Water Supply System General Design Considerations

By | April 7, 2020

Generally the design of any water supply system or water treatment process encompasses a broad area. Application of this general guide is dependent upon the type of system or process involved. The design basis for the system including the water source and treatment facilities shall be for maximum day demand at the design year.

Water supply and treatment system design shall consider the following:

  • functional aspects of the plant layout,
  • provisions for future plant expansion,
  • provisions for expansion of the plant waste treatment and disposal facilities,
  • access roads,
  • site grading,
  • site drainage,
  • walks,
  • driveways,
  • chemical delivery.

Design of Building Layout

Design shall provide details or recommendations for:

  • adequate ventilation,
  • adequate lighting,
  • adequate heating,
  • adequate drainage,
  • dehumidification equipment, if necessary,
  • accessibility of equipment for operation, servicing, and removal,
  • flexibility of operation,
  • operator safety,
  • convenience of operation,
  • chemical storage and feed equipment in a separate room to reduce hazards and dust problems.

The appropriate regulating authority must be consulted regarding any structure which is so located that normal or flood stream flows may be impeded.

Consideration for Utilities of Structure

Electrical Controls: Main switch gear electrical controls shall be located above grade, in areas not subject to flooding. All electrical work shall conform to the requirements of the National Electrical Code or to relevant state and/or local codes.

Standby Power: Dedicated Standby power shall be required by the reviewing authority so that water may be treated and/or pumped to the distribution system during power outages to meet the average day demand. Alternatives to dedicated standby power may be considered by the reviewing authority with proper justification.

Carbon monoxide detectors are recommended when fuel-fired generators are housed.

Workshop Space & Storage: Adequate facilities should be included for workshop space and storage consistent with the designed facilities.

Laboratory Facilities for Water Supply Facility

Each public water supply shall have its own equipment and facilities for routine laboratory testing necessary to ensure proper operation.

Laboratory equipment selection shall be based on the characteristics of the raw water source and the complexity of the treatment process involved.

Water testing laboratory test kits which simplify procedures for making one or more tests may be acceptable.

An operator or chemist qualified to perform the necessary laboratory tests is essential.

Analysis conducted to determine compliance with drinking water regulations must be performed in an appropriately certified laboratory in accordance with Standard Methods for the Examination of Water and Wastewater or approved alternative methods.

Persons designing and equipping laboratory facilities shall confer with the reviewing authority before beginning the preparation of plans or the purchase of equipment.

Methods for verifying adequate quality assurances and for routine calibration of equipment should be provided.

Water Testing Equipment’s

As a minimum, the following laboratory equipment shall be provided:

Surface water supplies shall provide the necessary facilities for microbiological testing of water from both the treatment plant and the distribution system.  The reviewing authority may allow deviations from this requirement.Water Supply System General Design Consideration

Surface water supplies shall have a nephelometric turbidimeter meeting the requirements of Standard Methods for the Examination of Water and Wastewater.

Each surface water treatment plant utilizing flocculation and sedimentation, including those which lime soften, shall have a pH meter, jar test equipment, and titration equipment for both hardness and alkalinity.

Each ion‑exchange softening plant, and lime softening plant treating only groundwater shall have a pH meter and titration equipment for both hardness and alkalinity.

Each iron and/or manganese removal plant shall have test equipment capable of accurately measuring iron to a minimum of 0.1 milligrams per liter, and/or test equipment capable of accurately measuring manganese to a minimum of 0.05 milligrams per liter.

Public water supplies which chlorinate shall have test equipment for determining both free and total chlorine residual by methods in Standard Methods for the Examination of Water and Wastewater.

Public water supplies which fluoridate shall have test equipment for determining fluoride by methods in Standard Methods for the Examination of Water and Wastewater.

Public water supplies which feed poly and/or orthophosphates shall have test equipment capable of accurately measuring phosphates from 0.1 to 20 milligrams per liter.

Other Physical facilities: Sufficient bench space, adequate ventilation, adequate lighting, storage room, laboratory sink, and auxiliary facilities shall be provided.

Air conditioning may be necessary depending upon the local climate.

Water Monitoring Equipment’s

Water treatment plants should be provided with equipment (including recorders, where applicable) to monitor the water as follows:

Plants treating surface water and ground water under the direct influence of surface water should have the capability to monitor and record turbidity, free chlorine residual, water temperature and pH at locations necessary to evaluate adequate CT disinfection, and other important process control variables as determined by the reviewing  authority.

Continuous monitoring and recording may be required.

Plants treating ground water using iron removal and/or ion exchange softening should have the capability to monitor and record free chlorine residual.

