in 1977. The design capacity is 5,500 tons per 24hours day, which means 230 tons/hour; however there is a 85% efficiency, which reduces the capacity to4,675 tons per day, which means 195 ton/hr. The 15% reduction is attributed to lack of cane (7.5%) andmachinery failure (7.5%).

Reception: The process begins receiving raw cane from the harvesters. Each package containing cane isweighted, sampled and analyzed to determine its sucrose content. Payment is based on these results.

The package is then unloaded using cranes in the cane field, or directly into the cane conveyor, which leadsto the shredding knives which break the rind and expose the inner core.

Milling: The cut cane goes then to a 4 mill tandem (trapiche); the first mill has 4 drums, with the Donellyfeed System. The rest of the mills has only 3 drums. In order to optimize sugar juice extraction, AImbibition@water is added (35%, cane based) to cane coming out from the third mill. Formol (10 lt, 10% solution) issprayed every 12 hours all along the milling system to prevent contamination.; also bacteria killer ( as Bropa272, and others) is added to the juice coming out from the last mill (3.75 ppm).

Purification: Once extracted, sugar juice has to be treated with Sulfur in counter current absorption columns.Lime (12.5% solution) is needed to neutralize the juice, before heating it to 110 EC. Then it goes to acontinuous clarifier, where a floculant agent is dosified by the sides. Fine bagasse is mixed with the solidscoming out from the clarifier. This mixture is filtered in a rotary vacuum system; liquid separated by thisfilter is returned to the process, while filter cake (cachaza) is stored outside before being used as fertilizer.The clarified juice is also filtered using 100 mesh, before going to evaporation, the next process.

Chemicals dosage, based on milled cane is: Sulfur 300 ppm, Lime 1600 ppm and Floculant 4 ppm.

Evaporation: This operation concentrates eliminates the water contained by the juice by evaporation. Thedensity is increased from 1.2 to 4.8 approx. No chemicals are added in this operation.

Boiling and Crystalization: The thickened juice is boiled in steam-heated pans under vacuum to produce amixture of crystals from the residual syrup which is crystalyzed in agitated and refrigerated Malaxorcrystalyzers.

Centrifugation, Drying, Packing: There are three quite similar parallel processes: A, C and semi-refined. Ineach one the crystals are spun in centrifugal machines to separate the crystals from the residual syrups.These syrups are recirculated a number of times to help the formation of crystals, exhausted syrups arecalled molasses (melazas) which are transferred to the alcohol plant. Semi-refined sugar consists of whitecrystals which, dried and packaged are the final product of Mill X.


3.1.2. Alcohol production.

Reception: Molasses coming from the sugar plant are weighted and analyzed before being stored in tankslocated in the alcohol plant.

Fermentation: Molasses at 85 Brix and 1.5 gr/cc is pumped to the process scale, and then goes to twoconsecutive tanks, where it is diluted to 60 Brix, and then to 26. This wort goes to two different destinies:one part goes to a third dilution until having 12 Brix, to feed the yeast cultivation tank; the bigger part goesto one of the six fermentation tanks. After a certain period, the fermented wort goes to a centrifuge, whereyeast is separated from the liquid phase. Part of the out coming yeast is subject to thermal treatment, dryingand packaging as dry yeast. The rest goes back to the fermentation process; the following chemicals areadded to this yeast: Virginiamicine, Sulfuric acid, urea and other nutrients like phosphate.

Distillation: The liquid coming out from the centrifuge is called wine, which, after stabilizing feeds the firstdistillation column. This column is previously heated, and its product is a phlegm at 50% in alcohol that feedsthe next column, where its concentration is diluted to 20% to facilitate removal of impurities. This 20%phlegm is pumped to the rectifying column, where concentration is increased to 96 degrees Gay Lussac,which complies with Government Quality Standards.

From the first column a residue is generated at the bottom: Vinasse, which is pumped to a reservoir to beused as a fertilizer.

3.1.3. Hydrolyzed Bagasse production.

Hydrolyzed Bagasse is produced from the bagasse that comes out from the mill, once produced is used ascattle feed. The process for hydrolyzation consists of auto-hydrolysis process divided in two phases:

In the first phase, bagasse is introduced to a steam pressurized chamber (18 kg/cm2, 220 d. C). There, theacetilic radical in the cellulose are transformed into acetic acid, which promotes hydrolysis of cellulose intodextroses and pentoses, making it edible for cattle feed.

The second phase consists of sudden steam release from the pressurized chamber, produces a rapidevaporation of the humidity content of bagasse, increasing its volume and softening the fiber, so it will beappropriate for cattle feed.

This by-product is brown colored and good smell, and its characteristics are similar to the usual cattle feed:grass. It is an excellent alternative in the dry seasons.

3.1.4. Sucrose yield analysis.

According the information received from Mill X, sugar cane has approximately 11.5% sucrose content.

