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+,PSFBO4PD&OWJSPO&OH _ Original Paper IUUQTEPJPSH,4&& *44/F*44/ s xj o v s Struvite v v} od Assessment of the Struvite Crystallization Process for Phosphate Removal and Recovery from a Sludge Treatment System of a Domestic Wastewater Treatment Plant * Seung Ryong Baek* Byung Joon Lee w s p }s *K-water ð œ i School of Disaster Prevention and Environmental Engineering, Kyungpook National University *K-water Water Environment Technical Center (Received July 19, 2017; Revised August 3, 2017; Accepted August 11, 2017) Abstract : Eutrophication and shortage of phosphate ore raise the necessity of phosphate removal and recovery from wastewater treatment plants. Especially, a sludge treatment system containing highly concentrated phosphate should be targeted for phosphate removal and recovery. This study thus aimed to evaluate the capability of the struvite crystallization process for phosphate removal and recovery from a sludge treatment system of a wastewater treatment plant. Analysis on phosphate concentrations and masses in the sludge treatment system revealed that digested sludge and centrate have phosphate concentrations and masses, high enough to adopt the struvite crystallization process. Chemical equilibrium modeling indicated that the struvite crystallization reaction substantially occurred with ph higher than 8 and Mg 2+ concentration 1.2 times higher than its theoretical requirement. A series of batch tests with digested sludge and centrate indicated that the phosphate removal reaction by struvite crystallization followed a first-order kinetics and reached over 80% removal efficiency at equilibrium. Aeration in the batch tests was found to purge CO 2 in sludge or centrate and increase ph up to 8.7, without adding NaOH. Thus, we concluded that the struvite crystallization process could be an efficient and economical process for phosphate removal and recovery from a wastewater treatment plant. Key Words : Phosphate, Recovery, Struvite, Digested Sludge, Centrate. m, k ² m, j î ¼ j j, Struvite m j Ð Ñ/m j ² Ð j º. ² j ¼jStruvite m a³ fa hj,, l j j Ð j, ß, flmj i m j Struvite m g, ô Mg 2+, ph î k j,, l l k Struvite m Ò j ¼k j º. Ð j, Struvite m m j jä d Ø º. flmj, k ²pH 8, Mg 2+ 1.2 ak j²ä d j º., Struvite m Ò j 1 Ð ô, Struvite m fl кj, ì ph Õ Ñ 80% jí º. Struvite m NaOH a g CO 2 nph 8.7 k, Mg 2+ e î a¼ m j, h j ¼ Struvite m j dºùº.., m, d d, m, 1., î ²j m Ù m ² j a jº. 1) dp h î Ø ² mj í m m Ø, Ð ² Ø Ð jº. 2~4) 80%a,,, î f Ø kn50 iùä Ø,,, î ²j m Ðj º. 5~7) /m a j f mj k l lm j², z ² ², j, î j ² jj ¼ j ² º. 8) j j ² k ² m Ðj m j, m j² }, j²ä ì j jº. 2,3,9) Corresponding author E-mail: bjlee@knu.ac.kr Tel: 054-530-1444 Fax: 054-530-1449

