Strategies of improvement of UASB reactor operation

Transkript

1 DEGREE PROJECT IN ENVIRONMENTAL ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2017 Strategies of improvement of UASB reactor operation DARIA KLESYK KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ARCHITECTURE AND THE BUILT ENVIRONMENT

2

3 Strategies of improvement of UASB reactor operation DARIA KLESYK June 2017

4 Daria Klesyk 2017 Master s Level Degree Project In association with the research group Water, Sewage and Waste Technology Department of Land and Water Resources Engineering Royal Institute of Technology (KTH) SE STOCKHOLM, Sweden Reference should be written as: Klesyk D., (2017) Strategies of improvement of UASB reactor operation SEEDEX 2017:23 i

5 Dedicated to my family ii

6 iii

7 Summary in Swedish Avloppsreningsverk letar efter nya och mer effektiva, miljövänliga och energieffektiva metoder för avloppsrening som samtidigt skulle möjliggöra effektiv avlägsning av organiskt material. UASBreaktorn som är en av de tekniker som använder anaeroba metoder uppfyller ovanstående krav. Reaktorns arbete kräver inte hög konsumtion av el och kemikalier och det möjliggör också produktion av biogas, vilket kan användas för själva avloppsreningsverkets behov. Arbetet fokuserade på att hitta de bästa förutsättningarna för UASBreaktorns arbete och skapa de bästa arbetsförhållandena för anaeroba bakterier. Forskningen utfördes under 5 månader vid en forskningsstation vid Henriksdals avloppsreningsverk i Stockholm. Baserat på litteraturstudier beslutades det att fokusera på hydraulisk uppehållstid, HRT. Studien var uppdelad i två perioder under vilka reaktorerna arbetade under olika HRT. Under andra perioden var HRT 20% högre jämfört med den första perioden och var 3,33 respektive 4,04 timmar. Forskningen baserades huvudsakligen på laboratorietester som utfördes 2 gånger per vecka på gripprover. De viktigaste parametrarna som analyserades var CODtot, CODsus och CODdis, parametrar som gav information om mängden organiskt material. Dessutom mättes temperatur, ph, NH4N och alkalitet under testet som processkontrollparametrarna. Dessutom övervakades temperaturen före inlopp till reaktorn, flödet och avloppsvattnets strömningshastighet kontinuerligt med användning av sensorer och datorsystem. Förändringar relaterade till förlängningen av HRT har inte givit upphov till de förväntade resultaten, så det har föreslagits nya potentiella lösningar för avlägsnande av organiskt material och ökad biogasproduktion. iv

8 v

9 Summary in English Sewage treatment plants are looking for new and more effective, environmentally friendly and energy efficient solutions for wastewater treatment which at the same time, it would allow for effective removal of organic matter. The UASB reactor as one of the technologies using anaerobic methods meets the above requirements. The work of the reactor does not require high consumption of electricity and chemicals and it also allows for the acquisition of biogas, which can be used for the needs of the wastewater treatment plant itself. This work was focused on finding the best conditions for the UASB reactor performance and create the best working conditions for anaerobic bacteria. The research was made during 5 months at a research station located at the wastewater treatment plant Henriksdal in Stockholm. Based on literature research, it was decided to focus on Hydraulic Retention Time, HRT. The study was divided into two periods during which the reactors worked with different HRT. In the second period HRT was 20% higher compared to the first period and was 3.33 and 4.04 hours respectively. The research was based mainly on laboratory tests performed 2 times per week on grab samples. The most important parameters analyzed were COD tot, COD sus and COD dis as parameters providing information on the amount of organic matter. In addition, temperature, ph, NH4N and alkalinity were measured during the test as the process control parameters. In addition, the temperature before inlet to the reactor, the flow and velocity of wastewater were monitored continuously using sensors and computer systems. Changes related to the extension of HRT have not produced the expected results, so new potential solutions for the removal of organic matter and increased biogas production have been proposed. vi

10 vii

11 Acknowledgement This thesis project would not be accomplished without the help and support from many people. In particular, I would like to express my greatest gratitude to my project supervisor Professor Erik Levlin for and my examiner Elżbieta Płaza for all the support and valuable leads as well as the opportunity to work at the research station for my research. Without their support, I would not find the thesis project in Hammarby Sjöstadsverkwhich providesthe best opportunity to work in a sereach station and the project report would not have been the same as present here. Special thanks go to doctor Józef Trela professor at at KTH and Jesper Karlsson for them kindly support and help let me quickly familiar with the laboratory work and facility in Hammarby Sjöstadsverk. I also want to thank everyone who made my life and study in Stockholm easier. Thank you! Stockholm, August 2017 viii

12 ix

13 Acronyms and abbreviations UASB Upflow Anaerobic Sludge Blanket Q Flow COD tot Total Chemical Oxygen Demand COD dis Dissolved Chemical Oxygen Demand COD sus Suspended Chemical Oxygen Demand COD inf Chemical Oxygen Demand at inlet to the UASB reactors COD out Chemical Oxygen Demand at outlet to the UASB reactors COD anx Chemical Oxygen Demand at inlet to the IFAS reactor N tot Total Nitrogen NH4N Ammonium NO2N Nitrite nitrogen NO3N Nitrate nitrogen MLSS Mixed liquor suspended solids VSS Volatile suspended solids P tot Total phosphorus HRT Hydraulic Retention Time OLR Organic Loading Rate SRT Sludge Retention Time x

14 xi

15 Table of content Summary in Swedish... iv Summary in English... vi Acknowledgement... viii Acronyms and abbreviations... x Table of content... xii Abstract Introduction Anaerobic wastewater treatment Theory of UASB reactor Review of the literature Anaerobic treatment of wastewater in UASB Type of wastewater treated UASB technology Treatment of grey water Treatment of black water Treatment of raw domestic wastewater Treatment of prescreened sewage Strength presettled sewage from the industrial area Municipal wastewater Aim of the study Material and methods Hammarby Sjöstadsverk research station Technological system Experimental strategy Sampling Physical analyses Temperature ph Total suspended solid Chemical analyses COD NH 4N NO 3 N NO 2 N Alkalinity Phosphorus Results and discussion xii

