Selüloz ve kağıt sanayii atıksularının havasız ve havalı biyolojik arıtılabilirliği

Abstract

Bu çalışmada SEKA/İzmit Kağıt Hamuru ve Kağıt Sanayii atıksularının havasız ve havalı biyolojik arıtılabi- lirligi incelenmiştir. Havasız Biyolojik arıtılabilirlik çalışmalarında, atıksuyun havalı biyolojik arıtıma girme den önce havasız arıtma prosesi ile arıtılabilirligi araştırılmıştır. Havalı biyolojik arıtılabilirlik çalışmasında ise, atıksuyun girişteki inert fraksiyon değeri Sı ve çözünmüş mikrobiyal ürün Sp değerinin belirlenmesi için deneysel çalışmalar yürütülmüştür. Birinci bölümde, tezin konusu ve kapsamı açıklanarak, çalışmanın önemine değinilmiştir. İkinci bölümde, selüloz ve kağıt sanayii üretim prosesleri verilmiştir, üçüncü bölümde, selüloz ve kağıt sanayiinde su kullanımı, atıksu miktar ve özelliklerinden bahsedilmiştir. Dördüncü bölümde, kağıt sanayii atıksuları için atıksu arıtma sistemleri, uygulanabilir arıtma metodları değerlendirilmiştir. Besinci bölümde, atıksudaki çözünmüş inert KOİ'nin belirlenmesi metodlarından bahsedilmiş, literatür bilgileri verilmiştir. Altıncı bölümde, deneysel çalışmalar iki ayrı bölüm seklinde yürütülmüştür. îlk olarak havasız on arıtma prosesi çalışması gerçekleştirilmiş, laboratuvar ölçekli yukarı akışlı bir model havasız çamur yatağı sisteminde, deney tesisinin ve sisteme beslenen atığın özellikleri ile deneysel çalışmada kullanılan analiz yöntemleri açıklanarak deney sonuçları tartışılmıştır. Yaklaşık 6 ay süren deneysel çalışmada, giriş KOİ değeri ortalama 1600 mg/lt olan kağıt fabrikası atıksuyu ile havasız çamur yatağı reaktör beslenmiştir. Reaktördeki aktif biyokitle konsantrasyonu ortalama 21000 mg UKM/lt değerinde kalmıştır. KOİ giderme verimi ise, atıksuyun karakteri (zor bozunan maddeler içermesi) nedeniyle ortalama % 52 mertebelerinde gerçekleştirilmiş tir. Deneysel çalışmaların 2. bölümü olarak, aynı atık suyun girişteki inert fraksiyonu Sı ve çözünmüş kalıcı ürün konsantrasyonu Sp m belirlenmesi için havalı biyolojik arıtılabilirlik çalışmaları yürütülmüştür. Çalışmada, laboratuvar ölçekli 6 lt'lik cam reaktör kaplarda, daha önce "i 50 glukoz ve %50 atıksuya aklime edilmiş bir ası mikroorganizma topluluğu kullanılarak çökeltilmis atıksu, süzülmüş atıksu ve glukoz çözeltilerinden oluşan reaktör 1 erdeki toplam ve çözünmüş KOİ değerleri yaklaşık 20 gün izlenmiştir. Elde edilen değerlere göre çizilen grafiklerden Sı ve Xı'ın yeni bir metoda göre çözüm yöntemleri araştırılmıştır.

