This document describes an easy respirometric method for optimizing the bioremediation of diesel-contaminated soil. Microcosm experiments were conducted with soil amended with nutrients and a bulking agent. Oxygen levels in the microcosms were periodically measured to calculate oxygen uptake rates, which indicated higher bacterial activity and diesel removal in microcosms with 30% bulking agent. This low-cost respirometric method provides a tool for screening bioremediation conditions without expensive chemical analyses.

1. EASY RESPIROMETRIC METHOD
EASY RESPIROMETRIC METHOD FOR THE OPTIMISATION OF
D FOR THE OPTIMISATION OF
D
DIESEL‐CONTAMINATED SOIL BIOREMEDIATION
DIESEL CONTAMINATED S
CONTAMINATED S
SOIL BIOREMEDIATION
Jubany I. Corcho D Rovira M Muelle A. Martí V. ,
Jubany I 1, Corcho D. 2, Rovira M. 1, Muelle A 2 ,Martí V 1,3
1CTM Technological Center Foundation Environmental Technology Area (UPC) Av B
CTM, Technological Center Foundation, Environmental Technology Area (UPC), Av. B
Bases de Manresa, 1, E‐08242 Manresa (Spain)
Bases de Manresa 1 E 08242 Manresa (Spain)
2 INTRAVAL S.L. Llull, No. 109, 2nd floor, E‐08005 Barcelona (Spain)
2 INTRAVAL S L Llull No 109 2nd floor E 08005 Barcelona (Spain)
3Department of Chemical Engineering Technical University of Catalonia (UPC) ETSEIB Av Diagonal 647 E 08028 Barcelona (Spain)
Department of Chemical Engineering, Technical University of Catalonia (UPC), ETSEIB, Av. Diagonal, 647, E‐08028, Barcelona (Spain)
INTRODUCTION
Petroleum hydrocarbon (TPH) contamination in soils is one of the ma environmental problems in Spain due to bad industrial and waste
ain
management practices performed in the last decades The biological treatment is one of the most cost‐effective treatments due to its low
decades. cost effective
investment and treatment costs (NFESC, 1996). A useful technique for the determination of bacterial activity in biological processes like the
biological il
bi l gi l soil treatment i the respiration technique that can b used to relate the O2 consumption with the contaminant removal. H
is h pi i h iq h be d l h pi ih h i l However
its potential has not been thoroughly exploited in the soil treatment fie This work shows a low cost and easy respirometric method for the
eld.
eld low‐cost
laboratory testing of contaminated soil The method was tested using m
soil. microcosms experiments with hydrocarbon‐contaminated soil
soil.
MATERIALS AND METHODS
MATERIALS AND METHODS
Microcosms setup Respirometic method:
A series of microcosms (Table 1) were set up for the treatment of Throughout the experiment, the oxygen of the air chamber of
diesel‐contaminated
diesel contaminated soil (16 7 g TPH/kg d m ) amended with
(16.7 d.m.) ith the jars was periodicall meas red b introd cing an o gen
as periodically measured by introducing oxygen
chemical nutrients (NFESC 1996) and a bulking agent (a mixture
(NFESC, probe into the jars through a hole in the lid which was sealed
of sawdust and wood chips) to provide optimal porosity. F
f d d d hip ) p id p i l p i y For with i l i g tape (Fig
i h insulating p (Figure 1) Th slope of the air oxygen
( 1). The l p
) f h i yg
each test an abiotic control (named 0) was also set up (with 4 g
test, concentration with time (d(O2%)/dt) was used to calculate the
HgCl2/kg soil).
g / g ) oxygen uptake rate (OUR in mg O2/d kg d.m.) using Eq. 1.
yg p ( g / g ) g q
Table 1. Experimental conditions of microcosms
p
Each microcosm
consisted on a 1 L 2.7421∙
2 7421∙ Vair d(O2%)
OUR = ∙ Eq.
Eq 1
Bulking agent
g g Nutrients
Test Microcosm glass jar containing M dt
(% in wet weight)
(% i t i ht) addition
dditi
160 g of the soil‐
soil
0 0, A
0 A 0 No bulking
b lki agent t Vair is the volume of air in each jar
1 0, A, , C
0, A, B, C 100 Yes mixture and added (in L) and M is the dry weight of
2 0, A, B, C 20 Yes water ( 0 % of
(70 f the il (in ) in the i
th soil (i g) i th microcosm.
3 0, A, B, C
0 A B C 30 Yes field capacity)
capacity).
Figure 1. Air chamber oxygen
Figure 1. Air chamber oxygen
Microcosms were k t f
Mi kept for 6 weeks at 20ºC TPH were
k t 20ºC. TPHs measurement of a microcosm setup.
measurement of a microcosm setup.
measured at the beginning and at the end of the experiment
experiment.
RESULTS
The oxygen measurements in the microcosms of Tests 1, 2 and 3 clearly showed oxygen consumption due to the biological activity.
Figure 2 shows th oxygen profile f T t 1 which was similar t Test 2 and 3 N li ibl oxygen consumption was d t t d i T t 0
Fi h the fil for Test hi h i il to Te t d 3. Negligible ti detected in Test 0.
This fact indicated that the contaminated soil without bulking agent and without added nutrients had no capacity to degrade TPHs As
t TPHs.
expected, oxygen i abiotic control microcosms did not change d t the i hibi i of b
p d, yg in bi i l i h g due to h inhibition f bacterial activity.
i l i iy
Figure 2. Oxygen
Figure 2 Oxygen profile of microcosms in Test 1
of microcosms in Test 1 Figure 3. OUR pr f l of Tests 1, 2 and 3.
i rofile f d Figure 4. Percentage of TPH removal
i f l
OUR was calculated for Tests 1, 2 and 3 (Figure 3). The OUR was c
, ( g ) clearly higher in Tests 2 and 3 than in Test 1 indicating that higher
y g g g
bacterial activity was taking place in these tests Based on these res
tests. spirometric results experimental conditions in Test 3 were the best
results,
conditions for bacterial activity. Therefore, it can be stated that t increase of the mixture porosity (due to higher bulking agent
the
concentration) f
t ti ) favoured th b t i l activity d t t d as oxygen re i ti rate. Thi was confirmed with TPH d t since hi h TPH
d the bacterial ti it detected espiration t This fi d ith data i higher
removal was obtained as higher was the porosity of the mixture (Figu 4)
ure 4).
CONCLUSIONS
An easy respirometric method was developed for testing the bioremediation potential of hydrocarbon‐contaminated soil. The method was based
hydrocarbon contaminated
on the periodic measurement of the air oxygen of jars containing the tested soil using an oxygen probe.
h d f h f h d l b
The method was used to detect the best amendment conditions for the biotreatment of a hydrocarbon‐contaminated soil without the need for
hydrocarbon contaminated
expensive chemical analyses as TPHs. Results obtained with the respirometric method were in agreement with results obtained with TPH analysis.
p y p g y
The developed method is a promising method to be used as a tool for sm scale screening tests previous to pilot or industrial treatments for waste
mall‐scale
mall
management companies that need cheap and reliable techniques
techniques.
REFERENCES
• NFESC (1996). Biopile design and construction manual. TM‐2189‐ENV. Naval Facilities Engineering Se
( ) p g g g ervice Center.