16 5.2. Extended analyses Organic matter removal in UASB reactor CODtot COD dissolved COD suspended ph Alkalinity NH4N Temperature Organic loading rate The efficiency of removal of organic matter in the UASB reactor Effect of HRT on UASB reactor operation Effect of UASB reactor operation for IFAS reactor operation Effect of COD removal in UASB reactor for IFAS reactor operation Dependence of removal of N from the value of alkalinity of influent wastewater Conclusions Reference Appendix A Characteristics of incoming sewage during extended analyses... I Appendix B Characteristics of outflow sewage during extended analyses... II Appendix C Summary of analyses results... III Appendix C Summary of analyses results... IV xiii

17 Abstract The Upflow Anaerobic Sludge Blanket (UASB) reactor is one from the most widely used anaerobic technology to remove organic matter from wastewater, popular mostly in countries with warm climate but use all over the world. UASB reactor have mainly advantages: during organic matter removal biogas is produced, low energy consumption and simplicity of work. This study evaluates the effect of hydraulic retention time (HRT) on COD tot removal and attempts to optimize the UASB reactor work on line 4 in Hammarby Sjöstadsverk research station in Stockholm. During the fourmonth study performed analyzes: CODtot, CODdis, CODsus as a measure of the amount of organic matter, ph, alkalinity, NH4, temperature of inlet and outlet wastewater. Analysis was focus on UASB reactor 1 and inlet to next step of wastewater treatment IFAS reactor. Studies were divided into two periods during which HRT was performed. In first period ( ) UASB reactors worked at HRT of 3.33h and in the second period ( ) UASB reactor 1 worked at HRT of 4.04 h and UASB reactor 2 worked at HRT of 2.99 h. The best result was achieved during the first period and the CODtot removal efficiency in reactor 1 was 73.75% with ORL 2,3 kg CODtot/m 3 *d. 1. Introduction Nowadays, when we aim at minimization of pollutant emissions into the environment efficient wastewater treatment is one of the important aspects of caring for the environment. In recent years with the financial and ecological reasons have been made efforts to minimize the costs of wastewater treatment and reduce the energy consumption associated with it. For these reasons, anaerobic treatment to efficient removal of organic matter is a good alternative to the aerobic biological waste water treatment because of lower energy consumption. As a results these processes are more environmentally friendly than aerobic processes Anaerobic wastewater treatment Anaerobic wastewater treatment methods are complex biological processes during which organic matter is converted to methane and carbon dioxide in the absence of oxygen. In these processes there are other types of electron acceptors for example CO 2, ferric iron, nitrate, sulphate or some organic compounds. (Gómez, 2011). Anaerobic wastewater treatment consists of processes such as hydrolysis, acidogenesis, acetogenesis and methanogenesis. 1

18 Fig. 1 Schematic diagram of carbon flow conversion in anaerobic digesters (adapted from Deepanraj B. et al, 2014) Anaerobic wastewater treatment have a lots of advantages: High removal these processes are highly effective processes, even in the case of a process with higher load or lower temperatures. Simplicity reactors for anaerobic processes are easy to build and processes are easy to operate. Low sludge production in anaerobic processes sludge production is lower than in aerobic processes because of the slower growth of anaerobic bacteria. As a result, the reactors may be smaller than the reactors in which the aerobic processes are carried out. Low energy consumption In anaerobic processes energy isn t consumed for oxygenation and agitation, so that the energy consumption is low until no warming is required. Flexibility These processes can be carried out in a wide range of temperatures, on sewage with different organic matter loads from urban waste water to wastewater from brewers, dairies and other types of industry. Low dosage of chemicals if a effluent to the reactor is stable no dosage of chemicals is required to control ph But anaerobic systems have also some disadvantages like low pathogen and nutrient removal so after this process it is required a posttreatment to remove it. Compared to the aerobics process, the start of the process is longer due to longer growth of methanogens bacterias. During anaerobic process hydrogen sulphid is produced so odors from reactors may be problematic Theory of UASB reactor One method for anaerobic processes of wastewater treatment is a UASB reactor. This technology as the main biological step in wastewater treatment began to develop in 2

19 the early 70's. In Upflow Anaerobic Sludge Blanket Reactor sewages are introduced from the bottom and then flows through the dense sludge bed. Sludge bed is formed mainly from the incoming suspended solid and anaerobic bacteria, which tend to form granules. Thanks to the natural turbulence associated with the flow and flow of the biogas particles, the wastewater is well mixed and sewage have good contact with sludge bed. UASB reactor may replace the primary settler, anaerobic sludge digester, the aerobic step and the secondary settler of aerobic treatment plant. Because of low removal of pathogen and nutrient sewages after UASB reactor still need treatment. UASB reactor can work in different combinations with various types of posttreatment for example: UASBSBR, UASB biofiler system, UASB stabilizing pond system or UASBdeamonificaion. (Seghezzo, L. et al 1998) Fig. 2 Schematic drawing of the UASB reactor (adapted from Chong, S. et al, 2012) There are many factors that affect the efficiency of organic matter removal and the production of biogas. These factors include: temperature, ph, ORL, HRT, velocity. Temperature anaerobic bacteria can work under psychrophilic, mesophilic and thermophilic temperatures however, below 20 C the activity of bacteria is lower. Therefore, the treatment of the main stream of waste water in Scandinavian countries can be a challenge for the need to heat up sewage before UASB reactor. The most recommended temperature is 35 C since this temperature removal of organic matter and biogas production are in balance but in a temperate climate, achieving that wastewater temperature at full scale would be very expensive. 3

