Download Water, sewer and storm water systems and services

Chapter 2
Water, sewer, and stormwater
systems and services
Integrated urban water system
Water supply infrastructure systems
Water supply system
Water supply infrastructure systems
Water supply systems must deliver enough water of high
quality at sufficient pressure for domestic, commercial,
industrial, and municipal uses.
Needs must be met during peak demand periods and
during drought, as well as during periods of average
supply and demand.
A percentage of the water is normally unaccounted for
through leakage and other losses.
Also, standby water for fire fighting is essential….
Water supply infrastructure systems
Data on surface water systems from the American Water
Works Association (AWWA) illustrate management
parameters that can be measured:
• Percentage of plant source water from lake, reservoir,
river, or blended groundwater.
• Plant design capacity in millions of gallons per day.
• Average-day production in millions of gallons per day.
• Peak-day production in millions of gallons per day.
• Plant expansions in procurement or construction phase.
• Expansions planned within the next 5 years in millions
of gallons per day.
Water supply infrastructure systems
Data on surface water systems from the AWWA
illustrate management parameters that can be measured:
• Pretreatment
• Permanent pilot plant availability
• Average chemical cost for surface water treatment per
millions of gallons
• Total costs for residuals treatment and disposal per
year
Water supply infrastructure systems
For groundwater, the AWWA reports illustrate
management parameters that can be measured:
• Total number of wells
• Number of well fields/clusters
• Number of entry points to the distribution system
• Average-day production across all wells in millions of
gallons per day
• Peak-day production across all wells in millions of
gallons per day
Water supply infrastructure systems
For groundwater, the AWWA reports illustrate
management parameters that can be measured:
• Capacity expansions in procurement or construction
phase and expansions planned within the next 5 years
• Surface water effects on groundwater
• Wellhead protection program status
• Average chemical cost for groundwater treatment per
millions of gallons
• Total costs for residuals treatment and disposal per year
Water supply infrastructure systems
For delivered water, the AWWA reports:
• Annual water production in millions of gallons per
year for groundwater, surface water, and finished water
purchased from other systems.
• Volume of water delivered annually in millions of
gallons for residential, commercial/industrial,
municipal government, agricultural, and other types not
previously listed.
Water supply infrastructure systems
1. Water supply treatment
• Water supply treatment systems vary from none at all to
advanced systems.
• Depend on quality of source water and planned uses.
• Classified as physical, chemical, and biological.
• Treatment systems are normally located in compounds and
buildings, and include concrete and steel tanks; filter
basins; equipment for pumping, screening, chemical feed,
and other mechanical operations; and electronic control
systems.
• Management of these infrastructure systems requires
different approaches from that of underground piping.
Water supply infrastructure systems
1. Water supply treatment
Unit treatment processes can be classified by type:
• Pre-sedimentation
• Initial mixing
• Flocculation
• Sedimentation
• Filtration
• Disinfection
• Advanced techniques (to treat against inorganic,
organic, and radiological compounds)
Water supply infrastructure systems
1. Water supply treatment
The AWWA’s database includes a more detailed list
(selected examples are shown):
• Raw Water Storage/Pre-sedimentation
• Aeration
• Pre- and post-disinfection (Chlorine, Chlorine Dioxide, Ozone, UV
Radiation)
• Lime/Soda Ash Softening
• Re-carbonation with CO2
• In-Line Hydraulic, Mechanical, and Static processes
• Aluminum Salts, Iron Salts
• PH and Alkalinity Adjustment (including for corrosion control)
• Activated Silica, Clays, Anionic Polymers, Cationic Polymers,
Nonionic, Granular Activated Carbon, Powdered Activated
Carbon, Adsorption, Air Stripping, and Other Treatment Practices.
Water supply infrastructure systems
2. Transmission and distribution infrastructure system
The AWWA describes four types of pipes:
• Transmission lines: lines that carry water from source to
plant or from plant to distribution system.
• In-plant piping: piping located in pump stations or
treatment plants.
• Distribution mains: pipelines that distribute water around
a community.
• Service (services): small-diameter pipes from
distribution mains to use points.
Water supply infrastructure systems
2. Transmission and distribution infrastructure system
Water supply infrastructure systems
2. Transmission and distribution infrastructure system
Water supply infrastructure systems
2. Transmission and distribution infrastructure system
Water supply infrastructure systems
2. Transmission and distribution infrastructure system
Several types of pipe materials are used in transmission
and distribution systems.
Design criteria include strength, durability, corrosion
resistance, flow capacity, cost, maintainability, and
effect on water quality
Water supply infrastructure systems
2. Transmission and distribution infrastructure system
Other key aspects of distribution systems include:
• Tapping: Pipes must be tapped to connect new services
or laterals to existing lines.
