J^w', 76 A

NBSIR 79-1770 DEC 1 3 1979

The Potential for Energy

Savings With Water Conservation

Devices

Robert L. Palla, Jr.

Center for Consumer Product Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

July 1979

Issued September 1979

Final Report

U S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

AU 0»

NBSIR 79-1770

THE POTENTIAL FOR ENERGY

SAVINGS WITH WATER CONSERVATION

DEVICES

Robert L. Palla, Jr.

Center For Consumer Product Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

July 1979

Issued September 1979

Final Report

U S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Luther H. Hodges, Jr., Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
.1

r • - ,5 ' • . ’ - ' 1 r ^
ABSTRACT

With t^he use of residential water saving devices, substantial

decreases in water consumption may be realized. Perhaps of even greater

significance, however, are the resultant reductions in water-related energy

requirements — for water supply, wastewater treatment, and water heating.

Through a survey of water-related energy use, a relationship between

water usage and energy consumption is developed. Results obtained indicate

that energy requirements for water heating far exceed those for water

supply and wastewater treatment. Based on estimates of residential water

consumption with and without water conserving products, the potential for

energy savings is assessed. Reduction in household water heating energy

consumption of about 35 percent are predicted with the use of "conventional"

water saving products. Also considered in this study are the energy saving

potentials of grey water recycling and grey water heat recovery systems.

Key Words

Energy; energy consumption; grey water; heat recovery; recycling;

residential; wastewater treatment; water; water conservation; water heating;

water usage

1

TABLE OF CONTENTS

Page

ABSTRACT i

LIST OF TABLES iii

LIST OF FIGURES iii

1. Introduction 1

2. Domestic Water Use In Perspective 1

3. Water-Related Energy Use 2

3.1 Energy Requirements for Water Supply 3

3.1.1 Obtaining Water 3

3.1.2 Treating Water 3

3.1.3 Distributing Water 5

3.2 Energy Requirements for Wastewater Treatment 5

3.3 Energy Requirements for Residential Water Heating 8

3.4 Water Related Energy Requirements — Summary 9

4. Domestic Water Use and Corresponding Energy Requirements 10

5. Potential For Energy Savings 10

5.1 Energy Savings Through Water Conservation 10

5.1.1 Effects of Reduced Flow 10

5.1.2 Water Saving Devices 13

5.1.3 Potential Savings 14

5.1.4 Actual Versus Predicted Savings 15

5.2 Energy Savings Through Water Recycling 17

5.3 Energy Savings Through Grey Water Heat Recovery 19

6. Conclusions 22

7. References 23

ii

LIST OF TABLES

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

Table 8.

Table 9.

Table 10.

Figure 1.

Energy Requirements for Water Treatment

Energy Requirements for Water Supply

Estimated Energy Requirements for Wastewater Treatment

Water Heaters In Service — Breakdown By Fuel Type

Energy Requirements for Water Heating

Current Residential Water Usage and Corresponding Energy

Consumption

Water Consumption of Standard and Water Saving Products

Residential Water Usage and Corresponding Energy Consumption With

Conventional Water Saving Devices

Percent of Jurisdictions Regulating the Water Consumption of

Plumbing Fixtures

Thermal Energy Flows for Grey Water

LIST OF FIGURES

Water Withdrawals and Fresh Water Consumption in the United

States in 1970

Figure 2. The Reuse Potential of Household Wastewater

1. INTRODUCTION

Recently, many danestic water conservation and water-related energy

conservation systems and devices have been proposed or have become

commercially available. These include products ranging from simple toilet

flush mechanisms to domestic water recycling and waste-heat recovery

systems. Potential benefits of using such devices are twofold — reduced

water consumption, and decreased water-related energy requirements (for

water supply, wastewater treatment and domestic water heating).

Unfortunately, while some devices require no additional energy for

operation, and may in fact save energy, others require operating energy far

in excess of any expected water-related energy savings. Accurate

determination of overall energy savings is difficult however, because

little information about the relation between water usage and energy

consumption is available.

In order to more accurately assess the energy saving potential of

water/energy saving devices, an analysis of water-related energy

consumption was performed by the Product Performance Engineering Division

of the Center for Consumer Product Technology, National Engineering

Laboratory, National Bureau of Standards. This work was funded by the

Office of Energy Related Inventions at the National Bureau of Standards, to

provide a basis for acceptance or rejection of products in this class under

their Energy-Related Invention Evaluation program.

This analysis included a study of energy use in water supply,

wastewater treatment, and residential water heating, as well as a survey of

state-of-the-art water saving and water-associated energy saving devices.

The results of the energy use study provided a means of translating water

consumption into energy consumption. Water-energy conversion factors

developed in the study were then combined with water usage values for

conventional and water-conserving plumbing fixtures and appliances, to

yield estimates of energy savings attainable through water conservation.

The effects of grey water recycling and grey water heat recovery on energy

usage were also determined.

The purpose of this report is to present the relationship between

water usage and energy consumption, but more importantly to show some of

the impacts of various water and water-associated energy saving devices on

energy consumption, for the impacts of these devices can be quite

significant.

2. DOMESTIC WATER USE IN PERSPECTIVE

Estimates of water use in the United States in 1970 indicate that an average of 1400 billion liters per day were withdrawn for all purposes

other than for hydroelectric power [1]. Most water withdrawn is returned

to a natural water course with only a minor change in quality, such as a temperature rise for power plant cooling water, but 24£ of withdrawals are

-1-
classified as consumption, that is, water not directly returned to a surface or ground water supply. The breakdown of water withdrawals and

consumption by category is shown in Figure 1.

Figure 1 - Water Withdrawals and Fresh Water Consumption in the United

States in 1970 [1]

WATER

WITHDRAWN

FRESH WATER

CONSUMED

Much of water consumption is associated with irrigation, and returns to the

natural water cycle through evaporation and transpiration. Water supplies

for irrigation require only minimal treatment and, of course, do not add to

the load on waste treatment plants. Accordingly, the cost and energy

required to supply water for irrigation is considerably less than for

potable water. Excluding irrigation and considering only potable water,

residential water usage accounts for approximately 40% of all fresh water

consumption [1]. In short, although water for domestic purposes amounts to

only a small fraction of all water uses, in terms of cost and energy

consumption it represents one of the highest use levels. Domestic water

usage is therefore extremely important when considering the energy aspects

of water consumption.

3. WATER-RELATED ENERGY USE

Energy is consumed in nearly every phase of water use — from

obtaining water (from a natural source) to disposing of wastewater and

sludge. Considerable amounts of energy are also required for domestic

water heating. In order to determine the significance of water-related

energy requirements and the potential for savings, energy consumption for

each process in the water use cycle must be evaluated. Energy requirements

for three major processes were considered in this study. These included

energy for

o Water Supply

o Wastewater Treatment

o Domestic Water Heating

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Based on the results obtained through energy analyses of each of these

areas, the effects of reduced water consumption, water recycling, and other

factors on energy consumption were then estimated.