20 ph Anaerobic processes are most effective in the range of 6,57,5 due to the fact that anaerobic bacteria work best in this range. All processes in UASB reactors have ability to selfcontrol the ph changes and there it is not required additional dosage of chemicals. OLR organic loading rate is the mass of soluble and particulate organic matter per unit area and per time of the reactor. Where: Q Influent rate V Reactor volume, 2.5 m 3 COD inf Total influent COD OOOOLL = QQ CCCCDD iiiiii V Low ORL (under 1,5kgCOD/m 3 d) Means to provide too little amount of substrate for bacteria. The optimal ORL range is 2,04,5 kgcod/m 3 d. HRT hydraulic retention time is a time that influent wastewater stays in the reactor. Bacteria need enough time to processing of organic compounds into biogas but if hydraulic retention time is longer the sludge production is larger and the reactor will be larger. Too short HRT and too high flow velocity can result in the discharge of granules from the reactor resulting in washout of biomass (Gomez, 2016). 2. Review of the literature For many years research has been conducted on the development of anaerobic processes, including the UASB reactor. In various research projects around the world, scientists conducted anaerobic processes in UASB reactors under various operating parameters. These processes were carried out on different types of waste water (industrial wastewater, municipal waste water, gray water, black water or synthetic wastewater) and on various scales (laboratory scales, pilot scales). In these studies, the researchers operated on process parameters mainly hydraulic retention time and temperature, in order to enable COD removal efficiency to be more and more effective. 4

21 Tab. 1a Review of literature NR Authors Tittle Place Typ of reactor V [m3] Typ of wastewat er HRT [h] ORL [kg COD/m3* d] OPERATION PARAMETERS UASB typ of sludge Temperat ure [ C] COD [mgo2/l] CODsol [mgo2/l] CODss [mgo2/l] CODcol [mgo2/l] CODdis [mgo2/l] BOD [mgo2/l] TSS [mgl/l] SRT ph 0 9 digested sewage sludge L. Seghezzo, G. Zeeman, J. B. van Lier, H.V.M. Hamelers, G. Lettinga A review: the anaerobic treatment of sewage in UASB and EGSB reactors Netherlan ds Smal pilot scale Full scale digested sewage sludge granular sludge raw 0 domestic 78 granular sludge sewage granular sludge granular sludge granular sludge > ,218 granular sludge Germany, Hamburg University of Technolog y, seedsludge from an anaerobic digester treating primary and secondary sludge 18 (1421) 681 (124) 268 (115) 291 (22) 134 (27) 2 T.A. Elmitwalli, M. Shalabi, C. Wendland and R. Otterpohl Grey water treatment in UASB reactor at ambient temperature Germany, Hamburg University of Technolog y, Germany, Hamburg University of Technolog y, Smal pilot scale 0,03 m3 gray wastewat er (21 24,5) 647 (137) 298 (101) 231 (86) 117 (40) 8 20 (1921) 682 (106) 327 (64) 219 (71) 136 (33) 5

22 NR Authors Tittle Place Leitao,R.C., Silva Filho, J.A., Sanders, W., van Haandel, A.C., Zeeman, G., Lettinga, G. Lohani, S.P., Bakke, R., Khanal, S.N. Elmiywalli, T.A., Otterpohl, R. The effect of operational conditions on the performance of UASB reactors for domestic wastewater treatment Load limit of a UASB fed septic tanktreated domestic wastewater Anaerobic biodegradability and treatment of grey water in upflow anaerobic sludge blanket (UASB) reactor Campina Grande city, Brazil Typ of reactor V [m3] pilot scale 0.12 pilot scale 0.25 Hamburg University of labolatory Technology, scale Germany Typ of wastewate r Tab. 1b Review of literature OPERATION PARAMETERS UASB ORL [kg HRT [h] COD/m3* d] typ of sludge Temperatu re [ C] COD [mgo2/l] CODsol [mgo2/l] CODss [mgo2/l] CODcol [mgo2/l] CODdis [mgo2/l] BOD [mgo2/l] 6 3 anaerobic sludge discharged from a m3 UASB prescreened 6 1 reactor witch had been operated for 27 C sewage 6 3 more than five years with raw sewage with am HRT of 6h anaerobic slurry (no granules) raw 8 2 obtained from domestic 6 3 manurefed biogas sewage 5 3 plant manurefed biogas plant (130) 308(162) 177(114) 133(36) grey water (4,8) (353 (131) 177(81) 117(40) (106) 310 (86) 236(90) 136(33) TSS [mgl/l] SRT ph l of granular sludge from a paper mill (261) 1201 (222) 6 S. Luostarinen W. Sanders, K. Kujawa Roeleveld, G. Zeeman Effect of temperature on anaerobi treatment of black water in UASBseptic tank systems Wageningen University, Netherlnds pilot scale 1 black water l of granular sludge from a paper mill (332) 2897 (1199) 460 (151) 588 (124) 2428 (1220) 269 (107) L of ludge from 1,2m3 reactor (6460) (479) 7 S. Saha, N.Badhe, D. Seuntjens, S.E. Vlaeminck, R. Biswas, T. Babdy Effective carbon and nutrient treatment solutios for mixed domesticindustrial wastewater in India India pilot scale 1 strength presettled sewage No inoculum (7782) 3495 (590) 1589 (373) (1209) 218 (97) 325 (85) 6

