Appendices

Appendix A: Glossary

Aeration

Aeration systems add air to water and can be used to oxidize taste and odour-causing compounds or iron.

Air stripping

Air stripping systems remove gases from water and may be used to remove objectionable concentrations of dissolved gases (e.g., hydrogen sulphide, carbon dioxide), trihalomethanes or volatile organic compounds (VOCs).

Areal Standard Unit (ASU) Count

A unit of measurement used in the evaluation of the number of aquatic plankton, frequently algae, in water (this number is sometimes called the standing crop). A small volume of water is examined microscopically and the number of areal standard units counted. One areal standard unit is equal to four small squares in a Whipple grid at a magnification of 200. Areal standard units represent the number per unit volume.

Backflow

A hydraulic condition, caused by a difference in pressures, which causes nonpotable water or other fluid to flow into a potable water system.

Backpressure

A pressure that can cause water to backflow into the water supply when a user’s water system is at a higher pressure than the public water system.

Backsiphonage

A form of backflow caused by a negative or sub-atmospheric pressure within a water system.

Blowdown

The continuous or intermittent removal of a portion of any process flow to maintain the constituents of the flow within desired levels.

The water discharged from a boiler, cooling tower or membrane water treatment system to dispose accumulated dissolved solids.

Capacity

The flow rate that a treatment process unit or process train or treatment plant is capable of producing. See also gross capacity, net capacity and rated capacity.

Carbon usage rate

A measure of the capacity of granular activated carbon or powdered activated carbon to remove a contaminant to a specified level. Usage rates are often expressed in terms of weight of activated carbon used per unit volume treated.

Cavitation

The formation and sudden collapse of vapour bubbles in a liquid, usually resulting from local low pressures, as on the trailing edge of a propeller. This phenomenon develops a momentary high local pressure that can mechanically destroy a portion of a surface on which the bubbles collapse. Cavitation can occur in pumps when the suction side has insufficient head for the current.

Certificate of Approval

A legal instrument issued by a Director under the Safe Drinking Water Act, 2002 to the owner of a municipal drinking-water system to authorize the establishment, replacement, alteration, use and operation of the system. With the implementation of the Licensing Program, a C of A will be replaced by a combination of a Drinking Water Works Permit (DWWP) for the establishment or alteration of the system and a Municipal Drinking Water Licence (Licence) to authorize the use and operation of the system.

Chemically enhanced backwash

Backwashing of a membrane with the addition of chlorine or other chemicals. Also referred to as maintenance clean or wash, enhanced flux maintenance, or extended backpulse clean.

Clean-in-place (CIP)

A chemical cleaning process in which the membrnes in a membrane water treatment system (1) are not removed from their housings (pressure vessels) or the system and (2) are cleaned by being exposed to cleaning solutions, which are commonly recirculated through the cleaning system and membranes.

Clearwell

A tank or vessel used for storing treated water. Typical examples of storage needs include (1) finished water storage to prevent the need to vary the rate of filtration with variations in distribution system demand, and (2) backwash water for filters. Clearwells are located on-site at a water treatment plant. A clearwell is also called a filtered-water reservoir.

Coagulant aid

A chemical added during coagulation to improve the process by stimulating floc formation or by strengthening the floc so it holds together better. Such a chemical is also called a flocculant aid.

Compound gauge

A compound gauge is used to measure atmospheric and vacuum pressure. The vacuum pressure is generally measured in mm of Hg. Atmospheric pressure is measured in kilopascals (kPa) or pounds per square inch (psi).

Concentrate

The concentrated solution containing constituents removed or separated from the feedwater by a membrane water treatment system. Concentrate is also called reject, brine, retentate or blowdown, depending on the specific membrane process.

Contaminant

Any physical, chemical, biological or radiological substance or undesirable matter in water.

Continuous monitoring equipment

Equipment that, at intervals appropriate for the process and parameter being monitored, automatically tests for the parameter directly in the stream (or in the case of UV application, through the stream) of water being treated or distributed, or in a continuous sample taken from the stream of water being treated or distributed, where a continuous sample is a continuous stream of water flowing from the stream of water being treated or distributed to the monitoring equipment.