Based on the total cane processed in 1997, we can calculate the following sugar balance:

Material % 1996 (*) 1997Tons

Raw cane 100 875,000 671,954Sugar content 11.5 100,625 77,275


Over 11,5% of sugar:Final product 79 79,494 61,047Losses in bagasse 2.5 2,516 1,932Losses in cachaza 2.0 2,013 1,545Losses in molasse 13.0 13,081 10,046Miscellaneous losses 3.5 3,522 2,705Total (over 11.5% of sucrose 100 100,626 77,275

3.2. Water supply to the sugar mill and alcohol plant

All of the water consumed in the sugar mill and alcohol plant is drawn from four deep wells. The outputof the wells and the final destination of the extracted water are summarized in the following table.

Well No. Output Destination of pumped water1 30-35 m;/hour The water extracted from well No. 1 is used in the Acampamento.@ Any water

which is not consumed in the campamento is discharged into the main waterstorage tank (V = 1,000 m;).

5 160 m;/hour7 155 m;/hour

All of the water extracted from wells 5 and 7 is discharged into the main waterstorage tank (V = 1,000 m;).

9 90 m;/hour The water extracted from well 9 is discharged into the concrete channel whichlinks the main water storage tank to the pump room.

The well pumps are generally operated 24 hours per day and any water which cannot be used in the sugarand alcohol plant simply overflows into the spray pond.

The water sent to the water storage tank drains into a concrete channel leading to the pump room, and three60 HP pumps lift the water from the concrete channel to a 20 m; elevated storage tank which supplies waterto the sugar and alcohol plants. The operation of the three 60 HP pumps is manually controlled by the pumproom operators who use the float level of the elevated storage tank to determine when the pumps should beturned on or shut off. In order to avoid running out of water in the sugar or alcohol plant, the operators tryto ensure that the elevated storage tank is always full of water. Any excess water sent to the elevatedstorage tank drains off through an overflow pipe and is discharged into the spray pond.

There are no water or flow meters on the principal water supply and distribution system; the Mill X=sspecific water consumption is therefore unknown. Given the lack of an effective water monitoring systemand automatic controls for the well and plant pumps, Mill X=s water consumption is excessive and couldpossibly be significantly reduced.

3.3. Water consumption of the sugar mill, alcohol plant and spray pond

The theoretical output of wells 5, 7 and 9 approximately coincide with the data provided in Mill X=sManifiesto Ambiental. The facility=s total water consumption can therefore be assumed to be equal to~10,000 m;/day or 415 m;/hour.

During the course of the audit, EP3 conducted measurements to determine approximately how much waterwas consumed in the sugar and alcohol plants and how much was discharged to the spray pond. Themeasurements, collected over a two hour period, are summarized below.

Water output from wells 415 m;/hr


Water consumption of sugar and alcohol plants 200 m;/hrOverflow of well water to the spray pond 415 m;/hr - 200 m;/hr = 215 m;/hr

Even though a two-hour long monitoring test cannot be considered to accurately represent the averageconditions of the plant, it is interesting to note that at times more than 50% of the water extracted from thewells is discharged directly into the spray pond.

3.4 Water use in the spray pond

The flows discharged into Mill X=s spray pond include 1) the recirculating cooling water of the barometriccondensers, 2) the Avegetal@ condensates from 9 Atachos de cocimiento@ and the last effect of theevaporators, and 3) the excess well water which overflows from the facility=s two water storage tanks. Thecooling water is recirculated from the spray pond to the barometric condensers using a battery of threepumps which have a flow capacity of 6,500 m;/hour.

The volume of vegetal condensates sent to the spray pond has a peak value of 260 tons/hour (based on thecapacity of the Atachos de cocimiento@ and of the evaporators) but averages 115 tons/hour. The averagetemperatures conditions in the spray are 45 C for the condenser water returning to the spray pond and 35C for the spray pond water.

Because of the addition of well water from the main and elevated storage tanks, there is a constant outflowwater from the spray pond. The effluent flow from the spray pond averages 200 m;/hour but can reacha peak of 400 m;/hour.

3.5. Wastewater

The two principal wastewater streams generated by the plant include the spray pond effluent and planteffluent.

Characteristics of the spray pond effluent:

C Average flow = 200 m;/hour

C Average COD = 250 ppm

C COD load from the spray pond = (200,000 lit/hr) x (24 hr/day) x (250 mg/lit) = 1,200 kg COD/day

C Depending on the quality of the spray pond effluent, this flow is either sent to the wastewater treatmentlagoons (when the COD > 500 ppm) or to an irrigation channel (when the COD < 500 ppm).

Characteristics of the sugar mill and alcohol plant effluent:

C Average flow = 100 m;/hour

C Average COD = 4,900 ppm

C COD load from the plant = (100,000 lit/hr) x (24 hr/day) x (4,900 mg/lit)= 11,800 kg COD/day


C The main constituents of the plant=s effluent are 1) wash water from floor and equipment cleaningoperations, 2) wash water used in the bagasse boilers, 3) water from the laboratories and 4) part of thesanitary wastewater produced by the facility (7 toilets that are used by 60 workers per shift).

