Kağıt endüstrisi ağartma atıksuyundaki klorlu organiklerin aktif çamur sistemleri ile giderimi

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1997Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 1997Kağıt endüstrisinin özellikle ağartma prosesinden kaynaklanan atıksular içerdikleri klorlu organik bileşikleri nedeni ile alıcı ortamda organizmalar üzerinde toksik etkiye yol açmakta ve biyolojik parçalanmaya direnç göstermektedir. Bu tezde yapılan çalışmalarda SEKA/Dalaman kağıt fabrikasından kaynaklanan ağartma prosesi atıksuyu kullanılarak klasik ve nitrifikasyonlu aktif çamur sistemlerinde dehalojenasyon mekanizması incelenmiştir. Çalışmanın ilk aşamasında nitrifikasyonlu aktif çamur sisteminde ağartma atıksuyunun da bulunması durumunda elde edilen amonyum giderim hızlan ve dehalojenasyon reaksiyonu incelemiştir. Kesikli ve sürekli sistemler için amonyum giderim hızı 0.016-0.075 ve 0.03-0.19 mgNH4/mgUAKM.g olarak bulunmuştur. Kesikli sistem çalışmalarında amonyum yükünün (NH4/UAKM) 0.12 den 0.45'e artması ile nitrifikasyon organizmalarının dehalojenasyon reaksiyon hızının 0.017 den 0.0062 mgICl/mgUAKM.gün'e düştüğü görülmüştür. Çalışmanın ikinci aşamasında klasik ve nitrifikasyonlu aktif çamur sistemleri kullanılarak dehalojenasyon reaksiyonunun yanısıra TOK ve amonyum giderimi incelenmiştir. Klasik aktif çamur sisteminde yükün 0.03'den 0.068 mgTOK/mgUAKM.g'ye arttırılması durumunda oluşan IC1 miktarı da 4.45'den 8.5 mg/l'ye artmıştır. AOX arıtım verimi de aynı şekilde %15'den %35'e artmaktadır. Nitrifikasyonlu aktif çamur sisteminde ise yükün 0.006'den 0.025 mgTOK/mgUAKM.g'ye arttırılması durumunda oluşan IC1 miktarında 10 mg/1 den 3.2 mg/l'ye azalma görülmüştür. Artan yüklerdeki AOX giderim verimi de %26'dan %6'ya düşmektedir. Bu çalışmalar sonucunda, nitrifikasyon sisteminde hakim ototrof bakterilerin klasik aktif çamur sistemindeki heterotrof bakterilere kıyasla artan klorlu organik yüklemelerine karşı daha hassas olduğu ve dehalojenasyon veriminin düştüğü, klasik aktif çamur sisteminde ise arttığı görülmüştür. Elde edilen optimum yüklemeler; aktif çamurda 0.05, nitrifikasyon sisteminde 0.015 mgTOK/mgVSS.gün olarak seçilmiştir. Aktif çamur sisteminde 8 mg/1, nitrifikasyonlu aktif çamur sisteminde de 9 mg/1 IC1 olmak üzere toplam 17 mg/1 IC1 artışı elde edilmiştir. Sistemdeki TOK ve NH4-N parametrelerindeki giderim verimi de sırasıyla %85 ve %95 olarak bulunmuştur.Chlorinated organic matter present in effluent from kraft mills employing either chlorine or chlorine dioxide in the bleaching process has become a matter of concern due to its recalcitrance to biological degradation, toxicity to aquatic species, genotoxicity and potential to accumulate in he fatty tissues of a variety of organisms. In order to reduce this impact to the aquatic environmental internal or external methods can be applied. The external technologies can be classified as mechanical, biological and physical-chemical methods. Many treatment processes in anaerobic and aerobic conditions have been investigated to treat the bleaching effluent in literature. Recent researches showed that nitrifying bacteria is able to dehalogenate many halogenated aliphatic and aromatic compounds, found in pulp and paper wastewater. Dehalogenation is the only known biodegradation mechanisms for certain chlorinated organic compounds. Dehalogenation products are generally less toxic and more readily degradable. Dehalogenaion of many compounds is known to occur within anaerobic microbial communities. Research studies are being carried out to understand the mechanisms of these reactions by using nitrifying bacteria and chlorinated organic containing synthetic wastewater in bioreactors and soils. The objective of this study was to determine the dehalogenation mechanism in sequential activated sludge and nitrification systems to asses of the applicability of a nitrification system following secondary treatment used for treatment of organochlorine compounds together with ammonium- nitrogen pollution in pulp and paper wastewater. Activated sludge and nitrification reactors were used throughout the experimental work. Aeration was carried out using porous diffusers and 8-9 mg/1 dissolved oxygen concentration was maintained in the reactors by controlling air flow rate with a needle valve in all experiments. The temperature of the liquid was kept in the range of 19±1°C by placing the thermostatically controlled heater in each reactor. Municipal activated sludge brought from a nearby wastewater treatment plant was used as seed. Biomass acclimation was achieved x by feeding the reactors with a mixture of synthetic solution and bleaching effluent for about 2 months. Influent and effluent samples were taken daily from each reactor and analyzed for pH, D.O., Oz and temperature. Feed solution for nitrification reactor was prepared by mixing bleaching effluent, nitrogen ((NH4)2S04), phosphorus (N^HPO^, alkalinity (NaHC03), in a feed container with tap water. The