Improving the energy balance between microwave pretreatment and anaerobic digestion with centrifuged biosludge

Abstract

The effect of pretreatment of raw biosludge (Bs) and centrifuged Bs (CBs) with microwave (MW) operated at constant conditions before an anaerobic digestion (AD) process on the energy requirement and production of hybrid system was investigated. With the successful breakdown of Bs and CBs by the MW irradiation, the soluble COD concentrations increased from average value of about 76 mg/L to 300 mg/L and 6400 mg/L for the Bs and CBs, respectively. After the MW disintegration, the protein and sugar concentrations were about 10 and 22 times higher in the pretreated samples compared to the biosludges. While, the total and volatile solids (TS and VS) concentrations in the liquor declined. The increase of readily bioavailable organics in pretreated samples improved about 22% CH₄ production in AD units, compared to the raw Bs and CBs. It was determined that the energy requirement of MW irradiation decreased about 3 times with the centrifugation of Bs. Although the applied whole models were well correlation, the kinetic analysis showed that Transference Function was the best model with the highest correlation coefficient (R² between 0.953 and 0.998) for predicting the most accurately CH₄ production. The nutrients concentrations in effluent of AD process was significantly higher than the liquors obtained after the MW irradiation was observed.

Keywords

Anaerobic digestion / Biosludge / Energy assessment / Microwave / Pretreatment

References

[1] AkbayHEG. Anaerobic mono and co-digestion of agro-industrial waste and municipal sewage sludge: biogas production potential, kinetic modelling, and digestate characteristics. Fuel, 2024, 355. 129468

[2] AlhraishawiA, AslanS, OzturkM. Methane production and nutrient recovery after applying microwave technology in sewage sludge pretreatment. Int J Environ Res, 2024, 18335.

[3] AlhraishawiA, AslanS, OzturkM. Methane production and struvite recovery from disintegrated biosludge at different microwave powers. Waste Biomass Valorization, 2025.

[4] AnthonisenAC, LoehrRC, PrakasamTBS, SrinathEG. Inhibition of nitrification by ammonia and nitrous acid. J Water Pollut Control Feder, 1976, 48835

[5] APHA (2005) Standard methods for the examination of water and wastewater standard methods for the examination of water and wastewater. American Public Health Association. Washington, DC. 2005;21^st edn.

[6] AslanS, AlhraishawiA, OzturkM. Effects of microwave irradiation at various temperatures on biosludge disintegration. Int J Environ Health Res, 2024, 8: 1-19.

[7] AziziA, HosseiniKE, HafezH, ElbeshbishyE. Improving single- and two-stage anaerobic digestion of source separated organics by hydrothermal pretreatment. Biochem Eng J, 2019, 148: 77-86.

[8] BhattacharyaSK, ParkinGF. The effect of ammonia on methane fermentation processes. J Water Pollut Control Feder, 1989, 1(8): 55-59

[9] BraunR, HuberP, MeyrathJ. Ammonia toxicity in liquid piggery manure digestion. Biotech Lett, 1981, 3(4): 159-164.

[10] CanoR, Pérez-ElviraSI, Fdz-PolancoF. Energy feasibility study of sludge pretreatments: a review. App Energy, 2015, 149: 176-185.

[11] ChanWI, WongWT, LiaoPH, LoKV. Sewage sludge nutrient solubilization using a single-stage microwave treatment. J Environ Sci Health: Part A, 2007, 42(1): 59-63.

[12] ChristodoulouA, StamatelatouK. Overview of legislation on sewage sludge management in developed countries worldwide. Water Sci Technol, 2016, 73(3): 453-462.

[13] Di CapuaF, SpasianoD, GiordanoA, AdaniF, FratinoU, PirozziF, EspositoG. High-solid anaerobic digestion of sewage sludge: challenges and opportunities. Appl Energy, 2020, 27815. 115608

[14] EskiciogluC, DrosteRL, KennedyKJ. Performance of continuous flow anaerobic sludge digesters after microwave pretreatment. Proc Water Environ Fed, 2006, 79(13): 526-540.

[15] EskiciogluC, DrosteRL, KennedyKJ. Performance of anaerobic waste activated sludge digesters after microwave pretreatment. Water Environ Res, 2007, 79(11): 2265-2273.

[16] EskiciogluC, TerzianN, KennedyKJ, DrosteRL, HamodaM. Athermal microwave effects for enhancing digestibility of waste activated sludge. Water Res, 2007, 11: 2457-2466.

