Glukozla beslenen kesikli reaktörlerde organik yüklemenin ayrışma kinetiği ve kalıcı ürün oluşumu üzerine etkisi
The effect of organic loading on biodegradation kinetics and residual product formation in glucose fed batch reactors
- Tez No: 68885
- Danışmanlar: PROF. DR. HASAN ALİ SAN
- Tez Türü: Doktora
- Konular: Çevre Mühendisliği, Environmental Engineering
- Anahtar Kelimeler: Aktif çamur sistemi, Ayrışma, Glükoz, Reaktörler, Activated sludge system, Dissociation, Glucose, Reactors
- Yıl: 1997
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Çevre Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Bu çalışmada, glukoz ile beslenen kesikli reaktörlerde başlangıç mikroorganizma (Xo) ve sübstrat (S0) konsantrasyonunun kalıcı ürün (Sr) oluşumuna etkisi incelenmiş, kinetik sabitlerin hesaplanmasında yeni bir integral denklem önerilmiş, ayrıca kinetik sabitlerin F/M (=So/Xo) oranlarıyla değiştiği gözlenmiştir. Birinci bölümde, aktif çamur sistemlerinin tasarımında giriş mikroorganizma ve sübstrat konsantrasyonları arasındaki oranın önemi vurgulanmış ve bu oranın kinetik parametreler ve kalıcı ürün üzerindeki etkisi belirtilerek çalışmanın amaç ve kapsamı açıklanmıştır. İkinci bölümde, aktif çamur sisteminde sübstrat giderimi, çoğalma mekanizmaları, F/M oram ve ürün oluşumu ile ilgili genel bilgiler verilmiş, özellikle ürün oluşumu üzerinde durularak, literatürde bu konuda yapılan çalışmalar değerlendirilmiş, mevcut eşitlik ve ifadeler açıklanmıştır. Üçüncü bölümde, aktif çamur sisteminde ölçüm yöntemleri ele alınmış, sübstrat, biyokütle ve karbonhidrat (glukoz) ölçümleri ayrıntılı olarak açıklanmıştır. Kinetik sabitlerin hesabına ait çalışmalardan bahsedilerek, glukoz ile ilgili kinetik sabitlerin değerleri tablolar halinde verilmiştir. Dördüncü bölümde, S0 ve Xo başlangıç konsantrasyonlanmn kalıcı ürün konsantrasyonunun değişimine etkisi incelenmek amacıyla yapılan deneysel çalışmalardan bahsedilmiştir. Materyal ve uygulanan metod tanıtılarak, farklı F/M oranlan ile beslenen reaktörlere ait S(KOI), X(Biyokütle), C(Glukoz), SR(Kalıcı Ürün) değerlerinin analiz sonuçlarının zamana göre değişimleri grafikler halinde verilmiştir. Beşinci bölümde, farklı F/M oranına sahip reaktör muhteviyatı analiz sonuçlarının literatür sonuçları ile uyumluluğunu karşılaştırmak amacıyla kinetik katsayıların belirlenmesi için yeni bir integral denklem elde edilmiştir. Denklemin en küçük kareler metodu kullanılarak çözümünden kinetik katsayıların değerleri belirlenmiş ve bu katsayıların F/M oranına göre değişimlerini veren eşitlikler tesbit edilmiştir. Ayrıca, ölçülen ve yeni denklemler yardımıyla hesaplanan parametre değerlerinin karşılaştırması tablo üzerinde gösterilmiştir. Altıncı ve son bölümde, çalışmada elde edilen sonuçlar ve öneriler özetlenmiştir. XVI
Özet (Çeviri)
SUMMARY Most of substances causing water pollution are organic in nature. These substances are biologically reduced, stabilized by microorganisms and become harmless for environment. Organics are converted into inorganic food elements, as a result of biological activities. Activated sludge system is a process whose aim is to remove organic matters in aerobic conditions. The most important parameter affecting on system performance and activitiy is the ratio between S substrate concentration and X microorganism concentration, that is S/X. While microorganisms decomposing organic substances, and synthesizing new cells they produce new products that can not be completely decomposed (inert). The aim of this study is to investigate whether it is possible or not to develope a mathematical model that can be used for estimation of inert product formation in the active sludge system with the aid of experimental studies depending on different So/Xo ratios of initial substrate and biomass concentrations. Before laboratory studies, an extensive review of literature studies about the nondegradable microbial product formation was examined, as a result of this review choosing the system of batch reactors was thought as the best way for experimental studies. Experimental studies were carried out in twenty five reactors consisting of a set of five reactors fed with glucose; each containing 100 mg/L, 200 mg/L, 300mg/L, 400 mg/L and 500 mg/L initial COD (S0) concentrations respectively for each of 100 mg/L, 200 mg/L, 300 mg/L, 400 mg/L and 500 mg/L initial microorganisms (Xo) concentrations. The experimentation matrix of organic loadings for those reactors are given in Table 1. Batch reactors were fed by glucose solutions. Since theoretical oxygen demand of glucose is 1.0667 gÜ2 per gram of pure glucose. Theoretically 93.75 mg glucose equals to 100 mg COD. Therefore multiplies of 93.75 mg were added to each of affore mentioned reactors in order to satisfy necessary initial COD concentrations. xvuTo provide mineral substances (Nitrogen and Phosphorus need of reactor environment) solutions of A and B whose combinations are given in Table 2 were added (10 ml from each) into 1000 mg COD/L of substrate solution. Table 1. The experimentation matrix of organic loadings F/M(=So/Xo) for established 25 reactors. Table 2. Contents of mineral salt solutions A and B. Solution A K2HP04, 320 g/L KH2PO4, 160 g/L NH4CI, 120 g/L Solution B MgS04.7H20, 1 5 g/L FeS04.7H20, 0.5 g/L ZnS04.7H20, 0.5 g/L MnS04.3H20, 0.5 g/L CaCl2, 2g/L The experimentation program was set in July 1995 and went on almost two years until the studies were