+,PSFBO4PD&OWJSPO&OH j Ñ m j4usvwjuf m fa 463 Ð m j¼h Struvite m º. Struvite²Mg 2+ +, NH 4, PO 4 3-a1:1:1 jj Magnesium Ammonium Phosphate (MAP) º. 10) Struvite m Ò j, e í Ø, j aa³j j n º² a º. 11,12) j m m î j² Struvite j j²l º. 10,12) z j fi j ¼ ô a a Ø, j ² k j j bj jº. j, m gjù l ¼ ² j j j ²ä º. ô, Struvite m /m,, ¼îº jj k j ² n Ù º. 6,13) ²Struvite m j, d p Ð a³j a³ faj j º.,, l l j Ð faj, f lmj i m j Struvite mflmj, mj Õ Struvite m PO 4 -P( ) ¼ Ñ, Mg 2+, ph Õî faj º. l l kj Struvite m Ò j( Ð ) faj j a³j faj º. 2. l struvite m faj j j¼h j ¼j kj º., ¼ j ¼j2014-2016 k, ¼ j, m, m, gjù PO 4 -P Ð d j, Struvite m a³j ¼ j j º. 2.2. Struvite m mj j Struvite m mj d j kl bb ¼j j Mg 2+, Ca 2+, K +, Na + 3-, PO 4, NH 4 +, Alkalinity, TDS, ph j º., Mg 2+, Ca 2+, K +, Na + 0.45 µm pore-sized CA membrane filter (Hyundai Micro, Korea) m Ñ n ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy) (Thermo Fisher Scientific, USA) m j 3- + j º. PO 4, NH 4, Alkalinity²bbStandard Methods 14) Ù Ñj j º., ph TDS ² IQ-40 (Hach, USA) j j º. bb k, Table 1 j º. Table 1. $IFNJDBM JOEJDFT BOE BOBMZUJDBM NFUIPET BEPQUFE JO UIJT SFTFBSDI *OEFY.FUIPE /PUF.H $B, /B *$1"&4 *OEVDUJWFMZ $PVQMFE1MBTNB"UPNJD &NJTTJPO4QFDUSPTDPQZ 10 "TDPSCJDBDJENFUIPE /) %JTUJMMBUJPOBOEUJUSBUJPO NFUIPE 4UBOEBSE.FUIPE1 4UBOEBSE.FUIPE /) "MLBMJOJUZ 5JUSBUJPONFUIPE 4UBOEBSE.FUIPE 2.1. ¼ j 5%4Q) &MFDUSPEFNFUIPE Fig. 1. 4DIFNBUJD EJBHSBN EFTDSJCJOH BQQMJDBUJPO PG 7JTVBM.*/5&2 GPS TJNVMBUJOH UIF TUSVWJUF DSZTUBMJ[BUJPO QSPDFTT 7JTVBM.*/5&2 DBMDVMBUFTUIFPVUQVUXJUIUIFJOQVUXBUFSDIFNJTUSZEBUB ¼jm jm 39 8m 2017 8

464 +,PSFBO4PD&OWJSPO&OH 2.3. Visual MINTEQ Visual MINTEQ (vminteq.lwr.kth.se)² m m (USEPA) j² mj fl ² mj j² È m ² kù, p Ù,, e ²mj fl j º. ²Struvite m PO 4 -P Ñ, Õ h fa j kvisual MINTEQ j º. Visual MINTEQ i ² Mg 2+, Ca 2+, K +, Na +, PO 4 3-, NH 4 +, Alkalinity, ph }j mj j j s j º(Table 1). Struvite m j mjfl, m e Ù ² k (Hydroxyapatite, Dolomite, Calcite, Magnesite î) mjfl j º. 15~17) Õ ² Ð 25 j, ph vð² jmj ØÐ j º. Fig. 1 Visual MINTEQ m º. 2.4. Struvite m l Struvite mflmj, e ô l PO 4 -P ÑÒ j faj j, j Struvite m j jpo 4 -P Ð a m ¼j l l kj º. ì ² n4 j j mj l j 20±1 Ð n lj º., Ð / j Ù m 1 L mi j fi m j g j º(Fig. 2). Visual MINTEQ faù Mg 2+ (PO 4 -P ¼ 1.5 ) aj, NaOH a j ph n l kj º. bb m ¼j 1 N NaOH j ph 7, 8, 9 j l kj º. l kø² Ò 5, 10, 30, 1 e, 2 e, 3 e, 6 e n j j 1.2 µm GFC j (Whatman, USA) Fig. 2. 4DIFNBUJD EJBHSBN PG UIF CBUDIUFTU BQQBSBUVT VTFE GPS FWBMVBUJOH UIF DBQBCJMUZ BOE LJOFUJDT PG UIF TUSVWJUF DSZTUBMJ[BUJPO QSPDFTT 1 n, 0.45 µm CA membrane j (Hyundai Micro, Seoul, Korea) j j ¼jPO 4 -P NH 3 -N j º. g k a p Ø, Ð j º. 3. 3.1. l k j Struvite m j PO 4 -P o d j j º. j Struvite m kpo 4 -P Ða p j² d j, k Ñ/m a³jpo 4 -P Ñ(m ) j j º. ¼ j, m, m, PO 4 -P вb b12.2, 85.88, 72.44, 37.4 mg/l º(Fig. 3 (a)). Å, gjùpo 4 -P 343.21 kg/d faø, bb m, m, g jùpo 4 -P 29.63 kg/d, 107.07 kg/d, 50.30 kg/d º. gjùpo 4 -P 100% k (a) (b) Fig. 3. B10 1 DPODFOUSBUJPOT JO UIF SFUVSO GMPX BOBFSPCJD EJHFTUFS PWFSGMPX EJHFTUFS TMVEHF BOE DFOUSBUF C SFTQFDUJWF SBUJP PG 10 1NBTTFTDPNQBSFEUPUIFUPUBM10 1NBTTJOUIFSFUVSOGMPX LHEJOUIFSFUVSOGMPX Journal of KSEE Vol.39, No.8 August, 2017