• Valves: Different kinds of valves are used for different
purposes, including shut-off, flow control, and bleeding
off of air. Common valve types are gate, butterfly,
globe, plug or cone, and ball valve.
• Hydrants: Fire hydrants are also important components
of distribution systems.
Water supply infrastructure systems
2. Transmission and distribution infrastructure system
• Services and meters: These provide for direct water
diversion and measurement.
• Pumps: If gravity is insufficient to maintain system
pressures and flows, pumping is used.
• Storage: Tanks of different kinds may be used for insystem storage.
Water supply infrastructure systems
The AWWA provides the following data on use of
materials in distribution systems
• Pipe material
(Asbestos-Cement, Cast-Iron (Unlined), Cast-Iron
(Cement- Mortar Lined), Concrete Pressure,
Ductile-Iron (Unlined), Ductile-Iron (CementMortar Lined), Fiberglass Reinforced Plastic,
Polyethylene (PE), Polyvinyl Chloride (PVC),
Steel, Galvanized, Copper, or other types not
previously listed) See Table 2.3
Water supply infrastructure systems
The AWWA provides the following data on use of
materials in distribution systems
• Customer service lines
(Copper pipe, Lead pipe, Polybutylene (PB) pipe,
Polyethylene (PE) pipe, Polyvinyl Chloride (PVC)
pipe, Steel pipe, Cast-Iron pipe, Galvanized pipe,
Asbestos-Cement pipe, or other types not
previously listed, and the percentage of lead pipe
that is replaced annually)
Water supply infrastructure systems
The AWWA provides the following data on use of
materials in distribution systems
• Fire service lines
(Ductile-Iron pipe, Polyethylene (PE) pipe,
Polyvinyl Chloride (PVC) pipe, Steel pipe, CastIron pipe, Copper pipe, Asbestos-Cement pipe, or
other types not previously listed, and the number
of dedicated fire service lines)
Water supply infrastructure systems
The AWWA provides the following data on use of
materials in distribution systems
Storage facilities
(welded steel elevated tanks, welded steel standpipes,
welded steel ground storage reservoirs, bolted steel
standpipes, bolted steel ground storage reservoirs,
composite tanks (concrete supporting an elevated steel
tank), conventional reinforced concrete, pre-stressed
concrete or types not listed.)
Fire hydrants and storage tanks are important components of
distribution systems. In addition, valves, meters, and service
connections require regular maintenance to function well.
Water supply infrastructure systems
The AWWA provides the following data on use of
materials in distribution systems
• Main breaks, hydrants, retention time
(data for total number of hydrants, number of main
breaks, and average and maximum retention times in the
distribution system)
Water supply infrastructure systems
Water supply planning
• Demands for water vary during the year and during
the day.
• Peak hour data fall in the range of 1.5 to 12.0 times
the average hourly demand.
• Peak day rates fall generally in the range of 1.2 to
4.0 times the average day rate for the year.
• Treated system storage will usually be adequate for
a few days of use, and raw water storage might be a
year’s supply or more, depending on variability of
supplies.
Water supply infrastructure systems
Management organizations for water supply
Today, there are about 57,000 water supply utilities in
the U.S.
Most of the population is served by large systems (309
very large systems of more than 50,000 connections
serve 44% of the population), and a large number of
small systems serve a much smaller population (35,063
systems with fewer than 500 connections serve 2.3% of
the population)
Water supply infrastructure systems
Management organizations for water supply
Most U.S. water supply utilities are city water
departments, with private water companies and specialpurpose districts rounding out the total number.
The publicly owned companies are usually part of a city
department, a separate city department under a water
board or water commission, or a separate utility district.
Water supply infrastructure systems
Trends in water supply systems
As population increases and the attendant environmental
water needs are recognized, it becomes more difficult to
find new, unused sources of supply.
For this reason, a number of new approaches are used to
develop water. These include the followings:
Water supply infrastructure systems
Trends in water supply systems
• Dual use of water: where reclaimed and impaired (damaged) waters are
•
used for non-potable applications
Conservation systems: where “new” sources are created by saving
water. See next slide….
Innovative storage: such as aquifer–storage–recovery (ASR) systems.
•
• Conjunctive use: where water from different sources, such as surface
•
and groundwater, are managed jointly and perhaps blended.
Re-use: in which wastewater is treated and used again.
• Point-of-use treatment systems: portable water purification devices
are self-contained units that can be used by recreation, military personnel,
survivalists from untreated sources
• Bottled water.
