Risk Assessment for Legionella sp. in Reclaimed Water at Tossa de

Risk Assessment for Legionella sp. in Reclaimed Water at
Tossa de Mar, Costa Brava, Spain
Authors: Rafael Mujeriego, PhD (Universidad Politécnica de Cataluña) and
Lluis Sala, (Consorci Costa Brava)
Spain-Costa Brava
Project Background or Rationale
Tossa de Mar is a Mediterranean coastal resort city in
southern Costa Brava (Girona, NE Spain) and member
of Consorci Costa Brava (CCB), the water supply and
sanitation agency for Costa Brava. Tossa de Mar’s
population goes from 6,000 people in winter to 60,000
people in summer. Its drinking water use is 264 mgd
3
(1 m /year), of which 20 percent comes from local
sources and the remainder from external sources: 52
percent is groundwater from the Tordera river aquifer
and 28 percent is desalinated water from Blanes
desalination plant, both located 9 miles (15 km)
southwest. Tossa de Mar was one of the leading cities
in Costa Brava to recognize the benefits of turning
wastewater into reclaimed water. Reclaimed water is
now a new municipal water resource for non-potable
use, with lower production and conveyance energy
requirements than the conventional sources.
government sources. The distribution system provides
reclaimed water to the main municipal services and
landscape areas, fire hydrants, and other publiclyowned facilities, such as the county’s dog shelter
(Figure 1) as well as to public spaces in new
residential areas. In addition, landscape irrigation with
reclaimed water at the Sa Riera Park is indirectly
supplying recharge water flows to the local stream,
avoiding its total summer desiccation and protecting its
fragile aquatic ecosystems.
Capacity and Type of Reuse
Application
The water reclamation plant (WRP) of Tossa de Mar
has a capacity of 0.22 mgd [35 m3/hr (840 m3/day)]
upgradable to 0.89 mgd (140 m3/hr). The current WRP
capacity represents 13 percent of the potable water
use during the peak tourist season. It includes:
coagulation-flocculation, lamella settling, rapid sand
filtration, and a combined disinfection process with
sodium hypochlorite and UV light. Reclaimed water is
3
stored in a 185,000 gallon (700 m ) tank, where it is
further chlorinated and mixed, and then pumped to the
reclaimed water distribution system. Reclaimed water
use for street cleansing and public garden irrigation
began in 2003 by water tanks loading at a hydrant
located at the doorstep of the WRP. By 2007 a
reclaimed water distribution system was already in
operation. The pipeline was brown in color with a blue
plastic film that says “Atención: Agua no potable”. By
mid 2011, the distribution system had reached a length
of 3.5 miles (5.7 km) after an investment of US
$477,000 (365,000 €) from municipal and regional
2012 Guidelines for Water Reuse
Figure 1
Reclaimed water use at Tossa de Mar dog shelter
(Photo credit: Lluis Sala)
Water Quality Standards and
Treatment Technology
Spanish water reclamation and reuse regulations are
established by Royal Decree 1620/2007. Reclaimed
water quality is defined by four main parameters:
parasitic helminth eggs, E. coli, suspended solids, and
turbidity. Other micro-biological parameters, like
Legionella sp. and physico-chemical parameters are
applicable to specific uses of reclaimed water.
Compliance is determined by the 90 percentile (P90)
of the series of water quality parameters recorded
during a water reuse period. Applicable limits for
current reclaimed water uses in Tossa de Mar are
E-107
Appendix E | International Case Studies
those for unrestricted urban use (Quality Use 1.2) with
SS, turbidity, parasitic helminths and E. coli P90
concentration limits below 20 mg/L, 10 NTU, 1
egg/10L and 200 cfu/100mL, respectively. Future midterm plans include the supply of reclaimed water for
irrigation of private gardens, which requires
compliance with quality limits for unrestricted
residential use (Quality Use 1.1): P90 values below
10 mg/L for SS, 2 NTU for turbidity, 1 egg/10L for
parasitic helminths and absence of E. coli (cfu/100
mL).
Since 2007, CCB is conducting an extensive
assessment of the overall Legionella infection risk
posed by the use of reclaimed water for irrigation of
urban and private gardens, following the Technical
Guidelines for the Prevention and Control of
Legionellosis established by the Spanish Ministry of
Public Health and Consumer Affairs. These technical
guidelines are used to assess such public health risk,
based not only on the microbiological quality of the
water (concentration of total aerobic bacteria, TAB <
105 cfu/mL), but also on several other parameters and
characteristics of the materials used in the distribution
and application system, such as pipelines and
sprinklers, among others. The upper limit of this index
is 100 and anything below 60 is considered to be a
“low infection risk” condition.
