A fully-automated  pilot-scale  biofilter  filled  with  coconut  fiber  as  packing  material  was  investigatedfor  treatment  of  ammonia-containing  off-gas  streams.  Coconut  fiber  was  completely  characterized  forphysical  and  chemical  parameters  and  biological  activity.  Biofilter  performance  was  assessed  in  a  pilot-scale unit in a set of continuous experiments varying the inlet ammonia concentration in a range of 45 to240 ppmv at a gas contact time of 36 seconds. Samples taken along the bed height as well as inlet and outletammonia concentrations were used to determine a maximum elimination capacity of 12 g NH3m?3h?1ata 80% removal efficiency. Some features related to nitrification inhibition encountered in the experimentsare also discussed.Peer ReviewedPostprint (published version

Diaz, O

Gabriel Buguña, David

Gamisans Noguera, Javier

Lafuente Sancho, Francisco Javier

Maestre, Juan Pablo

Martin, L

Ruiz, N

English

UPCommons. Portal del coneixement obert de la UPC

CHARACTERIZATION OF ORGANIC PACKING MATERIALS IN THEREMOVAL OF AMMONIA GAS IN AUTOMATED BIOFILTERSL. Martín1, N. Ruíz1, J. P. Maestre1, O. Díaz1, X. Gamisans2, D. Gabriel1, J. Lafuente11Department of Chemical Engineering, Universitat Autònoma de Barcelona, Edifici C, 08193 Bellaterra, Barcelona, Spain. david.gabriel@uab.es2Department of Mining Engineering and Natural Resources, Universitat Politècnica deCatalunya, Bases de Manresa 61-73, 08240 Manresa, SpainABSTRACTA fully-automated pilot-scale biofilter filled with coconut fiber as packing material was investigatedfor treatment of ammonia-containing off-gas streams. Coconut fiber was completely characterized forphysical and chemical parameters and biological activity. Biofilter performance was assessed in a pilot-scale unit in a set of continuous experiments varying the inlet ammonia concentration in a range of 45 to240 ppmv at a gas contact time of 36 seconds. Samples taken along the bed height as well as inlet and outletammonia concentrations were used to determine a maximum elimination capacity of 12 g NH3 m?3 h?1 ata 80% removal efficiency. Some features related to nitrification inhibition encountered in the experimentsare also discussed.INTRODUCTIONBiological waste air treatment techniques have become an excellent method for the controlof low concentrations of odors and volatile organic and inorganic compounds in large air stre-ams (Shoda, 1991). In addition, biofiltration is an inexpensive, environmentally friendly techni-que for waste air treatment compared with conventional techniques such as scrubbing or adsorp-tion. Biofilters efficiency is highly dependant on the characteristics of the packing material.Proper packing material selection based on physical, chemical and biological parameters is akey factor in the reactor performance since biomass development and activity depends on thepresence of a suitable support. Since operation of biofiltration units for waste gas treatment mayrequire a set of routine tasks implementation of programmable logic controllers (PLCs) in addi-tion to supervisory control and data acquisition systems (SCADAs) at pilot-scale levels is espe-cially useful for avoiding routine tasks, and ensures repeatability, diminishes human mistakesand allows a deeper knowledge attainment.The aim of this research was to characterize several physical and chemical properties of thecoconut fiber, an organic material used as packing material in biofilters. Also, the material wastested in a pilot-scale reactor to assess its performance in ammonia removal. MATERIALS AND METHODSBiofiltration pilot-plant construction and operationA biofiltration pilot-plant was constructed with special attention to automation (Figure 1).The main unit, the biofilter, is a 1.1 m long, 0.1 m internal diameter transparent PVC cylinderdivided in four packed bed modules. Coconut fiber filled the 4 modules with an effective pac-king height of 80 cm (20 cm each). Gas sampling ports were located along the bed height, whereelectrovalves allowed for automatic sampling. The top was fitted up with an automated port fora nutrient solution addition while the bottom was fitted with a automated liquid drain, both con-313Gaseous Emissions and Odourstrolled by the PLC. Gas flow rates for air and ammonia were measured and controlled usingmass flow controllers. Prior to the mixture, air passes through a humidification column to ensu-re a 99-100% RH in the air entering the biofilter. A timer controlled electrovalve added waterperiodically to maintain a water level in the humidification unit. Continuously monitored para-meters included temperature and relative humidity (Testo, Hygrotest 600 PHT), ammonia gas(Vaisala, AMT102) coupled