Requirements to produce high quality water

Requirements to produce high quality water Stephen Stanley, Ph.D., P.Eng. EPCOR Water Services

Capable Plant Model High Quality Treated Water Operation (process control) Capable Plant Administration Design Maintenance

Capable Plant • A capable plant means if it is managed, operated and maintained properly, the plant has the required infrastructure to meet all requirements • Criteria for capable plant largely dependent on regulation

Capable Plant • Requirements constantly changing as new information becomes available • turbidity requirements have gone from 5 NTU to 1 NTU to 0.5 NTU and now proposed to go to 0.3 NTU • Requirements for a capable plant also dependent on raw water source • ground water - disinfection • surface waters - filtration and disinfection

Capable Plant - Giardia Example

Capable Plant Multi-barrier Approach • Water treatment uses the concept of multi-barriers to meet treatment requirements • a number of treatment processes which are each barriers for contaminants • Giardia example for 4 log removal • Clarification 0.5 log removal • Filtration 2.0 log removal • Disinfection 1.5 log removal

Capable Plant - Cryptosporidium • One of the greatest challenges facing the water industry • Regulations just starting (US EPA and Canada) • Resistant to chlorine (loss of major barrier) • For conventional treatment must rely on particle removal • UV and ozone disinfection effective

Capable Plant - Regulation • Regulations generally based on the concept of reducing the risk associated with water to an “acceptable” level • other factors include available technology and economics • Poorer standards result in greater risk that public health can compromised • typically event related (when plant challenged)

Capable Plant - Summary • Requirements of a capable plant dependent on regulation • Also dependent on raw water source • Capability of plant restricted to design flow rates • A capable plant only provides the ability to produce high quality water if proper administration, maintenance and operational systems are in place

Adminstration • Relates to having administrative policies, and staffing and funding requirements needed to produce high quality water • Requires a commitment from senior administration to produce high quality water • Needs quality assurance and quality control programs to ensure high quality water • Must ensure adequate staffing and funding are available

Design • Design of a treatment facility must not only meet requirements for the capable plant but must also consider operational and maintenance realities • Design should also consider technical expertise required

Maintenance • To make a capable plant sustainable, regular maintenance must occur • Maintenance activities must consider operational constraints and must be planned accordingly • For critical systems redundancy may be required

Operations - Process Control • Water treatment of surface waters, especially those treating river waters is a very dynamic process • raw water quality may vary from a turbidity of 1 NTU to over 1000 NTU • water demand may vary by 3 times • Treatment plants must constantly vary operating conditions (chemical doses, flows, etc.)

Operations - Process Control • For process control require: • a measure of the state of the system • comparison of the current state to the desired state • an action (for example a change in chemical dose) to return the system to the desired state

Challenges in Process Control • Multiple and conflicting objectives • water quantity vs. water quality • disinfection vs. disinfection by-products • Multiple operating parameters • must simultaneously adjust more than one chemical dose and operating conditions

Challenges in Process Control • Long residence time in plant • if treated water turbidity increases and requires change in coagulant dose at front of plant, can have 3 to 5 hours of water in the plant that must pass through before change will be noticed • requires intermediate assessment of treatment process

Challenges in Process Control • No standard methods to determine proper chemical dosing • must rely heavily on operator experience • must ensure available tools are being used (jar tests)

Operations - Process Control • Upsets can occur in water treatment • Must have clearly defined emergency response plans • Should have programs such as a boiled water notice in place • Can not wait for illness

Production of High Quality Water • Requires not only a capable plant but proper administration, design, maintenance and operations • Failure in any of these areas significantly increases the risk to public health

The Challenge • Requirements for the production of high quality of water is largely independent of the size of the community • The complexity of the treatment system is largely dependent on the quality of the raw water • The challenge is implementing the requirements in smaller communities

Requirements to produce high quality water