3.1 ENERGY REQUIREMENTS FOR WATER SUPPLY

By water supply we mean the process of obtaining water, treating

(purifying) this water, and then distributing the water to points of use. Energy is consumed in each of these steps, both directly and indirectly.

Direct energy requirements are easily determined, from fuel bills for

instance, whereas indirect energy requirements, such as the energy expended

in constructing and maintaining a water project, are much more difficult to

evaluate. Indirect energy requirements represent less than 1055 of the

total energy required for a typical surface water storage and conveyance

system however, so first order estimates may be obtained by considering

only direct energy requirements [2].

3.1.1 Obtaining Water

In many parts of the country, water is obtained as surface water from

nearby rivers and lakes; other areas utilize ground water or obtain water

by other means. In 1970, surface water withdrawals comprised about 60% of

all water withdrawn for public and rural - domestic uses [1]. Surface

water is transported either by gravity flow or pimping, with minimal energy

requirements. Ground water, however, requires pumping from greater depths

than surface water and, therefore, significantly greater energy

expenditures. Additional pumping energy may also be required to deliver

the water to treatment plants and points of use at higher elevations.

Based on a combined motor and pimp efficiency of 79 percent, the

electric energy required to pump and transport municipal water supplies by

use of large pumps in good condition is estimated to be 3.5 x 1CT-5 watthours per liter (Wh/L) per meter of lift [2]. Pumping plants tend to be

more efficient in large sizes and energy requirements per meter of lift may

range from 2.5 x 10 to 4.5 x 10 - -5 Wh/L. Unfortunately, actual pumping

heights, which vary significantly with geographic location, are not well

documented. Energy estimates may be obtained however, by considering

"typical" conditions. Assuming, for example, an average ground water depth

of 60 meters, pumping energy requir ements of 4.5 x 10”-5 Wh/L per meter of

lift, and negligible energy requirements for surface water, the energy

requir ements for obtaining water are estimated at about 0.10 Wh/L.

3.1.2 Treating Water

Energy requirements for water treatment are dependent on the size and

type of treatment plant, and the treatment processes required. Water

treatment usually consists of the following processes: aeration,

flocculation - sedimentation, filtration, chlorination, and sometimes

fluoridation [ 3 ]. Energy is used directly to drive chemical transfer

equipment, chemical-feed equipment, flash mixers, flocculators, sludge

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collectors, backwash pumps, and metering pumps [4]. Additional energy is

required for sludge disposal, lighting, heating and air conditioning of

buildings, transport of chemicals to treatment plants, and production of

lime, soda ash, alum, chlorine, and other chemicals used [2].

Because plant design and equipment used varies among treatment plants,

operating energy requirements range considerably. For example, energy

requirements for treatment processes used in Kansas City, Missouri were 40

x

10~-^ watt-hours per liter of water treated (Wh/L) in 1972 [4], while the

average energy consumption for the East Bay Municipal Utility District

(EBMUD) system in California was about 7 x 10”^ Wh/L [2]. Energy

requirements for water treatment, on a nationwide basis, are expected to be

within this range.

Based on information from Hertzberg [ 3 ], Roberts and Hagan [2] have

estimated the average chemical requirements per liter of water treated at:

chlorine, 1.3 mg; alum, 3.9 mg; and lime, 5.7 mg. Chemical requirar.ents

may vary depending on initial and finished water quality, but these

estimates will be considered typical for our purposes. Chemical production

is reported to require about 3.3 Wh/g for chlorine [5], 3.0 Wh/g for alum

[6], and 0.95 Wh/g for lime (from calcium carbonate) 171 . The energy

requirements for chemical production per liter of water are therefore:

chlorine, 4.3 x

10“-* Wh; alum, 12.0 x10“-* Wh; and lime, 5.4 x

10“-* Wh.

The energy required to transport the necessary chemicals has been

estimated to be equivalent to 2.0 x

10“-* ’Wh for each liter treated [2].

Total energy requirements for water treatment are summarized in Table 1.

Table 1 - Energy Requirements for Water Treatment

Function Energy Requirements Per Liter

( 10“JWh)

Treatment Processes 7-40

Chemicals

Chlorine 4

Alum 12

Lime 5

Chemical Transporation 2

Total Energy for Water Treatment 30 - 63

-4 -
3.1.3 Distributing Water

After water treatment, most municipal systems require additional

pumping — to deliver water to elevations higher than the treatment plant,

to overcome friction losses in pipes, and to maintain service pressure.

Energy requirements for pumping are a function of distance and elevation

pumped, and can vary substantially. Kanasas City, Missouri, for example,

uses an average of about 0.5 Wh/L for distribution [4], while the EBMUD

system uses only 0.2 Wh/L [31. A national average has not been reported,

but typical pumping energy requirements are expected to be in the same

range. As an example, total on-site energy use for Washington Suburban

Sanitary Commission (WSSC) water plants for 1977 was reported to be 0.43

Wh/L [8] (not including chemical-related energy use) — within the range of

the estimates. The breakdown of energy requirements for water supply are

summarized in Table 2. Note that energy use for water treatment represents

only about 10% of the total energy requirements for water supply.

Function

Table 2 - Energy Requirements for Water Supply

Energy Requirements Per Liter

Obtaining Water

Treating Water

Distributing Water

(Wh)

0.10

0.03 - 0.06

0.2 - 0.5

Total Energy for Water Supply 0.33 - 0.66

On the basis of these reported values for energy consumption it

appears that energy requirements for water supply may be estimated at about

0.5 Wh/L. If all energy is supplied by electricity which is generated and

distributed at a typical efficiency of 33 percent, total primary energy

requirements (energy supplied to the generating station) for water supply

are approximately 1.5 Wh/L.

3.2 ENERGY REQUIREMENTS FOR WASTEWATER TREATMENT

Wastewater treatment is generally divided into three stages. These

are commonly referred to as primary, secondary, and tertiary treatment

processes and are characterized as follows:

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o Primary treatment — mechanical process in which large solids and

smaller suspended or dissolved solids are extracted generally by

settling and filtration.

o Secondary treatment — biological process in which bacteria consume

and decompose organic matter remaining after primary treatment.

o Tertiary treatment — chemical process which is designed to remove

inorganic chemical pollutants, and other materials.

Each of these treatment processes are composed of a series of unit

processes and operations, the order and types of which may vary from one plant to another. As individual processes and operations vary greatly in

energy consumption, "similar" treatment plants may have substantially

different energy requirements.

