Yün yıkama atıksularının asitle emülsiyon kırma metoduyla arıtılması üzerine bir araştırma

Abstract

ÖZET Yün yıkana atıksuları yüksek konsantrasyonlarda yağ ve askıda katı madde muhtevasıyla karakterize edilmektedir. Ayrıca noniyonik deterjan bulunan bu sularda yağlar emülsiyon halde bu lurmakt ad ır. Yün yıkanan atıksularının arıtılmasında henüz standart sayılabilecek bir metod geliştirilmemiş olmakla birlikte, kolay uygulanabilirliği ve diğerlerine göre ekonomik olması sebebiyle asitle emülsiyon kırma meto du geniş bir uygulama alanı bulmuştur. Bu metodda atıksuyun pH'ı asi- dik seviyelere (pH<3) indirilir, bu esnada karıştırma işlemi yapılır ve daha sonra bir çökelticiden geçirilir. Yaptığımız çalışmada, bu tür atıksuların asitle emülsiyon kırma metoduna göre arıtılmasında ka rıştırmanın, deterjan konsantrasyonunun ve pH'ın etkisi kesikli sistem çalışmaları ile incelenmiştir. Ayrıca atıksuyun orijinal deterjan muhtevasında ve pH <3'de karıştırmanın etkisi sürekli sistemde de incelenmiştir. Birinci bölümde, tekstil endüstrisinin Türkiye'deki önemi belir tilmiş, buna bağlı olarak yünlü sanayiinin durumu kısaca incelenmiş yün yıkama atıksularının arıtılmasının öneminden bahsedilmiş ve çalış manızın amaç ve kapsamı belirtilmiştir. İkinci bölümde, yün yıkama işlemi tanıtılmış ve yün yıkama atık sularının özellikleri çeşitli yönleri ile incelenerek, yıkama meto duna göre kirletici konsantrasyonlarındaki farklılık gösterilmiştir. Yün yıkama atıksularının arıtılması konusunda bugüne kadar yapılan çalışmalardan bahsedilmiştir. üçüncü bölümde, kolloidal haldeki kirleticilerin giderilme esas ları üzerinde durulmuş, stabilizasyon ve destabilizasyona tesir eden faktörler incelenmiştir. Kolloidlerin giderilmesinde karıştırmanın öneminden bahsedilerek, bu konuda geliştirilmiş kinetik ifadeler verilmiştir. Dördüncü bölümde, deneysel çalışmanın planlarması, inceleme yaptığımız işletmenin tanıtılması, deney düzeni ve teknikleri ile ya pılan çalışmalardan bahsedilmiş, pilot tesis ve tan ölçekli tesis tanıtılmıştır. Deney sonuçlarının değerlendirilmesinde kullanılan hesap yöntemleri incelenmiş, deney sonuçları verilmiştir. Beşinci bölümde, deney sonuçları çeşitli yönleri ile değerlen dirilmiştir. Deneysel çalışmaların sonunda atıksuda kalan kirletici madde (yağ, askıda katı madde, KOt) miktarlarını ve meydana gelen yağlı çamur hacimlerini, karıştırma şiddetine, deterjan konsantrasyonuna ve ph`ya bağlı olarak ifade eden genel bağıntılar çıkarılmıştır. Ayrıca kirleticiler arasındaki ilişkiler incelenerek, arıtma sonunda yapılacak basit ve ucuz analizlerle kirlilik tayini için grafikler verilmiştir. Altıncı bölümde, bulunan neticeler toplu halde özetlemiştir.

