Challenges to Recycle & Reuse Dyehouse Wastewaters

8/22/2019 Challenges to Recycle & Reuse Dyehouse Wastewaters

1/5

1x.

C H A L L E N GE S T O R EC YC L E A N D REUSEWASTEWATERSby Fred T. Eslirka

A t presentyou wiii find many dyehouse water con-servation practices in textiles. Already many textileoperations are using one bathdyeing procedure forfiber blends as opposed to earlier use of two stepdyeing. A ll shades and al l procedures, however, willnot lend itself to one bath dyeing. Caustic recovery isfairly well standard procedure where mercerizing orSanforizing i s done. There are many package dyeingfacilities that reuse the dye liquor cool back wateralone with fresh water as makeup water to replenishthe hot water supply. Much of dyehouse wash water i spresently reused. indigo dye recovery i s now in use.

Energy conservation through recycle/reuse i s alsopracticed in textiles. In caustic recovery the con-denser water of the recovery unit is fed back to thehot water storage tank of the dyehouse. Easy shadesutilizing simple dyeing procedures can be reused byadding necessary dyes to the recycle bath.

There are, however, some problems with energy orheat recovery in most dyehouse operations. All viabledyehouse operations presently in textilesareequippedwith dyehouse wastewater heat recovery systems.These systems normally can recover more waste heatthan can be utilizedby the dyehouse. A rule of thumbis that only 70% of the heat recovered will actually bereused by the dyehouse. Systems are sized for peakloads hydraulically and thermally and no dyehousewill afford a solid heat balance that can reuseal l heatrecovered.

I would like to share with you a few major activitiesof the Environmental Preservation Committee thatwill enhance your perspective of dyehouse waste-water recycle/reuse.

Over the past eight years there have been threemajor projects conductedbythe ATMI Committee inconcert with the Northern Textile Association and theCarpet and Rug Institute. The U.S. Environmental Pro-tection Agency (both R&D and Effluent Guidelines)also participated in these projects. The major studiesin chronological order were:1. Recommendationsand Commentsfor the Estab-

lishment of Best Practicable Wastewater Control

OF DYEHOUSE

lechnology Currently Available for the TextileIndustry. This study was completed J anuary15,1973. Hereinafter this will b e called the BlueBook study.Source Assessment: Textile P lant WastewaterToxics Study. Final Draft completed December,1977. Hereinafter we will refer to this as theMonsanto study.Technical and Economic Evaluation of BATEATextile Guidelines. This study was begun in 1976and completed in anuary, 1980. Hereinafter thiswill be called the BATEA study.

On J uly 24, 1972, representatives of A T M I wereinvited to Washington, D.C., for a meeting with theDirector, Office of Enforcement, EVA. At this meet-ing, these representatives were presented with a copyof a document, entitled Effluent Limitation Gui-dance for the Refuse Act Permit Program - TextileIndustry, and were asked to comment on the docu-mentas to its workability or suitability. As these guide-lines were some 36 pages long, the A T M I representa-tives requested a sufficient length of time for study,before commenting on them. In answer to thisrequest, ten days were granted, during which repre-sentatives of ATMI, the institute of Textile Technol-ogy (ITT), and Hydroscience, Inc., an independentconsulting concern, held discussions on the contentof these textile industry guidelines, and formulated acollective opinion on them. As a result of thesedelib-erations, a two-fold approach was decided upon.

Firstly, the text of the guidelines was criticallyreviewed and commented on. Secondly,itwas decidedthat so far as the tables of values of permissible pollu-tant levels were concerned, insufficient data wereavailable at that time, to form an opinion as to theirworkability and attainability. ATMI, therefore, re-turned to Washington on August 7,1972, to report toEPA with a constructive criticismof the text, and witha request for a 120-day period to carry out an all-encompassing study of the textile industry wastesituation, sponsored by ATMI, in conjunction with

3


2/5

....~


3/5

dischargers. These guidelines reguired Best AvailableTechnology Economically Achievable (BATEA) to beachieved by J uly 1,1983. On October 1,1974, ATMlfiled a petition for review of the textile industryBATEA guidelines with the US. Fourth Circuit Courtof Appeals. A T M I was joined in this action by theNorthern Textile Association and the Carpet and RugInstitute. The parties involved subsequently filed ajoint motion to delay the petition pending the reviewof the results of a cooperative study undertaken toevaluate the technical and economic achievabilityand impact on the textile industryof the promulgatedBATEA discharge limitations.