Cross-connection

The physical connection of a safe or potable water supply with another water (e.g. wastewater, treatment chemicals, or raw or partially treated water) supply of unknown or contaminated quality or such that the potable water could be contaminated or polluted.

CT

The product of disinfectant concentration (in milligrams per litre) determined before or at the first customer and the corresponding disinfectant contact time (in minutes). Units are milligram minutes per litre.

Demand

The amount of water used by consumers during a certain time interval from a water system.

Disinfection by-products (DBP)

A chemical by-product of the disinfection process. Disinfection by-products are formed by the reaction of the disinfectant, natural organic matter and the bromide ion (Br-). Some disinfection by-products are formed through halogen (e.g., chlorine or bromine) substitution reactions; i.e., halogen-substituted by-products are produced. Other disinfection by-products are oxidation by-products of natural organic matter (e.g., aldehydes-RCHO). Concentrations are typically in the microgram-per-litre or nanogram-per-litre range.

Disinfection Procedure

Procedure for Disinfection of Drinking Water in Ontario (PIBS 4448e01).

Downsurge

Pipeline pressure surge, which is negative because its magnitude is below the normal operating pressure of the pipeline.

Drinking-water system

A system of works, excluding plumbing, that is established for the purpose of providing users of the system with drinking water and that includes:

1. Anything used for the collection, production, treatment, storage, supply or distribution of water;
2. Anything related to the management of residue from the treatment process or the management of the discharge of a substance into the natural environment from the treatment system; and
3. A well or intake that serves as the source or entry point of raw water supply for the system.

Drinking Water Works Permit (DWWP)

A legal instrument issued by a Director under the Safe Drinking Water Act to the owner of a municipal drinking-water system to authorize the establishment, replacement or alteration of the system. With the implementation of the Licensing Program, the Certificate of Approval (C of A) will be replaced by a combination of a Drinking Water Works Permit (DWWP) for the establishment or alteration of the system and a Municipal Drinking Water Licence (Licence) to authorize the use and operation of the system.

Elevated tank

A water storage facility located on and supported by a tower constructed at an elevation to provide useful storage and pressure for a water pressure plane.

Empty bed contact time (EBCT)

A standard convention or measure of the time during which a water to be treated is in contact with the treatment medium. The empty bed contact time is calculated by dividing the empty volume in a contactor that will be occupied by the treatment medium by the flow rate:

• EBCT = V ⁄ Q Where (in any consistent set of units):
• V = the volume of the vessel
• Q = the flow rate

Because the treatment medium, such as granular activated carbon, will occupy some volume, the empty bed contact time overestimates the actual time that the flow resides in the contactor.

Fire protection

The ability to provide water through a distribution system for fighting fires in addition to meeting the normal demands of water usage.

Floating storage (floating on the system)

A method of operating a water storage facility such that daily flow into the facility approximately equals the average daily demand for water. When consumer demands for water are low, the storage facility will be filling. During periods of high demands, the facility will be emptying.

Flux

For a membrane separation process, the volume or mass of permeate passing through the membrane per unit area per unit time. Solvent (water) flux rate is commonly expressed in gallons per square foot per day, or cubic metres per square metre per second, or metres per second.

Gross capacity

The maximum flow rate into a treatment process unit or process train or treatment plant while producing treated water of acceptable quality.

Groundwater

The water contained in interconnected pores located below the water table in an unconfined aquifer or in a confined aquifer. For the purpose of this document, a raw water supply which is groundwater means water located in subsurface aquifer(s) where the aquifer overburden and soil act as an effective filter that removes microorganisms and other particles by straining and antagonistic effect, to a level where the water supply may already be potable but disinfection is required as an additional health risk barrier, unless the ministry has granted a drinking-water system relief, or requirements for exemption have been met in accordance with O.Reg. 170/03.

Groundwater under Direct Influence of Surface Water (GUDI)

Groundwater having incomplete/undependable subsurface filtration of surface water and infiltrating precipitation.

