Water is becoming a rare resource in the world. In India alone the International Water Management Institute (IWMI) predicts that by 2025, one person in three will live in conditions of absolute water scarcity (IWMI, 2003). It is therefore essential to reduce surface and ground water use in all sectors of consumption, to substitute fresh water with alternative water resources and to optimize water use efficiency through reuse options. These alternative resources include rainwater and greywater. This manual will focus on greywater treatment and its use as an alternative water resource in rural areas. 

Greywater is commonly defined as wastewater generated from bathroom, laundry and kitchen. Due to rapid industrialization and development, there is an increased opportunity for greywater reuse in developing countries such as India. This Manual provides theory and practices for greywater reuse in residential complexes with particular emphasis on schools.

Although India occupiesonly 3.29 million km geographical area, which forms 2.4% of the world\'s land area, it supports over 15% of world\'s population. The population of India as of March 1, 2001 was 1,027,015,247 persons (Census, 2001). India also has a livestock population of 500 million, which is about 20% of world\'s total livestock. However total annual utilizable water resources of the country are 1086 km which is only 4% of world\'s water resources (Kumar et al., 2005). Total annual utilizable resources of surface water and ground water are 690 km and 396 km respectively (Ministry of Water Resources, 1999). 

Consequent to rapid growth in population and increasing water demand, stress on water resources in India is increasing and per capita water availability is reducing day by day. 

In India per capita surface water availability in the years 1991 and 2001 were 2300 m(6.3 m /day) and 1980 m (5.7 m /day) respectively and these are projected to reduce to 1401 and 1191 m by the years 2025 and 2050 respectively (Kumar  et al., 2005). Total water requirement of the country in 2050 is estimated to be 1450 km which is higher than the current availability of 1086 km . Various options including rainwater harvesting and wastewater reuse will have to be considered to meet the anticipated deficit.

Organization of Manual

This Manual is organized in five chapters as depicted in Fig. 1 in addition to Chapter 1.Chapter 2 describes details on greywater such as sources, quantities, composition and greywater treatment options. Chapter 3 provides design specifications of various greywater treatment systems inclusive of components such as collection, filtration and application for possible reuse.

Chapter 4 describes water safety plans for small systems and its utility for minimizing/eliminating health risks. Health and safety requirements for greywater treatment and application are also included in Chapter 4.  A case study of greywater treatment system in 

Ashram school (hostel) is presented in Chapter 5. 

The objectives of this Manual are to assist in the promotion of acceptable long term greywater reuse practices and to promote conservation of good quality ground and surface water supplies by: Establishing acceptable means for greywater reuse as a guide for local government and Ashram schools.

• Setting minimum standards for design, installation and maintenance
• Preparation and execution of WATER SAFETY PLANS for minimizing health risks associated with greywater reuse 

Greywater treatment process varies from simple devices that divert greywater for direct application such as irrigation to complex systems involving sedimentation tanks, filters, bioreactors, pumps and disinfection systems. However, the basic objective of this manual is to initiate process of greywater treatment in India and keeping cost-effectiveness as a basis  theme. Simple treatment systems for non-contact use are also described. This manual provides acceptable solutions for reuse of greywater in unsewered areas that satisfies the performance objective and requirements. It may be appropriate for persons contemplating a greywater reuse system to consult a wastewater system designer or other suitably qualified person to consider the options available. 

This manual has been written specifically for practitioners involved in the operation, maintenance and management of water supplies in the developing countries.

These practitioners include the engineers, water quality analysts, scientists, sociologists and the professionals involved in monitoring and control of water safety in water supplies. The manual is designed to provide guidance to the practitioners on how to design, build and use a greywater system. It is written exclusively to enable the water suppliers to develop the greywater reuse system without having to depend on the external input.

Objectives and Target Audience

The objectives of this Manual are to assist in the promotion of acceptable long term greywater reuse practices and to promote conservation of good quality ground and surface water supplies by:

•  Establishing acceptable means for greywater reuse as a guide for local government and Ashram schools
•  Setting minimum standards for design, installation and maintenance
•  Preparation and execution of WATER SAFETY PLANS for minimizing health risks associated with greywater reuse 

Greywater treatment process varies from simple devices that divert greywater for direct application such as irrigation to complex systems involving sedimentation tanks, filters, bioreactors, pumps and disinfection systems. However, the basic objective of this manual is to initiate process of greywater treatment in India and keeping cost-effectiveness as a basis  theme. 

Simple treatment systems for non-contact use are also described. This manual provides acceptable solutions for reuse of greywater in unsewered areas that satisfies the performance objective and requirements. It may be appropriate for persons contemplating a greywater reuse system to consult a wastewater system designer or other suitably qualified person to consider the options available. 

This manual has been written specifically for practitioners involved in the operation, maintenance and management of water supplies in the developing countries.

These practitioners include the engineers, water quality analysts, scientists, sociologists and the professionals involved in monitoring and control of water safety in water supplies. The manual is designed to provide guidance to the practitioners on how to design, build and use a greywater system. It is written exclusively to enable the water suppliers to develop the greywater reuse system without having to depend on the external input.