C The plant wastewater is sent to Mill X=s wastewater treatment system composed of two batteries oflagoons arranged in series. The first battery consists of a series of 12 lagoons (total estimated volume= 140,000 m;) and the second consists of 8 lagoons. The treated lagoon effluent is either used toirrigate agricultural fields or discharged to the river X.

3.6. Wastes

The principal waste streams produced by Mill X include:

Vinasse: The vinasse produced by the alcohol plant is first sent to two unlined lagoons and then loadedonto tanker trucks and sprayed on cane fields. Mill X is in the process of developing a bio-ferlitizer project to make better use of its vinasse.

Cachaza: The cachaza, or filter mud, is currently collected and applied directly to agricultural fields asa soil fertilizer. In near future, the cachaza will be used as one of the primary ingredients inthe bio-fertilizer production.

Bagasse: The bulk of this material is burned in Mill X=s boilers and only a small portion of it isconsumed in the production of hydrolyzed bagasse, a feed supplement for cattle. In thefuture, bagasse will also be used as on of the principal raw materials for the bio-fertilizerproject.

Boiler ash: The boiler ash produced by Mill X=s bagasse boilers is used as a filler/compaction materialfor road construction or is applied to agricultural soils as a fertilizer.


CHAPTER 4ANALYSIS AND RECOMMENDATIONS

This chapter discusses the pollution prevention opportunities that were identified by the EP3 team at this facility. It contains the description of the recommendations and information on costs, benefits, obstacles and other issuesthat are related to their implementation.

Most of the recommendations given in this report are based on the observations, measurements and data gatheredby EP3 during the course of a week-long audit. Given this short time frame, EP3 is often unable reconfirm theaccuracy of the collected information and, therefore, the facility is strongly encouraged to verify, and correct ifnecessary, all inputs and calculations contained in this report.

4.1. Eliminate the discharge of lead from the facility == s laboratories

Current situation

< Both the cane and the sugar production laboratories use lead sub-acetate to clarify all product samples usedin sucrose analyses. The residues which remain on the paper filters are discarded along with the rest of MillX=s solid waste even though these contain a significant amount of lead. Approximately 10% of the lead usedin the analyses remains in solution in the product samples and is discharged in the plant=s drainage system. This lead eventually finds its way either to the lagoons or the irrigation channel.

< Lead is a toxic heavy metal which does not degrade in the environment; it accumulates in sediments ofstreams and ponds and is absorbed in the food chain. The use of lead sub-acetate in US sugar mills has beenbanned or severely restricted; all lead-containing residues must be stored in appropriate containers and sentto a site designed for the disposal of hazardous materials.

< The use of lead in Mill X=s laboratories can be estimated as follows:

Laboratory Average no. of samples Pb sub-acetate

Cane 500 samples/day 6 gr/sample

Sugar production 140 samples/day 6 gr/sample

Total 640 samples/day

Total use of Pb sub-acetate = (640 samples/day) x (6 gr/sample) x (180 days/harvest)= 691 kg Pb sub-acetate/harvest

Total use of Pb = (691 kg Ac Pb/harvest) x [(207 kg Pb) / (325 kg Ac Pb)]= 440 kg Pb/harvest


Pb discarded as solid waste = 90% x 440 kg Pb/harvest= 396 kg Pb/harvest

Pb discarded to lagoons = 44 kg Pb/harvest

Recommendations

< Replace the Pb sub-acetate with an alternative clarifying agent such as ABC (produced by Barlett ChemicalsCompany, Baton Rouge, Louisiana, USA). If the ABC clarifier is not available in Country X, Mill X could try todevelop an effective clarifying agent in conjunction with a local technical university. The principal ingredientsof a cane juice clarifier include AlCl3, lime, activated carbon and a flocculant.

< Consider changing the method used for sucrose determination by using an instrument that does not require sampleclarification (NIR spectroscope or dark field polarimeter).

< Until the use of lead sub-acetate is completely eliminated, Mill X should stop disposing lead-containing residuesin its general solid waste stream or discharging lead-containing product samples in the plant=s drainage system. All lead-containing substances (solids and liquids) should be collected, stored in suitable containers, and sent toan appropriate waste disposal site. In order to reduce the volume of hazardous wastes needing special disposalpractices, liquid samples could possibly be concentrated by evaporation.


4.2. Improve the quality of the wastewater discharged to the lagoons

Mill X should strive to reduce the contaminant load contained in the wastewater it currently discharges to its lagoonsystems. The principal benefits of improving the quality of Mill X=s raw wastewater include:

< Reducing the concentration of grease, organic matter and strong bases (NaOH) in its raw wastewater will improvethe performance of Mill X=s treatment lagoons and the quality of the treated effluent.

< The elimination or reduction of specific wastewater constituents, such as fecal coliforms and Na (from NaOH),will facilitate the use of the lagoons= treated effluent for agricultural purposes or make-up water for the spraypond.