In 1969, the average per capita consumption of electrical energy for

sewage treatment in the United States was 0.0573 kWh/day, whereas the

average overall residential consumption of electrical energy was 5.09

kWh/day [ 9 ]

Thus the total energy consumed in sewage treatment was

about one percent of the total residential consumption of electrical

energy. Nearly 1/3 of all wastewater treated in 1968, however, received

only primary treatment [10] — which requires considerably less energy than

more advanced treatment. The Federal Water Pollution Control Act of 1972

requires that by 1977 all publicly-owned treatment plants provide secondary

treatment. Because of funding limitations the act has not been completely

successful. Nevertheless, most waste facilities now provide treatment up

to the secondary level. Current energy consumption for wastewater

treatment might well be twice the 1968 rate!

Operation of facilities is the major component of energy consumption

in wastewater treatment. Because unit processes and operations have

widely varying energy consumptions and because there are innumerable

combinations of process flow sheets, the energy consumption of each

process and operation is generally estimated separately, then summed for

the entire system. Smith [9] has estimated the on-site electrical power

consumption for most of the conventional and advanced processes used to

treat municipal wastewater, and summed these estimates for various

combinations of processes. Energy requirements for three levels of

treatment commonly used are presented in Table 3. These energy

requirements are based on a 40 million liter per day plant size. For

smaller plants the energy consumption is slightly higher, while larger

facilities would have a somewhat smaller demand.

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Table 3 - Estimated Energy Requirements for Wastewater Treatment [91

Level of Treatment

On-site Energy Consumption

Per Liter Treated

(Wh)

Primary treatment 0.06

Secondary treatment

Primary plus trickling filters

Primary plus activated sludge

0.13

0.23

Tertiary treatment

Secondary treatment plus lime

clarification, filtration,

carbon adsorption 0.43

Secondary treatment plus

filtration and reverse osmosis 0.79

Roberts and Hagan [2] note that the preceding estimates may not be

representative for some conditions and should be adjusted upwards. But

later work by Roberts and Hagan [11], which is based in part on the work of

Smith [93, and includes indirect as well as direct energy requirements,

indicates that new, well-designed treatment plants (not necessarily

representative of existing plants) may have total primary energy

requirements of about the same magnitude as those predicted by Smith.

Based also on the work of Smith, Mills and Tchobanoglous [12] have

estimated the on-site operating energy requirements for a 40 million liter

per day activated sludge plant at 1.2 watt-hours per liter treated. The

variation in estimates is principally due to differences in assumed

values for aeration and heating energy consumption during the activated

sludge process.

A 1976 survey of municipal wastewater treatment needs [13] indicates

that more than 90 percent of all treatment plants have a capacity of less

than 20 million liters per day, with tertiary plants comprising less than

one percent of all plants. Also, mere than 50 percent of all secondary

treatment facilities utilize the activated sludge process [14]. On-site

energy requirements might therefore be approximated as those for an activated sludge plant. In view of the previously cited figures, a reasonable estimate for these energy requirements would be about 1.0 Wh/L.

Assuming all energy is supplied by electricity which is generated and

distributed at an efficiency of 33 percent, primary energy requirements for

operation are estimated at 3.0 Wh/L. This estimate is conservative, as in

practice many of the operational energy requirements are satisfied by

energy sources other than electricity, at a higher overall conversion

efficiency.

-7-
While the operation of facilities is the major component of energy

requirements for wastewater treatment, significant quantitites of energy

consumption are involved in the construction and maintenance of the

treatment facilities and equipment. Recent work by Smith [151 indicates

that energy used for construction of the treatment plant and the sewage

system might represent as much as 55 percent of the total energy consumed

over the life of the plant. For a typical treatment plant, Mills and

Tchobanoglous [12] estimate these requirements, in terms of primary energy,

to be about 0.6 Wh/L. The total primary energy requirements for wastewater

treatment, on a per unit basis, are therefore approximately 3-6 Wh/L.

3.3 ENERGY REQUIREMENTS FOR RESIDENTIAL WATER HEATING

In most of America's 70 million occupied housing units, water is

heated in a central water heater. Energy generally is supplied to the

heater as gas, oil, or electricity. Census data revealed the following

fuel-type breakdown in 1970 [16]:

Table 4 - Water Heaters In Service — Breakdown By Fuel Type

Fuel Type Percent of Occupied Households

Electricity

Natural Gas

Liquified Petroleum Gas (LPG)

Fuel Oil

Other and None

25.4

55.1

5.0

9.3

4.7

100.0

Several investigators [17,18] have analyzed heat flows in typical

residential water heating systems. These studies indicate that electric

water heaters operate at an efficiency of about 0.77 at point of use. Gas

and oil-fired units are estimated to have an overall efficiency of about

0.51. For an electricity generation and distribution efficiency of 33

percent, census and service efficiency data can be combined to yield a weighted water heating efficiency (in terms of primary energy) of 44

percent.

-8-
For actual water heater operation, the cold water inlet temperature

has been geographically, demographically , and seasonally averaged to a value of 12.8°C [19]. Using this temperature, and the weighted water

heating efficiency, the energy required to heat water can then be given as

a function of delivered water temperature. Water heating energy

requirements are presented in Table 5 for various water delivery

temperatures.

Table 5 - Energy Requirements for Water Heating

Delivery Temperature

12.0

21.1

37.8

40.6

54.4

60.0

62.

8

B

Water Heating Energy

Requirements Per Liter

(Wh)

0.0

22.0

65.9

73.3

110

125

132

A - corresponds to unheated water use

B - average water heater thermostat setting on new water heaters

3.4 WATER-RELATED ENERGY REQUIREMENTS — SUMMARY

In terms of primary energy, the estimated energy consumption that is

associated with each liter of water used in a household is broken down as follows:

o Water Supply 1.5 Wh

o Wastewater Treatment 3.6 Wh

o Water Heating 0-130 Wh depending on delivery temperature

-9-
Comparison of these values indicates that energy requirements

for water heating are an order of magnitude larger than for water

supply and wastewater treatment. Energy requirements for water

supply are less than half those for wastewater treatment, which in

turn comprise only about 0.2 percent of national energy utilization

[14]. Water heating energy requirements, however, are significant

on a national scale. They accounted for 3 percent of total energy

consumption in the United States in 1974 [16],

4. DOMESTIC WATER USE AND CORRESPONDING ENERGY REQUIREMENTS

Daily household water use for a family of four is frequently estimated

to be 965 liters [20]. Of this amount 243 liters passes through the water

heater [19]. The remainder is either used at cold water delivery

temperatures or mixed with hot water at points of use. Domestic water

usage patterns and delivery temperatures have been estimated by Bailey et

al. [20] and Muller [16] and are presented in Table 6 along with waterrelated energy requirements.