23 Tab. 1c Review of literature OPERATION PARAMETERS UASB NR Authors Tittle Place Typ of reactor V [m3] Typ of wastewater HRT [h] ORL [kg COD/m3*d] typ of sludge Temperature [ C] COD [mgo2/l] CODsol [mgo2/l] CODss [mgo2/l] CODcol [mgo2/l] CODdis [mgo2/l] BOD [mgo2/l] TSS [mgl/l] SRT ph India 8 Chernicharo, Anaerobic sewage C.A.L., van Lier, treatment: state of art., J.B., Noyola, A., constraints and Bressani Ribeiro, challenges. T., Full scale Brazil 9 10 Chong, S., Sen, T.K., Kayaalp, A., Ang H.M. Luostarinen, S.A., Rintala, J.A. The performance enhcements of upflow anerobic sludge blanket (UASB) reactors for domestic sludge treatment state of the art review Anaerobic onsite treatment of black water and dairy parlour wastewater in UASBsepitc tanks at low temperatures Small pilot scale Full scale Small pilot scae labolatory scale syntetic black water dairy parlour wastewater Subtropical climate temperature (55.2)+38.4(12.72) 0.279(0.105)+0.075(0.069) (289) 794 (300) 15 (22) 87 (19) (110.4)+38.4 (6) 0.215(0.215)+0.046(0.018) (313) 722 (298) 16 23) 107 (40) (100.8)+33.6(8.64) 0.301(0.155)+0.071(0.031) (375) 24 (30) 160 (75) 190 (363) 84 (43.2)+40.8(12.48) 0.179(0.058)+0.103(0.041) (182) 320 (190) 85 (45) 182 (67) (26.4)+38.4(6) 0.159(0.043)+0.144(0.057) (80) 281 (79) 60 (23) 212 (51) (19.2)+24 (10.32) 0.191(0.074)+0.240(0.104) (133) 329 (103) 101 (48) 266 (87) 400 7

24 NR Authors Tittle Place Typ of reactor V [m3] Typ of wastewate r HRT [h] Tab. 1d Review of literature OPERATION PARAMETERS UASB ORL [kg COD/m3*d] typ of sludge Temperatu re [ C] COD [mgo2/l] CODsol [mgo2/l] CODss [mgo2/l] CODcol [mgo2/l] CODdis [mgo2/l] BOD [mgo2/l] TSS [mgl/l] SRT ph 11 Luostarinen, S.A., Rintala, J.A. Anaerobic onsite treatment of kitchn waste in combination with black water in UASBseptic tanks at low temperatures labolatory scale syntetic black water black water kitchen waste (5.2) 0.368(0.119) (0.064) (345) 959 (307) 23 (18) 69 (38) 281 (70) (5.2) 0.406(0.143)+0.180( 0.086) (12.73)+31.2(5.52) 81.6(12.73)+31.2(5.52) 1161 (408) (0.147) (0.172) 20 (437) (0.189)+0.460(0.293) (488) 1048 (370) 1460 (478) 1808 (446) 18 (17) 105 (42) 340 (66) 74 (35) 387 (66) 760(220) 64 (27) 380(84) 590 (280) Halalsheh, M., Sawajneh, Z., Zu bi, M., Zeeman, G., Lier, J., Fayyad, M., Lettinga, G., Chan, Y.J., Chong, M.F., Law Ch.L., Hassell D.G., Treatment of strong domestic sewage in a 96 m3 UASB reactor operated at ambient temperatures: twostage versus singlestage reactor A review on the anaerobicaerobic treatment of industrial and municipal Amman, Jordan Full scale black water municipal ww domestic water (3.5) (354) (1.6) (250) (3.0) (241) (2.0) (468) (1.3) (344) (389 ) 174 (89) 301 (70) 376 (148) 1383(221 ) 157 (90) 236 (49) 417 (142) 1184(258 ) 208 (69) 252 (75) 431 (171) 1008( (104) 292 (99) ) 352 (154) 1005 (325) 181 (77) 303 (102) 404 (192) 14 Combined Anaerobic/Aerobic Secondary Municipal La Motta, E.J., Silva, E., Wastewater Treatment: Bustillos, A., Padron, H., PilotPlant Luque, J., Demonstration of the UASB/Aerobc Solids Contact System pilot scale municipal ww (20) 341 (85) 189 (69) 15 von Sperling, M., Freire, V.H., de Lemos Chenicharo, C.A., Performance evaluation of a UASBactivated sludge system treatment municipal wastewater Brazil pilot scale municipal ww (881) 269 (140) 443 (385) (542) 255 (179) 251 (379) (239) 262 (112) 115 (67) (174) 206 (83) 120 (44) (135) 243 (85) ) 8

25 NR Authors Tittle CODtot [%] CODsus [%] Tab. 1e Review of literature CODcoll[ %] OPERATION RESOULTS COD diss [%] CODsol [%] TSS [%] Alkality mg CaCO3/l PO4P Ortho PO4P Particulat e PO4P TKjN NH4N Particulat e NN L. Seghezzo, G. Zeeman, J. B. van Lier, H.V.M. Hamelers, G. Lettinga A review: the anaerobic treatment of sewage in UASB and EGSB reactors (5) 61 (12) 18(13) 23 (12) 24 (8) 16 (5) 39 (8) 24 (4) 4 (28) 29 (10) 2 T.A. Elmitwalli, M. Shalabi, C. Wendland and R. Otterpohl Grey water treatment in UASB reactor at ambient temperature 41 ( 13) 61 (20) 28 (22) 16 (16) 21,6 (9,1) 20,1 (9,9) 53 (32,2) 25,6 (2,3) 2,3 (26,1) 40,2 (6,2) 33 (7) 42 (6) 28 (27) 14 (33) 10,1 (2,9) 15,6 (2,8) 33,3 (62,8) 8,6 (72,6) 9

26 NR Authors Tittle CODtot [%] CODsus [%] CODcoll[%] R.C. Leitao, J.A. SilvaFilho, W. Sanders, A.C. van Haandel, G. Zeeman and G. Lettinga Sunil Prasad Lohani, Rune Bakke and Sanjay N. Khanal Tarek A. Elmiywalli, Ralf Otterpohl S. Luostarinen W. Sanders, K. Kujawa Roeleveld, G. Zeeman S. Saha, N.Badhe, D. Seuntjens, S.E. Vlaeminck, R. Biswas, T. Babdy The effect of operational conditions on the performance of UASB reactors for domestic wastewater treatment Load limit of a UASB fed septic tanktreated domestic wastewater Anaerobic biodegradability and treatment of grey water in upflow anaerobic sludge blanket (UASB) reactor Effect of temperature on anaerobi treatment of black water in UASBseptic tank systems Effective carbon and nutrient treatment solutios for mixed domesticindustrial wastewater in India Tab. 1f Review of literature OPERATION RESOULTS COD diss [%] CODsol [%] TSS [%] Alkality mg CaCO3/l PO4P Ortho PO4P Particulat e PO4P TKjN NH4N Particulat e NN (5,0) 83,5 (5,4) 51,7 (19,0) 50,9 (8,9) 52,3 (4,8) 79,4 (7,6) 29,2(19,8) 30,3 (7,6) 52,0 (12,0) 67,6 (17,2) 37,1 (17,5) 34,8 (20,5) (3) 89 (25) 6 (2) 91(6) 85 (12) 17(8) 10