The objective of the BATEA study was to evaluatethe treatment efficiency of processes identified asBest Available Technology Economically Achievableby EPA's Effluent Guidelines Division on textile indus-try wastewaters. The technical phase of this studyconsisted of defining the Advanced Waste Treatment(AWT) processes to be tested, designing and con-structing pilot units, surveying and selecting textileplants for pilot plant study, performing pilot plantstudies, evaluating pilot plant data and preparingconceptual BATEA plant designs, developing keyaspects of the cost functions for estimating BATEAcosts, and preparing project reports. Engineering-Science, inc., (ES) was selected as the engineeringconsultant to conduct the technical phase of thestudy.

To insure the success of the study and validity ofresults, i t was necessary to selecta group of plants thatwould be representative of the textile dyeing andfinishing industry. The following criteria were used toselect the participating plants:1. The textile mills must have operating secondary

wastewater treatment facilities.Z The effluent from the existing wastewater treat-

ment facilities must be generally within NPDESpermit levels.The wastewater treatment effluent must normallybe discharged directly to a natural water course.The textile manufacturing company must be wil-ling to participate in the study (financially andotherwise).The textile mill must be located such that it wd5compatible with location and other constraints ofthe study activities.

Engineering-Science designed and constructed twomobile pilot units. The experimental equipment wasbuilt into two 40-ft. trailers to facilitiate relocationfrom one textile plant to another. The trailers con-tained al l equipment necessary to test the followingAWT processes on a pilot scale.1. Chemical Coagulation/Clarification2.

3.

4.

5.

Multi-Media Filtration (with and without pre-

filter coagulant addition)3. Granular Activated Carbon Absorption4 . OzonationThese AWT processes could be tested individually orin combination with each other. Dissolved Air Flota-tion (DAF) was also tested with bench-scale equip-ment.

The pilot plants visited a total of 19 textile millsbetweenMay, 1977 and September, 1978. Experimen-tation was done to first screen potential treatmentprocesses, and then to collect sufficient continuousoperation data on candidate processes for the devel-opment of preliminary design criteria.

The selection of the recommended AWT processwas made for each of the 19 textile plants basedon thefollowing criteria:1.2.

Comparison of the treatment effectiveness of thecandidate AWT processes tested at the site.Comparison of the effluent quality of the candi-date AWT processes tested with the 1974 BATEAguideline values calculated for the plant.Comparative evaluation of the capital and opera-tional costs of the candidate AWT processestested that can technically achieve the BATEAeffiuent guideline values or if no AWT process i scapable of achieving the guideline values thencomparative costs of the AWT technologies pro-viding similar effluent quality.

If only one of the AWT processes tested achievedthe 1974 BATEA guideline values then it was therecommended AWT process for that plant. However,if all or none of the AWT processes could achieve the1974 BATEA guideline values then a comparison ofrelative treatment effectiveness of the processesand/or capital and operational costs was made inorder to select the recommended AWT process.

An analytical quality assurance program was estab-lished for the study to guarantee the proper collec-tion, analysis and record-keeping of the samples. TheQuality Assurance (QA) Program required thatapproximately ten percent of al l the samples were tobe used to establish the reliability of all the data. Theprogram utilized duplicate samples, reference sam-ples, round robin blind samples, and spike samples.There were six laboratories involved in developinganalytical data for the projects. The procedures usedduring the QA Program were reviewed and approvedby the Process Measurement Branches of IERL/EPA(Research Triangle Park, N.C. and Cincinnatti, Ohio)prior to the initiation of program activities.

Based on thedata obtained from field experimenta-tion, the treatment effectiveness of the various AWTtechnologies was determined for achieveing the J uly5 , 1974, BATEA guideline values. The following i s a

3.

5


4/5

summary of the conclusions and observations deve-loped from this study. More detailed information onthe study results i s available from EPA.1. Of the 19 plants tested, ten (53 percent) could

meet the 1974 BATEA guideline values (technicalparameters not necessarily economical parame-ters) with one or more of the AWT process tech-nologies. Nine of the plants (47 percent) failed tomeet the BATEA guideline values with any com-bination of AWT process technologies evaluated.The ability of the AWT processes to achieve theBATEA guidelines was judged based on statisti-cally predicted 30-day average and maximumdayeffluent concentrations.

