Date post: | 27-Mar-2015 |
Category: |
Documents |
Upload: | caroline-sawyer |
View: | 223 times |
Download: | 7 times |
EARLY WARNING SYSTEMS TO ENSURE DRINKING WATER
SAFETY
Presentation Agenda
Vulnerability & sensitivity of drinking water sources
Health effects
Sources of contamination
Early Warning System - » Definition» Structure & Function» Design Consideration» Data Management & Interpretation» Response
AquaVerity - CheckLight’s comprehensive solution
Components
Competitive edge
Vulnerability and Sensitivity of Drinking Water Sources
Surface water
Runoff
Ground water infiltration
Ground water
Infiltration from the surface
Injection of contaminants
Naturally occurring substances
Health effects caused by contaminated source water
Acute health effects mainly by -
viruses
pathogenic bacteria
parasites
protozoa
cysts
Chronic health effects mainly by -
volatile organic chemicals (VOCs)
inorganic chemicals (IOCs)
synthetic organic chemicals (SOCs)
Vulnerability Within the Distribution System
Backpressure can cause backflow to occur when a potable system is connected to a non-potable supply operating under a higher pressure than the distribution system by means of a pump, boiler, elevation difference, air or steam pressure, or other means.
Backflow is any unwanted flow of used or non-potable water, or other substances from any domestic, industrial, or institutional piping system back into the potable water distribution system.
Cross-connections and backflow represent a significant public health risk (US EPA, 2000b) by allowing chemical and biological contaminants into the potable water supply (a conclusion of the Microbial/Disinfection Byproducts Federal Advisory Committee (M/DBP FACA)).
A wide number and range of chemical and biological contaminants have been reported to enter the distribution system through cross-connections and backflow. Pesticides, sewage, antifreeze, coolants, and detergents were the most frequent types of contaminants reported.
Sources of Contaminants with Acute and Chronic Health Effects
Acute: Industrial activities Animal feeding operations Agriculture Septic systems and cesspools
Chronic: Industrial & commercial activities Agriculture Landfills & surface impoundments Urban uses
Early Warning System (EWS) Structure & Function
An effective EWS is an integrated system for deploying the monitoring technology, analyzing and interpreting the results, and utilizing the results to make decisions that protect public health.
An ideal contamination warning system that monitors toxic events in water should have the following features:
RapidSensitiveWide detection spectrum
ReliableContinuous
Fit for field testing User-friendly Inexpensive
EWS - Core Criteria
Currently, an EWS with all of these features does not exist.
However, there are some technologies that can be used to build an EWS that can meet certain core criteria:
provide rapid response
screen for a number of contaminants while maintaining sufficient sensitivity
perform as automated systems that allow for remote monitoring
Any monitoring system that does not meet these minimum criteria should not be considered an effective EWS.
EWS Design Considerations
There are many issues and water system characteristics that need to be considered when designing an EWS:
Planning and Communication
System Characterization
Target Contaminants
Planning and Communication
The objectives of the program should be defined clearly, and a plan should be developed for the-
Interpretation Use Reporting of monitoring results.
The plan should be developed in coordination with -The water utilityLocal and state health departmentsEmergency response units Law enforcement agencies
Local political leadership
System Characterization
The system should be characterized with respect to -
Access points
Flow and demand patterns
Pressure zones
If not already available, a hydraulic model should be constructed.
System vulnerabilities should be identified and characterized, preferably through a formal vulnerability assessment.
Target Contaminants
Even the most complex array of monitoring equipment cannot detect the entire spectrum of agents that could pose a threat to public health via contaminated water.
Thus, the design of an EWS should focus on contaminants that are thought to pose the most serious threat.
Many factors may go into this assessment, including:
the concentration of a particular contaminant that is necessary to cause harm
the availability and accessibility of a contaminant
the persistence and stability of a contaminant in an aqueous environment
the difficulty associated with detecting a contaminant in the water
EWS - The Tiered Approach
A balance between the need for screening function of the system (i.e., the ability to detect a wide range of contaminants) and the need for specificity (i.e., the ability to positively identify and quantify a specific contaminant) can be achieved through tiered monitoring.
