Encyclopedia of Environmental Science and Engineering, Volume I and II

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WATER AND WASTE MANAGEMENT SYSTEMS IN SPACE

INTRODUCTION

Environmental Control and Life Support System (ECLSS) is

the NASA terminology for the systems which allow people

to exist and work in confined spaces and in uninhabited loca-

tions and hostile environments. These systems supply air,

water, temperature and humidity controls to enable personnel

to survive and work under hostile conditions. The purpose

of this paper is to review the various devices that have been

developed for the recovery and reuse of liquid wastes in

spacecraft and space stations, and their possible terrestrial

applications.

A SHORT HISTORY OF U.S. SPACECRAFT

ECLS SYSTEMS

The U.S. spacecraft ECLS systems have grown in capa-

bilities and complexity as the spacecraft have grown and

the duration of their missions has been extended. Initial

systems were almost completely open loop, with only CO 2

removal in a closed loop. There was no recycling of water

or wastes. On the Orbiter, water is not recycled, but is

vented overboard. Air is recycled. Solid wastes are returned

to the earth. This system will be changed as the Orbiter

is reconfigured for longer duration missions. Due to the

high cost of transporting fresh water and oxygen into orbit,

the space station is designed to operate in an almost com-

pletely closed loop mode. Only solid body waste and trash

will be returned to the earth. Air and liquid wastes will be

recycled.

Regenerative systems have been evaluated by NASA for

the different functions of the ECLSS (Figure 1). 1 A partial list

of the various technologies is given in Table 1. The emphasis

is on purification and recycling the air and wastewater streams

for atmosphere revitalization and water recovery and manage-

ment. The high cost of transporting mass into orbit, approxi-

mately $22,000/kg, causes NASA to place a premium on low

weight, low volume, high efficiency, and low maintenance

requirements.^2

DRINKING WATER QUALITY STANDARDS

NASA has very strict standards for water consumed on the

shuttle, and even stricter standards for the proposed space

station. This is logical, as the water on the space station will

be continuously recycled, and hence the astronauts will be

exposed to this water for an extended duration. Table 2 lists

the present potable water standards for the shuttle and Space

Station Freedom (SSF), and compares these to the existing

EPA potable water standards. The SSF hygiene water stan-

dards are also shown in the table. These standards were

established early in the program.^3

In order that hardware designers should have constant

reference solutions to use when testing their equipment,

NASA found it necessary to determine the compositions of

urine and wastewater that would be produced on the space

station. Hence NASA analyzed average urine composi-

tion, and determined a chemical model for urine, which

could be made up and used to test recycling equipment.

Similarly, a chemical model formula for hygiene water,

i.e., water used for personal washing, laundry, and food

preparation, was derived. These model compositions for

urine and wastewater were then used to test individual items

of hardware and complete processing systems. However,

the final evaluation tests must include the processing of

urine and wastewater obtained from volunteers living in a

closed test environment.

TECHNOLOGIES TESTED FOR USE IN THE ECLSS

Various technologies were tested and/or evaluated for the

ECLSS systems, with the emphasis on the water and air revi-

talization systems. Less attention has been paid to the treat-

ment of solid waste, as this will only be required for long

space voyages and for long term inhabitation of stations on

the moon and planets. A number of water recovery and waste

management systems have been tested for application in the

space station. These systems have been evaluated by com-

paring them to the baseline technology that was originally

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