Water supply infrastructure systems
Trends in water supply systems
Water conservation
Strategies
In implementing water conservation principles there are a number of key activities that may be beneficial:
1.Any beneficial reduction in water loss, use and waste of resources.
2.Avoiding any damage to water quality.
3.Improving water management practices that reduce or enhance the beneficial use of water.
Household applications
Water-saving technology for the home includes:
1.
2.
3.
4.
5.
6.
Low-flow shower heads sometimes called energy-efficient shower heads
Low-flush toilets and composting toilets.
Dual flush toilets.
Faucet aerators.
Raw water flushing where toilets use sea water or non-purified water
Wastewater reuse or recycling systems, allowing: Reuse of gray-water for flushing toilets or watering gardens
and Recycling of wastewater by purification at a water treatment plant.
7. Rainwater harvesting
8. High-efficiency clothes washers.
9. Weather-based irrigation controllers
10. Garden hose nozzles that shut off water when it is not being used, instead of letting a hose run.
11. Low flow taps in wash basins
12. Swimming pool covers to reduce evaporation
Commercial applications
Agricultural applications
Water supply infrastructure systems
Future Trends in the Water Supply Industry
• As the population grows, use/capita will drop.
• Environmental pressures will increase; within 20 years,
30% of species will be threatened or endangered.
• Human Resources will continue to be a big challenge.
• Desalting will improve.
• Farmland will disappear.
• Global warming will be a factor.
Water supply infrastructure systems
Unresolved issues in the water supply industry are
summarized periodically. Some that recur are:
• Funding for capital and O&M
• Public health concerns and health effects
• Access to water and water rights
• Disinfection practices and issues
• Public attitudes and political issues
• Protecting watersheds and surface water quality
• Preparedness for emergencies and disasters
• Managing small water systems
• Bacterial re-growth in distribution systems
• Sludge disposal practices
• Unaccounted-for water
Wastewater infrastructure systems
• Wastewater systems include sewers, collectors, transmission
mains, treatment plants, outfall sewers, and sludge
management systems
• Wastewater systems collect, transmit, treat, and dispose of
water supplies used by domestic, industrial, commercial, and
public users.
• They are the mirror image of water supply facilities
38
Wastewater infrastructure systems
Wastewater: is all water has been used, as for washing,
flushing, or in a manufacturing process, and so contains
waste products; and sewage.
Sewage: is water that comes from the toilet areas alone.
Sewage is the waste matter carried off by sewer drains and
pipes.
Sewerage: is the physical infrastructure, including pipes,
pumps, screens, channels etc. used to convey sewage from
its origin to the point of eventual treatment or disposal.
Sewer: is an artificial, usually underground conduit for
carrying off sewage or rainwater. Part of sewerage, the
infrastructure that conveys sewage.
39
Wastewater infrastructure systems
Separate sewers transport only sanitary and industrial
sewage, which may have received pretreatment.
Combined sewers are systems that transport sanitary
sewage and storm drainage mixed together.
Combined sewers have overflow points for wet weather
when treatment plant capacities are exceeded.
40
Wastewater infrastructure systems
• Infiltration and inflow are important infrastructure
problems of sewers.
• Infiltration is wastewater that enters the system from
leaking joints, cracks, breaks, porous walls, or other
indirect means.
• Inflow is storm water that enters from roof drains,
catch basins, manhole covers, or other routes
41
Wastewater infrastructure systems
• Treatment plants improve wastewater to meet water
quality standards
• Demands on wastewater systems related to use of water
• By comparing water use and wastewater treatment
records, a percentage can be determined
• In the U.S., the percentages range from around 60% in
dry regions to around 85% in humid regions
42
Wastewater infrastructure systems
Collection and transmission systems
Whereas water supply systems are normally looped pipes
under pressure, wastewater systems are usually branched
and flow under gravity.
The public sewer is usually a local collector of eight
inches or larger that leads to manhole junctions.
The design of the system will provide a gradual downhill
grade through the system to keep the wastewater flowing
at a velocity that keeps sewers clean and transports
material in the wastewater.
43
Wastewater infrastructure systems
The most common collection system materials are:
• Asbestos cement pipe
• Brick masonry
• Clay pipe (vitrified) ‫المزجج‬
• Concrete pipe, plain, reinforced, pressure, and cast-inplace
• Iron and steel (cast iron, ductile iron, fabricated steel)
• Plastic pipe
44
Wastewater infrastructure systems
Wastewater treatment systems
• In general, wastewater utilities provide treatment so
that disposed waters do not harm the environment or
public health.
• From 1900 to 1970, treatment systems focused on
removal of suspended and floatable materials,
treatment of biodegradable organics, and elimination
of pathogenic organisms.