molar ratios HC03"/NH4 and NH4/HP04" were about 2 and 4, respectively. In the mean time activated sludge reactor was continuously fed with synthetic domestic wastewater and bleaching effluent. The reactor performance was monitored by measuring removal of ammonium, total organic carbon (TOC), adsorbable organic chloride (AOX), nitrite, nitrate, inorganic chloride, SS and VSS concentrations. Wastewater used in the experiments, was taken from chlorination and caustic extraction units of SEKA Softwood Pulp and Paper Mill. Some of the important polluting characteristics are COD: 778 mg/I, BOD: 100 mg/1, TOC: 325 mg/1, Id: 1200 mg/1 and AOX: 39 mg/1. Biodegradation performance of activated sludge-nitrification systems treating bleaching effluent was studied. Removal of organic chloride compounds was determined by monitoring chlorine concentration in organic form (AOX) and inorganic form (CI"). Conversion efficiency of chlorine from organic form to inorganic form that was indicated as AOX removal and IC1 release were investigated at different TOC loading rates. In addition, NH4 removal and N03 formation were measured in nitrification system. Batch type experiment was performed to find out the effect of NH4 loading on IC1 formation in nitrification system. The results showed that IC1 formation rate was decreased from 0.017 to 0.006 mglCl/mgVSS.d by increasing initial NH4/VSS from 0.13 to 0.45 (Fig.l). Nitrification rates were found to be 0.075-0.016 mgNH4/mgVSS.d between these ranges (Table 1). Figure 2 shows comparison of the experimental results from continuously feeding nitrification system with Monod curve. It was concluded that the nitrification rate of about 0.19 mgNH4/mgVSS.d, was rather low which may be attributed to the inhibition effect. In activated sludge system, bleaching effluent diluted with synthetic sewage was fed at loading rate of 0.03-0.068 mgTOC/mgVSS.d. Dehalogenation performance and treatment efficiency were examined by measuring inorganic chloride and TOC values in treated and untreated wastewater. TOC values correspond total concentration of both organic and halogenated organic compounds in wastewater. XI Table 1. Comparison of Nitrification removal rates with literature. mglCI/mgUAKM.g 0.005 0.09 0.19 0.29 NH4/UAKM J_ 0.39 0.49 Figure 1. IC1 formation rate. xn mgNH4/mgVSS.d 10 15 20 effl. NH4, mg/l Figure 2. Nitrification rate in the system. Effect of organic loading on dehalogenation was studied by monitoring released inorganic chloride (IC1) that was the product of dehalogenation reaction in the system. Amount of IC1 released was increased from 4.5 to 8.5 mg/l by increasing loading that means it was not effected dehalogenation mechanisms (Fig.3). 67- 85% efficiency in TOC removal was found in the system. The remaining TOC value in the effluent of activated sludge could be considered as the inert part of organic's and mostly undegraded organic halide. Released ICI, mg/l 10 8 - 6 0.020 0.030 0.040 0.050 mgTOC/mgVSS.d 0.060 0.070 Figure 3. Effect of TOC loading on released ICI in activated sludge system. xm The activated sludge effluent was fed to the nitrification system by adding ammonium and phosphate. IC1 and NH4 parameters were monitored in the system. NH4 concentration in the feeding was kept about 63-77 mgfl and TOC value was about 21 mg/L Dehalogenation and mineralization reaction were examined at increasing organic loading in nitrification system. All parameters were measured at steady-state conditions. TOC reduction was about l-4mg/L It was found that released IC1 value was decreased from 10 to 3.2mg/l at increasing organic loading (Fig.4). Comparison of released IC1 values with literature were given in Table 2. Nitrification reaction was also examined m the system and %94-98 removal efficiency in NH4 was achieved at the studied range of loading and %94-98 of removed NH4 was converted to NO3. Released ICI, mg/l 0.00 0.01 0.02 mgTOC/mgVSS.d 0.03 Figure 4. Effect of TOC loading on released ICI in nitrification system. xiv Table 2. Releases IC1 values in different biological treatment systems. ** (Nevalainen et al., 1993). (Puhakka and Jarvinen, 1992). *** (Puhakka et al., 1991) **** (Leuenberger et al., 1985) Decrease in released IC1 can be considered that dehalogenation mechanism of nitrifying organisms was inhibited by increasing loading of organic halide. About 0.05 and 0.015 mgTOC/mgVSS.d value can be chosen to obtain optimum release efficiency especially in IC1 in activated sludge and nitrification systems, respectively. Under these condition total released IC1 was found 17 mg/1, that obtained 8 mg/1 of which was obtained from activated sludge and 9 mg/1 from nitrification system. Removal efficiency in AOX was found 15-33% and 5-25% in activated sludge and nitrification systems, respectively. More IC1 production was found when compared with AOX removal. Measurement of IC1 releases may be more reliable to find degradation part of organic halide than measurement of AOX.DoktoraPh.D