The specific actions that Mill X can take to improve the quality of its raw wastewater include:

< Separate sanitary wastes from the mixed plant effluent.

< Pre-treat the plant effluent before it is discharged to the lagoons.

< Maximize the recovery of NaOH from the evaporators after cleaning operations.

< Improve the use of boiler wash water.

< Improve housekeeping practices.


4.2.1. Separate sanitary wastes from the mixed plant effluent

Current situation

< Seven of the toilets located in the sugar mill are connected to the plant=s main drainage system and dischargehuman waste to Mill X=s lagoons. These toilets are used by approximately 60 workers per shift.

< The presence of human wastes in the plant=s raw wastewater contaminates the treatment lagoons with fecalcoliforms. The anaerobic and aerobic treatment provided by the lagoons reduces the fecal coliformconcentration, but, even after passing through the first 12 lagoons, the partially treated plant effluent stillcontains a considerable number of fecal coliforms. In fact, the analysis of a water sample taken at the inletof the lagoons revealed that this partially treated wastewater (380 ppm COD/liter) still contained 4.3 x 103

fecal coliforms/100 ml.

< The high concentration of fecal coliforms in its treated wastewater may restrict the possible reuse of thelagoon=s effluent. Waters contaminated with fecal coliforms cannot be safely used in spray ponds (fecalcoliforms carried by fine airborne water droplets or mist pose a serious threat to human health), and theiruse in agricultural applications is restricted or strongly discouraged in many countries around the world.

Recommendations

< Eliminate the discharge of human wastes to the lagoons by connecting all of the plant=s bathrooms to oneor more septic systems (i.e., a septic tank followed by a disposal/infiltration field).

< If the soil characteristics around the plant are not suitable for the construction of a standard disposal field(for example because of high water table or excessively slow percolation rates), Mill X should considerinstalling an alternative disposal system to treat the septic tank effluent. Examples of alternative disposalsystem include intermittent sand filters, shallow pressure-disposal field trenches, and mound disposalsystems (see information package provided by EP3). Such systems are relatively simple to design andconstruct, and should be well within the capacity of a local sanitary engineer.

< The elimination of human waste from the plant=s mixed effluent will significantly reduce the risks associatedwith reusing the lagoons= treated effluent in the spray pond and cane and rice fields. Mill X should thereforeconsider using the lagoon effluent as make-up water for the spray-pond.


4.2.2. Pretreat the plant’s mixed effluent before discharging it to the lagoons

Current situation

< Mill X=s plant wastewater is discharged to an unlined earthen channel that connects the plant to the lagoons=pump station. Some natural sedimentation of the wastewater occurs between the plant and the pump station,but the channel is not equipped with any mechanism to effectively remove the settled sludge.

< Before reaching the pump station, the wastewater passes through a vertical mesh which is designed toprotect the centrifugal pumps. Although the mesh captures all large solid particles contained in thewastewater, it is too coarse to significantly reduce the load of suspended solids (SS) discharged to thelagoons. Furthermore, this mesh must be manually cleaned and thus requires the constant attention of thepump station operator.

< The channel is not equipped with a grease trap and, given that there are no grease traps anywhere in theplant, all of the grease and lubricants lost from the various pieces of equipment drains directly to the lagoons. Grease, oil and lubricants harm the bacteria which purify the wastewater in the lagoons and, thus, reducethe effectiveness of Mill X=s wastewater treatment system.

Recommendations

Mill X is planning to upgrade the channel connecting the plant to the pump station. While planning this upgrade,Mill X should consider the following issues.

< Include a coarse bar rack to remove large objects from the raw wastewater flow. In order to facilitatecleaning operations, the bar rack should be made of smooth bars inclined in the direction of the flow. Technical information on bar racks is provided in Appendix I.

< Line the channel with concrete and install a mechanism that can be used to remove the solids which settlefrom the wastewater. A standard sludge removal system for rectangular settling tanks, or channels, consistsof a scraper mechanism which travels along the bottom of the tank/channel and pushes the sludge towardsa collection hopper. The sludge which accumulates in the hopper is then removed from the settling channelwith a Atrash pump.@ Information on settling tanks is given in Appendix I.

< Install a flow-metering device to monitor the volume of wastewater discharged by the plant. The standardtypes of devices used to measure wastewater flows include V-notch weirs, rectangular weirs and Parshallflumes. By monitoring its wastewater discharge, Mill X will also be able to estimate its total waterconsumption.

< Install a screening device, such as a self-cleaning DSM screen or a rotating screen, after the settlingchamber. In order to avoid having to pump the wastewater to the screening device, the effluent of thesettling chamber should ideally drain by gravity to the screening device. A DSM or a rotating screen willbe significantly more effective than the existing mesh in protecting the wastewater pumps and in reducingthe BOD, COD and SS load discharged to the lagoons. By reducing the mass of solids entering the lagoons,Mill X will be able to reduce the accumulation of sludge in its lagoons and improve the quality of its treatedeffluent.