The studies conducted since 2007 indicate that:
1) TAB concentrations increase as water flows away
from the point at the WRP where sodium hypochlorite
is applied; 2) changes in TAB concentrations along the
network system provide valuable information on how
to manage the regrowth process and to maintain the
network within the safety limits required by the
Technical Guidelines; and 3) the overall infection risk
resulting for spray irrigation in urban areas,
considering the most unfavorable points of use
(sprinklers) and under the most unfavorable
microbiological conditions recorded, is just below 60
units, the limit officially set for “low infection risk”
conditions.
disinfecting all the sprinklers under its responsibility,
whether they use drinking or reclaimed water.
Project Funding and Management
Practices
The investment completed so far amounts to US
$477,000 (365,000 €), which was provided by the
Catalan Water Agency (CWA), CCB, Girona’s
provincial government and the city of Tossa de Mar.
Operation and maintenance of the water reclamation
plant has been assured by CCB, while operation and
maintenance of the reclaimed water distribution
system has been assured by the city’s technical
services. CCB is completing the official permitting
process necessary to become a wholesale reclaimed
water producer and supplier as prescribed by CWA. At
that time, CCB will be able to establish the appropriate
supply contracts with cities, which will be responsible
for managing the technical and economic aspects of
reclaimed water distribution to end users. In the event
that CCB becomes a wholesale supplier, the
responsibilities will be the same, as delegated under
Spanish Water Reuse Regulations (RD 1620/2007).
Institutional/Cultural Considerations
The use of reclaimed water in Tossa de Mar was
prompted by the severe drought of the late 1990s and
early 2000s. The high quality of reclaimed water and
the clear benefits of its use for non-potable uses
quickly raised a very positive perception from local and
seasonal residents. Since then, CCB has promoted a
high quality branding through CCB’s website,
municipality website, and Facebook page, of the nonpotable use of reclaimed water in Tossa de Mar.
Technical personnel wear white lab coats while
conducting the on-site water testing and sampling,
which has improved the citizen’s perception of the high
microbiological and aesthetic quality of reclaimed
water (Figure 2).
This monitoring program also provided useful
information for determining whether re-chlorination is
needed and where to apply it. Furthermore, Tossa de
Mar complies with the requirements of Royal Decree
865/2003 (2003) relative to the prevention and control
of Legionellosis, by systematically cleaning and
2012 Guidelines for Water Reuse
E-108
Appendix E | International Case Studies
References
Ministry of Public Health and Consumer Affaires (2003).
Royal Decree 865/2003 on the Hygienic and Public Health
Criteria for the Prevention and Control of Legionellosis. BOE
no. 171, pp. 28055-69. Retrieved on Sept. 7, 2012 from
<http://www.boe.es/boe/dias/2003/07/18/pdfs/A2805528069.pdf>.
Ministry of Public Health and Consumer Affairs. Technical
Guidelines for the Prevention and Control of Legionellosis in
Facilities. Retrieved on Sept. 7, 2012 from
<http://www.msc.es/ciudadanos/saludAmbLaboral/agenBiolo
gicos/guia.htm>.
Ministry of the Environment, Rural and Marine Affaires
(2007). Royal Decree 1620/2007 about the Spanish
regulations for water reuse. Boletín Oficial del Estado núm.
294, pp. 50639-61. Retrieved on Sept. 7, 2012 from
<http://www.boe.es/boe/dias/2007/12/08/pdfs/A5063950661.pdf>.
Figure 2
Reclaimed water quality monitoring in Tossa de Mar
(Photo credit: Lluis Sala)
Water Reuse Project of Tossa de Mar, CCB (2011).
WateReuse Barcelona 2011. Retrieved on Sept. 7, 2012
from
<http://www.waterbcn2011.org/download/Water%20Reuse%
20Project%20of%20Tossa%20de%20Mar.pdf>.
Successes and Lessons Learned
Water scarcity and the favorable assessment of the
energy balance of the municipal water cycle were the
main factors for the project development. The quick
and effective response of municipal services in close
collaboration with CCB and the CWA were
instrumental for the project success. The high
reclaimed water quality, its high quality branding, the
systematic follow-up studies and the educational
programs implemented have all contributed to assure
a very positive perception and acceptance from local
and seasonal residents. The very favorable results of
the Legionella risk assessment study have paved the
way for the extension of the use of reclaimed water to
irrigation of private gardens and possibly the supply of
reclaimed water for toilet flushing in the very near
future.
2012 Guidelines for Water Reuse
E-109