biodegradation and bioclogging in the unsaturated porous soil beneath sewer leaks

Acta hydrochim. hydrobiol. 32 (2004) 4−5, 277−286 277

Stephan Fuchsa, Biodegradation and Bioclogging in theHermann H. Hahna,Jochen Roddewiga, Unsaturated Porous Soil beneath Sewer LeaksMartin Schwarza,Robertino Turkovica

According to the potential risk for soil and groundwater caused by wastewater exfiltration,the processes of retention, transport, and transformation in the surrounding of leaky sew-a Institut fürers have been studied in detail. The importance of the microbial biomass and its spatialSiedlungswasserwirtschaft,

Universität Karlsruhe (TH), and temporal distribution are focused on in this paper. Considering two aspects i) degra-Adenauerring 20b, dation of wastewater compounds, ii) soil clogging, several experiments have been carried76131 Karlsruhe, Germany out under laboratory and full-scale conditions.

Besides the purification capacity the clogging of the pore space beneath a leak and itsstability are essential to assess the long-term impacts of exfiltrating wastewater on soiland groundwater. Deposition of particulate matter as well as microbial growth are respon-sible for decreasing pore space and hydraulic conductivity.According to the grain size of the soil, the water and mass flux, the availability of oxygen,and the filter length the removal rates vary in a wide range. For DOC from 30 to 73% andfor NH4

+-N from 0 to 99% removal were observed.The influence of the microorganisms on soil clogging has been quantified by detecting theconcentration of nucleic acids as an indicator for microbial biomass and activity. A corre-lation between the total biomass in the upper layers of soil and hydraulic conductivity couldbe drawn up.

Biologische Umsatzprozesse und Kolmation im ungesättigten porösen Locker-gestein im Umfeld von Kanalleckagen

Im Umfeld von Kanalleckagen wurden die Prozesse der Retention, des Stofftransportesund der Stoffumsetzung in abwasserdurchsickerten, ungesättigten Böden untersucht. DieAbfolge von biologisch katalysierten Umsetzungsprozessen sowie deren räumliche undzeitliche Ausdehnung stehen dabei ebenso wie die Frage des Biocloggings im Mittelpunktder Arbeiten. Dazu wurden Experimente an Bodensäulen und an einem großmaßstäb-lichen Modell einer Kanalleckage durchgeführt.Die ermittelten Reinigungsleistungen für die Parameter DOC und NH4

+-N schwanken beiden unterschiedlichen Versuchsbedingungen zwischen 30% und 73% bzw. zwischen 0%und 99%. Es wurden eindeutige Abhängigkeiten zwischen den erreichbaren Reinigungs-leistungen und der Korngrößenverteilung des Bodensubstrates, der Höhe der stofflichenBelastung, der Sauerstoffversorgung sowie der Länge der Filterstrecke festgestellt.Ausschlaggebend für die aus Leckagen resultierenden Boden- und Grundwasserbelastun-gen ist neben der Reinigungsleistung des Bodens der Umfang und die Stabilität der sicheinstellenden Selbstdichtung (Kolmation). Zwei Ursachen, der Eintrag von partikulärenSubstanzen sowie das Wachstum von Biomasse im durchsickerten Bodenkörper, sindverantwortlich für diesen Prozess. Durch die Bestimmung von Nukleinsäuren als Maßfür die Bildung von Biomasse (DNA) und deren Aktivität (RNA) konnte der Beitrag derMikroorganismen quantifiziert werden.

