Page 210 - Materials Chemistry, Second Edition

Determination of Pharmaceutical Compounds in Sewage Sludge 191

higher degradation under anaerobic conditions. In contrast, lagooning treatment
caused lower elimination of all the compounds detected (Martín et al., 2015).

9.3.3 ecoToxicological risk assessMenT of seWage
sluDge applicaTion onTo soils
Ecotoxicological risk assessment can be evaluated by means of risk quotient values
(RQ). RQ values were calculated for digested-sludge and compost organisms and for
soil organisms after soil application of digested sludge or compost. RQ values for
sludge organisms are calculated as the ratios between the measured environmental
concentration (MEC) in sludge and the highest concentration of the pharmaceutical
below which no adverse effect is expected to occur (predicted no-effect concentra-
tion [PNEC]). RQ values for soil organisms are calculated as the ratio between the
predicted environmental concentration (PEC) in soil after sludge application and the
PNEC of the pharmaceutical compound. The criterion usually applied to evaluate
the ecotoxicological risk is that proposed by Hernando (2006), which considers there
to be a high risk if RQ ≥ 1, a medium risk if 0.1 ≤ RQ ≤ 1, and a low risk if RQ ≤ 0.1
(Hernando et al., 2006; Verlicchi and Zambello, 2015). According to the European
Technical Guidance Document on Risk Assessment EUR 20418 EN/2 (EC-TGD,
2003), the concentration of a pollutant in soil after the first year of sludge application
is given by the equation

C sludge ×
PEC= APPL sludge
DEPTH soil × RHO soil
where:
C sludge is the concentration in dry sewage sludge
APPL sludge is the dry sludge application rate
DEPTH is the mixing depth of soil
soil
RHO is the bulk density of wet soil
soil
APPL sludge , DEPTH , and RHO values applied to agricultural soils are
soil
soil
2
0.5 kg m year , 0.20 m, and 1700 kg
−1
dw
−3
m , respectively (EC-TGD, 2003). Due to
the lack of toxicity data for soil and sludge
organisms, PNEC concentrations for soil
(PNEC ) and sludge (PNEC sludge ) organ-
soil
isms are evaluated from PNEC data for
aquatic organisms (PNEC water ) and the
sludge (K d sludge ) or soil (K d soil ) solid-water
partition coefficient of the pharmaceutical
compound (Martín et al., 2012b; Verlicchi
and Zambello, 2015):
PNEC sludge soil, = PNEC water × K d sludge soil,