It can be seen from Table 6 that water heating energy requirements

comprise more than 90 percent of all water-related energy consumption, with

bathing and clothes washing making major contributions. Also noted is the

fact that a substantial amount of energy is consumed in heating the cold

water used in toilets. This energy transfer is at the expense of the space

heating system, which has a weighted service efficiency near that for water

heating. Assuming a six month heating season, "cold water heating" (for

toilet, cooking, and drinking) accounts for nearly 9 percent of total

water-related energy requirements. While energy requirements for water

supply and wastewater treatment appear relatively insignificant, water

heating energy requirements are quite substantial. They should be of

primary concern when evaluating the energy saving potential of water/ energy

saving devices.

5. POTENTIAL FOR ENERC-Y SAVINGS

Water-related energy consumption may be reduced in many ways. These

range frcm developing more energy efficient methods of producing and

heating potable water and treating wastewater, to using water more

wisely in the home. Of interest in this study are the energy savings

which may be realized through use of water/energy saving devices or systems

installed at the residential level — in particular, water saving devices

and plumbing fixtures, and water recycling and grey water heat recovery

syStans.

5.1 ENERGY SAVINGS THROUGH WATER CONSERVATION

5.1.1 Effects of Reduced Flow

Water conservation will result in a reduction in the volume of water

processed at water and wastewater facilities, and the energy required for

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water distribution, chemicals, and other purposes. However, when one considers the portion of wastes treated at sewage treatment plants

attributable to household waste flows, in relation to (1) the ground water

infiltration into sewer lines (often 30 percent of waste flow [21]), and

(2) industrial waste flow, the maximum theoretical potential reductions in

sewage flow reaching the plant are only about 7 percent [22]. In

addition, because many energy-consumptive treatment processes and

operations are flow-independent, large volume flow reductions might result

in only small decreases in energy requirements for facility operation. A

sudden, substantial reduction in flow volume may even tend to increase

plant energy consumption for an existing facility. For example, a 53

percent decrease in wastewater flow experienced by Las Gallinas Valley

Sanitary District, Marin County, California during the drought of 1S77 was accompanied by a slight increase in operating energy consumption, due

supposedly to greater energy requirements for recirculation pumping within

the plant [23].

Although the reduction in flow volume resulting from use of water

saving devices or methods may not reduce energy consumption directly, the

flow reduction is in effect an increase in plant capacity. This

"increased" capacity would enable existing water facilities to serve a greater population with no increase in energy consumption. It might even eliminate or postpone the need for expansion or new construction of

facilities, and corresponding energy expenditures. In this respect there

is a direct relation between flow reduction and energy savings. Hence, for

each reduction in water consumption, all corresponding water-related energy

requirements may be considered saved.

Further benefits may be realized through flow reduction. Cole [24]

indicates that a substantial increase in the life of a sewage treatment

plant can be obtained if water saving toilets are required in all new

housing following that plant’s construction. In addition, the flow

reduction effect of water saving devices on sewage treatment processes will

result in small increases in detention times and waste concentrations.

These increases are beneficial in that they tend to increase treatment

efficiency [28]. Ground water infiltration, however, may overshadow any

benefit of household waste water flow reduction and must be corrected

before flow reductions will have impact [24]. Another benefit of water

saving devices is that if flow reducing devices are installed throughout

the home as original equipment, it should allow the water distribution

system to be scaled down, easing installation and saving money and energy

[25].

On the effect of water saving toilets on sewer systems, calculations

by Cole [24] show that the depth and velocity of flow in the sewer and in

the pipe connecting the house to the sewer are not reduced substantially

below those that exist in a sewer with standard 20 liters per flush toilets

unless the flush amount is reduced to 7.5 liters or less. On sewers that

serve a population of at least 500 persons the velocities and depths are

-12-
not substantially reduced for any of the predicted flush volumes. Sharpe

[22] notes that problems could develop in collection lines that service a population of fewer than 500 persons. In such cases conventional design

velocities may not be adequate for solids removal; and blockages, odor

problems, and excessive pipe corrosion will result.

5.1.2 Water Saving Devices

Water usage and thus water-related energy consumption can be

significantly decreased through use of danestic water saving devices and

methods. Water saving devices are fixtures attachments, inserts, or new systems which modify or replace standard plumbing fixtures and fittings;

and result in water consumption less than with the standard fixtures.

These products fall into three categories: retrofit or add-on type items,

replacement fixtures with "built-in" devices, and specialty items or

systems.

Retrofit devices are items which are added to existing fixtures or replace corresponding parts on the fixture or fitting. For faucets, these

devices include flow restrictors, aerators, and spray taps. Retrofit items

are generally inexpensive and easily installed — usually by the homeowner.

For toilets, water savings comparable to those for replacement "water

saver" units may be achieved with these devices, although the resulting

toilet performance in some cases may be inferior.

Water saving replacement fixtures appear and operate the same as standard units, but have integral water saving features. They are generally more expensive than conventional fixtures and may be used as direct substitutes for standard fixtures in new and replacement

installations. Recent Environmental Protection Agency studies [26,27]

indicate that various water saving devices are cost effective.

Specifically mentioned for retrofit applications are shower flow

restrictors, toilet inserts and dual- flush modifications for toilets. In

addition broad based prograns involving the free distribution of

inexpensive water-saving devices are thought to be economically justified

[26]. Water saving products are, in seme locales, required by code. In

areas where water saving devices are not required by code, a severe

constraint to widespread adoption of various water-saving devices has been

their general lack of availability. These devices are not usually carried

as stock items in most hardware and plumbing supply stores. Apparently the

demand for the items has not warranted their being routinely stocked, and

many of the newer devices are as yet little known in the plumbing trade

[ 22 ].

Specialty devices do not operate in the same manner as conventional

fixtures. They are generally more expensive than conventional water saving

fixtures, and their installation is more complex than fixture replacement.

Specialty devices offer greater water savings than conventional water

saving fixtures, but many require additional energy for operation. Use of

specialty items may be restricted due to cost and public acceptance

-13-
problems as well as local plumbing and health codes. Typical specialty

items include vacuum toilets, incinerating toilets, air-assisted

showerheads, and self-closing fixtures.

Milne [25] and Nelson [28] have compiled very complete directories of

currently available water-saving devices. Included by Milne are

discussions of such topics as the operational characteristics, estimated

water savings, cost considerations and public acceptance, for each type of

water saving device. More specific product information, such as flow rates

and design features of various devices on the market, is given by Nelson by

model for each manufacturer. The reader is referred to these works for a summary of state-of-the-art water saving products.

5.1.3 Potential Savings

In surveying currently available water saving products it becomes

apparent that two different levels of savings may be realized — one representing use of "conventional" type water saving products (retrofit

devices and water saving replacement products) and the second representing

the use of specialty devices or systems. Estimates of water consumption

for standard products, and for currently available conventional and

specialty water saving devices or systems are shown in Table 7. As

indicated in Table 7, sizeable reductions in water consumption may be

realized through use of conventional water saving devices. Greatest

savings are obtained, however, with specialty devices, which reduce water

use to a minimum.