SUMMARY AN INVESTIGATION ON THE TREATMENT OF WOOLSCOURING WASTEWATERS BY ACID CRACKING METHOD Woolscouring wastewaters are characterized with `their high suspended solids and grease content. Wastewaters also contain non-ionic detergents. Grease content of these wastes is in emulsified form. These wastewaters have harmful influence on receiving waters when they are diFectly discharged to surface waters, because of very high concentrations of pollutants which are known to be extremely toxic to aquatic life. Therefore high content of grease and suspended matter of this wastes makes them also very hazardous to the sewage system. On the other hand treatment of woolscouring waste waters by conventional methods is rather difficult and requires a pre- treatment stage which is known as grease removal. Although there have not been developed a standard treatment technique for woolscouring wastewaters, removal method of grease with acid- cracking process is being applied commonly due to its relative low cost and simplicity. In this method wastewater is first acidified in order to decrease its pH below 3 and agitated during this operation, then it is settled. Some doubts about the reliability on the performance of the acid- cracking method have arisen after introduction of non-ionic detergents in woolscouring process. vmIn this study an experimental investigation of the effect of pH, mixing intensity and detergent concentration on the efficiency of acid-cracking treatment of woolscouring wastewaters is carried out. A statistical approach is employed for the evaluation of the results. In the first chapter, importance of textile industry in Turkey is stressed, share of the wool industry in it is investigated.. Treatment requirements of woolscouring wastes are considered and the aim and concept of this study is outlined. In the second chapter, an outline of the woolscouring process is given. Characteristics of wastewaters originating from the process and quality variations with respect to different processes of scouring are delineated. Methods that have been employed for the treatment of woolscouring wastewaters are summarized. I are eval Relation and susp of the o agitat io Relation paramete methods n th uate s be ende pera n in s be r s w such e fi d co twee d so t ion tens twee hi ch as fth chapter the results of the experiments nsidering various aspects öf the process, n the concentrations of COD, oil and grease lids of the effluent and various parameters al parameters such as pH, detergent content ity, volume of sludge are developed, n the effluent quality parameters and the can be readily determined by low cost turbidity are developed and plotted. chapter. Results of the study are summarized in the sixth Results and finding of the study can be summarized as follows : Maximum and minimum values of woolgrease, CODand SS concentrations of the studied woolscouring waste waters are found as 4.3-12.3 g/1, 15.8-42.0 g/1 and 3.4-13.1 g/1, respectively. Pollutant loads are obtained as : 80-230 kg grease/ton product and 300-800 kg COD/ton product and 64-245 kg SS/ton product. Results of the study indicate that the emulsion breaking method of acid-cracking accompanied by agitation can be used as an efficient method of treatment for the woolscouring wastewaters which contains non-ionic detergents, Treatment performances are found to be inadequate when short agitation periods of 1-5 minutes are applied under the low velocity gradient of 200 sn~l. Under these conditions the effluent concentrations of grease and suspended solids exceed 1000 mg/1. The agitation period of 15 minutes yields oil and grease and suspended solids concentrations below 500 mg/1 which corresponds 90% grease, 95% suspended solids and 80% COD removals. Velocity gradient is measured and expressed in terms of dimensionless parameter G.t. Preexper iment s indicates that adequate treatment efficiencies of over 90% can be achieved with G.t values over 15. lO^. Relation between remaining grease concentration( C ) and G.t is analyzed statisticaly and best fit is obtained for a general exponential form. Resulting equation for batch-scale experiments is; C = 1,90. e~9'89'10 (G,t), g/1, (r=0.929) y For continuous system studies it becomes; C = 1,50. e`7'**10 (G>t), g/1, (r=0.908) The same form of regression is obtained between the remaining SS concentrations and G.t as; SS = l,3.e`9'7-10 {G-t), g/1, (r=0.912) Non-ionic detergent content of the wastewaters ranges from 300 to 400 mg/1. A study is carried out in order to determine the effect of detergent concentration upon effluent grease, SS and COD concentrations for pH values below 3 and for a constant agitation intensity of G.t : 2. 10^. For this purpose the non-ionic detergent is added to scouring wastewater up to 1500 mg/1 in addition to the original detergent content. A measurable change in treatment performances has not been observed for the additional detergent concentrations between 0-600 mg/1.But it is observed that increase in additional detergent concentrations over 600 mg/1 decreases pollutant removal efficiencies. The following exponential relationships between effluent grease and additional detergent (C.) and SS and C, concentrations are obtained statistically as : C = 0,2*7. e1'771'*0^, g/1, (r= 0.910) SS = 0,108. e 2,37.(Cd) g/1, (r= 0.939) The volume of settled slurry is also found to decrease linearly as a function of additional detergent content as follows : Vs = 37,31-(21,02).Cd (r= 0.951) Influence investigated for of pH on the removal efficiency is a constant G.t of 2.10^. pH is varied inves tigated or a constant <o.x ot z.j.u-'. pn ıs variea within the range of 2 and 5. Better destabilization of emulsified grease is observed for lower side of the pH range. Relations between pH and effluent grease concentrations are searched and following exponential expressions are found from regression-correlation analysis for remaining grease, suspended solids and COD concentration: C = 0,046.e°'896'pH, g/l,(r= 0.978) SS = 3,72.10`3.e1'416-pH, g/l,(r= 0.978) COD = 0,^81. e°'610-pH, g/l,(r= 0.9*8) The volume of slurry is a linear function of pH as ; V = 46,75 - 7,0.pH, % (r=0. 957) The above expressions are also illustrated graphically Since the concentrations of suspended solids in the oil and grease and suspended solids in the raw wastewaters are too high turbidity measurement cannot be applied. However, the turbidity and optical density measurements are found to provide a good indication of the quality of acid-cracking treated wastewaters. XIIt is shown in this study that using suspended solids concentrations of treated effluents can be predicted turbidity and optical density (0. d. )measurement s, and related expressions are given as; _3 SS = 0,1043.e4'68-10 `B, g/1, ( r= 0.904) SS = 0,3016.eO,d- - 0,30, g/1, (r= 0.972) Similarly, relations between grease and SS concentrations are analyzed and the following linear expression is obtained which is valid for different pH values ; SS = -0,207+0, 971. C, g/1, (r= 0.954) y Plots of the above three relationships are also given for 95 % and 99 % confidence limits. General relationships which are developed above are checked with data obtained from analysis of treatment effluents and also quantities of relative errors are determined. The last three relations can be applied in predicting effluent suspended solids concentrations within the relative errors of % 20 - 25 and % 5-10 for pollutant concentrations from 200 to 500 mg/1 and for those greater than 1000 mg/1 respectively. xn