• After 1972, standards were raised and treatment using
nitrogen and phosphorous was introduced.
• After 1980, more attention was given to public health
and treatments using toxic chemicals and trace
compounds that might have long-term health
consequences
45
Wastewater infrastructure systems
Wastewater treatment systems
• Peaking factors must be considered in wastewater plants.
• Domestic peaks may be two to five times the average
flows.
• Commercial and industrial peaks are between 1.5 and 2.5
times the average flows.
• Peaks at the treatment plant range between 1.8 and 4 times
the average.
• Low flows are usually not less than 0.4.
46
Wastewater infrastructure systems
Classification of wastewater treatment
Treatment systems are classified as primary, secondary, or
advanced (tertiary) treatment.
• Primary treatment consists of basic physical processes
such as: screening and sedimentation to remove floating
and solids that may settle.
• Secondary treatment consists of biological and chemical
processes to remove most of the organic matter.
• Advanced (tertiary) treatment, nutrients or special
constituents are removed.
47
Wastewater infrastructure systems
Classification of wastewater treatment
Wastewater treatment can also be classified as physical,
chemical, or biological.
Examples are the following:
• Physical unit operations (screening, mixing, flocculation,
sedimentation, flotation, filtration, gas transfer)
• Chemical unit processes (precipitation, adsorption,
disinfection)
• Biological unit processes (various biological processes,
such as activated sludge, trickling filter, stabilization
pond)
48
Wastewater infrastructure systems
Major contaminants removed by wastewater
treatment systems are the following:
• Suspended solids
• Biodegradable organics
• Volatile organics
• Pathogens
• Nutrients
• Heavy metals
• Dissolved organic solids
49
Wastewater infrastructure systems
Wastewater management issues focus on subjects as:
• Rewriting the Clean Water Act
• Security issues in the wastewater industry
• Toxic materials
• Costs of wastewater treatment
• Diffuse sources of pollution
• Total Maximum Daily Loads (TMDLs)
• Watershed management
• Storm water regulation
• Industrial pollution control
• Wastewater workforce renewal
50
Storm water infrastructure systems
Storm water systems consist of the minor storm water
system, which is similar to wastewater collection systems in
its use of gravity pipes to drain water from points of
generation to points of disposal; and major storm water
systems, which consist of large pipes and waterways of
different types.
In contrast to wastewater, storm water is generated at diffuse
points of land and building surfaces, rather than from points
of water use.
The storm water system is sometimes named “storm water
and flood control.
51
Storm water infrastructure systems
52
Even though the minor system contains small facilities, it requires
large pipes at downstream points.
53
Storm water infrastructure systems
For minor systems, the design storm varies in the range of 2 to
25 years, with common recommendations being 2 years in
residential areas and 5 to 25 years for commercial zones, where
less disturbance due to flooding can be tolerated.
For example, a 5-year design might be implemented with a rule
that storm drainage could be carried in a street gutter until the
quantity reached the top of a curb, and then an underground pipe
would be required.
Larger pipes would be required farther downstream in the
watershed.
The major systems are generally planned for the 100-year event
54
Storm water infrastructure systems
Storm water planning
• Drainage is regional and does not respect boundaries
between authorities or lands.
• Storm drainage is a subsystem of the urban water
system.
• Every urban area has two drainage systems (minor and
major).
• Runoff routing is a space allocation problem.
• Storm water problems should not be transferred from
one place to another.
• Urban drainage should be multi-purpose and multimeans.
55
Storm water infrastructure systems
Storm water planning
• Storm water systems should consider natural drainage
system functions.
• After development, storm water flows should remain at
predevelopment conditions and pollutant loadings should
be reduced.
• Storm water systems should be designed beginning at the
outlet.
• Storm water systems should receive regular maintenance.
56
Storm water infrastructure systems
Storm water planning
Planning for storm water systems requires monitoring data:
topographic, surveys, soils, and boundary data; hydrologic and
hydraulic data; regulatory and financial data.
Options include nonstructural and structural systems. Structural
systems can include natural and built systems, which can
include: major drainage ways, streets, storm sewers, inlets,
intersections, flow control devices, trash racks, detention, and
water quality mitigation structures.
Evaluating storm water systems entails recognizing that storm
water management systems provide drainage, flood control, and
water quality benefits.
57
Storm water infrastructure systems
Benefits of storm water systems include the following:
• Reduced flood damage and risk to life
• Land value enhancement
• Reduced traffic delays
• Reduced business and cleanup losses
• Reduced relief costs
• Increased recreation area
• Less disturbance
• Greater security
• Reduced health hazards
• Improved aesthetics
58