< Install small grease traps in all floor drains which carry significant amounts of grease/oil mixed in with thewastewater. Installing small grease traps close to areas where the grease/oil discharge actually occurs maybe more effective, and less expensive, than installing a large grease separation unit at the plant=s outlet. Because of its high flow (100 m;/hour) and high temperature (>50EC), the plant wastewater could probablynot be effectively processed through a standard grease separation unit.


4.2.3. Maximize the recovery of NaOH from the evaporators after cleaning operations

Current situation

< Each day one of Mill X=s 8 evaporators is taken out of service, cleaned and given a maintenance check. Theevaporator tubes are generally descaled with a high-pressure power-wash system, but, whenever necessary,the evaporators are given a more thorough cleaning with a concentrated NaOH solution.

< After each NaOH cleaning cycle, the used cleaning solution is drained to a storage tank, refortified, andeventually reused in the following NaOH cleaning cycle. The NaOH solution is reused as many times aspossible; it is discarded only once or twice during the entire production season.

< After draining the spent NaOH solution, the evaporator is washed with water to eliminate NaOH residues andother impurities. The wash water used in this operation is discharged to the plant=s drainage system andmixes with the plant=s effluent. According to the Mill X=s lab technician, this wash water still containsenough NaOH to significantly raise the pH of the wastewater that exits the plant and enters the treatmentlagoons. Since the anaerobic bacteria are very sensitive to pH variations, it is probable that this periodicdischarge of NaOH affects the performance of the lagoons.

Recommendations

< Mill X should consider maximizing the recovery of NaOH from the evaporators. This measure will slightlyreduce the plant=s consumption of NaOH, but, more importantly, it will reduce the shock loadings of highpH wastewaters to the lagoons.

< Mill X should consider adopting the following procedure to recover most of the NaOH currently lost withthe wash waters.

C After completing the NaOH cleaning cycle, drain the NaOH solution to the NaOH storage tank (ascurrently done).

C Give the evaporator a short Afirst rinse@ with a water spray. Collect the rinse water and drain it of theNaOH storage tank. The duration of the first rinse should be long enough to remove most of theremaining NaOH, but short enough to minimize the dilution of the NaOH solution contained in thestorage tank.

C After draining the Afirst rinse@ water to the NaOH tank, use the standard process to thoroughly rinsethe evaporator. The water from this Asecond rinse@ should contain little NaOH and should notsignificantly affect the pH of the plant=s effluent.

C In the following NaOH cleaning cycle, the NaOH solution (now a mixture of NaOH solution and firstrinse water) is refortified and pumped to the dirty evaporator.

Note: C The practice of recovering and reusing first rinse waters is successfully practiced in manyindustrial processes.


C The recovery of the first rinse water will gradually increase the volume of the recoveredNaOH solutions. However, this excess volume can be eliminated by evaporating the excesswater either in the storage tank or in the evaporators themselves.

C In order to implement this measure, Mill X may have to increase the size of the existingNaOH tank.


4.2.4. Improve the use of boiler wash water

Current situation

< A continuous stream of water is used to remove ashes from the stacks of the bagasse boilers. This wateris recirculated in a closed loop between the boiler and a sedimentation tank, or Aash well.@

< The ash boxes of the boiler=s combustion chambers are flushed with water approximately 3 times per day. After leaving the ash boxes, this wash water also drains to the Aash well.@

< Whenever the water stored in the Aash well@ is considered to be too dirty for further reuse, it is pumped toa drainage channel and sent to the lagoons. The Aash well@ is then replenished with hot water from theAvegetal condensate@ storage tanks. It is estimated that the Aash well@ is pumped out 4 times per day, andapproximately 90 m; of dirty water are sent each day from the boilers to the lagoons. This dirty water hasa low COD content (~170 ppm COD) but contains suspended ash particles which eventually settle in thelagoons.

< Every day Mill X uses a large quantity of water from the vegetal condensate tanks to spray the ash pile and,sometimes, the bagasse pile.

Recommendations

< Instead of using clean vegetal condensates to spray the ash and bagasse piles, Mill X should consider usingthe dirty boiler wash water that is stored in the ash well. Ideally, all of the dirty boiler wash water presentlysent to the lagoons could be disposed on the ash and bagasse piles. The benefits of this recommendationinclude:

C The suspended solids contained in the boiler wash water would be sent to the ash pile rather than thelagoons. This will reduce the SS load to and the accumulation of sludge in the lagoons.

C This will reduce the amount of vegetal condensates consumed in boilers auxiliary operations (sprayingash piles and washing ash boxes).

< Consider installing a DSM or a rotating screen to reduce the concentration of SS in the boiler wash water. This measure should improve the quality of the recycled water, reduce frequency at which the ash wellmust be replenished with new vegetal condensates, and facilitate the use of the dirty boiler wash water tospray the ash piles (reduces the possibility of clogging the hose nozzle).