2. The treatment effectiveness of the individualAWT processes were as follows:a. Coagulation/clarification was a candidate

process in wool finishing, knit fabric finish-ing, carpet mills, and stock and yarn dyeingplants and demonstrated reasonable treat-ment effectiveness for reduction of most ofthe parameters measured. However, coagula-tion/clarification was not a feasible process inwool scouring and woven fabric finishingplants due to the inability to identify an effec-tive coagulant or very high coagulant dosagerequirements.Multi-media filtration performed well in mostcases for TS S removal. If the TSS value of theBPT effluent was approximately 100mg/l orless, then multi-media filtration was effectiveas an initial process for TSS reduction. Multi-media filtration was also an effective processfor reducing TSS after coagulation/clarifica-tion.Granular carbon adsorption performed wellwhen compared to other AWT processes fororganic and color removal in wool scouring,wook finishing, woven fabric finishing, knitfabric finishing, and carpet mills. However,granular carbon adsorption was not effectivein achieving the BATEA guideline values a tone of the two stock and yarn dyeing plants,nor at s ix of the ten woven fabric finishingplants. In some cases, it was observed that aportion of the organic removal occurredfrom physical filtering rather than an adsorp-tion mechanism. In certain instances, solubleorganics were re-introduced into the waste-streamas a result of the desorption.Ozonation didachieve color reduction belowthe BATEA guideline values at selected sites,but did not reduce C OD below the BATEAlimits.Dissolved air flotation ( D A F ) was notfound to

b.

c.

d.

e.

beas effective a method for TSS reduction asthe coagulation/clarifier process.

Both the textile industry and EPA learned from theBATEA study. The1974 BATEA Guidelines were setbyEPA using outside contractors who used review ofexisting literature as a primary source of information.Some of the results of these technologies were takenfrom other industries and mathematically transferredto textiles. When you scale up from laboratory tests tofull operation on these processes, you obtain quitedifferent results. You can transfer technology, butyou cannot consistently transfer results.

To summarize the BATEA study, none of the AWTsperformed as expected for textiles as a whole. MostAWTs showed a great deal of variation within a seg-ment of textile dyeing and finishing. All the AWTswere extremely expensive to construct and operate.AWTs will treat toxic materials better than secondarybiological treatment for many of the priority pollu-tants.Having shared the history of cooperative effortbetween the textile industry and EPA with you, onemightask How does this affect recycle reuse of dye-house wastewaters? In my view there are both eco-nomic and environmental justifications for dyehousewastewater treatment that would allow recycle/reuse.

Environmentally these AWTs would be justified totreat toxic wastes to allow reuse or direct discharge toa stream. The BATEA study and Monsanto study havefurnished EPA a broad data base showing that textiledyehouse wastewaters are not toxic and the sludgesgenerated by biological secondary waste treatment ofthese wastewaters are not hazardous. Environmentaljustification cannot be made for application of AWTsto dyehouse wastewaters that have been properlytredted with biological secondary treatment.

On the economic issue, it is still far less expensive totreat surface or groundwater or purchase water frommunicipalities than to use AWTs that will allow recyc-le/reuse of dyehouse wastewaters.The state of the artin wastewater heat recovery i s such that energy costscan be reduced a t far less cost and better control ascompared to AWTs. To be sure, there are a few sitespecific dyeing and finishing operations where aneconomic case might be made, but these are few andfai between.

While economics i s a formidable challenge torecycle/reuse oi dyehouse wastewaters, particularlywhen there i s little need for the AWTs environmen-tally, recycle/reuse has other challenges. Firstly, thereare no minimum standard specifications set for pro-cess water required for dyeing textiles. Most dyerswant the process water as close to chemically purewater as the dyehouse filter plant will produce, or themunicipality will furnish. To my knowledge, little


5/5

researchhasever been done to set minimum processwater standards for a l lcategories of dyeing. Secondly,the use of sizes in knitting and weaving plus use ofcarriers and electrolytes in dyeing interfere withmany wastewater treatment systems, or pass throughthem.To conclude, let me list for you the challenges t h a t

must be met before recycle/reuse of dyehouse waste-waters will be commonplace in textiles:1. Development of economic, reliable treatment

systems that can handle non segregated waste

streams from dyehouses.2.

3 .

4.

Research to determine minimum standards fordye process water by textile industry category.Institutionof size recovery by textiles in generalprior to dyeing.Research to eliminate or minimize the use of car-riers and electrolytes in dyeing.

a C h a i r m a n , A T M l E n v i ro n m e n t al C o m m i t t e e , A m e r ic a nT h r ea d C o m p a n y , P.O.Box 880, O l d For t , N C 28762

7

Documents

Challenges to Recycle & Reuse Dyehouse Wastewaters