[17] EskiciogluC, ProrotA, MarinJ, DrosteRL, KennedyKJ. Synergetic pretreatment of sewage sludge by microwave irradiation in presence of H₂O₂ for enhanced anaerobic digestion. Water Res, 2008, 42(18): 4674-4682.

[18] FangG, ZhouX, WeiW. Enhancing anaerobic biodegradability and dewaterability of sewage sludge by microwave irradiation. Int J Agric Biol Eng, 2017, 10(2): 224-232.

[19] GilA, SilesJA, ToledoM, MartínMA. Effect of microwave pretreatment on centrifuged and floated sewage sludge derived from wastewater treatment plants. Process Saf Environ Prot, 2019, 128: 251-258.

[20] HephzibahD, KumaranP, SaifuddinNM. Comparison of the effects of continuous flow microwave pre-treatment with different intensities on the anaerobic digestion of sewage sludge for sustainable energy recovery from sewage treatment plant. Int J Bioeng Life Sci, 2015, 9(12): 1070-1074

[21] HoutmeyersS, DegrèveJ, WillemsK, DewilR, AppelsL. Comparing the influence of low power ultrasonic and microwave pre-treatments on the solubilisation and semi-continuous anaerobic digestion of waste activated sludge. Bioresour Technol, 2014, 171: 44-49.

[22] JackowiakD, BassardD, PaussA, RibeiroT. Optimisation of a microwave pretreatment of wheat straw for methane production. Bioresour Technol, 2011, 102(12): 6750-6756.

[23] JeongSY, ChangSW, NgoHH, GuoW, NghiemLD, BanuJR, JeonBH, NguyenDD. Influence of thermal hydrolysis pretreatment on physicochemical properties and anaerobic biodegradability of waste activated sludge with different solids content. Waste Manage, 2019, 85: 214-221.

[24] JiangL, ShenQ, ZhangQ, ZengY, WangW, MaoY, JiF. Microwave-alkali treatment with water elutriation to enhance waste activated sludge solubilization for carbon sources and nutrients recovery. Chem Eng J, 2021, 421. 129727

[25] KatakiS, WestH, ClarkeM, BaruahDC. Phosphorus recovery as struvite: recent concerns for use of seed, alternative Mg source, nitrogen conservation and fertilizer potential. Resour Conserv Recycl, 2016, 107: 142-156.

[26] KavithaS, Rajesh BanuJ, KumarG, KaliappanS, YeomIT. Profitable ultrasonic assisted microwave disintegration of sludge biomass: modelling of biomethanation and energy parameter analysis. Bioresour Technol, 2018, 254: 203-213.

[27] Kor-BicakciG, Ubay-CokgorE, EskiciogluC. Effect of dewatered sludge microwave pretreatment temperature and duration on net energy generation and biosolids quality from anaerobic digestion. Energy, 2019, 168: 782-795.

[28] KoupaieEH, EskiciogluC. Conventional heating vs. microwave sludge pretreatment comparison under identical heating/cooling profiles for thermophilic advanced anaerobic digestion. Waste Manage, 2016, 53: 182-195.

[29] LiL, KongX, YangF, LiD, YuanZ, SunY. Biogas production potential and kinetics of microwave and conventional thermal pretreatment of grass. Appl Biochem Biotechnol, 2012, 166(5): 1183-1191.

[30] LiaoX, LiH, ChengY, ChenN, LiC, YangY. Process performance of high-solids batch anaerobic digestion of sewage sludge. Environ Technol, 2014, 34(21): 2652-2659.

[31] LiaoX, LiH, ZhangY, LiuC, ChenQ. Accelerated high-solids anaerobic digestion of sewage sludge using low-temperature thermal pretreatment. Int Biodeterior Biodegrad, 2016, 106: 141-149.

[32] LiuJ, YuD, ZhangJ, YangM, WangY, WeiY, TongJ. Rheological properties of sewage sludge during enhanced anaerobic digestion with microwave-H₂O₂ pretreatment. Water Res, 2016, 98: 98-108.

[33] LiuJ, JiaR, WangY, WeiY, ZhangJ, WangR, CaiX. Does residual H₂O₂ result in inhibitory effect on enhanced anaerobic digestion of sludge pretreated by microwave-H₂O₂ pretreatment process?. Environ Sci Pollut Res, 2017, 24: 9016-9025.

[34] LiuJ, YangM, ZhangJ, ZhengJ, XuH, WangY, WeiY. A comprehensive insight into the effects of microwave-H₂O₂ pretreatment on concentrated sewage sludge anaerobic digestion based on semi-continuous operation. Bioresour Technol, 2018, 256: 118-127.