Recently, rapid industrialisation has caused an increased environmental pollution especially the water pollution restricting the beneficial use of water re sources. At the beginning, the biological treatment was used to reduce the problems caused by domestic wastewater which then has been applied with an increasing success to treat industrial wastewaters. Biological treatment has been carried out for a large number of additional purposes. The aerobic pro cesses in biological treatment systems have been exten sively applied due to their high treatment efficiencies, low hydraulic retention times and they are easy to operate and control. However, their high operating costs and practical problems which has been appeared espe cially in high strength wastewaters, have increased the interest in anaerobic wastewater treatment. Anaerobic processes which can supply their own energy requirements and produce very little excess sludge sre there fore a desirable alternative. Anaerobic treatment is a biological process in the absence of oxygen for the stabilisation of organic matters by conversion to Cf-U and inorganic end products such as carbondioxide and ammonia. In this process, the organic wastewater constituents Are converted by anaerobic microorganisms first into volatile carboxylic organic acids and after into acetic acid, which is then decomposed to methane and carbondioxide in an additional biochemical reaction step. The process provides a number of significant benefits over aerobic methods. The advan tages of anaerobic treatment are low production of stabi used biological waste solids, no energy requirements for aeration, the production of methane gas which is a useful end product, low nutrient requirements, possibility to handle the system at very high loading rates and the preservation of anaerobic sludge without feeding for many months. It has also been drawbacks such as the sensitivity of anaerobic bacteria to inhibition caused by a large number of compounds, the slowness of the start-up period and it requires an adequate treatment for the removal of remaining BOD, ammonia, and hydrogen sulphide which give the effluent a strong and unpleasant odour. The most common anaerobic treatment systems are anaerobic filters (AF), the upflow anaerobic sludge blanket (UASB) reactors, anaerobic fixed film (AFF) pro cess, anaerobic attached film expanded bed (AAFEB) pro cess and anaerobic fluidised bed (AFB) reactors. All of these systems have their own advantages and limita tions during the operational conditions for their proper performance. The success of the process depends on a suitable microbial population. The physiology and biochemistry of these anaerobic microorganisms which give the engineering systems their special character istics. Basically, on the other hand, the anaerobic pro cesses are not stable than aerobic ones. Because anaerobic processes are operating with rather small safety factors and have very poor process control. Anaerobic processes ara used successfully for a wide variety of industrial wastewaters. These systems can be performed with aerobic processes too. Industrial wastewaters which cause the increase of water pollution are treated usually by biological waste water treatment systems that are mainly known as acti vated sludge. The identification of influent characte ristics with regard to organic content is quite useful from the process kinetics point of view in design and operational strategy for biological wastewater treatment. Since wastewaters consist of complex organic matters and it is not possible to measure the organic content each of them individually, it is necessary to use collective parameters such as total organic carbon (TQC), chemical oxygen demand (COD) and biochemical oxygen demand. To determine the influent characteris tics, one of the most commonly used parameter is chemical oxygen demand. While this parameter iş fre quently preferred to others, it is not dif ferenciâting organic content between biologically degradable fraction and inert fraction. Wastewaters usually contain a very wide spectrum of organics with respect to biodegradability. The ini tially soluble inert fraction passes through the acti vated sludge system in an unchanged form. This fraction is not critical in conventional wastes. Since it causes the misinterpretation of biological treatability results especially in strong industrial wastes it becomes sign i- nificant. It also makes it difficult to determine efflu ent limitation criteria expressed in terms of COD for a number of industrial categories. xi The importance of soluble inert COD concentration of wastewater has been underlined in literature and methods for the determination of this fraction have been developed. However, these methods do not account the impact of inert soluble metabolic products resulting from micro bial activity in activated sludge systems. Thus, incorrect results are reached due to the interference of soluble inert metabolic products on the initially soluble inert COD value, the target of the measurement. In activated sludge systems, the microbial