© 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

Submerged biological filters to treat . A laboratory experience

A, Matarti, M.A. G6mez, A. Ramos, M. Zamorano & E. Hontoria Civil Department. Granada Universip, Spain.

Abstract

Leachate treatment systems installed at landfill sites have advanced a great deal in sophistication and reliability, Leachate recirculation, biological and physiochemical treatment processes are used to treat this wastewater but all treatment seem to need a combination of two or more methods to obtain an effluent with suitable properties to eliminate environmental problems, A system for leachate disposal must be simply and economic; it must require the least possible amount of energy to operate and minimum staff involvement. Biological filters could be a new to treat landfill leachate with standard characteristics. Aerobic and anaerobic systems could be used to treat landfill leachate with biological filters. Results obtained for two pilot plants show that this treatment could be an efficient alternative, with COD and suspended removal depending on hydraulic loading rate under aerobic or anaerobic conditions. A new pilot plant, with aerobic and anaerobic reactors, is necessary to determine the design parameters of the system.

1 Introduction

Wastes in landfill undergo physical, chemical and biological changes resulting in solubilisation or suspension of high of organic matter in a phase called Ieachate (l). Landfill Ieachate is a complex wastewater and it always contains a high strength of pollutants which have an adverse effect on the enviromnent (2). The composition of these Ieachates depends on waste composition and age, landfill surface, landfill operation and climatic conditions. © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

690 Waste Management and the En~irownent

The most important characteristics of leachate which could influence treatment are: high of organic and inorganic substances, irregular production depending on the amount of rainfall, variations in the biodegradable fraction of organic substance depending on the age of landfill, and the low or negligible concentration of phosphorous (3) These Ieachate characteristics impose operational difficulties on treatment processes not normally found when treating wastewater of high strength and volume. Different treatment strategies are therefore required to match a treatment to the changing Ieachate volumes and strengths during the filling phase and aftercare of a landfill (3). In an effort to control the pollution caused by landfill leachate, many treatment processes have been studied, such as leachate recircultaion, biological methods and physiochemical methods. Leachate recirculation is a process to enhance stabilisation of active and in-situ treatment of problematic Ieachates. Pohland & Kim (4) have documented the benefits of increasing landfill moisture content and liquid movement through the fill; these benefits are associated with increasing utilisation opportunities, reduced leachate treatment requirements, avoidance of long-term monitoring and liability, and potential for landfill and reuse (5). Biological methods include aerobic and anaerobic processes (3,6). Leachate from landfill may contain substances which are able to limit biological treatment efficiency, such as: metals, compounds, ammonia, chloride and sulphide. However, the sensitivity of biological treatment processes in the presence of toxic compounds is reduced by several factors (3). Aerobic and anaerobic treatment processes used with landfill leachate are: aerated lagoons, activated plants, trickling filters, rotating biological contractors, anaerobic lagoons, anaerobic digesters and anaerobic filters. Physiochemical treatment processes have been tested by many researchers that have studied different treatment with sanitary landfill Ieachate such as: -precipitation (7), elimination of and suspended solids (8), chemical oxidation to eliminate cyanide, phenol and other organic pollutants (9), active carbon to of some organic compounds or to nitrogen reduction (10) and stripping with vapour to remove ammonia (11). One of the new developments of Ieachate treatment is the with , as: (8), and (12) and reverse (13). All discussed and tested treatment technologies seem to present a non suitable substitute for biological Ieachate treatment. One solution could be an optimum combination of two or more methods or the development of other treatment technologies. A system proposed for leachate disposal must be simply and economic; it must require the least possible amount of energy to operate and minimum staff involvement. Submerged biological filters have support materials to biofilm grown; this support is not moving and completely submerged in wastewater, running always as a filter (13). Some of the advantages of this treatment are: treatment plants can be built inside structure, no secondary clarification is needed, is a simply system © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

Waste Management and the En~’irownent 69] and requires a low amount of energy to operate and minimum staff involvement, it has no moving parts and a high density filter medium with the possibility to get high organic removal rate per unit volume (14,15). Landfill leachate may contain substances which are able to limit biological treatment efficiency but the main characteristic of the system and its application to treat wastewater with high salt concentration (16) or with pollutants as phenol or heavy metals (17) and its application to industrial wastewater with similar composition make to think that submerged could be use to treat landfill leachate. The objective of this research was to know the possibility of an application of submerged filter to treat landfill leachate. This research has been developed with two laboratory pilot plant.