Keywords: Wastewater, Soil, Column Experiment, Full-scale Model

Schlagwörter: Abwasser, Boden, Säulenexperiment, Großversuchsstand

Correspondence: S. Fuchs, E-mail: [email protected]

DOI 10.1002/aheh.200400540 © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

278 S. Fuchs et al. Acta hydrochim. hydrobiol. 32 (2004) 4−5, 277−286

1 Introduction

Based on optical inspection a statistical analysis reveals theextent of damages in the public sewer systems of Germany[1]. Due to the results of this analysis 17% of the total sewersystem needs to be restored immediately or in short termand another 10% requires medium-term measures [1]. Thisassessment leads to investments of about 45 billion c withinthe next years. However the environmental risk related tothe damages identified by optical inspections is a point ofdiscussion. Bütow et al. [2] saw a correlation between heavydamages like pipe bursts or visible leaks and exfiltrationrates. In contrast Dohmann and Haußmann [3] stated thatoptical inspections do not provide satisfying results to esti-mate the amount of exfiltrating wastewater. In a series oflaboratory and full-scale experiments they, as well as Bütowet al. [2] found that exfiltration rates and pollutant loads de-pended on the water level in the sewer, the concentration ofwastewater compounds, and the properties of soil beneaththe leak. Considering different circumstances they calcu-lated minimal and maximal amounts of exfiltration whichranged between 33 Mio m3 a�1 and 440 Mio m3 a�1.

The wide range of these values and the calculated maximummay illustrate the given uncertainties and underlines thenecessity of further research. In order to improve the knowl-edge about leaky sewers and the threat for soil and ground-water resources a DFG research unit was founded at theUniversity of Karlsruhe (TH) working in detail on trans-formation, retention, and transport processes related towastewater infiltrating into the soil texture.

This paper focuses on the results obtained for the DOCdegradation, nitrogen transformation, and microbial growthin sandy soils which may be seen as characteristic subsur-face substrates in many cities in the Rhine valley.

2 Objectives

The hydraulic conductivity of porous soil beneath a sewerleak or in any sand filter system declines with the depositionof particulate matter by physical transport or chemical pre-cipitation and microbiological growth in the pore space [4,5]. The growth of biomass which seals wastewater infiltratedpore space, as described by Błazejewski [5] for constructedwetlands, depends on conditions like nutrient supply, whichcan be described as DOC, nitrogen, and phosphorus input.Furthermore ammonification, nitrification, and denitrificationare microbiologically catalysed transformation processeswhich serve as a sensitive indicator for the availability of oxy-gen [6, 7]. Considering these fundamentals the followingaspects had to be investigated in different experiments:

© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A) Localization of the main zones of biodegradation beneathleaky sewers

B) Quantification of the effectiveness of DOC and NH4+-N

removal for various types of soil and wastewater

C) Identification of the most important process parameters

D) Quantification of the extent and stability of bioclogging

To reach these aims column experiments under variation ofhydraulic and substance loads, grain size, and duration ofwastewater application were conducted. For each experi-ment the input and output was analysed and mass balancesfor DOC and nitrogen were done. At the end of each experi-ment the DNA and RNA concentrations in soil samples fromseveral layers beneath the point of infiltration were deter-mined. The DNA concentration was used as an indicator forbiomass and the RNA concentration as an indicator formicrobial activity. Several columns were rinsed from bottomto top with drinking water after a period of wastewater trick-ling in order to simulate a rising groundwater table, whichmay wash out accumulated wastewater ingredients [8] andbiomass near the leak. To prove and validate the laboratoryresults analogous experiments were conducted at a full-scale model at the wastewater treatment plant of the cityof Karlsruhe.

3 Experimental set-up

In one-dimensional experiments sand filled columns of dif-ferent sizes (Fig. 1) were fed with different types of waste-water from top. The columns were used to investigate thedegradation rates (large columns) and the effects of bioclog-ging (small columns). A full-scale model of a leaky sewerembedded in a sand filled container was designed to provethe results from the columns under three dimensional, morerealistic conditions.

3.1 Small columns

The small columns (length 50 cm, width 91 mm in diameter),which allow the most experimental variations, were filled with4 cm fine gravel (2...6.3 mm) at the bottom and a layer of43 cm sand. In the reported campaign a middle-sand domi-nated material (column I-S7, bulk density 1.6 kg L�1, Table2) and coarse-sand dominated material (column I-S3, bulkdensity 1.6 kg L�1) were used. All columns were kept indarkness at a constant temperature of 20 °C. Except for theweekends they were charged daily at one point of time with690 mm (4.5 L) wastewater. The wastewater was takenweekly at the grit chamber of the municipal wastewater treat-ment plant Karlsruhe and stored at 4 °C to minimize biologi-cal and chemical degradation. Before charging the concen-tration of settlable solids was reduced by sedimentation over

Acta hydrochim. hydrobiol. 32 (2004) 4−5, 277−286 Biological Processes beneath Sewer Leaks 279

Fig. 1: Laboratory columns.