+,PSFBO4PD&OWJSPO&OH j Ñ m j4usvwjuf m fa 465, m, m, gjùpo 4 -P bb 8.63%, 31.20%, 14.66% º(Fig. 3(b)). gjùpo 4 -P ¼ PO 4 - P Ða Struvite m ä d Ø º. m m ²PO 4 -P 40% j j Ða Struvite m Ñ/m n ä Ùº. j, m Struvite m j ³ ¼, h q î a, Struvite a m Ða ä dºùº. j, Struvite m j, PO 4 -P Ñ 15% Struvite Ða a a ä dºùº. ô, Struvite m ¼ Ð gjj² m ( m g j) j²ä jä dºùº. 3.2. Visual MINTEQ jstruvite mflmj Struvite m Ñ, Õ h faj kmjfl ÈVisual MINTEQ j º. Table 2² ¼ j m Struvite m j mj s, V-minteQ m Ø º. Struvite m ²pH Mg 2+ ²È, m, ² Struvite m Ð j jmg 2+ Ða j ä º. j ph² m 7.1 Struvite m Ð j ²º ä, 8.1 m Ð í º. Visual MINTEQ i Struvite m j, Table 2 mj e jnmjflðº, Struvite Å a ³j d j j º. j, Visual MINTEQ m È m j, m Struvite m j j¼ Mg 2+ j Õ flmj kj º. Fig. 4(a) z, Struvite, Hydroxyapatite (Ca 10 (PO 4) 6 (OH) 2)a 0.06 ~ 0.145 mmol/l, Dolomite (CaMg(CO 3) 2)a 0.32 ~ 0.46 mmol/l ¼ j º. m j, Hydroxyapatite k5 ~ 14 mg/l PO 4 -Pa ÑÚ d j, ph 7, 7.5 Õ ² PO 4 -P Ñ ¼ j º(Fig. 4(b)). j, ph 8, Hydroxyapatite jpo 4 -P Ñ 10~20% Ð í º. z Hydroxyapatite, Dolomite²fl l j, ô í m в Struvite m Ð j ± ä º. j, Hydroxyapatite²Mg k m k 2+ ²ä º. ô, ²Celen î 15) Ù z, Hydroxyapatite, Dolomite î Table 2. *OQVU EBUB VTFE GPS DIFNJDBM FRVJMJCSJVN TJNVMBUJPO PG TUSVWJUF DSZTUBMMJ[BUJPO VOJU NH- FYDFQU Q) /VUSJFOUT $BUJPOT.JTDFMMBOFPVT 10 1 /) / $B.H, /B Q) "ML 5%4 %JHFTUFSTMVEHF p p p p p p p $FOUSBUF p p p p p p p (a) (b) Fig. 4. 3FTVMUT GSPN 7JTVBM.*/5&2 DIFNJDBM FRVJMJCSJVN TJNVMBUJPO GPS UIF EJHFTUFE TMVEHF EPTFE XJUI.H B TPMJE DPODFOUSBUJPO NNPM- GPSNFE CZ 4USVWJUF )ZESPYZBQBUJUF BOE %PMPNJUF DSZTUBMMJ[BUJPO BOE C 10 1SFNPWBM NH-CZ4USVWJUFBOE )ZESPYZBQBUJUF DSZTUBMMJ[BUJPO ¼jm jm 39 8m 2017 8

466 +,PSFBO4PD&OWJSPO&OH (a) (b) Fig. 5. 5IF PVUQVU PG UIF 7JTVBM.*/5&2 TJNVMBUJPO GPS UIF TUSVWJUF DSZTUBMJ[BUJPO QSPDFTT XJUI B EJHFTUFE TMVEHF BOE C DFOUSBUF m Ða± í Visual MINTEQ È j, Struvite m Þ flm j kj º. Struvite m flmj j, Visual MINTEQ i j m, Ñg, Õ kmg 2+ ph Ð j, npo 4 -P Ð f º. Ð Mg 2+ Struvite m 0 ( aj ), 1, 1.2, 1.5, 2 j, ph²7, 8, 8.5, 9 m flmj kj, npo 4 -P Ð j º. ² Fig. 5 z 3 i hlj, Mg 2+, ph bb x, y, n PO 4 -P Ð z j º. Mg 2+ Ø ² Struvite m Ñ ä, Mg 2+ 1.2 PO 4 -P 80% ÑaØ º. j ph 8 PO 4 -P 80% ÑaØ j ²Struvite m j º. Struvite 3- m PO 4, NH 4 +, Mg 2+ 1:1:1 j²è j, m º. jph 7.5 j ph 8, ph² Struvite m j } d Ø º. Mg 2+ ¼ 1.5, 2 m j Ð Ñ Å ¼Ø ²ä, ph²8 Ñ Å ¼Ø ²ä d Ø º. ô, j m, ¼k Struvite m j, j k ²Mg 2+ 1.2, ph 8 j jº² º. (a) (b) Fig. 6. #BUDI UFTU SFTVMUT GPS JOWFTUJHBUJOH TUSVWJUF DSZTUBMMJ[BUJPO LJOFUJDT 5IF UXP TFUT PG CBUDI UFTUT XFSF QFSGPSNFE XJUI B EJHFTUFE TMVEHFBOE CDFOUSBUF Journal of KSEE Vol.39, No.8 August, 2017