2 Materials and Methods

2.1 Laboratory pilot plants

The laboratory pilot plants used in this study consisted of two submerged biological filters reactors; the fwst running in aerobic conditions and the second in anaerobic conditions. Both reactors had the same dimensions: height of reactors, 30 cm and diameter of reactors, 6.5 cm. Leachate without previous treatment was introduced on the top of the pilot plants from a 50 Iitre deposit with a peristaltic . Treated effluents were collected tiom the bottom of the reactors. The aerobic system used a compressor to introduce air at the bottom of the reactor. A schematic diagram of these plants is shown in Figure 1,

INFFLUENT INFFLUENT

\ ii PERISTALTIC PUMP

T

*

\ i

-f AEROBIC REACTOR LEACHATE DEPOSIT ANAEROBIC REACTOR

Figure 1: Pilot plants schematic diagram

Both reactors were packed with clayey schists (2-7 mm average size, 1.78 g/cm3 apparent relative density and 2,18 g/cm3 real relative density), a ceramic material, with high surface area and special shapes, from brick industrial waste. © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

692 Waste Management and the En~irownent

Aerobic and anaerobic reactors were running with several hydraulic loading rates (O.18 to 0.7 m3/m2/d)by changing leachate flow. Several recirculation rates (200, 400 and 800%) were assayed as with 0.36 m3/m2/dhydraulic loading for both reactors. A continuous air flow (6.79 m3/m2/d ) was maintained in aerobic reactor.

2.2 Landfill leachate characterisation

Landfill leachate used in this research was taken from a landfill facility in Granada, Spain (Loma de Manzanares, Alhendh); it is a high density landfill where wastes are disposed from an urban waste comporting and recovery plant. Average parameters of this leachate show that this is a young leachate: COD 17.045 + 1.045 mg 02/1, total nitrogen 976 ~ 15 mg/1, pH 7.87 ~ 0.26, conductivity 14.84 ~ 3,79 S/cm and suspended solids 676 + 97 mg/1.

2.3 Analytical methods

Every 24 hours, water samples (50 ml) were collected flom the inlet and the outlet of the columns, obtaining three replicates for each assay, COD, pH, total nitrogen and suspended were routinely monitored in all samples. was measured using COD closed reflux micro method (18), Absorbance of the digestate was measured calorimetrically at 600 nm and the COD concentration was calculated tlom a , prepared with potassium acid phthalate. Chloride interference was avoided with silver nitrate. Previous to nitrogen determination, total nitrogen was oxidised to nitrate by boric and persulfate digestion. Nitrate was measured using an ion (IC) system with conductivity detection (Dionex@ DX-300). Separation and elution of the anions were carried out on an anion analytical column (Ionpac@ AS 14) using a carbonate/bicarbonate eluent and a sulphuric regenerant. Suspended solid were determined by vacuum filtration through a pre- weight glass filter (0.45 pm), them dried for 24 h. at 105° C (18) and pH was monitored by electrometric methods.

3 Results and Discussion

Submerged biofilm systems used to treat industrial and municipal wastewater have demonstrate a high efficiency in organic matter elimination (15,17). So, an adequate yield in organic matter removal can be expected for landfill leachate. Different COD removal efficiencies were observed between aerobic and anaerobic system (Figure 2). Effluent COD depends on hydraulic loading in the aerobic system, showing significant statistical differences for each hydraulic loading assayed (P <0’05, 95 ?40 confidence level), Medium yields in COD © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

Waste Management and the En~’irownent 693

removal varied between 32°/0for the larger hydraulic loading tested and 88°/0for the minor. Effluent COD does not depends on hydraulic loading in the anaerobic system, in this case medium yields in COD removal were between 7 and 38 0/0 and no significant statistical differences were observed. Low COD removal efficiency with anaerobic system could be because anaerobic biological processes are slower and long retention periods are needed to produce low strength and well clarified effluents (19).