Table 7 - Water Consumption of Standard and Water Saving Products

Device Water Consumption

Standard Products[29] Current Water Saving Products

Conventional [29] Specialty

( liters)

Toilets (liters/ flush) 19-27 13 2°

Showerheads A (liters/min) up to 45 11 2

E

Clothes Washers (liters/load) 100-200 60-72B -

Dishwashers (liters/load) 28-60 28

C -

Faucets A

(liters/min) up to 19 6 2

F

A - flow rate is selected by user

B - front-loading model

C - short-cycle setting

D - vacuum- toilet (requires energy for operation)

E - air-assisted showerhead (requires energy for operation)

F - spray taps -14-
It has been estimated that a complete replacement of plumbing fixtures

and appliances by their currently available water saving counterparts would

result in a 34 percent saving in residential water consumption [21].

Reduced water requirements and corresponding energy usage with conventional

water-saving products are shown in Table 8.

Comparison of these figures with those in Table 6 reveals that through the

use of water-saving devices and fixtures, water-related energy requirements

may be reduced by 35 percent. Over 90 percent of these savings are in

water heating energy. Residential water heating accounts for 3 percent of

total national energy usage, hence, this reduction in energy requirements

is roughly equivalent to a 1 percent decrease in national energy use.

Specialty devices offer even greater reductions in water-related

energy consumption. They must be selected judiciously, however, as some

types of devices consume far more energy in operation than they save. In

the case of air-assisted showerheads, operating energy (used to run an air

compressor) is small compared to the energy saved in hot water heating.

Incinerating toilets, on the other hand, require input energy far in excess

of any water-related energy savings. Operating energy requirements for

each water saving device under consideration should be weighed against

expected water-related energy savings.

5.1.4 Actual Versus Predicted Savings

The volume of water expended in a water consuming activity is a result

of the interaction between user and plumbing fixture. The user has

specific needs or desires — ranging from clean hands to clean toilet bowls — and operates the fixture until these requirements are met. The water

consumed in doing so is a function of user habits and plumbing fixture

characteristics. While fixture flow characteristics may be improved

through use of water saving devices, projected flow reductions might not be

realized with some devices because fixture performance may degrade or

because actual water usage patterns may differ from those assumed. For

example, shower flow restrictions which reduce maximum water flow rates

from 20 to 10 liter/min will save little or no water if flow rates of

around 10 liter/min are already being used. There is a serious lack of

reliable data pertaining to the rates and durations of water flow commonly

used in the home. Until this gap is filled, there will remain no firm

basis on which to predict water/ energy savings.

Actual water savings realized through large scale water conservation

programs may fall short of predicted reductions for another reason — many

hones are already equipped with water saving devices. A 1979 survey of

plumbing codes reveals that an increasing percentage of jurisdictions now

regulate the volume of water used in plumbing fixtures, at least in new

plumbing installations [30]. Table 9 illustrates the increasing awareness

of the need for water and energy conservation in plumbing codes. Figures

given in Table 9 represent percentages of jurisdictions regulating the

various items listed.

-15-
Table 8-

Residential

Water

Usage

and

Corresponding

Energy

Consumption

With

Conventional

Water

Savings

Devices

on •=r ^r no c

ON

CO ON rH no r- rH f- o • • • • • • • • m H

LO o rH o =rno

s_

<u < -p "O <02 O <u

-*-> <d to

to 03

_

X

-pc

0) -p

03

<u

s_

i- GO

<D

C

Cl. •«-( „ -P

CO (0 -P <U C nr

<DE J-

<13 (0 t-4-> •P 03 = !2

CT

<d cc

til a,

ja <u 3 5^

S-) (D

>>

03 X

CO no LO LO in zr CO 0O nO no rH rH o o CM • • • • • • • • o o O O o o o C\J o C— no o o no

NO ON nO rH in rH c

r—

CM no NO* in o H o’ o

t-H no

M3 ON =T no c

CM CM NO no CM rH o o O o ON o o’ o* o* o* o’ o* o

03 S

>>

s_

rH NO

0) r-t X i

03 <D P i.

co

a S -P ^—

rH MO NO o rH NO NO

•P 03 x

C_3 o H o* o o* rH o’ o*

O 0) k 9- Q. B

Q. 0) <C b->

CM 43- =r NO CM

S_

<13 i—

-P rH

CO C\J

co Q

<13 ao

03

CO

in in o — r-

rH no

no

GO

C

C -i—

c

CD •p CO CO c C _o >n o 00 CO -P CO c J, >.

•rH

p c CD

X CO CD

O P j 1 03 •H X CO 3 4-> •H i—

o rH -o co X o CO H <0 c •rH -p O 3 CO pi > •H p o CO rp •P •H CO -p o

Cz-i E-* CQ o x

X o <

16

Based

on

estimates

obtained

in

Section
Table 9 - Percent of Jurisdictions Regulating the Water

Consumption of Plumbing Fixtures [30]

Device Percent of Jurisdictions Regulating Water Consumption

1977 1978 1979

Toilets 9 23 32

Shcwerhead flow rates 7 20 51

Faucet flow rates 6 17 35

(Note: these figures do not represent percent of residences).

5.2 ENERGY SAVINGS THROUGH WATER RECYCLING

Water recycling is considered, by some, to be the ultimate means of

water conservation. Through recycling, household water consumption may be

significantly reduced and with some systans nearly eliminated. Bailey et

al. [20] have considered the reuse potential of household wastewater in

terms of treatment required before reuse, and reasons for treatment. As

shown in Figure 2, a whole realm of reuse possibilities for household

waterwaste systems exist. Some schemes require only minor wastewater

treatment before reuse, while others call for complete renovation of

wastewater

Figure 2 - The Reuse Potential of Household Wastewater [20]

Potential Household Water Sources

Potable

Supply

Sink

(Kitchen)

Sink

(Bathroom) u

V

sin

<d £aQ

&

c3a

Shower

or

Bath

V

rH£ Point of Water Use / "ha "hA ^ia "ha "hA "HA Sink (Kitchen)

/ *HA "hA X

HA "hA V % Sink (Bathroom)

/ "ha "HA "ha XHA

XHA "ha Water Heater / "ha "hA

SHA X

KA "hA "ha Dishwasher

l/ sdha seha 3DHA sdha sd

k/ XHA Shower or Bath / S A S

A

3 a S

A S

A "ha laundry

/

3DHA SD

HA

3Dha sd

iia se

h; "ha Outdoor Faucet / sd

e sd

e sd

e

sd

e sde "e House Heating Sys.