Gt

The product of the velocity gradient, G (expressed in units per second), and the flocculation or mixing times (in seconds).

Hydropneumatic tank (or pressure tank)

A tank that is used in connection with a water distribution system for a single household, for several houses, or for a portion of a larger water system, which is airtight and holds both air and water, and in which the air is compressed and the pressure is transmitted to the water.

Instantaneous flow rate

A flow rate of water measured at particular instant, such as by a metering device.

L10

The predicted service life, for a given population of identical bearings operating under controlled conditions, for which 90% will meet or exceed the predicted life, and 10% will fail before reaching that value.

Langelier saturation index

The most known of the calcium carbonate (CaCO₃) saturation indexes, the formula for the Langelier index is based on a comparison of the measured pH of a water (pHa) with the pH the water would have (pHs) if at saturation with CaCO₃ (calcite form) given the same calcium hardness and alkalinity for both pH cases. The basic formula is LSI = pHa pHs.

Material safety data sheet (MSDS)

Information on the use, handling and storage of specific chemicals or products. Material safety data sheets contain mandated types of information concerning physical characteristics, reactivity, required personal protective equipment and other safeguards.

Mass transfer zone (MTZ)

The place in an adsorption or ion exchange bed where the concentration of adsorbate in solution is changing with depth. The concentration gradient corresponds to the gradual transition of the adsorbent or ion exchange resin from fresh (or virgin) to spent (or exhausted). Aeration or air-stripping columns also have mass transfer zones as the gas or liquid changes from under-saturated to the equilibrium concentration with height.

Membrane backwash

A cleaning operation that typically involves periodic reverse flow to remove particulate accumulated on the membrane surface. Also referred to as backpulse, backpulse clean, or flux maintenance.

Membrane reject

The material retained or filtered out by the membrane. Also known as membrane concentrate.

Ministry

The Ontario Ministry of the Environment.

Municipal Drinking Water Licence

A legal instrument issued by a Director under the Safe Drinking Water Act to the owner of a municipal drinking-water system to authorize the use and operation of the system. With the implementation of the Licensing Program, the Certificate of Approval (C of A) will be replaced by a combination of a Drinking Water Works Permit (DWWP) for the establishment or alteration of the system and a Municipal Drinking Water Licence (Licence) to authorize the use and operation of the system.

Muskeg

A bog, usually a sphagnum bog, frequently covered with grassy tussocks, growing in wet, poorly drained boreal regions, often in areas of permafrost.

Net capacity

The daily flow rate from a treatment process or treatment plant accounting for process losses and in-plant water uses, as well as otherwise productive time that a unit or process train is off-line for backwash, routine maintenance or repair.

Net positive suction head (NPSH)

A measure of the pressure at the suction side of the pump, including atmospheric pressure and vapour pressure of the liquid being pumped.

Peak demand

The maximum momentary load (expressed as a rate) placed on a water treatment plant, distribution system or pumping station. It is usually the maximum average flow in one hour or less, but it may be specified as instantaneous.

Permeate

For a pressure-driven membrane treatment process, the portion of the feed solution that passes through the membrane.

Point of impingement

Any point on the ground or on a receptor, such as nearby buildings, located outside the emitter’s property boundaries at which the highest concentration of a contaminant caused by the aggregate emission of that contaminant from a facility is expected to occur.

Primary disinfection

A process or a series of processes intended to remove and/or inactivate human pathogens such as viruses, bacteria and protozoa, potentially present in influent water before the water is delivered to the first consumer.

Rated capacity

Volume of treated water that meets all applicable Ontario drinking water quality regulations including the aesthetic water quality objectives and that may be made available by the water treatment plant for delivery to the drinking-water distribution system in any 24 hour period (usually provided as a rate in m³/d).

Rate controlling step

The slowest elementary process in a sequence. The products of a sequence of processes can be formed no faster than the rate of the slowest step in the sequence. Therefore, if one of the steps in a sequence is much slower than all the others, the rate of the overall reaction will be limited by, and be exactly equal to, the rate of this slowest step.