with a log register of actuations to pumps and valves. A structuredcontrol system with a PLC (Siemens, S7-314C-2DP) and a commercial SCADA software(Siemens, WinCC v.5.2) were used to automate the pilot-plant Analytical methods for packing material characterizationCoconut fiber used as packing material in the pilot-scale biofilter was obtained from a full-scale biofilter at a municipal solid waste composting facility that mainly treats ammonia andvolatile organic compounds from the foul air of the facility.Leacheate conductivity and pH were measured with lab probes prior to filtering. LeacheateCOD was measured according to Standard Methods (1995). Cl-, NO2-, SO42-, NO3-, PO43- weredetermined by capillary electrophoresis in a Quanta 4000E unit (Waters). NH4+ was measuredin a continuous flow analyzer (Baeza et al., 1999). Buffering capacity, water and organic mattercontent and water holding capacity (WHC) were determined according to Test Methods for theExamination of Composting and Compost (1995). Water retentivity of the packing material wasdetermined according to Hirai et al. (2001). Coconut fiber porosity and specific surface area andelementary analysis for C, N, H and S content of the packing material were performed in outsi-de laboratories. RESULTS AND DISCUSSIONPhysical and chemical parameters of coconut fiber from a full-scale biofilterA complete characterization of the packing material was performed prior to setting up thepilot-scale biofilter (table 1). Coconut fiber was characterized for parameters that do not requi-re a sample pre-treatment, while “water phase” parameters were determined by mixing waterand coconut fiber in a proportion of 1:25 volumes, then stirred for 1h, and leacheate aliquots fil-tered in 0.22 µm cellulose filters prior to the analysis. Some of the parameters determined are inherent to the material such us the pore size, the spe-cific surface area, material density, CHNSP content and organic matter content and thus compa-314Sustainable Organic Waste Management for Enviromental Protection and Food Safety TapwaterTreatedgasAirsupply(10)(4)(8)(2)(6)(5)(7)(1)(9)(3)(7)(6)Airsupply(7)(7)(7)(7)(7)Figure 1. Schematic of the biofiltra-tion pilot-plant. (1) Biofilter, (2)Humidification column, (3) Nutrientsreservoir, (4) Relative humidity andtemperature sensor, (5) Ammonia gascylinder, (6) Mass flow controllers,(7) Normally closed electrovalve, (8)Normally opened electrovalve, (9)Pump, (10) Ammonia gas sensor.rable to other materials characterized in the literature (Ramírez-López et al., 2003). In particu-lar, a high specific surface area of the coconut fiber, similar to this of peat, is a favorable cha-racteristic for biofiltration applications. In any case, low pore size of the material may lead tobiomass growth over the surface of the coconut fiber, thus reducing the specific surface areaavailable for pollutant degradation. Other parameters shown in Table 1 depend on the operating conditions of the biofilter.Compared to inorganic materials tested at the same space velocity (Hirai et al., 2001), 100 h-1,4 to 5 times lower water retentivity was found for coconut fiber. Also, coconut fiber at 70%water content is able to absorb up to 5.5 times its own dry weight in water, notably higher thana WHC of 2.8 g H2O·g dry material-1 reported for peanut shells as suitable packing material forbiofiltration applications (Ramírez-López et al., 2003). In any case, analyses were useful inorder to gain knowledge prior to setting up the pilot-biofilter unit and to understand some ope-rating conditions in the full-scale biofilter. Performance of coconut fiber in biofiltration of ammoniaAn experiment was undertaken in the pilot biofilter once the coconut fiber withdrawn froma full-scale biofilter was fully characterized for physicochemical parameters. No inoculationwas needed since the full-scale biofilter had been running for more than 2 years at averagedammonia inlet concentrations of 40 ppmv. Four step increases were performed to the ammoniainlet concentration (0-45, 45-120, 120-240, 240-180 ppmv) to reach a new steady-states after aminimum of 3 days. Empty bed retention time was always 36 seconds at a gas flow rate of 10.47L min-1. Watering was performed once per day at 0.383 L·d-1.Gas samples were taken automatically from inlet and outlet streams, as well as from the threesampling ports along the bed height of the biofilter. Figure 2a shows the profiles at the steady-state for ammonia gas concentration along the bed height. Inlet ammonia concentrations up to120 ppmv were completely removed, but in all cases a sharper decrease is observed in the lowermodule of the biofilter, which indicates a major biological activity in this