+,PSFBO4PD&OWJSPO&OH j Ñ m j4usvwjuf m fa 467 3.3. l jstruvite mò j Fig. 6²¼ j m, kj Struvite m l e¼ PO 4 -P Ð ä º. m, ¼ j Struvite m Ò j l кj² ÈÙ ² e 3-6 e Ð º. j, Ù z Struvite mò j l 1 Ð ô º. 17~20) l d Ù j, ph j g k n pha 9 кj ²ä d Ø º. ² g k m ÙCO 2 a a Ø ph a Ùä dºùº. j e º ÐNaOH(a º) îph h aj Ðg ph p Struvite m a mj ²ä º. 7) j, Struvite m g j j ( Š ) Ùä dºø, kn h g ¼j faa p j ä dºùº. Fig. 7 j m l Struvite m n, flðºnph (PO 4 -P, NH 3 -N) º. } j z, ph NaOH j g kco 2 a jå Ð8.7 j²ä d Ø º. Struvite m fln, m PO 4 -P вbb10~15, 4 mg/l, ²80% PO 4 -P Ñ º. Å, NH 3 -N вStruvite m j j¼ º10 ÑÚ ²È ²Free Ammonium j (stripping) k dºùº. 21,22) Struvite m Ñ/ m º jí j ² m º. Ð Struvite m j j j² ² Struvite m j, j p, ¼î j j ² m j º. k¼j²¼h Ostara Pearl R (Ostara Nutrient Recovery Technologies Inc., Vancouver, Canada) (www.ostara.com) º. Ostera Pearl k o p j Struvite í, m j ²k a ¼h Struvite m º. n k¼j²¼h AirPrex TM (CNP-Technology Water and Biosolid GmbH, Schwarzenbek, Germany) (www. cnp-tec.com), Struvite m j k, j gjj Ð ² º º. l Struvite j ² m jº, j í Struvite m m j p, ¼ î j² ä j ä dºùº. m a Fig. 7. Q) 10 1 /) /DPODFOUSBUJPOTNFBTVSFEBUUIFCFHJOOJOH XIJUFBOEBUUIFFOE CMBDLPGUIFCBUDIUFTUTPG TUSVWJUF DSZTUBMMJ[BUJPO ¼jm jm 39 8m 2017 8

468 +,PSFBO4PD&OWJSPO&OH Òj 6~12 e Ð e a g j (m a e ) j Struvite m Ð jí Ùº, p, ¼ n a dº Ùº. kn, } m Struvite k Ùº, g /m j Ð l j Struvite /m j dºùº. 4. j / m j Struvite m fa k l j fa, Visual MINTEQ m j struvite m flmj j ph h f a, l jstruvite mò j kj º. k º z Ùº. 1) Struvite m PO 4 -P Ð gj j² m j²ä j,, ¼î k k ² m, Ð Struvite m k ² j² ä jº. 2) Struvite m k ²pH 8, Mg 2+ 1.2 aj²ä j ph² Ð j² Ð j² j } º. 3) Struvite m, NaOH g pha 8.7 j, Mg 2+ ¼, e î a¼ m j h j ¼² aø ä dºù º. j, g, î ô á a j j ä º. Acknowledgement 2016 ¼ m } kù º. References 1. Weon, S. Y., Park, S. K. and Lee, S. I., Removal of Nitrogen and Phosphorus Using Struvite Crystallization, J. Korean Soc. Environ. Eng., 22(4), 599~607(2000). 2. Jo, Y. M., Chun, B. H. and Park, C. J., Recovery and Recycle Technologies of Phosphorous from River and Water Treatment Plants, Korean Ind. Chem. News, 14(5), 1~11 (2011). 3. Choi, W. J., Park, K. M., Yoon, B. G., Kim, M. C. and Oh, K. J., Recovery of Presource from Sewage Sludge by a Struvite-forming Method, J. Korean Soc. Environ. Eng., 31(7), 557~564(2009). 4. Lee, S., Kim, C., Park, J., Choi, D. and Ahn, J., Comparison of Steel Slag and Activated Carbon for Phosphate Removal from Aqueous Solution by Adsorption, J. Korean Soc. Environ. Eng., 39(5), 303~309(2017). 5. Le Corre, K. S., Valsami-Jones, E., Hobbs, P. and Parsons, S. A., Phosphorus Recovery from Wastewater by Struvite Crystallization: A Review, Crit. Rev. Environ. Sci. and Technol., 39(6), 433~477(2009). 6. Abe, S., Phosphate removal from dewatering filtrate by MAP process in full scale experiment at Seibu Wastewater Treatment Plant, Proceedings 4 th CIWEM & JSWA Technology Exchange Workshop, pp. 260~277(1995). 7. Bergmans, B., Struvite recovery from digested sludge, PhD Dissertation, Delft University of Technology, the Netherlands (2011). 