Laborsäulen.

at least 6 hours. To avoid stirring during charging a porouscartridge filled with glass pearls (7 mm in diameter) was in-stalled at the upper sand layer on top of each column.

The development of the hydraulic conductivity was con-trolled by recording the time required to collect 1 L outflow.Samples from the wastewater inflow and outflows weretaken for chemical analyses.

The sand of column I-S7 (middle-sand dominated, mS) wasdismounted in layers after 24 days when the column wasclogged. Column I-S3 (coarse-sand dominated, cS) was dis-mounted after 60 days. Soil samples were taken of eachlayer for analysing chemical parameters and for detectingthe amount of biomass.

3.2 Large columns

The large columns (length 100 cm, width 20 cm in diameter)which were designed for long-term experiments were filledwith a middle-sand dominated substrate (bulk density1.6 kg L�1) on a bed of gravel. They were gas proofed and


stored at 15 °C in darkness. These columns were fed con-tinuously from top with particle-free double concentratedOECD wastewater as described in Schlegel [9] and with twodifferent flow rates, 235 mm d�1 (8 L d�1) for column S4 and470 mm d�1 (16 L d�1) for column S3.

Samples of the inflowing and outflowing wastewater weretaken three times a week. After running 120 days soilsamples at different depths were taken through drills fromthe side. Afterwards the flow direction was changed and thecolumns were flushed slightly from bottom to the top withtap water for a period of 70 days. The effects of a risinggroundwater table should be studied in this experiment. Afterthe flushing soil samples were taken to be compared to priortaken samples.

3.3 Full-scale model

In the full-scale model (Fig. 2), which was installed and oper-ated at the municipal wastewater treatment plant (WWTP)Karlsruhe, a sewage pipe (DN 200, PVC) with a defined leak(crack across the pipe, 150 mm length, 3 mm width) was


Fig. 2: Full-scale model at WWTP Karlsruhe.

Großversuchsstand auf der Kläranlage Karlsruhe.

mounted in a sand-filled container (middle-sand dominatedwith a bulk density of 1.6 kg L�1, 3 � 1.5 � 1 m). In threelevels beneath the sewer tensiometers, TDR-antennas, soilmoisture samplers, and temperature sensors were mounted.The bottom of the container was divided into eight runofffunnels.

Over a period of 8 months a continuous stream of 6.7 L s�1

of wastewater was pumped through the pipe. The infiltrationrate through the leak in the sand bed decreased from 2.3 to0.4 L d�1 within 107 days. The percolated water from every

Table 1: Parameters considered in the experiments.

Übersicht der Mess- und Analyseparameter in den verschiedenen Experimenten.

In situ Soil samples Effluent samples

Hydraulic physical Hydraulic physical Biological Heavy Chemical parametersparameters parameters parameters metals

Nonmetals Heavy metals

Moisture tension Soil moisture DNA Copper NH4+, NO3

�, CopperSoil moisture Loss on ignition RNA Zinc NO2

�, SO42�, Zinc

Temperature Pore volume Iron Cl�, BSB, LeadHydraulic conductivity CSB, DOC, Iron

TOC, TIC,KS4,3


runoff was collected separately to determine the amount ofwater and its chemical parameters. After a runtime of 8months the sand was removed in layers. Soil samples weretaken in each layer especially in the areas directly beneaththe leak.

3.4 Chemical analyses

Several parameters have been analysed during or followingthe experiments (see Table 1). The results presented in thispaper refer mainly to the chemical parameters DOC, am-monia, and nitrate.


Fig. 3: A typical HPLC chromatogram from a sand sample.(a) The complete chromatogram with the KCl gradient. (b) Asection of the same chromatogram showing the tRNA-,rRNA-, and the DNA-peak.

