Performance assessment of modified biosand filter with
an extra disinfection layer
Banu Sizirici Yildiz
ABSTRACT
Biosand filters (BSFs) have been used widely as an efficient, inexpensive, and appropriate point-of-
use technology. Several organizations are promoting filters without adequate testing, which may not
lead to sufficiently safe devices. The objective of this study was to evaluate the performance of a
modified biosand filter (MBSF) with an extra disinfection layer (brass or zero valent iron (ZVI)) and
three layers of underdrain in a range of parameters including Escherichia coli, total coliform,
turbidity, pH, and dissolved oxygen. On average, a 91.29% reduction (log 1.43) in total coliform, 98.7%
reduction (log 2.6) in E. coli and 88.71% reduction in turbidity were observed for the control. There
was a 90.11% reduction (log 1.41) in total coliform, 98.2% reduction (log 2.25) in E. coli, and 88.5%
reduction in turbidity for MBSF brass. A 96.93% reduction (log 1.81) in total coliform, 97.33%
reduction (log 2.36) in E. coli and 91.5% reduction in turbidity for MBSF ZVI were observed. Adding
brass as a disinfection layer in MBSF did not improve bacteria and turbidity removal rates. Adding ZVI
as a disinfection layer gave better turbidity and total coliform removal relative to control and MBSF
brass. Water quality remained within drinking water standards for all filters.
Banu Sizirici Yildiz
Civil Environmental and Infrastructure Engineering
Department,
Khalifa University,
PO Box 127788, Abu Dhabi,
UAE
E-mail: banu.yildiz@kustar.ac.ae
Key words | brass, disinfection layer, modified biosand filter, zero valent iron
INTRODUCTION
Inadequate water quality, which supports endemic trans-
mission of pathogenic organisms and high rates of
morbidity and mortality, is a serious problem in underdeve-
loped and developing countries. Therefore, appropriate
technologies are needed for disinfection of drinking water
to enable safe use. However, since large municipal infra-
structures are often unavailable, the technologies must be
inexpensive and operate at the level of a small community
or single dwelling. Biosand filters (BSFs) have been used
widely as an efficient, inexpensive, and appropriate technol-
ogy for removing particles and microbial hazards from
filtered water at household level in developing countries
and rural communities (Duke et al. ; Murphy et al.
; Ngai et al. ).
BSFs use biological and physical removal mechanisms.
The biological layer, composed of algae, bacteria, diatoms,
zooplankton and particles settled above the sand, breaks
down organic particles in the water biologically and strains
out very small particles from water (Devadhanam Joubert &
Pillay ; Juarez et al. ; Kubare & Haarhoff ).
These microbial communities are capable of metabolizing
contaminants by mediating oxidation reduction reactions
(Zhu et al. ).
Laboratory scale BSFs provide significant improvement
in water quality, with removal of up to 95–99% for fecal coli-
form contamination, up to 99% for total coliform, up to 96–
98.5% for Escherichia coli (E. coli), and up to 88–92% for
turbidity (Duke et al. , Stauber et al. ; Campos &
Outhwaite ; Ngai & Baker ).
Modified BSFs with an additional adsorbent medium such
as a biomass layer or metal particles have been investigated
through several studies. Metal and metal oxide nanoparticles
containing magnesium oxide, copper, iron and silver exhibit
antimicrobial properties or growth-inhibiting activity. The
266 © IWA Publishing 2016 Journal of Water Supply: Research and Technology—AQUA | 65.3 | 2016
doi: 10.2166/aqua.2016.103