/ 3 A S

A

! a

SASA "ea Toilet

Treatment Required Before Use: / Ho treatment required D Disinfection

S Minor Chemical and physical

treatment

X Complete renovation

Reasons for ‘treatment: H Health

E Engineering

A Aesthetic

-17-
Although the reuse of wastewater from any appliance or drain is

technically possible if given suitable treatment and a suitable piping

system, it may not be economically or aesthetically feasible. Through an analysis of various reuse schemes and techniques for treating the wastes

produced, Bailey et al. [20] have concluded that "Advanced waste treatment

schemes other than simple filtration and disinfection are generally not

practical for a normal household. Most households could not meet the

operating expenses or provide the operating attention required by the

majority of the advanced treatment systems. Even when an extensively

treated water is reused for all purposes but drinking the costs are prohibitive. The only economical and practical reuse is the filtration and

reuse of wash waters for toilet flushing, and in areas where aerobic

treatment is economical, the filtration and reuse of the aerobic effluent

for toilet flushing."

A system which has received a great deal of development efforts

involves the recycling of bathing and laundry wastewaters (both referred to

as grey water) for toilet flushing and possibly outside irrigation. A

typical recycling system provides for the collection of grey water through

conventional plumbing, and transport into a settling tank. The settled

wastewater is generally processed through some type of filter (paper

cartridge, diatomaceous earth, or sand) and then disinfected prior to

storage and reuse. Siegrist et al. [31] report that at least one such

recycle system is commercially available at a cost of $2500 plus shipping.

The annual operating costs, as estimated by the manufacturer, are $45 per

year. This cost includes the filter cartridges, disinfectant and energy

for operation.

Separate grey water and toilet water drainlines are required with the

recycle system. Installations in existing homes would, in most cases,

require replumbing toilets on a new, separate drain line — an expensive

proposition which would likely offset any system savings. In new construction homes, however, separate grey water drain lines could be

installed with minimal effort and expense, making recycling systems more

economically attractive.

Cohen and Wallrnan [31] report that, two prototype grey water recycling

systems were installed at three homes and were monitored for a period of

one year. One recycling system included storage, cartridge filtration,

liquid chlorine disinfection, and reuse, while the other included storage,

diatomaceous earth filtration, chlorine tablet disinfection, and reuse. The waste flow reduction achieved by the units averaged about 40 liters per

capita per day or 24 percent of the total daily wastewater flow. The

recycle systems were found to be manageable, simple to use, and capable of

reliable and safe operation. The operation of conventional flush toilets

was not impaired by the recycled grey water and the performance of the

systems was found to be aesthetically acceptable to the users. Maintenance

of the units - replacement of filter cartridges and disinfiction chemicals

- was typically required at one to three month intervals. The costs for

the "homebuilt" systems were about $500-$600 installed, and yearly

-18-
operating costs were $21 to $45. Another limited field study of a similar

prototype system by McLaughlin [333 generated results which were basically

similar to those found by Cohen and Wallman.

In addition to the grey water recycling studies cited, efforts have

been directed toward evaluating the feasibility of recycling a portion of

the total household wastewater flow for toilet flushing. As part of the

Boyd County Demonstration Project, four recycle systems were installed to

serve five homes [34]. These recycle systems included an aerobic treatment

unit to which all wastewater generated in the home was transported. The

effluent from the aerobic unit flowed into a settling chamber from which

the effluent was either processed further for recycling or directed to a disposal system. The performance of the recycle system was monitored

closely for a period of one year. Based on analyses of six samples of the

recycled water, the recycle systems were found to produce a generally clear

and odorless water, low in biological oxygen demand (BOD) and suspended

solids, with zero fecal coliform counts. Also noted was a high degree of

consumer satisfaction with the day-to-day use of recycled water [31]

.

If all toilet flushing requirements were met by a recycle system, a flow reduction similar to that for a non-water toilet would be achieved —

379 liters per day or 39 percent of the total daily flow. From Table 6,

however, it is seen that water-related energy requirements would be reduced

by only 6.1 kWh/day or 12 percent. This reduction includes a 9 percent

savings in water heating. Depending on the length of heating and

cooling seasons, thermal energy lost from grey water during recycling will

result in additional energy savings or added cooling load. Recovery of

this waste heat is considered in the following section.

5.3 ENERGY SAVINGS THROUGH GREY WATER HEAT RECOVERY

All water which enters a conventionally plumbed household passes

directly to the sewer or septic tank after use (except water which is used

for purposes such as drinking and car washing). Grey water comprises more

than half this volume and carries significant amounts of thermal energy.

With a grey water heat recovery system a portion of this heat may be

transferred to incoming cold water (or ambient air during the heating

season) , resulting in decreased energy requirements for water and space

heating, respectively.

At present, systems for recovering waste energy from domestic drain

water are not commercially available. However, several demonstrationtype installations have been made in the United States and Europe.

Descriptions and analyses of some of these systems are given by the

literature [35,36,37].

From estimates of water usage and delivery temperatures given in Table

6, the thermal energy delivered to the points of water use is found to be

18.5 kWh/day (relative to a 12.8°C inlet water temperature) . Maximum

-19-
possible heat recovered would be significantly less than this due to (1)

thermal losses from grey water (before entering the drain), piping, and

storage vessels, and (2) the inability to utilize all waste heat. Some

waste heat is not utilized because long retention time would be required to remove most of the available heat from wastewater. During this time hotter

wastewater would become available and would displace the cooler wastewater.

Energy which is transferred from pipes and other equipment to ambient

surroundings represents an energy gain during winter (heating) months, but

a thermal load during summer (cooling) months. These losses may be of the

same magnitude as the energy recovered. As a result, the energy saving

potential of the grey water heat recovery system is highly dependent on the

duration of heating and cooling seasons.

The temperature of grey water, as it enters the drainage system is of

prime importance in determining the thermal losses fran grey water. Little

research has been performed in evaluating this parameter, and reliable

temperature estimates are not available. For purposes of calculating the

thermal losses from gre^ water, which occur before entering the drain, a temperature drop of 5.5°C (10°F) from delivery temperature was used.

The thermal losses from grey water while enroute to the heat exchanger

are dependent on several factors including (1) pipe diameter, material, and

length, and (2) water usage patterns. The use of thermal insulation on drain pipes would reduce thermal losses somewhat, but in many retrofit

installations insulating the drain pipes may not be practical. Drain pipe

heat loss may be estimated by considering a 9 meter section of 50 mm

diameter copper drain pipe. To raise the pipe temperature, approximately

2.5 watt-hours are required per Celsius degree increase, whereas to

maintain an elevated temperature, about 8.5 watts are required (lost) per

degree above ambient air temperature. For each function shown in Table 6,

the drain pipe temperature will be raised approximately from ambient

temperature (21.1°C) to the delivery temperature for that function. In

addition, convective pipe losses will occur for the duration of the event.

Estimates obtained in this fashion represent the minimum energy available

for recovery, since the pipe may be warm for a previous water draw when a second draw is made.

The thermal losses from grey water can be estimated by assuming a 5.5°C decrease in grey water temperature before entering the drain, and

calculating pipe heat loss based on water delivery temperatures and

durations, and the preceding heat loss rates. Calculated values for heat

loss and available energy are presented in Table 10.