27 Tab. 1g Review of literature NR Authors Tittle CODtot [%] CODsus [%] CODcoll[%] 8 9 Chernicharo, C.A.L., van Lier, J.B., Noyola, A., Bressani Ribeiro, T., Chong, S., Sen, T.K., Kayaalp, A., Ang H.M. Anaerobic sewage treatment: state of art., constraints and challenges. The performance enhcements of upflow anerobic sludge blanket (UASB) reactors for domestic sludge treatmentstate of the art review COD diss [%] CODsol [%] TSS [%] Alkality mg CaCO3/l PO4P Ortho PO4P Particulat e PO4P TKjN NH4N Particulat e NN 10 Luostarinen, S.A., Rintala, J.A. Anaerobic onsite treatment of black water and dairy parlour wastewater in UASBsepitc tanks at low temperatures (4.0) 97 (3.0) 21 (85) 54 (17) 93 (3.9) 98 (2.7) 58 (39) 70 (16) 94 (3.3) 98 (2.6) 50 (32) 71 (19) 84 (13) 90(11) 77(40) 70(19) 86 (4.9) 91 (8.7) 66 (36) 77 (11) 82 (6.3) 86 (15) 62 (24) 70 (20) 11

28 Tab. 1h Review of literature 11 Luostarinen, S.A., Rintala, J.A. Anaerobic onsite treatment of kitchn waste in combination with black water in UASBseptic tanks at low temperatures OPERATION RESOULTS 91 (4.6) 98 (1.9) 11 (55) 97 (1.8) 92 (3.9) 98 (2.2) 35 (45) 98 (1.3) 88 (9.2) 96 (4.0) 38 (39) 95 (2.9) 91 (4.1) 98 (1.3) 28 (38) 97 (1.3) Halalsheh, M., Sawajneh, Z., Zu bi, M., Zeeman, G., Lier, J., Fayyad, M., Lettinga, G., Chan, Y.J., Chong, M.F., Law Ch.L., Hassell D.G., Treatment of strong domestic sewage in a 96 m3 UASB reactor operated at ambient temperatures: twostage versus singlestage reactor A review on the anaerobicaerobic treatment of industrial and municipal wastewater 53 (16)+4(29) 57 (22) +0.2 (54) 57 (30)+3(64) 25 (18)+3 (64) 46 (22)+ 4(57) 50 (13)+10 (21) 63 (12)+9 (36) 2(45) (71) (34)+ (72) (12) 46 (60) 62 (8) 55 (12) 57 (23) 27 (14) 60 (19) 51 (16) 50 (13) 54 (20) 23 (18) 55 (27) 58 (6) 53 (14) 61 (19) 37 (17) 62 (26) La Motta, E.J., Silva, E., Bustillos, A., Padron, H., Luque, J., von Sperling, M., Freire, V.H., de Lemos Chenicharo, C.A., Combined Anaerobic/Aerobic Secondary Municipal Wastewater Treatment: PilotPlant Demonstration of the UASB/Aerobc Solids Contact System Performance evaluation of a UASBactivated sludge system treatment municipal wastewater Data in parentheses standard deviation 12

29 2.1. Anaerobic treatment of wastewater in UASB In a review by Seghezzo, L. et al (1998) included research work from the Netherlands in 1983, 1986, 1992 by difference research teams. These processes were carried out both on a small scale0,03 and 0,12 m 3 and on a full scale respectively 6, 20 and 120 m 3. In each case, these processes were carried out at low temperatures below 20 C. Processes were conducted using digested sewage sludge or granular sludge. In smaller scale reactors, the COD unfiltered removal efficiency was higher than in larger scales. Also in small scale projects, the COD removal efficiency was comparable regardless of the type of precipitate used. For processes carried out in large scale COD removal efficiency was lower as compared to reactors of smaller volume. This is due to the fact that in largescale processes many different factors affect the course of the process. In addition, in the case of the largest reactor of 120m3, the process was carried out at lower HRT 27h compared to the other processes. In this case, COD removal efficiency and COD sol were lowest at 1634% and 2051%, respectively. In a review by Yi Jing Chan et al (2009) the advantages of using anaerobicaerobic treatment of industrial and municipal wastewater are presented. UASB reactor is one of the anaerobic methods included in the review. In this article are show differences combination of UASB reactor with aerobic step. In table 1 point 13 are showed only for municipal and domestic wastewater as the most representative for this thesis however, a significant part of this article focuses on the treatment of industrial effluents. These effluents are characterized by many high concentrations of organic matter, among others wool acid dying wastewater COD in inlet to reactor mg/l, food solid waste leachate COD in UASB reactor inlet mg/L or starch industry wastewater mg/l. because of this, no reference was included in the literature. In the treatment of industrial waste water treatment efficiency removal in the combination of anaerobicaerobic treatment was very high and has reached even 98% and in UASB reactor the removal efficiency has reached even 93% with HRT equals 1 day for starch industry wastewater. In case of municipal wastewater and domestic sewage efficiency of COD removal was lower one of study (3547%) but for second one was on high level 6984% which is very satisfying value. In this review operational temperature is not include Therefore, it cannot be determined whether or organic matter concentration was determinant of effectiveness in a particular study. In a review by Siewhui Chong et al (2012) is presented a comprehensive review of wastewater treatment systems in which UASB reactors are used with different solutions as a next step of wa stewater treatment among others: SBR, activated sludge, downflowhanging sponge, trickling filters. However, in any case was the IFAS reactor treated as a next step of wastewater treatment. Some results from this review are presented in Table 1 point 9. In a review by Chernicharo, C.A.L. et al (2015) are include studies from countries with high temperature mainly India and Brasil. This review focuse on fullscale anaerobic sewage treatment plants treating municipal sewage. Efficiency of wastewater treatment in different parts of the world is very varied and varies in turn: in India: 2975% of organic matter as COD tot, Brazil 5877%. 13