Ion exchange plants for nitrate removal should continuously monitor and record the treated water nitrate level.

Sample Taps: Sample taps shall be provided so that water samples can be obtained from each water source and from appropriate locations in each unit operation of treatment, and from the finished water. Taps shall be consistent with sampling needs and shall not be of the petcock type. Taps used for obtaining samples for bacteriological analysis shall be of the smooth-nosed type without interior or exterior threads, shall not be of the mixing type, and shall not have a screen, aerator, or other such appurtenance.

Facility Water Supply Requirements

The facility water supply service line and the plant finished water sample tap shall be supplied from a source of finished water at a point where all chemicals have been thoroughly mixed, and the required disinfectant contact time has been achieved. There shall be no cross‑connections between the facility water supply service line and any piping, troughs, tanks, or other treatment units containing wastewater, treatment chemicals, raw or partially treated water.

Wall Castings: Consideration shall be given to providing extra wall castings built into the structure to facilitate future uses whenever pipes pass through walls of concrete structures.

Water Meters: All water supplies shall have an acceptable means of measuring the flow from each source, the washwater, the recycled water, any blended water of different quality, and the finished water.

Water Supply Piping Color Codes

To facilitate identification of piping in plants and pumping stations it is recommended that the following color scheme be utilized:

Water Lines

Raw or Recycle: Olive Green

Settled or Clarified: Aqua

Finished or Potable: Dark Blue

Chemical Lines

Alum or Primary Coagulant: Orange

Ammonia: White

Carbon Slurry: Black

Caustic: Yellow with Green Band

Chlorine (Gas and Solution): Yellow

Chlorine Dioxide: Yellow with Violet Band

Fluoride: Light Blue with Red Band

Lime Slurry: Light Green

Ozone: Yellow with Orange Band

Phosphate Compounds: Light Green with Red Band

Polymers or Coagulant Aids: Orange with Green Band

Potassium Permanganate: Violet

Soda Ash: Light Green with Orange Band

Sulfuric Acid: Yellow with Red Band

Sulfur Dioxide: Light Green with Yellow Band

Waste Lines

Backwash Waste: Light Brown

Sludge: Dark Brown

Sewer (Sanitary or Other): Dark Gray

Other

Compressed Air: Dark Green

Gas: Red

Other Lines: Light Gray

For liquids or gases not listed above, a unique color scheme and labeling should be used. In situations where two colors do not have sufficient contrast to easily differentiate between them, a six‑inch band of contrasting color should be on one of the pipes at approximately 30 inch intervals.

The name of the liquid or gas should also be on the pipe.  In some cases it may be advantageous to provide arrows indicating the direction of flow.

Disinfection Requirements

All wells, pipes, tanks, and equipment which can convey or store potable water shall be disinfected in  accordance with current applicable regulatory procedures.

Quality plans or specifications shall outline the procedure and include the disinfectant dosage, contact time, and method of testing the results of the procedure.

Operation & Maintenance Manual

An operation and maintenance manual including a parts list and parts order form, operator safety procedures and an operational trouble-shooting section shall be supplied to the water works as part of any proprietary unit installed in the facility. This manual must accompany the basic O&M instructions from manufacturers.

Provisions shall be made for operator instruction at the start‑up of a plant or pumping station.

Safety & Security Requirements

Consideration must be given to the safety of water plant personnel and visitors. The design must comply with all applicable safety codes and regulations that may include the Uniform Building Code, Uniform Fire Code, National Fire Protection Association Standards, and state and federal OSHA standards.

Items to be considered include noise arresters, noise protection, confined space entry, protective equipment and clothing, gas masks, safety showers and eye washes, handrails and guards, warning signs, smoke detectors, toxic gas detectors and fire extinguishers.

Security measures shall be installed and instituted as required by the reviewing authority. Appropriate design measures to help ensure the security of water system facilities shall be incorporated.

Such measures, as a minimum, shall include means to lock all exterior doorways, windows, gates and other entrances to source, treatment and water storage facilities.

Other measures may include fencing, signage, close circuit monitoring, real-time water quality monitoring, and intrusion alarms.

Flood Protection: Other than surface water intakes, all water supply facilities and water treatment plant access roads shall be protected to at least the 100 year flood elevation or maximum flood of record, as required by the reviewing authority. A free board factor may also be required by the reviewing authority.

Miscellaneous Considerations

Chemicals and water contact materials shall be approved by the reviewing authority or meet the appropriate ANSI/AWWA and/or ANSI/NSF standards.

Consideration must be given to the design requirements of other federal, state, and local regulatory agencies for items such as safety requirements, special designs for the handicapped, plumbing and electrical codes, construction in the flood plain, etc.