Greywater Reuse

Water Management in Residential Houses

Felipe Francisco Michelin

Arizona State University

February 2015 

ABSTRACT

Water, a natural resource that is used by the human was always sign of greatness. Previously, each person was responsible for finding and picking up water, which became a complicated task and therefore did not generate unnecessary water expenses. With the industrialization and construction of large cities, the use of water becomes an easy and inexpensive task, generating a major concern in terms of scarcity. Over time, new methods have been designed to try to minimize this problem and they have been used increasingly by the population, helping the environment and reducing costs, the use of residential graywater.

 

1. INTRODUCTION

Everyone knows that the planet earth, seen by the space, is blue. In fact, is hard to understand how we can suffer from lack of water. The answer is: more than 99% of the world water is not for consumption, as we can see in Figure 1.

Figure 1: Composition of the Earths water supply (from http://www.omsolar.net/en/system_z/img/graph_composition.gif, visited on 2/7/15 at 9:00 AM)

The increase in the world population and urbanization leads to decrease the natural resources. But only the people mentality can change this world fact, with the water sustainable management. The optimization of the reuse of water should be massively implemented in the future residences. Nowadays, with the lack of water, governments are trying to regulate new ways to conserve water resources. Water reuse, regarded as an exotic option, is today an important alternative.

A small fraction of the planet’s water is always turning into fresh water through a continuous process of evaporation and precipitation. Approximately 40 million m3 of water are transferred from the oceans to the land each year, renewing the supply in quantity many times more than is necessary for the current population of the planet. The problem arises from the distribution uneven rainfall and misuse that is made of collected water. Today there are 26 countries with 262 million of people that fall under the category of areas with lack of water (Mancuso 2003).

The purpose of these processes is sustainability and water conservation, rather than discharging the treated water to surface waters such as rivers and oceans. In some cases, recycled water can be used for stream flow augmentation to benefit ecosystems and improve aesthetics.

The first thing to be done with respect to water is save. Reducing consumption as much as possible, avoiding spend generated by the initiatives of reusing water. It is the most rational water. But when it is no longer possible to reduce consumption, we have to reuse it as best as possible so that it is also economically viable and rewarding.

2. METHODS

2.1 GRAYWATER

Graywater refers to the reuse of water drained from baths, showers, washing machines, and sinks (household wastewater excluding toilet wastes) for irrigation and other water conservation applications. Contrary to common belief, graywater is not a benign product - it may contain bacteria and other potential pathogens. Graywater has the potential to achieve notable water conservation, but best practices must be employed to ensure safe use of graywater. (Waskom and Kallenberger, 2014).

2.2 TREATMENT

There are several ways to treat graywater from cheap devices that take the water directly into to the toilet or garden irrigations, to complex equipment that make up the biological treatment of water, with sedimentation tanks, bioreactors, filters, pumps and disinfectants systems.

The principal reasons why graywater may need to be treated are: Remove substances that may harm plants, human health, wider environment and substances that may clog the graywater system.

2.2.1 METHODS

There are a lot of methods we can use to treat the water. Each one corresponding to how the water will be used in the future.

Filtration: The first level of treatment, which blocks solid materials, such as hair, lint and food particles entering in the graywater system.

Settlement and Floatation: After the filtration, some materials, more denser than water still in the system. With the settlement and floatation, these denser materials fall out to the bottom of the tank, while the grease, oils and other small particles will float forming a surface scum layer. The other part of the liquid may be used.

Disinfection: The disinfection method is only used if there is risk of human contact with the graywater. If required, is generally with biological treatment.

2.3 USE OF GRAYWATER

Primary Reuse: These reuse systems directly use the water from domestic sections, as shower, toilet and laundry. As you can see in the Figure 2, the system doesn’t have a complex treatment system.

Figure 2: Primary Reuse (from http://www.engineeringcivil.com/a-step-towards-sustainable-water-management-grey-water-reuse.html visited on 2/7/15 at 9:00 AM)

This simple manual system, with low maintenance requirements admits the immediate use of graywater. It has low capital and operating cost. However, the treatment provided is limited. Odor and other problems may occur.

Secondary Reuse: These systems the water has to be treated and stored for toilet/flush system and garden watering. This method is most common used at multiple occupancy buildings.

Figure 3: Secondary Reuse (from http://www.engineeringcivil.com/a-step-towards-sustainable-water-management-grey-water-reuse.html visited on 2/7/15 at 9:00 AM)

While this system has high degree biological treatment, being suitable for treating all kind of wastewater for reuse application and the capacity to be stored, it