Typisches HPLC-Chromatogramm für die untersuchtenSandproben. (a) Kompletter Verlauf und KCl-Gradient. (b)Ausschnitt der tRNA-, rRNA- und DNA-Peaks.

DOC was analysed in accordance with the German Stand-ard Methods [10]. It is quantified by measuring the DIC andDC of the filtrate (0.45 µm) with catalytic oxidation at 800 °Cand detection by NDIR-gas analyser. Ammonium was deter-mined by photometry according to the German StandardMethods [11]. Nitrate was determined by anion-exchangechromatography with conductivity detection.

3.5 DNA- and RNA-analyses

The concentrations of DNA and RNA were analysed usinga method which was developed by Dell’Anno [12] and ad-apted for wastewater-polluted soils by Schwarz [13]. Soilsamples were taken in a vial and dropped into liquid nitrogen


for conservation and to support the removal of the biofilmsfrom soil surface. For the extraction of RNA and DNA 0.4 gof a sample were added to a Tris-HCl buffer (6.05 g Tris,5.08 g NaCl, 3.70 g ethylenediaminetetraacetic acid, 2.0 gsodium dodecyl sulfate and 8.1 mL of HCl (33%) were dis-solved to 1 L of DEPC-treated water and adjusted to pH 8.0with NaOH) and sonicated six times. Subsequent centrifu-gation (5 min at 3000 g) and filtration (0.45 µm celluloseacetate filter) excise heavy and large cell components. Thegained supernatant was injected (10 to 100 µL) into theHPLC which was equipped with a nucleogen anion-ex-change column. The nucleic acids adsorbed to the anion-exchange column and were eluted by applying a urea bufferwith an increasing KCl gradient. For the quantification ofnucleic acids a multiple wavelength detector at 260 nmwas used.

Figure 3 shows an example for a HPLC chromatogram.Interfering substances (e.g., proteins and humic sub-stances,) elute at low KCl concentrations and produce twolarge peaks within the first minutes (Fig. 3a).

4 Results and discussion

4.1 Removal rates

The purification capacity of soil is well known and used forthe treatment of municipal wastewater. An example hasbeen the “Rieselfelder” of Berlin where the raw wastewaterwas applied on soil surface for nearly 100 years [14, 15].Recently this capacity is used in reed beds or constructedwetlands for the treatment of municipal wastewater, com-bined sewer overflows, and storm runoff [16, 17]. Consider-ing the basic requirements of construction and operationhigh and stable removal rates were achieved with these sys-tems. However the involved processes and the specific par-ameters responsible for good or weak purification results arestill a topic of intense research [18]. Taking into account thesite-specific conditions in urban subsurface soil it can be as-sumed that similar effects and removal rates occur beneathleaky sewers. In Table 2 the average elimination rates forammonia and DOC observed under the different experimen-tal set-ups are listed.

The elimination rates for both DOC (30...73%) and ammonia(0...99%) scatter over a wide range of values. Strong depen-dencies could be seen between the varied parameters andthe elimination rates. The best results were achieved in thefull-scale model. The extreme low hydraulic loads in thisexperiment were caused by a partial clogging. This leads toa quantitative nitrification and a very high DOC degradation.The full-scale experiment was always characterized by aero-bic conditions.


Table 2: Elimination of DOC and NH4+-N in the different experimental scales.

Erreichte DOC- und NH4+-N-Rückhalte in den verschiedenen Experimenten.

Small-scaled columns Large-scaled columns Full-scale experimentAerobic conditions Anaerobic conditions Aerobic conditions

Column name I-S3 I-S7 S3 S4

Filter material coarse middle middle middle middlesand sand sand sand sand

Hydraulic load 690 mm d�1 690 mm d�1 235 mm d�1 470 mm d�1 22...4 mm d�1*

Input NH4+-N 38 mg L�1 38 mg L�1 54 mg L�1 54 mg L�1 30 mg L�1

Input DOC 64 mg L�1 64 mg L�1 132 mg L�1 132 mg L�1 75 mg L�1

Elimination NH4+-N 20% 52% 8% 0% 99%

Elimination DOC 35% 68% 42% 30% 73%

* Drawn on the flowed through area of the layer directly beneath the leak which has 1044 cm2.