inert product formation in the effluent stream can be minimised by making suitable adjust ment in the design and operational conditions. Whereas the influent and the effluent soluble inert concentration of wastewater remains unchanged. Therefore, it is important to determine the initial inert soluble COD fraction of wastewater correctly. In this study, anaerobic and aerobic biological treat ability of SEKA/îzmit Pulp and Paper Factory wastewaters has been experimentally investigated. In anaerobic biolog ical treatability studies, the treatability of wastewater by an anaerobic process has been achived. In aerobic biological treatability studies, determination of initially inert fraction, (Si) of wastewaters and soluble residual microbial products (Sf») have been conducted experimentally. In the first chapter, the scope and the general objec tives of this study were underlined and the importance of the study was defined. The production processes in the pulp and paper industry are generally given in the second chapter. In pulp and paper industry, from the use of water, the amount of wastewater and characterictics are discussed in the third chapter. Favourable wastewater treatment systems for the wastewater of Pulp and Paper Industry and applicable treatment methods have been as sessed in the fourth chapter. Literature survey associated with anaerobic treatment is given in this chapter in which microbiology and biochemistry of anaerobic processes and environmental factors affecting the performance of such processes are explained. In the fifth chapter, the determination methods of the soluble inert COD of wastewater has been discussed and literature survey is given. Laboratory studies are explained in the sixth chapter through experimental set-up and methods. On this study, experimental studies have been conducted in two parts. First, anaerobic treatability study has been achieved with a laboratory scale Model Up-flow Anaerobic Sludge xil Blanket system. Analyses methods used at the experimental study, the model plant and influent waste characteristics as explained has been discussed in experimental results. In the experimental study which continued approximately six months with the paper factory wastewaters, the anaerobic sludge blanket reactor has been fed with the influent having a COD value of İ600 mg/1, anaerobic sludge blanket reactor has been fed. Organic loading rates were ranged from 0.6a to 6.34 kgC0D/m3-day. The samples were collected and analyzed for at least 3 times per week. Active biomass concentration in reactor is remained average in 21000 mgVSM/1 value. The COD removal efficiency is achieved 52% because of the characteristics of the used wastewater. The results of this study showed that anaerobic treatment can be successfully applied to pulp and paper wastewaters before the aerobic process. In the second part of the experimental study, deter - mination of the initially inert fraction (Si) of the same wastewater and aerobic biological treatability studies are conducted. In this study, particulate inert COD (Xi) and soluble inert COD (Si) has been determined experimentally by a new developed method. In this method, separate reactors containing settled wastewater, filtered wastewater and glucose are operated as batch reactors with addition of sufficient seed micro organism culture and the experiment has been continued for a period sufficient to mineralise the biodegradable matters completely. The decrease of COD value has been observed by measuring the COD values in each of reactors and the experiment was stopped when the COD values stayed unchanged. At this point, soluble and total COD has been measured. Calculation steps are as follows! In reactor I, total COD at the end of the test, C« ?= Sa ?*- Sf. + Xi + Xp. + Ss (5.35) Where j Cm s Ultimate COD in settled wastewater Sı î Inert soluble substrate concentration Sp» s Inert soluble product concentration Xi : Inert particulates concentration Xp s Inert particulate product concentration So s Soluble substrate concentration In reactor II, soluble COD in filtered wastewater at the end of the test, Cpr ' ss Si +? St=> +? Xf> ' + Ss ( 3. OS ) where ; xiii Cr' : Ultimate COD concentration in filtered wastewater Sp» s Inert soluble substrate in filtered wastewater Xp»' s Inert particulate product in filtered wastewater (5.36) ACQDi = Co - Cr where, Co s Initial COD in settled wastewater ACQDa = So - C«' (5.39) where. So : Initial COD in filtered wastewater (5. 16) (5. 41) (5.42) ACQD*. In equation (5.35), Se» value is supposed to be very low (approximately 2<^/3 mg/1). The results have shown that the wastewater tested has 527 mg/1 of inert soluble substrate concentration (Si) and inert particulates concentration (Xi) has been found as 6 mg/1. Moreover, it has also calculated that inert soluble product concentration (Sp») and inert particulates concen tration (Xp») Are 51 mg/1 and 167 mg/1, respectively. It is noted that effluent soluble COD can not be aerobically reduced below 564 mg/1, due to the generation of residual fractions and the amount of inert fraction.