A 16000 B 20000 14000- 12000- = 15000 s 10000- s & 6000. g ,0000

E 6000- s ~ 4000- ~ 5000 2000 0. = o = 123 45678 9 40 12345678 9 10

Days Days

Figure 2: Effluent COD concentration (mg/1)in aerobic (A) and anaerobic (B) processes at different hydraulic loading: “W“0.18 m3/m2/d, “A” 0.35 m3/m2/d,“O” ().53m3/m2/d,“*” 13.7m3/m2/d

Removal efficiency in COD of these two systems is not enough, so several recirculation rates were researched with 0.36 m3/m2/d hydraulic loading. Analysis of COD variance, in aerobic reactors, showed significant differences (P

Figure 3: Means and 95 percent LSD intervals yields of COD removal (%) in aerobic processes depending on recirculation rate. © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

694 Waste Management and the En~irownent

The analysis of variance of suspended solids removal efficiency, in aerobic and anaerobic reactors, shows non significant differences (P>O’05, 95°/0 confidence level) between different hydraulic loading (Figure 4). These results are justified by the packed structure of the support material, roughness of biofilm surface which facilitates suspended solid attachment and low water flow velocity (20). Submerged biological filters offer a simple and compact treatment process without secondary if filter support is suitable. In the aerated submerged biological filter, erosion caused by rising air bubbles increased the fraction of fine particles in the effluent, taking in account the limited characteristics of the type of laboratory pilot plant used in this research. Suspended solids effluents in the aerobic reactor are higher than in the anaerobic reactor, achieving mean removal efficiencies of 20°/0 and 64°/0 for aerated and anoxic reactors respectively.

A ,00 B 600 I 600 = 500 p 400 : 300 ~ 200 100 o~ o~ 123456789 10 123456789 10

Days Days

Figure 4: Effluent suspended solid (S.S.) concentration (mg/1) in aerobic (A) and anaerobic (B) processes at different hydraulic loading: “1”0.18 m3/m2/d, “A” ()+35m3/m2/d,“.” ().53 m3/m2/d,“*” ().7m3/m2/d,

Analysis of variance of total nitrogen removal efficiency, in aerobic and anaerobic reactors, showed significant statistical differences (P < 0’05, 95°/0 confidence level) between different hydraulic loading (Figure 5). However no significant statistical differences were shown between process. Total nitrogen removal efficiency in the aerobic reactor achieving an average 5 ‘/0and the mean removal efficiency in the anaerobic reactor is only 3 ‘?40.These values are typical of nitrogen removal by assimilation (21) Evidence of vitrification in the aerobic system was observed because high nitrate concentration in treated effluent was detected. This nitrogen transformation was not detected in anaerobic column where ammonium was the main nitrogen compound. Nitrate presence in anaerobic column would help to organic matter removal at the same time as a considerable total nitrogen removal would occur by denitrification (22). A combination of two separate biological reactors (aerobic and anaerobic) would favour vitrification and denitrification process with landfill leachate and high yield in carbon matter and total nitrogen removal would be detected © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

Waste Management and the En~’irownent 695

A B

Figure 5: Effluent total nitrogen concentration (mg/1)effluent in aerobic (A) and anaerobic (B)processes atdifferent hydraulic loading: “_’’0.18m3/m2/d, “A” 0.35 m3/m2/d,“O” 0.53 m3/m2/d,“*” 0.7 m3/m2/d.

4 Conclusions

This research shows that submerged biological filters are a suitable substitute to other treatment of landfill Ieachate although it will be necessary to define the design parameters of the new system, with the same support material, Future developments could be estimated based on the present discussion about the use of this system to treat Ieachate. The most important aspect of this solution is that it requires the least possible amount of energy to operate and minimum staff involvement. The encouraging results obtained show the need to build a new pilot plant with two reactors, one anaerobic and another aerobic, in order to remove organic material, suspended solids and nitrogen; it will be necessary to develop recirculation rates to obtain best results.

Acknowledgements

The research work was made possible with the financial support of Fomento de Construcciones y Contratas S.A (FCC). The authors would like to thanks this International Company for its support, and Professor Lorenzo Giusti fi-om the University of West of England (United Kingdom) for his helpfi.d translation notes.

