Examination of the effect of wastewater composition in dynamic wastewater treatment simulation

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Veronika Rácz
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1 THESES OF DOCTORAL(PHD) DISSERTATION Examination of the effect of wastewater composition in dynamic wastewater treatment simulation Author: Pásztor István Consultant: Dr. Kárpáti Árpád University of Pannonia Doctoral School of Chemical Engineering and Material Sciences 2010

2 1. Backgrounds, objective Activated sludge wastewater treatment has been modeled for decades, the number of published models is over dozen. The availability of commercial wastewater treatment simulators made it possible to apply dynamic wastewater treatment simulation in engineering practice, too. The objective of the dissertation is to summarize the knowledge till now and represent new results about dimensioning of wastewater treatment plants by the use of simulation and examination of wastewater composition for modeling purposes. The examinations are geographically focused on Hungary or rather the Middle Transdanubian region. 2. Applied Methods The research was performed on two fields: firstly examination of wastewater composition for modeling purposes and determination of base data for design, secondly the comparison of standardized dimensioning procedures and activated sludge models. The author analyzed wastewater samples from the Middle Transdanubian region of Hungary by laboratory measurements set by standards and protocols. The examinations focused on determination of base data for modeling such as: COD fractions, forms of nitrogen, ratio of composite variables and alkalinity. The author performed model comparing investigations using the average results of wastewater composition measurements as base data. In the closing chapter the case study of the simulation of wastewater treatment plant development of Balatonfőkajár proved that the new results of wastewater composition can be applied successfully in design and consulting practice. 2

3 3. New scientific results 1.) 1.1) The COD fraction ratios of municipal wastewater of the Middle Transdanubian region of Hungary (inert soluble 4.6 %, readily biodegradable substrate 21.9 %, inert particulate 23.7 %, slowly biodegradable substrate 49.8 %) fall within the range of measurements in related literature. The notable difference observed was in the amount of soluble inert COD, where the measured value was 4.6% while the mean data from literature was 7.5%).The results can serve as guideline if WWTP specific COD fractions are not available to calibrate activated sludge models in the Middle Transdanubian region or in areas with similar consumption habits. 1.2.) Input models of wastewater treatment simulators use ratios to calculate composite variables (TSS, VSS, BOI 5 ). Examining municipal raw wastewater samples in the Middle Transdanubian region of Hungary, I determined the average values of these ratios: VSS/TSS = 0,72; BOD 5 /COD b =0,69; XKOI/VSS= 1,91. The measured average values fall within the range of measurements in related literature. 3

4 2.) 2.1.) The total alkalinity of raw communal wastewater in the Middle Transdanubian region was found to be high: averagely 15.3 ( ) mmol/l), because of the high density of sewage. The background alkalinity of hard tap water accounted for almost half of the alkalinity measured (mean: 7.0 ( ) mmol/l). The measured alkalinity of effluent wastewater (mean: 7.7 ( ) mmol/l) was way above the critical value (1.5 mmol/l) at which nitrification can occur. 2.2.) According to my measurements in the Middle Transdanubian region the total alkalinity of raw wastewater can be estimated using the following function provided the total alkalinity of tap water and the ammonium concentration of sewage are known. S ALK,SZV. = S ALK,VÍZ + K * S NH4 + 2,884 mmol/l ; where: S ALK,SZV = Calculated total alkalinity of raw wastewater (mmol/l) S ALK,VÍZ = Total alkalinity of tap water (mmol/l) S NH4 = Ammonium-nitrogen concentration of wastewater (mgn/l) 1 K = Proportional factor = 0,0556 mgn/l The novel formula revealed a not negligible segment of the total alkalinity, which is independent of the ammonium content of sewage and tap water alkalinity. 4

5 3.) If the function of total alkalinity estimation is built in the influent model of the WWTP simulator, the total alkalinity becomes a variable dependent on ammonium concentration instead of being a preset parameter. The simulations performed with the improved influent model showed that relevant nitrification inhibition cannot occur in WWTPs having a minimum 50% denitrification efficiency, typical Hungarian tap water background alkalinity (3 8 mmol/l) and wastewater ammonium-nitrogen concentration (<100mgN/l). 4.) A wastewater treatment technology dimensioned by ATV-A 131 German standard was checked by activated sludge models that were not calibrated. The following results were observed: With the same input and technological parameters, the ATV standard results to 10-25% higher excess sludge production than the examined models. This may lead to the oversizing of wastewater and sludge treatment capacities. The technology dimensioned by the standard method can meet the effluent discharge limits according to all examined activated sludge models (ASM1, ASM2d, Mantis, Newgeneral) with the exception of effluent total nitrogen concentration calculated by ASM3. The oxygen demand determined by the ATV standard is close to the values calculated by simulation. The nitrogen content of excess sludge according to the ATV standard is lower than the values of model calculations. Therefore nitrogen removal through nitrification and denitrification is more emphasized, so the reactor volume of aerobic and anoxic reactors may became over overinsured according to the ATV standard. 5

