Approximately 60% of water that is consumed is converted to Greywater.

The term “Greywater” can be defined as untreated wastewater generated either directly or indirectly by human activities having no fecal contamination.

When this untreated wastewater is stored, even for short periods, the water often clouds and turns grey in colour. This is why it is called as greywater.

Greywater is also referred to as Sullage or foul water.

While greywater looks dirty, it can be used for several different applications before being completely discarded into the sewage system for treatment.

Sources of Greywater

By defination all greywater is waste water, but not all waste water is greywater. Some definitions include the water sourced from various kitchen appliances while the others don’t.

Some common sources of greywater are:

Basins/Sinks

Showers

Washing Machines

Kitchen Appliances

Washing of cars

Washing of homes/offices

The exact sources of greywater may vary according to countries and organizations.

Quality of Greywater

The quality of the greywater determines the applications for which it can be used effectively. Greywater is usually warm and contains different types of organic matter and some nutrients.

Here is a list of common sources of greywater.

Source Possible Contents Washing Machine Suspended Solids(dirt,lint), organic material, oil and grease, sodium, nitrates and phosphates (from detergent), bleach Dishwashers Organic Material, suspended solids (food particles),bacteria, detergent, oil, grease Shower, washbasins Bacteria, hair, organic material, suspended solids (skin, particles), oils, soap, shampoo, toothpaste Kitchen Sinks Bacteria, organic matter, suspended solids (food particles), fat, oils, grease, soap, detergent residue Floor and other washing wastes Dirt, soap, detergent, bacteria

Typical Composition of Greywater

Parameter Unit Range/Value Suspended Solids mg/L 45-330 Turbidity NTU 22-200 BOD 5 mg/L 90-290 Nitrite mg/L <0.1-0.8 Ammonia mg/L <0.1-25.4 Total Kjeldahl Nitrogen mg/L 2.1-31.5 Total Phosphorus mg/L 0.6-27.3 Sulphate mg/L 7.9-110 pH – 6.6-8.7 Conductivity mS/cm 325-1140 Sodium mg/L 29-230

Depending on how the greywater is managed, its contents and nutrients can prove to be beneficial to the various applications.

Quantity of Greywater

Greywater quantity keeps on varying based factors such as :

Number of members in the household or offices

Age distribution of members

Lifestyle characteristics

Water usage patterns

Climatic and environmental conditions

It is estimated that greywater makes up approximately 60% of all wastewater. This means that 60% of all water that is consumed will be converted to greywater.

As identified by standard water requirements, an individual can consume approximately 135 lpd. Based on this, it would imply that an individual can generate approximately 81 L of greywater per day.

Greywater generated by an individual:

Per day = 81 L

Per Week = 567 L

Per Month = 2,430 L

Per Year = 29,565 L

Applications or Uses of Greywater

Greywater has varied applications as non-potable water depending on its source and composition. Though it is not impossible to use untreated greywater, treated greywater has more applications.

Toilet Flushing

Gardening, Irrigation or Landscaping

Firefighting

Heat Reclamation

Industrial Use

Car Washing

Ornamental uses in fountains, artificial waterfalls

Significance of Greywater Reuse

Resusing of greywater enables the utilization of an on-site resource which would other wise be wasted. Greywater reuse helps in

Conserving of fresh water or potable supplies

Reusing of nutrients

Groundwater recharging

Reducing load on waste water treatment plants thus saving money spent by authorities

Reducing water wastage

Reducing energy consumption

Guidelines for Greywater Reuse

In order to reuse greywater effectively, the following objectives help establish the basic guidelines.

Prevention of Public Health Risk Possible disease transmission arising from improper greywater reuse

Ensuring the greywater systems do no pose any harm to the environment or native ecosystems

Protection of Groundwater Surface Water Land and Vegetation



Working of the Greywater System

The working of the greywater system consists of four steps:

Collection of Greywater Several methods can be employed to collect greywater from all its different sources. It is highly recommended to install proper plumbing in order to collect this greywater since it requires less maintenance and can transfer the collected greywater directly to its designated storage. Storage and Treatment Collected greywater is immediately stored. It is recommended that collected greywater be stored for less than 24 hours. In order to store this greywater for longer periods for various applications, it should be filtered to remove suspended solids and particles and then be treated with Chlorine or Iodine.

Based on the application for which the greywater is going to be used, different treatment procedures may also be adopted. Use of Greywater

Methods to collect Greywater

In order to reuse greywater, it is imperative to collect the said greywater. The following methods can be adopted for the same:

Manual Collection – To collect using bucket or jug by hand

Simple Piping – To collect using plumbing connections and systems between source and storage tank or area of application

Integrated Sewage and Piping – To collect using plumbing connections and systems between all sources and the collection tank with provisions for treating the greywater with chlorine or iodine for longer storage.