414
Alcalde et al.
Bacteroides fragilis are also used as pathogen indicators (Jofre et aI., 1986), but
they were not included in this study.
Many researchers investigated the microorganisms removal mechanisms in
WSP to identify the main parameters involved, but the results are conflicting.
Almost all these works were focused on fecal coliform removal and very little
work has been carried out to determine bacteriophages behavior as pathogen
indicators in WSP treatment systems. This information is needed to evaluate the
reliability of bacteriophages as indicator organisms.
The purpose of this work is to examine the fate of three pathogen indicator
microorganisms (fecal coliforms, F-specific bacteriophages and somatic
coliphages) in a combined system of waste stabilization ponds and stabilization
reservoirs to determine the efficiency of the treatment regarding the
microorganisms removal and to identify the main parameters involved in it,
considering the potential utility of phages for treatment system and environmental
monitoring.
2 Materials and Methods
2.1 The Treatment Site
The treatment plant, consisting of a series of WSP, three waste stabilization
reservoirs (WSR) and a large operational storage, is located several km west of the
City of Arad, Israel (Figure 1, Table 1). The rocky pond actually performs as an
horizontal trickling filter. Daily flow rate varies from 5,000 m 3 /day up to 5,500
m 3 /day.The obtained effluent is used for irrigation of a variety of crops such as
almond trees, wheat, barely, sunflower and alfalfa, under on surface and
subsurface drip systems.
2.2 Monitoring and Laboratory Assays
Wastewater samples were collected (grab samples) three to four times per month
from June 2000 untill February 2001. The main inlet and pond outlets were
choosen as sampling locations (Table 2). Although it is mentioned, the anaerobic
pond C was almost always out of order, so we did not take it into account.
Conventional methods were employed for the analysis of the physico-chemical
parameters (APHA, 1995).
Fecal coliforms assay. Fecal coliforms content was determined according to
the membrane filtration technique as described in APHA, 1995 (Ref. 9222-D).
Bacteriophages assay. The detection and enumeration of somatic coliphages
and F-specific bacteriophages was carried out using standard procedures (ISO
Alcalde et al.
Bacteroides fragilis are also used as pathogen indicators (Jofre et aI., 1986), but
they were not included in this study.
Many researchers investigated the microorganisms removal mechanisms in
WSP to identify the main parameters involved, but the results are conflicting.
Almost all these works were focused on fecal coliform removal and very little
work has been carried out to determine bacteriophages behavior as pathogen
indicators in WSP treatment systems. This information is needed to evaluate the
reliability of bacteriophages as indicator organisms.
The purpose of this work is to examine the fate of three pathogen indicator
microorganisms (fecal coliforms, F-specific bacteriophages and somatic
coliphages) in a combined system of waste stabilization ponds and stabilization
reservoirs to determine the efficiency of the treatment regarding the
microorganisms removal and to identify the main parameters involved in it,
considering the potential utility of phages for treatment system and environmental
monitoring.
2 Materials and Methods
2.1 The Treatment Site
The treatment plant, consisting of a series of WSP, three waste stabilization
reservoirs (WSR) and a large operational storage, is located several km west of the
City of Arad, Israel (Figure 1, Table 1). The rocky pond actually performs as an
horizontal trickling filter. Daily flow rate varies from 5,000 m 3 /day up to 5,500
m 3 /day.The obtained effluent is used for irrigation of a variety of crops such as
almond trees, wheat, barely, sunflower and alfalfa, under on surface and
subsurface drip systems.
2.2 Monitoring and Laboratory Assays
Wastewater samples were collected (grab samples) three to four times per month
from June 2000 untill February 2001. The main inlet and pond outlets were
choosen as sampling locations (Table 2). Although it is mentioned, the anaerobic
pond C was almost always out of order, so we did not take it into account.
Conventional methods were employed for the analysis of the physico-chemical
parameters (APHA, 1995).
Fecal coliforms assay. Fecal coliforms content was determined according to
the membrane filtration technique as described in APHA, 1995 (Ref. 9222-D).
Bacteriophages assay. The detection and enumeration of somatic coliphages
and F-specific bacteriophages was carried out using standard procedures (ISO