30 2.2. Type of wastewater treated UASB technology In previous research work in UASB reactors, satisfactory results have been achieved in the case of gray water, black water, raw domestic wastewater, prescreened sewage and mixed wastewater (domestic and industrial wastewater). In 2.2. point is not included industrial wastewater treatment is not included due to small conetnion to pilot scale reactor discussed in this master thesis Treatment of grey water In the paper by Elmitwalli, T.A. et al (2007) the process was carried out in a UASB reactor with a volume of 0.03 m 3 on gray water with was collected from the inlet sewerpipe in first septictank in the settlement. The UASB reactor was operated at an HRT of 20, 12 or 8 hours for 140, 105 and 93 days, respectively. The best results were achieved with a 12hour HRT and a temperature of C. In case of longer HRT 20 hours removal of COD removal was lower mainly because of low temperature 1421 C. These studies have shown that both HRT and temperature are the determinants of COD removal efficiency and will not achieve the expected results only by adjusting one of the parameters. During the experiment, the study also involved the removal of various forms of phosphorus and NH4N. Removal efficiency of nutriens remained at a low level regardless of temperature and HRT. In paper by Elmiywalli, T.A. and Otterpohl, R. (2007) have been presented the study made at Hamburg University of Technology. The small UASB reactor (7l) was operated at HRT of 16,10 and 6h for 95,91 and 86 days, respectively and worked on gray water. UASB reactor worked in a temperaturecontrolled room at 30 C. The average COD tot removal efficiency ranged from 52 to 64% in UASB reactor, COD dis removal efficiency ranged from 34,8 to 50,9% and COD sus removal efficiency ranged from 67,6 to 83,5%. The highest removal efficiency was achieved with the highest HRT = 16h. In addition, during the experiment, nutrient removal efficiency was measured. At each stage of the removal process were low. At the longest HRT (16h) the removal of NH4 and orthop was negative due to hydrolysis of particulate N and P Treatment of black water In paper by by S. Luostarinen et al (2005) The paper presents the results of two studies on UASB reactors working in the serial connection. Reactors worked on synthetic black water and on dairy parlour wastewater. UASB reactors worked under low temperatures respectively 20, 15, 10 C for both kind of wastewater. Efficiency of COD removal was much higher than in previously reported for real black water, especially in temperature 10 C when usually removing of organic matter is really low. Efficiency of COD tot removal was above 90% for black water (BW) and above 80% for dairy parlour wastewater (DPWW), COD ss above 95% for BW and around 90% for DPWW and COD dis respectively for BW and DPWW between 5471% and 7077%. These results may suggest that prepared wastewater can contain components that allow for high efficiency even at very low temperatures. 14

31 In paper by S. Luostarinen et al (2007) results of research conducted in 3 UASB reactors are presented. UASB reactors had diffracts volumes and was operated on different operational parameters but all reactors worked with black water. First reactor with volume 1,2 m3 was operated more than 13 years and published research concerned the 1st and 13th years of reactor s work. Reactors was operated with long HRT 4,3d, 4,1d (1 st reactor) and 29d (2 nd and 3 rd reactor). During studies at such a long HRT, the temperature had no significant effect on the efficiency of the processes. During colder periods UASB reactors work more as a settler accumulating COD sus with no biogas production but is still more effective than conventional septic tank. In article by Halalsheh, M. and others (2005) are present results of 3 years long studies on full scale UASB reactor which in first period worked as a two chamber reactor with volume of 60 and 36m 3 respectively. In second and third period only first chamber of reactor worked. In each of the study periods, the results of the study were divided into periods: summer and winter. Over the whole period of time, the wastewater entering the reactor had a similar concentration of organic matter mg/l (CODtot), but in summer periods when the wastewater temperature exceeded 20 C, the removal of organic matter was higher. The removal efficiency was higher in the second and third periods despite the smaller reactor volume due to the longer HRT Treatment of raw domestic wastewater The paper by Lohani S.P. et al (2015) presents the results of the study on septic tank UASB reactor combined system. This system was operated with wastewater from a girls dormitory and staff quarters at Kathmandu University in Nepal. Wastewater was collected in a septic tank with a volume above 13,5m 3 and HRT=18h and next was pumped to UASB reactor with a volume 250L and anaerobic slurry without granules obtained from manurefed biogas plant manurefed biogas plant. UASB reactor was operated at different HRTs 18,12,8,6,5 and 4h. The reactor worked at HRT until the effectiveness of COD removal stabilized, and the steps lasted successively: ½ month (HRT=18h), 1.0 month (HRT=12h), 1.5 month (HRT=8h), 2 month (HRT=6h), 1 month (HRT=5h) and 1 month (HRT=4h). The average COD tot removal efficiency ranged from 15 to 56% in UASB reactor, COD dis removal efficiency ranged from 8 to 35% and COD sus removal efficiency ranged from 22 to 72%. The highest removal efficiency was achieved with the highest HRT = 18h. In the next stages of the experiment they had different waste temperature it ranged from 9 to 22 C. Despite the low wastewater temperature of 9 C for a high HRT of 12h, the removal efficiency of COD was significantly higher than for a higher wastewater temperature (22 C) but HRT Treatment of prescreened sewage The paper by Leitão et al (2005) presents the results of the study in Campina Grande city, Brazil. During this experiment in pilot scale worked 8 UASB reactors with a volume of 120 L. There were inoculated with anaerobic sludge discharged from a 5m3 UASB reactor witch had been operated with raw sewage with HRT equal to 6 hours. The process was carried out at ~27 C. In set 1 five of them worked on the same HRT=6h under different loadings of COD and the same HRTs 6h. In set 2 three UASB reactor were operated with approximately the same COD inf (~800mg/L) but with different HRTs (from 1 to 6h). In set 1 the best results were achieved with a 15