-20-
Table 10 - Thermal Energy Flows for Grey Water

Energy Delivered Losses Before Losses From Energy Available

Function to Point of Use

A Entering Drain Pipes at Heat Recovery Tar

(kWh/ day)

Bathing 9.78 1.93 0.04 7.81

Clothes Washing 4.26 0.84 0.07 3.35

Dishwashing 3.12 0.36 0.06 2.70

Lavatory 0.97 0.19 0.03 0.75

Utility 0.61 0.12 0.01 0.48

Total 18.7 3.44 0.21 15.1

A - referenced to a cold water inlet temperature of 12. 8°C

B - based on a 5.5°C temperature drop

The energy content of the grey water entering the heat recovery tank

(15 kWh/day) is simply the energy delivered to point of use less the

thermal losses from grey water. If grey water from all sources is

utilized, the volume of grey water passing through the heat exchanger is,

from Table 6, 541 liters/day. The average thermal energy of the grey water

entering the heat exchanger is therefore 28 Wh/L (relative to a 12.8°C

incoming cold water temperature) . This corresponds to an average grey

water inlet temperature of 37°C.

The energy recovered from delivered grey water is dependent on the

type of heat removal device used. Heat recovered using a grey

water/potable water heat exchanger is expected to be about 4.4 kWh/day or roughly 20 percent of all primary water heating energy requirements.

Wastewater exit temperatures would be approximately 30°C with such a device. A more sophisticated system, which uses a heat pump to transfer

the thermal energy, would produce lower wastewater exit temperatures and

would save considerably more than this amount. Water heating energy

savings of nearly 55 percent were achieved with the heat pump equipped

system described by Ebersbach [36].

Depending on local costs of water and power, grey-water systems may be

cost effective on a residential scale. Unfortunately, they are not readily

available. Careful attention to health codes will, of course, be necessary.

-21-
6 . CONCLUSIONS

Through use of commercially available water saving devices, household

water use could be reduced by 3^ percent. Water-related energy

requirements would be decreased by 35 percent, with over 90 percent of all

savings in the form of reduced energy requirements for water heating.

These water-related energy savings are equivalent to nearly a 5 percent

reduction in total residential energy consumption. Specialty water

conserving devices or systems offer even greater saving, but the operating

energy requirements of these devices should be carefully considered as they

may negate water-related energy savings.

Residential water recycling is an effective means of reducing water

consumption. However, advanced waste treatment schemes other than simple

filtration and disinfection are generally not practical for a normal

household. By reuse of grey water for toilet flushing, savings similar to

that for a non-water toilet would be achieved — 379 liters per day.

Energy savings equivalent to 9 percent of residential water heating energy

might also be realized. Residential water recycling systems do not yet

appear cost effective, and would violate local plumbing and health codes in

most areas.

Grey water heat recovery systems have the potential to cut water

heating energy consumption by half. The concept has been successfully

demonstrated in several pilot system installations but such systems are not

currently commercially available or cost effective for single family

installations. Compliance with local codes may present a problem.

-22-
7.

REFERENCES

1. Murray, R. C. and E. B. Reeves, "Estimated Use of Water in the United

States in 1970," Geological Survey Circular 676, U.S. Geological

Survey, Washington, D.C.

2. Roberts, E. B. and R. M. Hagan, "Energy Requirements of Alternatives

in Water Supply, Use, and Conservation: A Preliminary Report,"

California Water Resources Center, University of California at Davis,

Contribution No. 155, December 1975.

3. Hertzberg, L. B., Manager of Plant Engineering, East Bay Municipal

Utility District. Short paper presented at the "Workshop on Energy

Requirements of Alternatives in Water Supply, Use, and Conservation,"

Davis, California, December 17, 1974.

5.

O'Brien, W. J., "Municipal and Industrial Water Supply," The Role of

Water in the Energy Crisis, Karen E. Stork, ed., Preceedings of a Conference, Lincoln, Nebraska, October 23-24, 1973.

5. State Water Resources Control Board, Energy Task Force, "Effects of

Energy Shortage on the Treatment of Wastewater in California,"

Sacramento, California, April 1974.

6. Garber, W. F., G. T. Ohara, and S. K. Raksit, "Energy Assessments of

Certain Wastewater Treatment and Solids Disposal Processes," ASCE

Journal of the Environmental Engineering Division, June 1975.

7. Battelle Columbus Laboratories, "Energy Use Patterns in Metallurgical

and Nonmetallic Mineral Processing, (Phase 4 - Energy Data and

Flowsheets, High-Priority Commodities)," U.S. Bureau of Mines,

Contract No. S0144093, June 27, 1975.

8. Personal Communication from Mr. Arthur Brigham, Washington Surburban

Sanitary Commission, Washington, D.C.

9. Smith, R., "Electrical Power Consumption for Municipal Wastewater

Treatment," U.S. Environmental Protection Agency, Environmental

Protection Technology Series, EPA-R2-73-281, July 1973.

10. "Municipal Waste Facilities in the United States," Statistical

Summary, 1968 Inventory, U.S. Department of Interior. Federal Water

Quality Administration, 1968.

11. Roberts, E. B. and R. M. Hagan, "Guidelines for the Estimation of

Total Energy Requirements of Municipal Wastewater Treatment

Alternatives," A Report to State Water Resources Control Board by

University of California at Davis, August 1977.

-23-
12. Mills, R. A. and G. Tchobanoglous, "Energy Consumption in Wastewater

Treatment," Energy. Agriculture and Waste Management . W. J. Jewell,

ed., Proceedings of the Seventh National Agricultural Waste

Management Conference, Syracuse, New York, April 16-18, 1975.

13. Chamblee, J. A., "Cost Estimates for Construction of Publicly-Owned

Wastewater Treatment Facilities Volume 2. Summaries of Technical Data

Categories I-IV. 1976 Needs Survey," U.S. Environmental Protection

Agency, Washington, D.C., February 10, 1977.

14. Wesner, G. M., L. J. Ewing, T. S. Lineck, and D. J. Hinrichs, "Energy

Conservation in Municipal Wastewater Treatment," U.S. Environmental

Protection Agency, Contract No. EPA-68-03-2186 Task 9, March 1978 (In

Press)

15. Smith, R., "Total Energy Consumption for Municipal Wastewater," U.S.

Environmental Protection Agency, Environmental Protection Technology

Series, EPA-600/2-78-149, August 1978.

16. Muller, J. G. , "The Potential for Energy Savings Through Reductions

Through the Use of Flow Reducing Devices and Other Conservation

Methods." Water Conservation With Water Saving Devices . Theordore B.

Shelton, ed., Proceedings of a Conference, Rutgers University, New

Brunswick, New Jersey, November 30, 1976.