4.2.5. Improve housekeeping practices

Current situation

< Product leaks and spills invariably occur in the various stages of sugar production. Although most leaks andspills have only a minor effect on the plant=s productivity, they can account for a significant portion of thepollutant load contained in the plant=s wastewater. The importance of minimizing leaks/spills and keepingproducts out of the wastewater stream becomes evident when one considers the COD content of the sugarmill=s intermediate products. For example,

COD of mixed juice ~ 50,000 mg/literCOD of raw cane juice ~120,000 mg/literCOD of thickened juice ~600,000 mg/liter

< The grease and lubricants which drip from the plant=s machinery generally fall to the floor and find their wayto the floor drains. Since Mill X does not have grease traps, the grease and lubricants are eventuallydischarged to the lagoons and affect their operations.

Recommendations

< Fix all product leaks and repair damaged pump seals. Even a small leak of cane juice (0.5 liter/minute) canincrease the load to the lagoons by 90 kg COD/day (equal to a population equivalent of 650 people).

< Instead of cleaning product leaks/spill with a water hose, Mill X should consider absorbing the spilledproduct with bagasse. The bagasse is then collected and burned in the boilers. ADry cleaning@ spills/leaksrequires little labor and can significantly reduce the COD load to the lagoons.

< Install drip pans wherever possible to capture grease/lubricants Adrips@ and prevent these products fromreaching the plant floor. Dispose of the captured grease/lubricants in an appropriate manner.

< Whenever possible, the grease and lubricant which collects on the plant floor or equipment should be drycleaned instead of hosed down.

< Install grease traps on all drainage channels which carry a significant amount of grease/lubricants (forexample in the floor drain which services the trapiche). A grease trap placed in a floor drain which carriesa small flow of cool wastewater will be much more effective than a large grease trap placed at the outlet ofthe plant.


4.3. Reduce Mill X== s water consumption

The volume of water currently used by Mill X is excessive and the plant should strive to use water moreefficiently. By reducing its water consumption, Mill X will:

< minimize water shortage problems during droughts;

< reduce the volume of wastewater discharged to its lagoons, increase the retention time of the wastewaterin its lagoons, and improve their performance;

< eliminate the need to discharge any treated wastewater to the river X (Mill X could become a Azero effluentplant@);

< increase the service life of the wells and pumps;

< reduce the amount of energy consumed in pumping operations.

The specific actions that Mill X can take to conserve water include:

< reduce water use at the spray pond;

< minimize water use and losses in plant operations;

< reduce the amount of water used to cool down the evaporators.


4.3.1. Reduce the use of water for the spray pond

Current situation

< In sugar mill spray ponds, the evaporation and wind drift losses are nearly compensated by the vegetalcondensates collected by the barometric condensers. However, fresh water is generally added to the spraypond, either continuously or periodically, to replenish excessive drift losses and maintain the concentrationof contaminants at an acceptable level. In plants that recirculate barometric condenser water, the COD ofspray pond water generally ranges between 3,000 and 15,000 mg/liter (source: Nota Sobre Tecnologia deControle, Fabricacao de Acucar e Alcool, Companhia de Tecnologia de Saneamento Ambiental).

< It appears that the volume of water added to Mill X=s spray pond is excessive. In fact, measurementsshowed that the addition of well water to the spray pond can, at times, exceed 200 m;/hour. Furthermore,the dilution of the spray pond water is such that the average COD concentration in the pond water ismaintained at only 250 mg/liter.

< The addition of well water is believed to help cool the spray pond water. However, calculations includedbelow indicate that the cooling effect of the well water may be negligible.

< The overflow from the spray pond is currently used for irrigation. But, whenever the COD of the spraypond water rises above 500 ppm, Mill X is forced to send this flow to its treatment lagoons. The additionof the spray overflow to the lagoon triples volume the effluent needing treatment and affects theperformance of the lagoon.

< Currently, all excess well water which cannot be used in the plant is discharged to the spray pond. If MillX wishes to reduce its total water consumption by reducing the well water flow to the spray pond, it willneed to install a system to automatically control the operation of its well and plant pumps.

Recommendations

Mill X should consider reducing the volume of well water added to the spray pond, and operating its spray pondat a higher COD level (for example, 3,000 mg/liter). If this measure is implemented, the spray pond overflowwill have to be treated at all times, but its volume will be significantly reduced and should not affect the lagoons=performance.

Input, assumptions and calculations

a) Calculation of the overflow rate needed to maintain a COD level of 3,000 mg/l in the spray pond

C Current overflow rate from the spray pond = 200 m;/hour

C Current COD of the spray pond overflow = 250 mg/liter

C These calculation assume that Mill X will reduce the flow of well water to the pond until the averageCOD concentration in the pond, and in the pond overflow, reaches 3,000 mg/liter.