First tier - continuous, real-time screen for a range of contaminants utilizing a broad-based screening technology such as assays designed to detect changes in toxicity.
Second tier - a positive result from the first stage would trigger the second stage of confirmatory analysis using more specific and sensitive techniques.
A positive result from the confirmatory analysis would trigger a response action.
Tiered Response Model
Increasing:
Certainty
Response
Cost
Observed Water Quality Change
)determined by broad-based continuous screening(
Automated Sample Collection
Confirmation Bioassay
Chemical Analysis
If positive
Public health Regulatory or Remedial Action
If positive
Broad Based Continuous Screening
A major problem in the development of early warning water quality monitoring systems is that there are an almost unlimited number of potential contaminants that could threaten a water asset.
While many products have been developed that monitor for specific contaminants or specific types of contaminants, it is impractical to design a system that can detect every potential threat to water quality.
One approach is to use biological organisms as living "sentinels" that will warn operators of contamination.
Sophisticated continuous and automatic biomonitors are now available that detect and alert whenever a notable change occurs in the behavior of the sensing organisms (such as, bacteria, fish, algae, mussels, daphnia).
Bioassays - Applications & Benefits
Mapping to identify toxicity/concentration hotspots
Selection of samples for further/more expensive analysis
Mapping after pollution incidents/accidents
“While there are several different organisms that can be used to monitor for toxicity (including bacteria, invertebrates, and fish), bacteria-based bio-sensors are ideal for use as early warning screening tools for drinking water security because bacteria usually respond to toxics in a matter of minutes”. [EPA - Biological Sensors for Toxicity-Water and Wastewater Security Product Guide]
The Luminescent bacteria provided by CheckLight offer the unique advantage of both automatic and hand held testing capabilities.
EWS Technology Selection
Performance of the chosen field deployable monitoring technology must meet the data quality objectives of the monitoring program that were defined during the design of the EWS and include:
Specificity
Sensitivity
Accuracy
Precision
Recovery
False positives/negatives rates
Alarm Levels
For the alarms to be triggered at the appropriate levels, one must identify the concentrations at which the agents pose a threat to human health.
The basis for setting alarm levels will depend on the capability of the EWS employed.
The alarm should be triggered by a combination of events, not a single detection, which may be a false positive.
Sensor Location and Density
The location and density of sensors in an EWS is dictated by the results of the system characterization, vulnerability assessment, threat analysis, and usage considerations.
Proper characterization of the distribution system, including usage patterns, and the location of critical system nodes (e.g., hospitals, law enforcement and emergency response agencies, government facilities, etc.) is necessary to design an effective monitoring network.
However, even if sensors can be optimally located within a distribution system, there may not be sufficient time to prevent exposure of a portion of the public to the contaminated water.
At best, monitoring conducted within the distribution system will provide time to limit exposure, isolate the contaminated water, and initiate mitigation/ remediation actions.
Data Management, Interpretation, and Reduction
One of the challenges of a continuous, real- time monitoring system is management of the large amounts of data that are generated.
Use of data acquisition software and a central data management center is critical.
The data management system should be capable of performing some level of data analysis and trending in order to assess whether or not an alarm level has been exceeded and minimize the rate of false alarms.
At a minimum, the system should notify operators, public health agencies, and/or emergency response officials.
In some cases, it may be appropriate to program the data management system to initiate preliminary response actions, such as closing valves or collecting additional samples. However, these initial responses should be considered simple precautionary measures, and public officials should make judgments regarding decisive response actions.
Acknowledgement; this presentation was adopted in part from: Safeguarding The Security Of Public Water Supplies Using Early Warning Systems: A Brief Review .J Hasan et al. Journal Of Contemporary Water Research And Education Issue 129, Pages 27-33, October 2004.
Response
The possible responses when an EWS triggers an alarm may include-
Modification to the drinking water system (e.g., shutdown, addition of disinfectants, etc.)
Notification (e.g., boil water advisory) either to the general public or to target communities or Subpopulations
Additional data gathering or monitoring
Follow-on surveillance and epidemiologic studies
No action, or some combination of these
The type of response will be dependent on the nature of both the threat to and the nature of the drinking water system, including the population it serves.