The discontinuous charging of the small columns with waste-water also guaranteed aerobic conditions. The observed ni-trification may serve as an evidence for this. Neverthelesssignificant lower elimination rates were registered in the col-umns, even if these were packed with the same soil as thefull-scale model. One reason for the declining eliminationrates can be seen in the height of these sand filters � thesand layer was only 43 cm thick. The high load applied tothe columns exceeds the adsorption capacities of the filtermaterial and leads to increased effluent concentrations. Afurther decrease of the elimination rates was observed in thecolumn with coarse sand (I-S3) which had a smaller sorptionsurface and also a shorter contact time due to the higherhydraulic conductivity than in the column that was filled withmedium size sand.

The lowest elimination rates occurred in the gas proof col-umns S3 and S4 which were fed continuously. Soon afterthe start of the experiments columns S3 and S4 becameanaerobic and an ammonia breakthrough occurred at thefifth day of operation. The DOC removal in these columnsdepended on dissolved oxygen in the applied wastewaterand on the oxygen which rested in the columns from thestart of the experiment. With increasing loads the removalrate decreased, in the worst case to zero.

The results of the aerobic soils match to the survey ofv. Felde [6]. She found in discontinuously charged columnswith daily ammonia loads between 0.5 mg cm�2 d�1 and 1.5mg cm�2 d�1 removal rates higher than 99% NH4

+-N. Theseremoval rates range in between the full-scale experimentand the small-scaled columns.


4.2 Nucleic acid distribution

The determination of DNA concentration in soil requires onlyvery little soil samples. Using this method the space beneaththe column surface and/or the artificial leak can be analysedin layers of 1 to 2 centimetres. Thus the distribution and ac-tivity of biomass can be studied in detail. In Figure 4 DNAand RNA contents versus the depth from the high loadedanaerobic columns S3 and S4 are depicted.

All experiments reveal an accumulation of biomass and bio-activity in the very first centimeters of the soils after tricklingof OECD wastewater. The density of biomass decreaseswith depth in a sharp gradient. Higher loads of dissolvedorganic matter lead to higher biomass yields. Moreover,experiments of Schwarz [13] demonstrate that a correlationbetween the share of particulate organic matter and the ex-tent of accumulation of biomass at the soil surface is given.Schwarz [13] found the sharpest DNA-gradient using realwastewater from combined sewer overflows.

In case of the high loads applied in columns S3 and S4 andthe resulting anaerobic conditions the RNA concentration in-creased significantly above the DNA concentration.

In general the full-scale model exhibits analogous results.As can be seen in Figure 5 the nucleic acid concentrationsdecrease with a very sharp gradient. That is partly causedby the particulate organic matter in the wastewater, whichwas accumulating at the surface of the soil. But the gradientis sharper than in other column experiments or vertical filters


Fig. 4: DNA and RNA concentrations in several depths in the lower-loaded column S3 and the higher-loaded column S4.

DNA- und RNA-Konzentrationen in verschiedenen Tiefen der geringer (S3) und höher (S4) beaufschlagten Säulen.

Fig. 5: DNA and RNA concentrations of the full-scale experiment.

DNA- und RNA-Konzentrationen im Großversuchsstand.

fed with wastewater containing particles [13]. The reasonwas that the organic matter input at the full-scale model wasextremely low compared to other experiments. Already in adepth 6 cm below the leak the nucleic acid concentrationswere near to the limits of determination. The concentration


straight below the leak was comparable to these in the col-umn experiments of Schwarz [13]. In contrast to all columnexperiments the RNA concentration was near or at zero.This indicated a marginal bioactivity and matched with thevery low nutrient load of the full-scale model.


Fig. 6: Decrease of hydraulic conductivity versus DNA concentration in the upper soil layers (0 to 2 cm).

