INTRODUCTION

Pollution of water resources by improperly or inadequately treated wastewater (sewage) contaminates ecosystems, drinking water supplies and is a leading cause of human disease worldwide (some 3.5 million people, mostly children under 5 die every year, about 9,000 people every day, from diseases caused by sewage pollution such as diarrhoea, cholera and typhoid). In addition to urgent human health issues, we know that untreated sewage is a leading cause of global coral reef decline, oxygen depletion, fish kill and ecological degradation of rivers and lakes - with the increasing pollution of already limited underground water tables and sources of our drinking water.

Yet, this is not the fault of what is called "sewage" but rather by the way we handle some of its components. In organic-type wastewater from human habitations for example, urine and faeces are among the very few natural substances of extreme ecological importance; their richness and potential productivity are such that they were highly valued for millenaries in human societies throughout the globe. Faecal matter (which when mixed with water is commonly called "black water") is very rich in nutrients: 5-7% nitrogen and 3-5% phosphorus, while urine is even more concentrated. These two elements ("materials") alone belong to the most valuable nutrients there are, often referred to in the field of Ecology and Botany as 'limiting factors' to plant growth because of their relative scarcity and irreplaceable value. These nutrients are the main components of most chemical fertilizers. Life promoting, both to microbes and plants, these materials greatly facilitate the formation of rich soils.

Used for centuries as potent fertilizers, urine and faeces are being treated today mostly as waste to be disregarded, and in order to evacuate them, mixed with water: it takes minimally per person and per year 3,000 liters to 54,000 liters of water, with an average of 6,000 liters just to move 700 kg excreta, which, in addition to wasting a precious resource, spreads the pathogens (disease causing organisms) in the environment. Organic wastewater especially becomes a problem when it is released in great quantities: when sewage coming from a few humans is released to the milieu, it often breaks down and biodegrades without being a dangerous source of contamination (unless close to a water table). But when population increases, what is otherwise rich and life bearing, becomes dangerous and disease causing: directly sent to natural groundwater, rivers or oceans, this mixture of water becomes a toxic pollution, as an increasing quantity of these elements eventually exceeds ecosystems' natural capacity of digestion and causes eutrophication by excessive nutrients.

Wastewater Gardens^® (WWG) ecotechnology belongs to the family of constructed wetlands. What WWG units do is reproduce the conditions of natural wetlands, called by scientists the "kidneys of the Earth" for their high capacity of water recycling in the biospheric cycles. Unlike many natural wetlands however, WWG belongs to the family of subsurface flow designs, which means that at no moment is the sewage water in contact with the air, thus preventing all bad smells, mosquito breeding or accidental human contact.

A variety of natural mechanisms effectively treat effluent and purify all water which passes through a wetland, in this case through your WWG unit. These mechanisms are biological, chemical and physical. One of the principal factors of purification are plants which are able to live in water saturated soils, directly assimilating nutrients (especially nitrogen and phosphorus) and metals, removing these "pollutant" elements from the water and incorporating them into their plant tissue. The top part of the plants above the gravel brings down oxygen to the roots, which in turns enables microorganisms to live. A kind of symbiosis develops whereby the plants are consistently nourished via the water and its nutrients, among which some of the breakdown material produced by the microbes able to live through the oxygen generated by the same plants.

Highly efficient at removing potentially harmful compounds before they reach rivers, lakes and the ocean, wetlands also support diverse vegetation and provide important habitat for many animals which are essential to the overall health of the Earth's ecosystem. In addition to their purifying capacity, constructed wetlands literally create life. Plants are our "3rd lung" as they create the oxygen which we need to breathe, and metabolize carbon dioxide which we exhale; they are also important contributors to the rain cycle.