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ENH 424 Study Guide - Midterm Guide: Nitrification, Distillation, Activated Carbon

Environmental Health
Course Code
ENH 424
Marilyn Lee
Study Guide

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ENH 424 Midterm Review
Lecture 1-Introduction
Drinking water in Canada
o 89% of Canadians rely on municipal water systems, 9% use private wells
o Guelph/Waterloo use ground water aquifers rather than lake water
Water-borne illness in Canada
o Estimated 100,000 illnesses/year
o No systematic collection and surveillance is fragmented/outbreaks not always reported
Burden of water-borne illness
o Globally 1.8 billion people use faecally contaminated drinking water source
Walkerton Outbreak
o May-June 2000, 65% of population was hospitalized with gastrointestinal infections ,
resulting in 7 deaths
o Had significant public health and economic impacts
o Brought considerable attention to water quality issues in Ontario
o Operators lacked proper training and expertise, MOE inspection failed to detect poor
operator practices
o Preventable by use of continuous chlorine residual/turbidity monitors
Multi-barrier approach
o Advocated by Health Canada to protect drinking water quality
Lecture 2-Drinking Water Legislation, Systems and Standards
Municipal water treatment plants
o Coagulation and Flocculation
Chemicals (alum, iron, salts) added to aggregate smaller particles and form
larger ones through coagulation
Floulatio asi stirs ater, partiles further lup ito flos
o Sedimentation
Gravity causes flocs to settle to bottom, can then be removed
o Filtration
Conventional-most common, dual-media filter of anthracite & sand
Direct-no sedimentation process, requires low turbidity water
Slow sand (gravity filtration) and diatomaceous earth (pressure filtration)-
mostly for water of low turbidity
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Membrane-microfiltration and ultrafiltration, frequently require some source of
o Disinfection/Distribution
primarily chlorine but sometimes UV or ozone included
other chemicals may be added to prevent distribution systems corrosion
fluoride may be added to prevent tooth decay
free chlorine residual-hypochlorous acid considered powerful disinfectant, low
levels maintained in drinking water distribution systems to ensure safety of
water after it is treated
Chloramination-application of ammonia and chlorine to produce a combined
chlorine residual (in the form of monochloramine), weak disinfectant but
sometimes used as it is highly persistent and less likely to form by-products
Drinking Water Legislation
o Ont. Reg. 170 covers sampling, testing, disinfection, reporting requirements for
municipal drinking water systems enforced by MOECC inspectors
o MOHLTC oversees small drinking water systems (SDWS) under Ont. Reg. 319/08
Designated Facilities
o Provide drinking water to people more at risk to illness, must follow special
requirements such as schools, health care facilities, restaurants, parks, campgrounds,
seiors failities, urseries, uiersities/olleges, eergey shelters
SDWS: Ont. Reg. 319/08
o Any place where general public has access to a washroom, drinking fountain, shower
o Hotels, seasonal trailer parks w less than 5 connections, community centers, places of
worship, golf clubs, provincial parks, commercial facilities
o Must have a designated trained operator and notify MOH before construction or
alteration and receive written permission before operating
o Must make any test results available for public inspection during business hours
o For seasonal systems (closed more than 60 days consecutively)
Sample for E. Coli
Notify MOH with opening date, contact info, test results
o Risk Assessment
Categorized as high, moderate or low risk usig MOHLTC ‘isk Categorizatio
(RCat) tool
High risk systems inspected every two years
Moderate/low risk systems inspected every four years
RCat considers source water, sampling history, treatment/distribution,
operations, users
o *Directives-required actions for operator based on RCat assessment, SDWS operators
may be required to
Install treatment devices
Establish specific frequencies, locations, methods of sampling
Sample specific biological, chemical, radiological or other parameters
Conduct other operational tests
Maintain specific records
Meet specified training requirements
Post/maintain warning signs for users to not consumer water (MOH approved)
o Adverse events-operators immediately report every adverse observation
(contamination, back flows, inappropriate water filtration) and adverse test results
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o Treatment
Required for surface water supplies, optional for groundwater supplies
Must be in continuous operation when water is supplied/maintained
Must maintain chlorine residual of 0.05mg/L or 0.25mg/L chloramine
Water treatment must be cut off if other treatment is used
Adequate supply must be stored safely and securely nearby
o Sampling
Generally taken at point where water enters distribution system
Chlorine residual samples taken anytime microbiological sample are taken
All testing to be done in licensed labs
Operators to follo orretie atios id a aderse oseratio/test result
occurs such as
Checking/fixing equipment
Shock chlorination
Flushing distributive system
Notifying users to boil water/use alternate source
Resampling and testing
Notifying MOH
Drinking Water Standards: Ontario
o Ont. Reg. 169/03 lists enforceable standards in drinking water
o Includes Maximum Acceptable Concentrations (MAC), aesthetic objectives (AO) and
operational guidelines (OG)
Drinking Water Guidelines: Canada
o Published by Health Canada, updated regularly and posted online
o To be considered for guidelines contaminants should meet all of the following criteria
Exposure could lead to adverse health effects in humans
Frequently detected or could occur in a large number of drinking water supplies
Could be found in drinking water levels sufficient to cause adverse health effects
Microbiological Standards
o Monitoring for all pathogens that could be present not technically or economically
feasible, faecal indicator bacteria used to verify microbiological safety of drinking water
E. Coli must not be detectable
Enteric protozoa 2-3 log reduction according to O. Reg. 170/03, minimum 3 log
reduction according to Health Canada
Indicator Organisms
o E. Coli indicates recent faecal contamination
o Total coliforms used to determine how well drinking water system is operating, can
survive and grow in distribution system so may not indicate contamination
o Municipal treatment plants should be tested weekly for E. Coli/total coliforms
o SDWS should be sampled once every 3 months
o Detection of E. Coli indicates inadequate treatment
o Detection of total coliforms in consecutive samples from the same site or more than
10% of samples in a given period should be investigated
Enteric Viruses and Protozoa
o Commonly associated with human waterborne illness
o Can survive for extended periods in water, high infectious
o Should be controlled using multi-barrier approach
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