completed in April 1997. Each reactor with two liter reaction volumes run twice in order to prevent any unexpected change in environmental and analytical circumstances. Reactors were acclimated about two weeks to their loading conditions before sampling procedures. Experiments were conducted at room tempratures (20 ° C). Reactors were kept in water bath in winter conditions to preserve constant temperature. Reactors were fed with glucose for the last time for sampling. Thirty mililiter sample was withdrawn for analyses of biomass (X), glucose (C) and COD (S) for 15 min, 30 min, 60, 90, 120, 240, 300 minutes (and so on) until glucose concentrations reach to the value of zero. Analytical procedures given in:“American Standard Methods for Examination of Waters and Wastewaters”were followed. Glucose was determined by the colorimetric anthrone method. The principle of glucose measument depends xvinon treatment of saccarides with anthrone (9-10 dihidro - 9 keto anthracene) in strong acidic conditions (98 % H2SO4 with a dencity of 1.84 g/ml). Absorbance readings of standard glucose solutions and samples were done at 620 nm wave length on a Lapospec model spectrophotometer. Daily COD analyses were continued for about ten to thirty days in order to trace the course of residual microbial product (Sr). Water losses due to evaporation inducing from aeration were compensated by aerated distilled water before each daily sampling procedure. The results of S (COD), X (Biomass), C (Glucose) and SR (residual product) values, from each reactors, together with the Food/Microorganism ratio are given as in Table 3 are presented in Figure 1. 600 c o O U 200 <zf X*“ 100 3 -f- 4 -4- t(day) 5 6 ?+- 10 X,mgMLSS/L X.mgMLVSS/L. S^ngCOD/L C,mgGlucose/L SRmgCOD/L 12 4 8 t(hour) Figure 1. The results of S(COD), X(Biomass), C(Glucose) and SR(residual product) values (F/M=l 00/500 mgCOD/mgMLSS). Although the purpose of this study was to investigate the effect of initial biomass and substrate concentrations on the amount of residual microbial product (Sr) produced, kinetic coefficients were also determined by Integral equation: £»J- = AJr\l + Y(S0-S)j-B.t (D XIXresulting from definition of biological yield, growth rate and substrate utilization rate ofMonod. Where; A = l + -^-; (A>0,A>\,A>B,a>0) (2) Y.KS B = jy; (B>0,a>0) (3) X0 + Y.S0 = a (4).a S = substrate concentration, (M/L ) S0 = initial substrate concentration (M/L ) \im = maximum specific growth rate (1/T) Ks = half saturation concentration for substrate (M/L3) Y = yield coefficient t = time Xo = initial biomass concentration (M/L ) Y/Xo is a prerequisite parameter in the above equation for determination of p.m and Ks from a set of t and S values, however standard deviation of estimated S values from measured ones are not so much sensitive to biological yield coefficient (Y). Therefore, biological yield of each reactor was calculated by dividing the over all formed biomass (AX) to the quantity of consumed substrate (AS) in the logaritmic growth region. Although numerical values of kinetic coefficients are in harmony with the given ones in the literature, Ks saturation coefficients and Um maximum specific growth rates increases with increasing F/M ratios respectively as; Ks= 11.368 (F/M)048 + 7.428, (R=0.988; SD=±0.12) (5) and; um = 5.8 (F/M) 0753 + 0.762 (R=0.959; SD=± 0.15) (6) for \im values of F/M < 1; with F/M=400/300=1.333 and F/M=400/200=2, consisting of sixteen points, and; M”,= 3.066. in]- J +3.301 ; (R=0.975; SD=± 0.086) (7) for |xm values of F/M > 1, consisting of six (or seven) points. xxco X <D ¥ o e T-< (N ^O 00 o\ VO in 00 00 ^ 2 - ON VO VO en 2 ^ en oo oo TI CS en vo o en o in oo o o ^* <N m ?* -n- m Tf Tf -çj- r^- ^- ^f tJ- m CM m in in cs XXIHowever yield coefficients slowly decrease with increasing F/M ratios as ; Y = 0.546e“°034(F/M) ; (R=0.5708; SD=± 0.00393) (8) Soluble residual microbial concentration Sr values of twenty five reactors chance as a function of F/M as follows; 161.7(F/M)139 S« = 22015:(f/Mr ; (* = °”7' SD = TO52?) (9) These stadies showed that; 1) It is observed that all generally parameters affected the F/M (Food/Microorganism) ratios. 2) Equation 1 was obtained from the integration of substrate removal and microbial growth equations. When this equation was fitted to experimental data using the MATHCAD programme, it was observed that there was a good correlation. 3) The kinetic coefficients such as Ks, \ım, Y and Sr parameters, that were found by the solution of equation 1 using the least squares method were expressed in terms of Food/Microorganism (F/M) ratio. 4) It is observed that reactors having same F/M ratios had same soluble microbial residual product (Sr) concentrations. 5) Moreover, Sr which consumed at a ratio approximately 2 % - 5 % of Sr during the ten days test period and decomposition period was also longer at high F/M ratios. 6) After decomposable part of Sr was formed, a small amount of inert product is formed in the reactor. 7) The concentrations of inert product which were measured after the 10th day were equal to the values of COD which were measured at the end of 24 hours when glucose was completely used up. 8) It was observed that more inert product existed in the reactors which had high S0 concentrations, and it was determined that the inert product increased gradually with the increasing of F/M ratio. xxn
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