32 COD load of 298 mg COD/L64%. Under COD loading less than 300 mgo 2/L COD tot and COD settled removal efficiency were lower than 10% compared to processes with higher load. For the second period when the processes were conducted with different HRTs, there was a large difference between the efficiency of removing COD in different reactors. In the case of a reactor operating with HRT = 6h achieved COD tot removal efficiency equal to 57% and the reactor was operating at HRT = 1h this efficiency was only 36.6%. This proves that in the case of waste water at the same temperature and for a similar load of COD higher HRT possible to achieve higher efficiency of COD removal Strength presettled sewage from the industrial area The paper by Saha, S., et al (2015) shows results of work of UASB reactor in pilotscale (82,5 L). UASB reactor worked on mixed wastewater from industrial area and residential area of Nagpur city in India and obtained from an STP at Breda in The Netherlands. These wastewater had higher COD loads than domestic wastewater. COD removal efficiency in both study periods was over 90% and removal efficiency of SS was over 80% Municipal wastewater In paper by La Motta et Al (2007) are present results of UASB reactor in laboratory scale which worked with aerobic post treatment step Aerated Solids Contact Chamber. Organic matter removal in UASB reactor was low average removal efficiency was 34%, and TSS average removal efficiency was 36% but as anaerobic system with aerobic post treatment UASB reactor have high potential. In paper by von Speling et al (2001) are presented results of working on system UASB reactor with activated sludge. Studies was divided into 5 periods with different HRT for aerobic reactor. In case of UASB only during first period rector worked with HRT equals 6h but after this time HRT was stable and equals 4h. First period was period for adapt so results for this period was not calculated. During this studies the effectiveness of organic matter removal ranged between 6885% and higher removal was achieved during second and third period when COD concentration was higher. In these periods efficiency achieved respectively 84 and 85% while CO tot concentration was respectively 734 and 555 mg/l. As literature study showed UASB reactors have big potential Especially in combination with aerobic treatment as nest step of wastewater treatment. UASB reactors are best for cleaning industrial wastewater with high concentration of organic matter or for black water or sewage from the distribution canal (without rainwater). This kind of reactors work more efficiently at higher temperatures, however, satisfactory results are also achieved at temperatures above 20 C. The effectiveness of the work is also influenced by the HRT, but its impact is not unequivocal. However, in most publications longer HRT has a positive impact on the work of the reactor. 16

33 3. Aim of the study The aim of this study was an attempt to optimize of UASB reactor which work in low temperatures (~20 C) on wastewater from Henriksdal Wastewater Treatment Plant in Stockholm. By optimizing the reactor is meant increase of organic matter removal and increase of biogas production in case of low temperature of wastewater and low organic matter load. The aim of study was divided into five parts: Literature and publications study get acquainted with the theoretical basics of anaerobic sewage treatment, UASB reactor and earlier research. Enhanced characteristics of the UASB reactor based on inflow and outflow sewage. Study on the effect of HRT on COD removal efficiency Study on the effect of COD load on COD removal efficiency Study of influence of UASB reactor operation on deammonification process performance 4. Material and methods 4.2. Hammarby Sjöstadsverk research station Hammarby Sjöstadsverk is research station located in on top of Henriksdals WWTP in Stockholm. At the research station several research projects related to the new wastewater treatment processes are being carried out. The research aims at optimizing processes in Scandinavian countries and implementing environmentally friendly processes. Projects are working on sewage delivered to the sewage treatment plant in which the research station is located. 17

34 Fig. 3 UASB reactors, Hammarby Sjöstadsverk research station 4.3. Technological system The research was carried out on one of the technological lines existing at the research station, whose technological scheme was presented below. The study focused on two UASB reactors and the IFAS reactor, which directly affected the efficiency of the UASB reactors. 18

35 Fig. 4 Schematic drawing of the technological system Raw sewage after preliminary mechanical treatment going to the flotation process and the presedimentation. Next wastewater is going to twochamber mixing tank from which wastewater goes to the reactors. Each reactor has a volume of 2.5m 3 and reactors work parallel. Before each of the UASB reactors, the waste water is heated to about 20 C in heat exchangers. Wastewater after treatment in UASB reactor 1 goes to the filters in which the part of suspended solid flowing from the UASB reactor is removed. The filter station consists of four filters: a basket filter, two twine filters and a mesh filter. Filters were replaced 23 times per week depending on the quality of the waste water. Filtration effluents are sent to a 2.5 m 3 averaging tank. From the averaging tank wastewater is pumped into an IFAS reactor of volume 200 liters where the forms of nitrogen are removed. Wastewater from UASB reactor 2 is not further treatment and goes to the sewer system Experimental strategy The study was conducted over four months: Before starting analysis UASB reactors for a long period of time working at a constant HRT equal 3.33h and constant velocity equal1.17 m/h. During the research it was decided to one operate parameters HRT because hydraulic retention time has big effluence on efficiency of the process. Longer HRT give more time for the granules to take up organic matter from the wastewater. Additionally thanks longer HRT less sludge escape from UASB reactor due to lower velocity however sludge bed is compacted giving less mixing of granules and water. In case of shorter HRT mixing of granules and water is more effective but velocity of wastewater is higher so more granules can leave rector and granules have less time to wastewater treatment. The work of the reactors can be divided into two periods. In the period previous reactor operating parameters were maintained and the 19