17. Arthur D. Little, Inc., "Study of Energy Saving Options for

Refrigerators and Water Heaters," Prepared for Federal Energy

Administration under contract No. CO-04-50228-00, May 1976.

18. Hoskins, R. A. and E. Hirst, "Energy and Cost Analysis of Residential

Water Heaters," Oak Ridge National Laboratory, ORNL/CON-IO, June 1977.

19. Kweller, E., "Results of Survey of Utility Companies for Energy

Consumption of Water Heaters," PSD, PSAD, National Bureau of

Standards, Washington, D.C., April 2, 1975.

20. Bailey, J. R., R. J. Benoit, J. L. Dodson, J. M. Robb, and H.,

Wallman, "A Study of Flow Reduction and Treatment of Waste Water from

Households," Water Pollution Control Research Series, U.S.

Environmental Protection Agency, Washington D.C., December 19, 1969.

21. Fowell, A. J., A. Bransdorfer, P. Fletcher, R. J. Orend, H. J. Pavel,

and G. H. Williams, "Water and Water-Related Conservation in

Buildings," Presented at USNCCIB/CIB International Symposium on Water

Supply and Drainage, National Academy of Sciences, Washington, D.C.,

September 28-30, 1976.

22. Sharpe, W. E., "Water Conservation With Water Saving Devices," Water

Conservation With Water Saving Devices. T. B. Shelton, ed.,

Proceedings of a Conference, Rutgers University, New Brunswick,

New Jersey, November 30, 1976.

-24-
23. Personal Communication from Mr. James T. Emanuel, Las Gallinas Valley

Sanitary District of Marin County, California.

24. Cole, A. C., "The Impact of Home Water-Saving Toilets on Wastewater

Collection and Treatment," Water Conservation With Water Saving

Devices , T. B. Shelton, ed., Proceedings of a Conference, Rutgers

University, New Brunswick, New Jersey, November 30, 1976.

25. Milne, Murray, Residential Water Conservation, California Water

Resource Center Report No. 35, University of California at Davis,

March 1976.

26. Chan, M. L., "The Cost-Effectiveness of Pricing Schemes and Water

Saving Devices," Proceedings of a Conference on Water Conservation and

Sewage Flow Reduction with Water Saving Devices . W. E. Sharpe and P.

W. Fletcher, ed., The Pennsylvania State University, University Park,

Pennsylvania, July 1975.

27. Schaeffer, R. K. , "Socioeconomic Considerations for Domestic Water

Conservation," Proceedings of a Conference on Water Conservation and

Sewage Flow Reduction with Water Saving Devices . W. E. Sharpe and P.

W. Fletcher, ed. , The Pennsylvania State University, University Park,

Pennsylvania, July 1975.

28. Nelson, J. 0. , North Marias Little Compendium of Water Saving Ideas , North Marin County Water District, Novato, California, 1976.

29. Department of Water Resources, "Water Conservation in California,"

Bulletin No. 198, State of California, Department of Water Resources,

Sacramento, California, May, 1976.

30. DE/Domestic Engineering . "How Codes Combat Water Waste" March 1979.

31. Siegrist R. L. , T. Woltanski, and L. E. Waldorf, "Water Conservation

and Wastewater Disposal," Proceedings of the Second National Home

Sewage Treatment Symposium , published by American Society of

Agricultural Engineers, December 12-13, 1977.

32. Cohen, S. and H. Wallman, "Demonstration of Waste Flew Reduction from

Households," Environmental Protection Technology Series, National

Environmental Research Center, Environmental Protection Agency,

Cincinnati, Ohio, September 1974.

33* McLaughlin, E. R., "A Recycle System for Conservation of Water in

Residences Proceedings of a Conference on Water Conservation and

Sewage Flow With Water Saving Devices , W. E. Sharpe and P. W.

Flectcher, ed., The Pennsylvania State University, University Park,

Pennsylvania, July 1975. State University, University Park,

Pennsylvania, July 1975.

-25-
34. Waldorf, L. E., "Boyd County Demonstration Project," Proceedings of

the National Conference on Less Costly Wastewater Treatment Systems

for Small Communities, U.S. Environmental Protection Agency, Reston,

Virginia, April 1977.

35. Arthur D. Little, Inc.," Design, Development and Demonstration of a Promising Integrated Appliance," prepared for Energy Research and

Development Administration under Contrast No. E-(04-3)-1209, September

1977.

36. Ebersbach, K. F., "Heat Recovery from Waste Water in Domestic

Buildings," Energy Use Management — Proceedings of the International

Conference , Volume 2, R. A. Fazzolare and C. B. Smith, ed., Tucson,

Arizona, October 24-28, 1977.

37. Long, C. H., "Integrated Home Energy System,"

Proceedings of the First Southeastern on Application of Solar Energy , S. T. Wu and D. L. Christenson, ed. , Huntsville, Alabama, 1975.

38.

Baker, L. K.," The Relationship Between Water and Energy Use and

Conservation," Proceedings of 1976 Summer Workshop on an Energy Extension Service . University of California, Berkeley,

California, May 1977.

-26-
BS-114A (REV. 9-78)

U.S. DEPT. OF COMM. 2.Gov* t. Accession

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBSER 79-1770

x> ,

TITLE AND SUBTITLE 5. Publication Date The Potential for Energy Savings With

Water Conservation Devices 6. Performing Organization Code

7. AUTHOR(S)

Robert L. Palla, Jr.

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

10. Project/Task/Work Unit No.

W.

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, state. ZIP)

National Bureau of Standards

Office of Energy Related Inventions

Washington, D.C. 20234

13. Type of Report & Period Covered

14. Sponsoring Agency Code

r

15. SUPPLEMENTARY NOTES

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or leas tactual summary of moat significant information. If document includes a significant bibliography or

literature survey, mention it here.) With the use of residential water saving devices, substantial decreases in

water consumption may be realized. Perhaps of even greater significance,

however, are the resultant reductions in water-related energy requirements - for water supply, wastewater treatment, and water heating.

Through a survey of water-related energy use, a relationship between water

usage and energy consumption is developed. Results obtained indicate that

energy requirements for water heating far exceed those for water supply and

wastewater treatment. Based on estimates of residential water consumption

with and without water conserving products, the potential for energy savings

is assessed. Reduction in household water heating energy consumption of

about 35 percent are predicted with the use of "conventional" water saving

products. Also considered in this study are the energy saving potentials of

grey water recycling and grey water heat recovery systems.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

Energy; energy consumption; grey water; heat recovery; recycling;

residential; wastewater treatment; water; water conservation; water heating;

water usage

18. AVAILABILITY Unlimited

I I For Official Distribution. Do Not Release to NTIS

I I Order From Sup. of Doc., U.S. Government Printing Office, Washington, DC

20402, SD Stock No. SN003-003-

I I Order From National Technical Information Service (NTIS), Springfield,

VA. 22161

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