Current COD load discharged by the spray pond = (200 m;/hour) x (250 mg COD/liter)= 50 kg COD/hour

Future overflow rate from the spray pond = (50 kg/hour) / (3,000 mg/liter)= 17 m;/hour

Note: These calculation show that, by reducing the spray pond overflow from 100 m;/hour to 17 m;/hour,the COD of the pond water will increase from 250 mg/liter to 3,000 mg/liter.

b) Calculation of the water savings achieved by operating the spray pond at an average COD of 3,000 ppm

C These calculations assume that the evaporation and drift losses are greater than the inflow of vegetalcondensates into the pond. Therefore, any reduction in the spray pond overflow equals a reductionin the volume of well water added to the spray pond.

C At the present time, the average output of Mill X=s wells is estimated at 10,000 m;/day.

Reduction in the water consumption of the spray pond = (200 m;/hr) - (17 m;/hour)= 183 m;/hr= 4,390 m;/day= 44% of the plant=s total water use

Note: These calculations show that Mill X could reduce its total water consumption by 44% by reducingthe overflow rate of its spray pond to 17 m;/hour and operating its spray pond at a COD level of 3,000mg/liter.

c) Calculation of the effect of well water dilution on water temperature in the spray pond

C Estimated well water temperature = 20EC

C Average water temperature in the spray pond = 35EC

C Average temperature of the water discharged by the barometric condensers = 45EC

C Estimated water flow from the barometric condensers to the spray pond = 6,500 m;/hour

C Current average overflow from the spray pond = 200 m;/hour

C The heat capacity of water is 1,000 kcal/m;/EC

The total amount of energy dissipated by the spray pond is:

Edissipated by pond = (6,500 m;/hr) x (45EC - 35EC) x (1,000 kcal/m;/EC)= 65x106 kcal/hr


The total amount of energy dissipated by the addition of well water to and the overflow from the spray pond is:

Edissipated by well water = (200 m;/hr) x (35EC - 20EC) x (1,000 kcal/m;/EC)= 3x106 kcal/hour= 4.5% of the total energy dissipated by the spray pond

Note: These calculations seem to indicate that the addition of well water to the spray pond plays only a minorrole in reducing the water temperature in the spray pond. Therefore, if Mill X decides to reduce the volume ofwell water added to the spray pond, this action is not expected to significantly affect the temperature andperformance of the spray pond.

d) Effect of adding the spray pond water overflow to the treatment lagoons

C Average characteristics of the current influent to the lagoon: 100 m;/hour, 4,900 mg COD/liter

C Average characteristics of the spray pond=s future effluent: 17 m;/hour, 3,000 mg COD/literIncrease in flow sent to the lagoons = (17 m;/hr) / (100 m;/hr)

= 17 %

Current COD load to the lagoons = (100 m;/hr) x (4,900 mg/liter)= 490 kg COD/hr

Future COD load to the lagoons = (490 kg COD/hr) + [(17 m;/hr) x (3,000 mg/liter)]= 541 kg COD/hr= a 10% increase in the COD load to the lagoons

Note: The preceding calculation show that if the all of the future spray pond overflow (17 m;/hour) is sent tothe lagoons it will increase the pollutant load to Mill X=s wastewater treatment system by only 10%. It wouldtherefore appear that the implementation of this recommendation should not greatly affect the performance of thelagoons.


4.3.2. Minimize water use and losses in plant operations

Although Mill X=s management and workers are conscious of the need to conserve water, there are still plentyof opportunities to further reduce the plant=s water consumption. Mill X should, for example, consider thefollowing water conservation measures.

< Restrict the use of the water hoses that are used to wash floors or in non-essential cleaning operations. < Equip all water hoses with spray guns.

< Improve the quality of the floors in areas that are frequently cleaned. Smooth floors can be washed witha minimum amount of water. Furthermore, rubber scrapers can be used to complement water hoses whenwashing smooth floors.

< Use drip pans to prevent soiling the floor with grease and lubricants.

< Shut faucets and hoses off as soon as they are no longer needed (e.g., sink faucets in the laboratories). Arunning faucet can needlessly waste more than 700 liters/hour.

< Periodically remind all workers that Mill X=s management is concerned about water conservation issues. Use signs and posters to reinforce Mill X=s water conservation program.


4.3.3. Reduce the amount of water used in cooling down the evaporators

Current situation

< Before starting the manual cleaning operation of an evaporator, it must be cooled to allow the workers toenter inside the evaporator shell. The evaporator is cooled by flushing it with a continuous stream of waterduring approximately 30 minutes. Measurements taken by EP3 revealed that the cooling of a singleevaporator consumed from 70 to 90 m; of well water (2,300 to 3,000 liters/minute during 30 minutes).

< Towards the end of the cooling operation (last 10 minutes), the water discharged from the evaporator isalmost as cool as the well water which is drawn from the tap. This fact indicates that the flow of coolingwater is excessively high.

Recommendations

< After obtaining the fog lights that will allow the workers to operate more than 2 high-pressure hoses insidethe evaporator, Mill X should consider decreasing the flow of cooling water and increasing the duration ofthe cooling period. By optimizing the flow of cooling water, Mill X could significantly increase the amountof heat absorbed by each gallon of water that is used in the cooling operation.