References

[1] Imai A,, Onuma K., Inamori Y. & Sudo R. Biodegradation and adsorption in refractory Ieachate treatment by the biological fluidized bed process. Water Research. 29 (2), pp. 687-694, 1995. [2] Chiang L,, Chang J. & Wen T. Indirect oxidation effect in electrochemical oxidation treatment of landfill leachate. Water Research. 29 (2), pp. 671- 678, 1995. © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

696 Waste Management and the Ernironment

[3] Cossu, R,, Stegmann, R., Andeottola, G, & Cannas, P. Sanitary Landjlling Process. and Environmental Impact. Academic Press. London, 1995. [4] Pohland F.G. & Kim J.C. In situ anaerobic treatment of leachate in landfill . Water Science Technology 40 (8), pp.203-2 10, 1999. [5] Debra R. & A1-Yousfi A. The impact of leachate recirculation on municipal solid waste landfill operation characteristics. Waste Management and Research, 14, pp. 337-346, 1996. [6] Urase T., Salequzzaman M., Kobayashi S., Matsuo T., Yamamoto K, & Suzuki N. Effect of high concentrations of organic and inorganic matters in landfill leachate on the treatment of heavy metals in very low concentration level. Water Science Technology. 36(12), pp. 349-356, 1997. [7] Gau, S,H. & Chang, F.S. Improved Fenton Method to Remove Recalcitrant Organics in Landfill Leachate. Water Science Technolo~. 34(7-8), pp.455- 462, 1996. [8] Qasim R. & Chiang W. Sanitary Landjll Leachate: Generation, Control and Treatment. Technomic Publishing Co. EE.UU. 1994. [9] Steensen, M. Chemical oxidation for the treatment of leachate-process comparison and results from full-scale plants. Water Science and Technology, 35, pp. 249-257, 1997. [10] Horan N.J., Gohar H. & Hill B. Application of a granular activated carbon- biological fluidised bed for the treatment of landfill Ieachate containing high concentrations of ammonia. Water Science and Technology.36, pp. 369-375, 1997. [11] Leonhard K,, Eisner P., Haase W. & Wilderer P. Distillative treatment of liquid industrial wastes. Water Science and Technology. 30, pp. 139-147, 1994. [12] Bueno J.L., Sastre H,, Lavin A,G., FernAndez S. y Cuervo M, Contaminacidn e ingenieri’a ambientak (IV). Degradaci6n del suelo y tratamiento de residues. F.I.C.Y.T. Madrid. 1995. [13] Martinez J.L.; Garcia J,J.; Benito V.; Ferrandiz A,; Rubio M. y Zarzo D. Estudio del tratamiento de lixiviados de RSU mediante 6smosis inversa. Proc. del II congreso sobre desalacibn y reutilizacidn del siglo XYI. Asociaci6n Espafiola de desalacion y reutilizaci6n, Alicante noviembre 2001. [14] Zamorano M., Gomez MA., Gonzalez J., Hontoria E. Material soporte y fuentes de carbono en procesos de Iechos inundados, Tecnoambiente. 52, pp. 39-42.1995. [15] Osorio, F. & Hontoria, E, Optimization of Bed material Height in a Submrged Biological Aerated Filter, Journal of Environmental Engineering. 127. pp. 974-978.2001, [16] Park, E.J.; See, J.K.; Kim, M.R.; Jung, H,; Kim, J,Y. and Kim, S.K. acclimation of Immobilized Freshwater denitritier. Aquacultural Engineering. 24, pp. 169-180.2001. © 2002 WIT Press, Ashurst Lodge, Southampton, SO40 7AA, UK. All rights reserved. Web: www.witpress.com Email [email protected] Paper from: Waste Management and the Environment, D Almorza, CA Brebbia, D Sales & V Popov (Editors). ISBN 1-85312-907-0

Waste Management and the En~’irownent 697

[17] Nkhalambayausi-Chirwa, E.M. and Wang, T,T. Simultaneous Chromium (VI) and phenol degradation in a fixed-film culture biorreactor: reactor performance, Water Research. 35(8), pp. 1921-1932.2001. [18] APHA, AWWA and WEF, Standard methods for the examination of water and wastewater. 18* ed. American Public Health Association. Washington. D.C, 1992. [19] Herbert, H.P.F., Chen, T.; Li, Y.Y. & Chui, H.K. Degradation of phenol in wastewater in an upflow anaerobic blanket reactor. Water Research. 30(6). pp. 1353-1363.1996, [20] Characklis, W,G, & Marshall, K.C. . Wiley. New York, 1990, [21]Bitton, G. Wastewater . Wiley-Liss Inc. New York. 1994, [22] Horan, N.J.; Lowe, P. & Stentiford, E.I. Nutrient Removal fi-om Wastewaters. Technomic, Basel. Switzerland, 1994