8. De-Bashan, L. E. and Bashan, Y., Recent advances in removing phosphorous from waste water and its future use as fertilizer (1997-2003), Water Res., 38, 4222(2004). 9. Park, N., Chang, H., Lim, H., Ahn, K. and Kim, W., Empirical Study on Applicability of Phosphorus Recovery Process in Wastewater Treatment Plant, J. Korean Soc. Environ. Eng., 39(1), 40~49(2017). 10. Borgerding, J., Phosphate deposits in digestion systems, J. Water Pollut. Control Fed., 44(5), 813~819(1972). 11. Battistoni, P., Pavan, P., Prisciandaro, M. and Cecchi, F., Struvite crystallization: a feasible and reliable way to fix phosphorus in anaerobic supernatants, Water Res., 34(11), 3033~3041(2000). 12. Fujimoto, N., Mizuochi, T. and Togami, Y., Phosphorus fixation in the sludge treatment system of a biological phosphorus removal process, Water Sci. and Technol., 23, 635~ 640(1991). 13. Matsumiya, Y., Yamasita, T. and Nawamura, Y., Phosphorus Removal from Sidestreams by Crystallisation of Magnesium- Ammonium-Phosphate Using Seawater, Water and Environ. J., 14, 291~296(2000). 14. APAH, AWWA and WEF, Standard Methods for the Examination of Water and Wastewater. 21th Ed. American Water Works Association, Washington DC, USA(2005). 15. Celen, I., Buchanan, J. R., Bruns, R. T., Robinson, R. B. and Raman, D. R., Using a chemical equilibrium model to predict amendments required to precipitate phosphorus as struvite in liquid swine manure, Water Res., 41(8), 1689~ 1696(2007). 16. Ali, M. I. and Schneider, P. A., A fed-batch design approach of struvite system in controlled supersaturation, Chem. Eng. Sci., 61, 3951~3961(2006). Journal of KSEE Vol.39, No.8 August, 2017

+,PSFBO4PD&OWJSPO&OH j Ñ m j4usvwjuf m fa 469 17. Ali, M. I. and Schneider, P. A., An approach of estimating struvite growth kinetic incorporating thermodynamic and solution chemistry, kinetic and process description, Chem. Eng. Sci., 63, 3514~3515(2008). 18. Nelson, N. O., Mikkelson, R. L. and Hesterberg, D. L., Struvite precipitation in anaerobic swine lagoon liquid: effect of ph and Mg : P ratio and determination of rate constant, Bioresour. Technol., 89, 229~236(2003). 19. Mehta, C. M. and Batstone, D. J., Nuclearting and growth kinetics of struvite crystallization, Water Res., 47, 2890~ 2900(2013). 20. Rahaman, M. S., Ellis, N. and Mavinic, D. S., Effects of various process parameters on struvite precipitation kinetics and subsequent determination of rate constants, Water Sci. and Technol., 57(5), 647~654(2008). 21. Rahman, M., Salleh, M. A. M., Rashid, U., Ahsan, A., Hossain, M. M. and Ra, C. S., Nuclearting and growth kinetics of struvite crystallization, Arabian J. Chem., 7, 139~155(2014). 22. Wang, S., Hawkins, G. L., Kiepper, B. H. and Das, K. C., Struvite Precipitation as a Means of Recovering Nutrients and Mitigating Ammonia Toxicity in a Two-Stage Anaerobic Digester Treating Protein-Rich Feedstocks, Molecules, 21, 1011(2016). ¼jm jm 39 8m 2017 8