Water Purification

A. Input: filtered white water from bio-bed
B. Outputs:

1. clear water storage
2. brine to bio-bed sub-surface

Slow Sand Filtration (SSF)

Probably the oldest water treatment method is filtering through a meter or more of sand, which will remove many microorganisms, most debris, and most toxins. As this filter ages, a gelatinous layer called the schmutzdecke forms near the top. The composition of any particular schmutzdecke varies, but will typically consist of a complex biofilm matrix of bacteria, fungi, protozoa, and rotifera. The top of the schmutzdecke needs to be skimmed regularly to maintain flow rates. SSF systems are typically laid out vertically

Soil Bed Reactor (SBR)

Similar to SSF method, sewage is trickled through a soil matrix containing organic media and plant roots on which complex biological processes take place. The symbiotic relationship that is normally established between the plant roots and microorganisms living on and around these roots is very complex and important in the wastewater treatment process. This process not only removes organic chemicals, but is also thought to contribute to the reduction of other polluting substances including pathogenic bacteria and viruses. It has been shown that roots of aquatic plants such as bulrush, reed, soft rush and water iris excrete substances that can either partially or completely kill pathogenic bacteria while not harming beneficial bacterial. The aerobic zone around the aquatic root system can also support, in addition to bacteria, the growth of large numbers of protozoa which feed on bacteria, viruses and particular organic matter. SBR systems are typically laid out in a horizontal aspect.

Irradiation

Either heat or UV radiation can be used to sterilize waterborne microorganisms.

Distillation/Atmospheric Water Generation

Using standard plumbing parts, glass, etc., it is possible to assemble a solar still to provide pure, distilled water. Greenhouses inherently act as solar stills, evaporating water from soil and transpiring from plants and animals, then condensing it on structural surfaces. An atmospheric water generator (AWG) is a device designed to extract potable water from humid ambient air. Water vapor in the air is condensed by cooling the air below its dew point, exposing the air to desiccants, or pressurizing the air.

An AWG is designed to render potable water, but may simultaneously dehumidify the air. Indeed, many atmospheric water generators operate similar to dehumidifiers: air is passed over a cooled coil, causing water to condense. The rate of water production depends on the ambient temperature, humidity, the volume of air passing over the coil, and the machine's capacity to cool the coil. These systems reduce air temperature, which in turn reduces the air's capacity to carry water vapor. This is the most common technology. As a rule of thumb, Cooling Condensation atmospheric water generators do not work efficiently when the temperature falls below (65°F) or the relative humidity drops below 30%. The cost-effectiveness of an atmospheric water generator depends on the capacity of the machine, local humidity and temperature conditions and the cost to power the unit.

Ionic

Microbiological studies indicate that silver ions kill microorganisms. Simply storing silver in water helps. Running a small DC current (i.e. from a cheap solar battery charger) through two silver electrodes submerged in the water distributes the ions and is said to make the water a disinfectant.

Reverse Osmosis (RO)

Reverse osmosis filtration makes use of a selective membrane. The result is that the brine is retained on the pressurized side of the membrane and the pure water is allowed to pass to the other side. In order to be "selective," this membrane should not allow large molecules or ions through the pores, but should allow smaller components of the solution (such as the solvent) to pass freely. This method requires high pressure (and hence power) and generates large quantities of brine.