Abnahme der hydraulischen Leitfähigkeit in Abhängigkeit von der DNA-Konzentration in den oberen Sandschichten (0 bis 2 cm).

One aim of these investigations was to elucidate the interac-tion between biomass concentrations and hydraulic conduc-tivity of the soil, as reported by Vandevivere [19] or Schwarz[13]. For this purpose the hydraulic conductivity at beginningand at the time of taking samples was compared to the maxi-mum of DNA concentration in several similar experiments.Figure 6 compiles the results of these experiments.

Plotting the reduction of the hydraulic conductivity againstthe DNA concentration in the upper layers of the columns asignificant correlation appears. When the DNA content ex-ceeds 275 µg g�1 a total clogging of the soil was found inthe filter filled predominantly with medium sand. Referring toSchlegel [9] the DNA represents 0.45 to 1.2% of the drymatter of a bacterial cell. With regard to the tested filter sub-strates (pore space 36%) that implies that only 10 to 26%of the pore space is filled with bacteria. The observed totalclogging can be explained by the production of bacterialexopolymers (EPS). The amount of EPS can vary in a widerange depending on several conditions like nutrient andwater supply or hydraulic factors [4]. Therefore under certainconditions the EPS can have a vital effect in decreasing thepore space and in causing a total clogging in the substrates.Further experiments must be carried out to determine theinteraction between DNA and hydraulic conductivity for sev-eral substrates found in urban subsurface varied by theirgrain size and granulometries.

Comparing DNA and RNA concentrations from severalexperiments, it is obvious, that the “specific bioactivity” ex-


pressed as ratio between RNA and DNA content defined asm(RNA)/m(DNA), given in µg µg�1, increases with the was-tewater load applied to the column. Furthermore it wasshown that the columns became anaerobic when this loadexceeds a critical value (no NH4

+-N elimination, see columnsS3 and S4). Considering these phenomena it could be sup-posed that anaerobic systems generally achieve higherspecific bioactivities. The RNA/DNA-ratio may provide anappropriate indicator whether aerobic or anaerobic reactionsprevail within the systems. To confirm this thesis anotherexperiment result shall be described. The DNA content inthe column S3 reached 24 µg g�1 after 120 days (Fig. 7a).Taking this concentration and the corresponding RNA con-centration an average specific bioactivity of 2.5 µgRNA/µgDNA, ranging between 1.8 and 3.3 was calculated.(Fig. 7c). During the very first days the column accumulatedwastewater compounds, the reactions switched to anaerobicconditions and biodegradation was incomplete. During thefollowing backflushing when the soil was supplied withoxygen rich water a spontaneous and rapid consumption ofthe accumulated organic matter took place and the DNAcontent at the top of the column increased significantly to133.5 µg g�1. Simultaneously the specific bioactivitydropped to values around 1...2.2 µg g�1 (s. Fig. 7c)

In all experiments carried out with different soils and typesof wastewater the same trend was found: Aerobic systemslike the full-scale sewer model or the intermittently chargedcolumns resulted in a RNA/DNA-ratio around 1. In contrastto this the investigated anaerobic systems like the high


Fig. 7: DNA concentration and RNA/DNA-ratio before and after backflushing.

DNA-Konzentration und RNA/DNA-Verhältnis vor und nach dem Rückspülen der Säulen.

loaded columns showed RNA/DNA-ratios distinctly higherthan 2. The following arguments may help to explain theseeffects. An aerobic bacterium is able to gain 38 mol ATP outof 1 mol glucose, anaerobic bacteria only get 5 mol ATP andthere are several organisms necessary to achieve a com-plete mineralization [9]. That means i) that the biomass pro-duction in an aerobic state is significantly higher than in ananaerobic state and ii) the specific activity in an anaerobicsystem must be higher to get the same yield. Thus theRNA/DNA-ratio may be a reliable indicator for an aerobic oranaerobic system.