Raw water

Water from the supply source prior to treatment.

Recovery clean

Recirculating a cleaning solution and/or soaking the membranes in a cleaning solution to restore the membrane transmembrane pressure. Also known as clean-in-place (CIP).

Recovery rate

In a membrane water treatment system, the fraction of the feedwater that is converted to permeate, filtrate or product. Recovery is sometimes called permeate recovery, product water recovery, feedwater recovery, or conversion.

Residuals

Any gaseous, liquid, or solid by-product of a treatment process that ultimately must be disposed of. For example, in a fixed-bed filter for removing particles from water, both the filter backwash water and the solids in the backwash water are residuals. A residual is often called a sludge.

The concentration of free available disinfectant (chlorine) remaining after a given contact time under specified conditions or treatment chemical after the final process (i.e. in the treated water).

Secondary disinfection

The maintenance of a disinfectant residual in the distribution system to protect the water from microbiological re-contamination, reduce bacterial re-growth, control biofilm formation, and serve as an indicator of distribution system integrity (loss of disinfectant residual indicating that the system integrity has been compromised). Only chlorine, chlorine dioxide and monochloramine provide a persistent disinfectant residual and can be used for the maintenance of a residual in the distribution system.

Sludge

A term that is being replaced by the term residuals. It has the following meanings:

The accumulated solids separated from a liquid, such as water, during processing.

Organic deposits on the bottoms of streams or other bodies of water.

The removed material resulting from chemical treatment, coagulation, flocculation, sedimentation, or flotation (in which case the sludge is called float) of water.

Any solid material containing large amounts of entrained water and collected during water treatment.

Specific throughput

The volume of water passed through an ion exchange resin bed or water treatment system before the exchanger or system reaches exhaustion.

Standpipe

A high tank, usually small in diameter compared to height, for holding water. This water is used to maintain pressure in a water supply system and as storage for fire protection.

Storage tank

A compartment used to accumulate the product water from a water treatment unit so that sufficient quantity, pressure, or both are available for intermittent periods of higher flow rate water use.

Surface Water

Water bodies (lakes, wetlands and ponds, including dug-outs), water courses (rivers, streams, drainage ditches), infiltration trenches and areas of temporary precipitation ponding.

T10

The length of time during which not more than 10% of the influent water passes through a process. The use of T10 ensures that 90% of the water will therefore have a longer contact time.

Tank

A structure or container used to hold solids or liquids for such purposes as aeration, disinfection, equalization, holding, sedimentation, treatment, mixing, dilution, feeding, or other handling of chemical additives.

Technical Support Document

Technical Support Document for Ontario Drinking Water Standards, Objectives and Guidelines (PIBS 4449e01).

Total dynamic head (TDH)

The difference in height between the hydraulic grade line on the discharge side of the pump and the hydraulic grade line of the suction side of the pump. This head is a measure of the total energy that a pump must impart to the water to move it from one point to another.

Treated water

Water that has been subjected to treatment processes.

Turndown ratio

The ratio of the design range of an instrument to the range of acceptable accuracy or precision.

Velocity Gradient (G)

A measure of the mixing intensity in a water process. The velocity gradient, which is expressed in units per second, is dependent on the power input, the viscosity and the reactor volume. Very high velocity gradients (greater than 300 per second) are used for complete mixing and dissolution of chemicals in a coagulation process, whereas lower values (less than 75 per second) are used in flocculation to bring particles together and promote agglomeration.

Water works

Any part of a drinking-water system including collection, production, treatment, storage, supply and distribution of water, or any part of such works.

Watershed

The drainage basin area contained within the bounds specified by a divide and above a specified point on a stream. A watershed is also called a catchment area, drainage area or drainage basin.

Wet Well

A pumping wet well is used to ensure that a minimum volume is available to be pumped to subsequent unit processes or the distribution system. The level in the wet well may vary, and the pumping rate may be changed, to respond to needed changes in the flow rate and to permit continuous plant operation.

Appendix B: Units of measure

Appendix C: Acronyms & Abbreviations

Appendix D: Table of references

PIBS 6881e