The ETV-Verified ToxScreen Technology Serves
as the Basis for the
AquaVerity
The comprehensive Solution for Water
Utilities to Ensure Drinking Water Safety
and Quality
AquaVerity Components
CCB - Continuous Contamination Biomonitor
PCB - Portable Contamination Biomonitor
CAS - Control & Analysis Software package
SIS - Solution Implementation Service package
Tiered Response Model
Increasing:
Certainty
Response
Cost
Observed Water Quality Change
)determined by broad-based
continuous screening(
Automated Sample Collection
Confirmation Bioassay
Chemical Analysis
If positive
Public health Regulatory or Remedial Action
If positive
PCB-TOX SPOT
CCB-TOC
AquaVerity
xxx
CheckLight’s Value Proposition
Functional Benefits:
Early detection of contamination in drinking water
Enabling to pinpoint location & boundaries of contamination sources
Reducing direct & indirect costs of illnesses & deaths
Saving lives, pain & agony
Reducing liability
Emotional Benefits:
Providing a sense of safety & security
Reducing perceived risk of malpractice/liability
For deployment in monitoring stations positioned at
strategic locations
Includes various monitoring models & re-fill reagent kits
(for detecting chemical & biological contaminants)
Easily integrated with other systems
Suspicious samples are captured by an automatic
sampler for further analysis
Easy installation, operation and maintenance
No need for adjustments due to changing
environmental conditions
Remotely operated & controlled
Requires minimal operator intervention
CCB - Continuous Contamination Biomonitor
Enables remote operation and control of multiple
CCB units from a control center.
Provides tools for long term research and rapid
response during emergency situations
Software add-ons enable the integration and
communication of AquaVerity with 3rd party
devices & management systems (such as
SCADA/GIS).
CAS – Control & Analysis Software
Graphic display of response to potential heavy metal contaminants
Graphic display of response to potential organic contaminants
Contamination alert
Instrument malfunction
All clear
CAS – User Interface
How does the AquaVerity solution
compare to competitive offers on the
market?
EWS Matrix (1)- Detection & Warning Capabilities
FactorMulti-ParameterOther Biomonitors
CheckLight’sAquaVerity
Method5-6 sensors5-20 live organismsOne million luminescent bacteria
Detection spectrum5-6 parametersWide range of contaminants, including unknown types.
Determines toxicityNoYesYes
Discrimination between organic & heavy metals Contaminants
NoNoYes
Detection sensitivity
Medium (depends on the parameter)
HighHigh
ContaminationBoundaries assessment
PartialNoYes, by using the portable detectors
EWS Matrix (2)- Implementation
FactorMulti-ParameterOther BiomonitorsCheckLight’sAquaVerity
Installation & maintenance
Complex due to variability of sensors used
Complex & requires on going human supervision
Very simple to install & maintain. Unattended operation.
Adjustment to changing water environment
ComplexComplexNo adjustment needed.
Effective coverage in large water networks
Limited to wide distribution. Depends on parameters mix & complexity
Limited distribution due to complexity & costs
Wide distribution possible due to simple installation, minimal training & maintenance.
On-Going usageMedium – requires skills & training
Complex - Requires skilled personnel & special training
Effort is minimal - reagents replacement once a month.
Overall reliabilityMedium. Depends on parameters used.
Low to Medium. Depends on biota used & environment. conditions
Very high. Includes built-in control mechanism.
Future EnhancementsunknownUnknownUpgrade re-fill kits with enhanced detection capabilities
EWS Matrix (3) - Cost Effectiveness
FactorMulti-ParameterOther BiomonitorsCheckLight’sAquaVerity
Initial capital investment
Low to very highDepending on chosen parameters
Medium to very highMedium
On going costsMedium due to complexity of sensors arrays and baseline build up
High due to the required human supervision
Low due to minimal intervention
Total cost of ownership
Medium to highHighLow to medium
Positioning
Sensitive to a broad range of
contamination sources
Reliable
Cost effective
Easy to operate
Customer oriented
CheckLight Ltd
P.O. Box 72, Qiryat Tivon 36000, Israel
Tel: 972 4 9930530 Fax: 972 4 9533176
[email protected] www.checklight.biz