6 5.) Every well-calibrated activated sludge model should be able to yield results that are close to actual values. However, in actual design, the valuable model is that which can produce realistic results in partly calibrated or uncalibrated state. In comparing the performance of various uncalibrated models (ASM1, ASM2d, ASM3, Mantis, Newgeneral), diverse results were observed, namely: The ASM3 model with default parameters performs lower denitrification activity and results to higher effluent total nitrogen concentration; its parameter set is too pessimistic. The ASM1 yields the biggest excess sludge production. Its sludge contains the greatest quantity of nitrogen and the effluent total nitrogen concentration is the lowest. As a consequence, this model calculates the smallest oxygen requirement. From a design perspective, the ASM1 may lead to an undersized anoxic reactor. The new general model yields the smallest excess sludge production, which means that the model may result to an undersized total reactor volume at a given sludge age. The uncalibrated ASM2d and Mantis models did not result to any extreme values for the examined properties (effluent quality, oxygen demand, nitrogen content of sludge, temperature dependency of nitrification). Therefore these models can be the most suitable for general design tasks. 6

7 4. Publications Articles in scientific journals: [1] Pásztor, I.; Thury, P.; Pulai, J. (2009) Chemical oxygen demand fractions of municipal wastewater for modeling wastewater treatment. International Journal of Environmental Science and Technology 6(1): (impakt faktor:1,417) [2] Thury, P.; Fazekas, B.; Pasztor, I.; Pitas, V.; Balasko, L.; Karpati, A. (2009) Novel N removal with some industrial realization in Hungary. Hungarian Journal of Industrial Chemistry, Veszprém 37(1): 5-9 [3] Pásztor, I.; Sulyok I.; Cserháti G.; Varga, Gy., I.; Kuti, J. (2008) A balatonfőkajári szennyvíztisztító telep jelenlegi üzemének és fejlesztésének számítógépes szimulációja. Vízműpanoráma 2008/1 [4] Pásztor, I.; Kárpáti, Á.; Szentgyörgyi, E.; Varga, Gy., I. (2007) A szennyvíz lúgosságának jelentősége a szennyvíztisztítási technológiák tervezésében és modellezésében. MASZESZ Hírcsatorna máj-jún. [5] Holenda, B.; Pásztor, I.; Kárpáti, Á.; Rédey, Á. (2006) Comparison of one-dimensional settling tank models. E-water, Journal of the European Water Association, [6] Pásztor, I.; Szentgyörgyi, H.; Holenda, B. (2006) Comparison of activated sludge flock structure and microbial fauna of two Hungarian wastewater treatment plants. Hungarian Electronic Journal of Science Environmental engineering section [7] Kárpáti, Á.; Pulai, J.; Pásztor, I.; Thury, P. (2005) A szennyvíztisztítás költségmegoszlása számítások és üzemi adatok alapján I.-II: rész Építési Piac, március, április [8] Pásztor, I. (2004) Gyökérmezős szennyvíztisztítás, rész Környezetvédelem 2004 (7-8 és 8-9), BME OMIKK 7

8 Conferences: [9] Pásztor I.; Sulyok, I. (2010) SBR technológiájú szennyvíztisztító telepek szimulációja, tervezése és üzemeltetési tapasztalatai. Energiahatékonyság a szennyvíztisztításban és szakaszos üzemi technológiák (SBR) hazai tapasztalatai című szakmai konferencia, Zsámbék, október. 15. [10] Pásztor I.; Sulyok, I. (2006) Kis és közepes szennyvíztisztító telepek automatizálásának előkészítése dinamikus szimulációval. Kis és közepes szennyvíztisztító telepek automatizálása című Magyar Víziközmű Szövetség szakmai nap, Budapest, november 16. [11] Pásztor, I.; Kárpáti, Á.; Holenda, B. (2006) A szennyvíztisztítás szimulációja és hasznosítása a hazai gyakorlatban. Csatornázás és szennyvíztisztítás európai és hazai- gazdasági kérdései című Országos Konferencia, Lajosmizse, május [12]Thury, P.; Pásztor, I.; Kárpáti, Á. (2006) A hódmezővásárhelyi kétlépcsős szennyvíztisztító egyedi iszaphozama, XII. Nemzetközi Vegyész Konferencia október [13] Pásztor, I.; Sulyok, I. (2005) Az eleveniszapos szennyvíztisztítás szimulációs vizsgálatának metodikája, alkalmazás a tervezési üzemeltetési gyakorlatban, XX. Országos Környezetvédelmi Konferencia, Siófok Szeptember [14] Pásztor, I.;Thury, P. (2004) A foszfor szerepe a szennyvízgazdálkodásban, X. Nemzetközi Környezetvédelmi és Vidékfejlesztési Diákkonferencia, Mezőtúr, 2004.július School-book, study-aid: [15] Dulovics, D.; Gilyén E.; Holenda B.; Kárpáti, Á.; Lázár L.; Mosonyi, E.; Németh, N.; Pulai, J.; Reich, Gy.; Pásztor, I. (2005) Általános információk a környezetvédelemről, ismeretek a szennyvíztisztítás fejlesztéséről. Tanulmány-gyűjtemény No.12, , Veszprémi Egyetem, Környezetmérnöki és Kémiai Technológia Tanszék 8

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