[35] MehdizadehSN, EskiciogluC, BobowskiJ, JohnsonT. Conductive heating and microwave hydrolysis under identical heating profiles for advanced anaerobic digestion of municipal sludge. Water Res, 2013, 47(14): 5040-5051.

[36] Náthia-NevesG, BerniM, DragoneG, MussattoSI, Forster-CarneiroT. Anaerobic digestion process: technological aspects and recent developments. Int J Environ Sci Technol, 2018, 15: 2033-2046.

[37] PalettaR, CandamanoS, FilippelliP, LoprestoCG. Influence of Fe₂O₃ nanoparticles on the anaerobic digestion of macroalgae Sargassum spp. Processes, 2023, 111016.

[38] PalettaR, CandamanoS, BrunoMDL, DesiderioG, CastroYA. Effect of unconventional pretreatments on the morphology and biochemical methane potential of Sargassum spp. Algal Res, 2025, 86. 103915

[39] ParkWJ, AhnJH, HwangS, LeeCK. Effect of output power, target temperature, and solid concentration on the solubilization of waste activated sludge using microwave irradiation. Bioresour Technol, 2010, 101(1): S13-S16.

[40] PassosF, UggettiE, CarrèreH, FerrerI. Pretreatment of microalgae to improve biogas production: a review. Bioresour Technol, 2014, 172: 403-412.

[41] RaniRU, KumarSA, KaliappanS, YeomI, BanuJR. Impacts of microwave pretreatments on the semi-continuous anaerobic digestion of dairy waste activated sludge. Waste Manage, 2013, 33(5): 1119-1127.

[42] SahaM, EskiciogluC, MarinJ. Microwave, ultrasonic and chemo-mechanical pretreatments for enhancing methane potential of pulp mill wastewater treatment sludge. Bioresour Technol, 2011, 102(17): 7815-7826.

[43] SuschkaJ, GrübelK. Nitrogen in the process of waste activated sludge anaerobic digestion. Arch Environ Prot, 2014, 40(2): 123-136.

[44] SyaichurroziI, BasyirMF, FarrazRM, RusdiR. A preliminary study: effect of initial pH and Saccharomyces cerevisiae addition on biogas production from acid-pretreated Salvinia molesta and kinetics. Energy, 2020, 20715. 118226

[45] TangB, YuL, HuangS, LuoJ, ZhuoY. Energy efficiency of pre-treating excess sewage sludge with microwave irradiation. Bioresour Technol, 2010, 101(14): 5092-5097.

[46] TyagiVK, LoSL. Microwave irradiation: a sustainable way for sludge treatment and resource recovery. Renew Sust Energy Rev, 2013, 18: 288-305.

[47] UgwuSN, EnweremaduCC. Biodegradability and kinetic studies on biomethane production from okra (Abelmoschus esculentus) waste. S Afr J Sci, 2019, 115: 7-8.

[48] VeluchamyC, KalamdhadAS. Enhanced methane production and its kinetics model of thermally pretreated lignocellulose waste material. Bioresour Technol, 2017, 241: 1-9.

[49] YanY, ChenH, XuW, HeQ, ZhouQ. Enhancement of biochemical methane potential from excess sludge with low organic content by mild thermal pretreatment. Biochem Eng J, 2013, 70: 127-134.

[50] YigitCB, OnurGA. Critical review for microwave pretreatment of waste-activated sludge prior to anaerobic digestion. Curr Opin Environ Sci Health, 2020, 14: 1-9.

[51] YuanH, GuanR, WachemoAC, ZhuC, ZouD, LiY, LiuY, ZuoX, LiX. Enhancing methane production of excess sludge and dewatered sludge with combined low frequency CaO-ultrasonic pretreatment. Bioresour Technol, 2019, 273: 425-430.

[52] ZahanZ, OthmanMZ, MusterTH. Anaerobic digestion/co-digestion kinetic potentials of different agroindustrial wastes: a comparative batch study for C/N optimization. Waste Manage, 2018, 71: 663-674.

[53] ZhangB, JiM, WangF, LiR, ZhangK, YinX, LiQ. Damage of EPS and cell structures and improvement of high-solid anaerobic digestion of sewage sludge by combined (Ca(OH)₂+multiple-transducer ultrasonic) pretreatment. RSC Adv, 2017, 7(37): 22706-22714.

[54] ZouX, YangR, ZhouX, CaoG, ZhuR, OuyangF. Effects of mixed alkali-thermal pretreatment on anaerobic digestion performance of waste activated sludge. J Clean Prod, 2020, 259. 120940

Funding

Sivas Cumhuriyet Üniversitesi(M-2022-838)

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