5 Conclusions

The retention and degradation of dissolved organic matterin a soil matrix has a wide range, depending on grain size,the quality of infiltrating wastewater, oxygen supply, and theresidence time in the unsaturated zone. In order to estimatethe environmental risk related to leaky sewers it is necessaryto consider these parameters in addition to optical inspec-tion. In the framework of the reported project some importantinterrelations could be described quantitatively.

The distribution and quantity of biomass was determined asa function of the nutrient input and the grain size distributionof the tested filter substrates. Its role in soil clogging pro-cesses was proven. A strong correlation between biomass,detected as DNA concentration, and reduction of hydraulicconductivity was found. In middle-sized sands the clogging


happens on or near the surface, which could be proven bymeasuring DNA concentration in several depths.

The RNA/DNA-ratio may be used as an indicator whetherthe conditions are mainly aerobic or anaerobic. This givesinformation for the modelling of wastewater degradation andretention in wastewater loaded soil.

Under the tested flow conditions a complete clogging of soilcould not be observed neither in the column experiments norin the full-scale model.

In future experiments the correlation between DNA concen-tration and hydraulic conductivity will be extended on othergrain sizes and granulometries considering the most fre-quent subsurface substrates in urban area. These experi-ments will include both, loamy substrates and gravels.

The full-scale experiment will be continued with other formsof leaks in order to explore the influence of size and form ofleaks and exfiltration rate. Furthermore the effects of a risinggroundwater table, which was studied in the columns only,will be a focus of further full-scale experiments, too.

In the last phase of the project the impact of leaking stormwater sewers on soil and groundwater will be investigated.The run-off component from roofs and streets [20] is sup-posed to contain pollutants in higher concentrations and tohave worse retention or consumption properties.


Acknowledgements

The presented work was founded by the Deutsche For-schungsgemeinschaft DFG (German Research Foundation)within the Research Unit FOR 350 „Gefährdungspotentialvon Abwasser aus undichten Kanälen für Boden und Grund-wasser“ (Risc Assessment of Sewage from Leaking Sewersfor Soil and Groundwater). The authors would like to thankthe DFG and all other members of the research unit for goodcooperation. We give special thanks to the Tiefbauamt of thecity of Karlsruhe and the stuff of the WWTP for supportingus in the operation of the full-scale model.

This paper is dedicated to our inspiring colleague Dr. MatthiasEiswirth, who has been taken from our side far before time.

References

[1] Berger, C., Lohaus, J., Wittner, A., Schäfer, R.: Zustand

der Kanalisation in Deutschland. ATV-DVWK, Eigen-

verlag, 2001.

[2] Bütow, E., Krafft, H., Rüger, M., Lüdeke, J.: Gefährdungs-

potential von undichten Kanälen bei industriellen und ge-

werblichen Grundstücksentwässerungsleitungen und die

Ableitung von Empfehlungen zur Revitalisierung defekter

Entwässerungsleitungen. UBA Forschungsbericht 210,

2001.

[3] Dohmann, M., Haußmann, R.: Belastung von Boden und

Grundwasser durch undichte Kanäle. Abwasser Spezial II,

GWF 137 (15), S2�S6 (1996).

[4] Baveye, P., Vandevivere, P., Hoyle, B. L., DeLeo, P. C.,

Sanchez de Lozada, D.: Environmental impact and mecha-

nisms of the biological clogging of saturated soils and

aquifer materials. Crit. Rev. Environ. Sci. Technol. 28 (2),

123�191 (1998).

[5] Błazejewski, R., Murat-Błazejewska, S.: Soil clogging

phenomena in constructed wetlands with surface flow.

Water Sci. Technol. 35 (5), 183�188 (1997).

[6] v. Felde, K., Kunst, S.: N- und CSB-Abbau in vertikal

durchströmten Bodenfiltern. GWF Gas Wasserfach:

Wasser-Abwasser 133, 40�1408 (1996).

[7] Kristiansen, R.: Sand filter trenches for purification of sep-

tic tank effluent: II The fate of nitrogen. J. Environ. Qual.

10, 358�361 (1981).