< Mill X should also consider using a forced air flow (driven by a fan) in conjunction with a fine spray ofcooling water to minimize the volume of water needed to cool the evaporator. If the fan is used to drive anair flow from the top to the base of the evaporator, it will also help remove the water mist which currentlyhampers visibility inside the evaporator.


4.4. Reduce the volume of dilution water added to the product

Current situation

< The juice collection tank located at the base of the sulfitation tower is equipped with spray nozzles that areused to control the build-up of foam. The nozzles are operated continuously and discharge from 15,000 to20,000 liters of water per day.

< It was noted that when the spray nozzles are turned off, it takes approximately 15 minutes for the foam toreach the top of the tank.

< All of the water that is added to the cane juice in any part of Mill X=s process must eventually be removedby evaporation. For example, it is estimated that the evaporation of the water added in the sulfitation tankwould require, if evaporated at atmospheric pressure, from 8.1x106 to 9.4x106 kcal per day (or 9,400 to12,500 kWh/day). It is therefore in Mill X=s best interest to minimize, wherever possible, the dilution of itsproduct with water.

Recommendations

< Whenever possible, Mill X should try to avoid any unnecessary dilution of its product. In the case of thesulfitation tank, Mill X could consider reducing the addition of water by:

C installing a timer to periodically (every 10 to 15 minutes) turn on the spray nozzles for a short periodof time;

C instruct workers to periodically flush out the foam with a water hose equipped with a spray gun;

C instruct worker to periodically flush out the foam with a spatula or a skimmer.


CHAPTER 5CONCLUDING REMARKS

What is pollution prevention?

Pollution control focuses on handling and treating wastes after they have been generated. Given the globaltrend towards stricter controls over industrial effluents, solid waste, and air emissions, this traditional approachis becoming increasingly expensive and only adds to the product cost without adding to its value or quality. Incontrast to pollution control, pollution prevention focuses on minimizing or eliminating waste at its source . As a result of waste minimization and improved process efficiency, investments in pollution prevention or cleanproduction measures yield financial savings and often have payback periods of less than one year.

The financial, environmental and other benefits of a comprehensive pollution prevention program include:

< achieving the efficient use of raw materials;

< improving process efficiency and reducing production costs;

< reducing the amount of waste that must be treated and disposed of;

< reducing the design capacity and thus the capital cost of waste treatment systems;

< reducing the operations cost of the waste treatment systems;

< reducing the disposal costs for solid and liquid wastes;

< facilitating compliance with environmental regulations;

< reducing liability from the discharge or disposal of wastes;

< improving the energy efficiency of production processes;

< improving product quality by gaining a better understanding and control of the production processes;

< improving worker=s health and safety by minimizing exposure to harmful substances;

< improving the public image of the facility.

The general requirements for the implementation of a comprehensive pollution prevention program include:

< modifying current production processes to improve materials = use and reduce waste generation;

< improving the control and monitoring of waste-related parameters in production processes;

< fostering the reuse of process wastes and energy efficiency;


< improving workers= training on proper equipment operation and process control;

< improving general housekeeping practices in the facility;

< investing in cleaner production equipment instead of end-of-pipe treatment systems.

The specific benefits and requirements of the pollution prevention opportunities identified for this facility duringthe course of the EP3 audit are summarized in Chapter 1.

Taking action

The objective of the EP3 program is to foster the implementation of pollution prevention measures in theparticipating facilities. In order to achieve this goal, the local EP3 office and EP3/Washington will continue toprovide technical support and guidance to facilitate the implementation of the proposed recommendations.

One of the keys to a successful pollution prevention program is establishing a comprehensive action plan to guidethe preparation, implementation and monitoring of process modifications. Below is a checklist of the main stepsthat are generally included in such action plans.

1) Establish a core group of plant staff to evaluate the options provided in this report. Review the data andcalculations, determine if any information was misconstrued by the audit team and if necessary make theappropriate adjustments to the report=s calculations and results.

2) Prioritize the recommendations in accordance with their potential value to your facility and ease ofimplementation.

3) Conduct a detailed technical and an economic evaluation of the selected options. Obtain price quotationsfor the required equipment or plant modifications. Ask appropriate questions such as: Is training necessaryfirst? Will production need to be stopped? Will the vendor provide acceptable service? Will the changecreate other environmental problems?

4) Solicit employees= input and ideas on the selected recommendations.5) Develop an implementation schedule.6) Implement the recommendations and provide the required training to the personnel.7) Establish a mechanism to measure the effects of the implemented recommendation and pollution prevention

progress within the plant. Track relevant accounting information such as waste treatment and disposalcosts, water and sewer costs, energy and raw materials consumption and costs.

8) Establish routine auditing procedures to ensure that the standard operating practices are respected. Rotatethe auditing duties among all process operators.

9) Regularly evaluate the facility=s operations to identify ways to increase productivity and reduce materials,water and energy use.

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