36 radiators started working on another HRT of 4.04 and 2.99h for the first and second reactors in order to potentially increase the efficiency of the reactors Sampling The studies were conducted on grab samples taken at each stage of the process at the same time. All analyzes were done 2 times a week. Wastewater samples were collected at three collection points (fig. 3): Sampling point 1 effluent of the presettler as a effluent to UASB reactor Sampling point 2 The highest sampling point in the reactor UASB as the effluent of UASB reactor Sampling point 3 Inlet into the IFAS reactor as a waste water sample after purification in UASB reactors and after filtration. Fig. 5 Sampling point 2 Scope of analysis in each sampling point is presented in the table below. Sampling point Tab. 2 Parameters analyzed at sampling points Parameters COD tot COD dis COD sus ph Alkalinity Nh4N Temp

37 Research conducted during the work at the station can be divided into two types: Basic research performed twice a week, consists of analysis: temperature, ph, COD tot, COD dis,nh4, alkalinity Extended study made between one times a week. Extended study include all the basic analysis and suspended solid, total nitrogen, NO2, NO3, total phosphorus Physical analyses Temperature The temperature of wastewater was measured on a unfiltered sample of wastewater at the inlet and outlet of the UASB reactor. For temperature measurement was used phmeter with probe for temperature phmetr WTW ph330i ph The ph of was wastewater was measure on a unfiltered sample of wastewater at the inlet and outlet of the UASB reactor and at the inlet of anammox reactor. For ph measurement was used phmeter with probe for temperature WTW ph330i Total suspended solid Total suspended solid was make during first 4 weeks as a part of extended studies to preliminary analysis of wastewater. TSS was measured 1 per week and made on samples at the inlet and outlet of the reactor. Samples were filtered on 40 mm diameter glass filters. During each analysis, two samples of the total suspended solid were made and on the basis of this two samples the average was made. After filtration, the filtrate were dried at 105 C for 5 hours. After drying the samples and reweighing the sample, a total suspended solid is calculated Chemical analyses During all analyzes the results were read using WTW photolab 6600 UVVI9 spectrophotometer. During COD analyses was also used Thermoreactors Merck Spectroquant TR COD COD as a measure of the amount of organic compounds contained in wastewater was measured in a sample filtered and unfiltered at the inlet and outlet of the UASB reactor and at the entrance to the IFAS reactor. We used for the analysis WTW cuvette tests for COD in the range ml and mgo2/l. COD tot is COD measured in unfiltered sample, COD dis is COD measured in the filtrate of filtered sample and COD sus is COD tot minus COD dis NH 4 N NH4N was measured in a filtered sample and at the inlet and outlet of the UASB reactor and at the entrance to the IFAS reactor. Analyzes was make with WTW cuvette tests for NH 4N in the range 480 mg/l NH 4N. 21

38 NO 3 N NO 3N was measured in a filtered sample and at the inlet and outlet of the UASB reactor and at the entrance to the IFAS reactor. Analyzes was make with WTW cuvette tests for NO 3N in the range mg/l NO 3N. NO 3N was analyzes only during extended analyzes NO 2 N NO2 N was measured in a filtered sample and at the inlet and outlet of the UASB reactor and at the entrance to the IFAS reactor. Analyzes was make with WTW cuvette tests for NO2 N in the range mg/l NO2 N. NO2 N was analyzes only during extended analyzes Alkalinity Alkalinity was measured in a filtered sample and at the inlet and outlet of the UASB reactor and at the entrance to the IFAS reactor. analyzes was make with WTW cuvette tests for NH 4N in the range 0.48 mmol/l Phosphorus Phosphorus was measured in a filtered sample and at the inlet and outlet of the UASB reactor and at the entrance to the IFAS reactor. Analyzes was make with WTW cuvette tests for P tot. Phosphorus was analyzes only during extended analyzes. 5. Results and discussion 5.2. Extended analyses During one month at the beginning of the conducted study between was make extended wastewater analysis, which included, in addition to standard analyzes, additional analyses allowing full characterization of wastewater. Extended analysis was make one time per week. During extended analysis the wastewater entering the UASB reactors was characterized by a relatively constant composition. In extended studies, the sample at the outlet of the reactors was collected before the inlet to the filter station. 22

39 Removal efficiency [%] Time CODtot CODsus CODdis Fig. 6 Variability of COD removal efficiency during extended COD tot concentration varied between mgo 2/L and average concentration of COD tot was 281 mgo 2/L standard deviation was COD dis concentration varied between mgo 2/L and average concentration of COD dis was mgo 2/L standard deviation was COD sus concentration varied between mgo 2/L and average concentration of COD sus was mgo 2/L standard deviation was During this period, the variability of organic matter concentrations, particularly in the case of unfiltered wastewater, was mainly related to the dilution of sewage by melting snow flowing into the sewer. In the case of nitrogen compounds both the variability of total nitrogen concentrations and the other forms of nitrogen is maintained at a relatively constant level. N tot average concentration was:41.25 mg N/L, standard deviation: 3.49 mg N/L, minimum value: mgn/l and maximum value: 46 mg N/L. NH4N average concentration:34.40 mg NH4N/L, standard deviation 3.91 mg NH4N/L, minimum value: mgnh4n/l maximum value: mg NH4N/L. NO2N and NO3N compounds represent a negligible percentage of total nitrogen and their average concentrations in the influent were respectively 0.08 mgno2n/l and 0.08mgNO3N/L. Also, the concentration of phosphorus in the wastewater entering the reactor was maintained at a constant level and the average phosphorus concentration in that period was 3.95 mg PO4P/L (with standard deviation 0.35 PO4P/L). Also, the other analyzed parameters did not show higher variability in the analyzed period the average value of the total suspended solid remained at the level mg/l (SD 9.74 mg/l), ph8.20 (SD 0.18), temperature C (SD 0.69 C), alkalinity 4.48mmol/L (SD 0.19 mmol/l). 23