[8] Dohmann, M. (Ed.): Wassergefährdung durch undichte

Kanäle: Erfassung und Bewertung. Springer, Berlin, 1999.

[9] Schlegel, H. G.: Allgemeine Mikrobiologie. 7., überarb.

Auflage. Thieme, Stuttgart, 1992.

[10] Norm DIN EN 1484 � Wasseranalytik � Anleitungen zur

Bestimmung des gesamten organischen Kohlenstoffs

(TOC) und des gelösten organischen Kohlenstoffs (DOC).


August 1997. In: Wasserchemische Gesellschaft � Fach-

gruppe in der Gesellschaft Deutscher Chemiker, in

Gemeinschaft mit dem Normenausschuß Wasserwesen

(NAW) im DIN Deutsches Institut für Normung e. V. (Ed.):

DEV Deutsche Einheitsverfahren zur Wasser-, Abwasser-

und Schlamm-Untersuchung, Verfahren H3. 40. Lieferung,

Wiley-VCH, Weinheim und Beuth, Berlin, 1998.

[11] Wasserchemische Gesellschaft � Fachgruppe in der Ge-

sellschaft Deutscher Chemiker, in Gemeinschaft mit dem

Normenausschuß Wasserwesen (NAW) im DIN Deutsches

Institut für Normung e. V. (Ed.): DEV Deutsche Einheitsver-

fahren zur Wasser-, Abwasser- und Schlamm-Unter-

suchung � Kationen (Gruppe E) � Bestimmung des

Ammonium-Stickstoffs (E5) (DIN 38406-E5-1). 12. Lie-

ferung, Wiley-VCH, Weinheim und Beuth, Berlin, 1983.

[12] Dell’Anno, A., Fabiano, M., Duineveld, G. C. A., Kok, A.,

Danovaro, R.: Nucleic acid (DNA, RNA) quantification and

RNA/DNA-ratio determination in marine sediments: com-

parison of spectrophotometric, fluorometric and high per-

formance liquid chromatography methods and estimation

of deterial DNA. Appl. Environ. Microbiol. 64, 3238�3245

(1998).

[13] Schwarz, M.: Mikrobielle Kolmation von abwasserdurch-

sickerten Bodenkörpern, Nucleinsäuren zum Nachweis

von Biomasse und Bioaktivität. Dissertation, Universität

Karlsruhe, 2004. Institutsverlag Siedlungswasserwirt-

schaft, Universität Karlsruhe.

[14] Scheytt, T., Grams, S., Asbrand, A.: Grundwasser-

strömung und �beschaffenheit unter dem Einfluss

100jähriger Rieselfeldbewirtschaftung. Wasser Boden 52(9), 15�22 (2000).

[15] Strohbach, B.: Böden der Rieselfelder im Bereich des

Forstamtes Buch � Entstehung und Eigenschaften.

Wasser Boden 52 (9), 4�8 (2000).

[16] Reed, S. C., Cites, R. W., Middelbrook, E. J.: Natural Sys-

tems for Waste Water Management and Treatment. 2nd

Edition. McGraw-Hill, New York, 1995.

[17] Kadlec, R. H., Knight, R. L.: Treatment Wetlands. Lewis

Publisher, Boca Raton, 1996.

[18] MUNLV: Retentionsbodenfilter � Handbuch für Planung,

Bau und Betrieb. Ministerium für Umwelt und Naturschutz,

Landwirtschaft und Verbraucherschutz des Landes

Nordrhein-Westfalen (Ed.), Düsseldorf, 2003.

[19] Vandevivere, P., Baveye, P.: Saturated hydraulic con-

ductivity reduction caused by aerobic bacteria in sand

columns. Soil Sci. Am. J. 56 (1), 1�13 (1992).

[20] Duncan, H. P.: Urban Stormwater Quality: A Statistical

Overview. Report 99/3, Cooperative Research Centre for

Catchment Hydrologie, Monash University, Victoria 3800

Australia, 2003.

[Received: 18 February 2004; accepted: 16 August 2004]

biodegradation and bioclogging in the unsaturated porous soil beneath sewer leaks

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