zone of the reactor.Also, notice in Figure 2a that a decrease in the ammonia removal percentage was found in thelower module for an inlet ammonia concentration of 180 ppmv. This was related to a nitrifica-tion inhibition since leacheate analysis for ammonium, nitrite and nitrate showed a progressiveincrease in the nitrite and ammonium concentration coupled to a decrease in the nitrate produ-ced after the experiment of 120 ppmv (data not shown). Performance was assessed in terms ofelimination capacity (EC) and removal efficiency (RE) against the ammonia loaded (L) to the315Gaseous Emissions and Odours   No pre-treatment methods  Pre-treatment required methodsC (% dry weight)  H (% dry weight)  47.32 ± 0.12  5.69 ± 0.12  Buffering capacity  (g SO42-·kg material-1)  22 ± 1N (% dry weight) 0.52 ± 0.01 COD (g COD·kg material-1) 12.2 ± 1.2S (% dry weight) Not detected pH 7.74 ± 0.01P (% dry weight) 0.23 ± 0.00 Conductivity (µS cm-1) 1047 ± 42Water content (%) 72.8 ± 3.2 NH4+       (g N·kg material-1) 0.36 ± 0.05Organic matter (% dry weight) 96.4 ± 3.0 Cl-          (g Cl-·kg material-1) 0.5 ± 0.1Pore size (Å) 109 ± 1 NO2-             (g N·kg material-1) 1.93 ± 0.1Specific surface area (m2.g-1) 0.75 ± 0.10 SO42-   (g SO42-·kg material-1) 0.70 ± 0.03WHC (g H2O·g dry material-1) 5.5 ± 0.6 NO3- (g N·kg material-1) 0.49 ± 0.05Water retentivity (%·d-1) - 31 ± 7 PO43- (g P·kg material-1) Not detectedTable 1. Physicochemical characteristics of coconut fiber used in this study. Deviation reported as thestandard deviation of a set of three replicates per sample.reactor (Figure 2b), where EC= Q·(Cin-Cout)/V , RE=((Cin-Cout)/Cin)·100 and L=Q·Cin/V. Themaximum elimination capacity was around 12 g NH3·m-3·h-1 at a 80% removal efficiency, thusloads higher than 12 g NH3·m-3·h-1 would not enhance the efficiency of the biofilter. Althoughthe full-scale biofilter where the packing was withdrawn was operated at the same gas contacttime than the pilot-scale biofilter, 36 seconds, the ECmax found in the pilot-scale unit is notablyhigher than the value found in the full-scale reactor (4,3 g NH3·m-3·h-1).CONCLUSIONSA complete characterization in terms of physical, chemical and biological properties of coco-nut fiber as packing material in ammonia removing biofilters was performed. Coconut fiber hassome interesting properties such as high specific surface area, high WHC and a balanced C/N/Pratio in order to be used as carrier material in biofilters. Experiments performed with the coco-nut fiber in a fully automated pilot-scale biofilter showed reasonable ammonia elimination capa-cities of up to 12 g NH3·m-3·h-1 at a 80% removal efficiency. Results found herein may be impro-ved if higher biomass activity could be achieved in the upper modules of the biofilter that wouldenhance ammonia removal, even if nitrification inhibition by nitrification by-products requiresfurther research.REFERENCESAPHA. 1995. Standard Methods for the Examination of Water and Wastewater. 19th edition, AmericanPublic Health Association, Washington DC.Baeza, J.A., Gabriel, D., Lafuente, J. 1999. An expert supervisory system for a pilot WWTP. Environ.Modell. Softw., 14: 383-390Cárdenas, B, Ergas S., Switzenbaum M. 1998. Characterization of Compost Biofiltration Media. J. Air &Waste Manage. Assoc., 49: 784-793.Hirai,M.; Kamamoto,M.; Yani,M.; Shoda,M. 2001. Comparison of the biological H2S removal characteris-tics among four inorganic packing materials. J. Biosc. Bioeng., 91: 396-402. Shoda, M. 1991. Methods for the biological treatment of exhaust gases. In: Biological Degradation ofWastes. A.M. Martin (ed.) Elsevier Applied Science, London. 1991. pp. 1-30.U.S. Composting Council. 1995. In: P.B. Leege and W.H. Thompson (ed.) Test methods for the examinationof composting and compost. USCC, Bethesda, MD. 1995. 316Sustainable Organic Waste Management for Enviromental Protection and Food Safety 0501001502002503000 10 20 30 40 50 60 70 80 90Packed bed heigth (cm)NH3concentration(ppmv)C0: 45 ppmvC0: 240 ppmvC0: 120 ppmvC0: 180 ppmv 01020304050607080901000 10 20 30 40 50 60 70 80L (g NH3 m-3 h-1)EC(gNH3m-3h-1 )RE(%)100% removal line ECRE§(a) (b)Figure 2. a) Ammonia concentration along the bed height; b) Elimination capacity and removal efficiencyprofiles for ammonia inlet concentrations of 45, 120 and 240 ppmv.

Characterization of organic packing materials in the removal of ammonia gas in automated biofilters

https://upcommons.upc.edu/bitstream/handle/2117/134310/Mart%c3%adn.pdf?sequence=1&isAllowed=y

Characterization of organic packing materials in the removal of ammonia gas in automated biofilters

Abstract

Similar works

Full text

Available Versions

UPCommons. Portal del coneixement obert de la UPC