Channels - Open channels are important to regulate the flow rate among ponds. Wherever possible these should be constructed from soil or other materials such as bricks instead of concrete, to allow for easy modification.
Photo: This squash grows among mixed crops including cabbage (lower part of photo), corn and sugar cane. This integration reduces plant disease and improves site productivity by taking advantage of differing soil and water conditions on the site. Petropolis, Brazil
Vegetation areas - Garden areas are essential to economic and nutrient productivity of the site. They usually constitute up to 50 percent of the total area of the facility.
These garden areas are divided into several sub-areas each with their own characteristics:
- Dykes surrounding fish ponds
- Dykes surrounding macrophyte ponds
- Final polishing areas after the macrophyte ponds
Topsoil - For all these areas it is important to retain the topsoil in a separate location during construction so the soil could be used to cover the most productive growing areas.
Final polishing area:
- Consists of underground and above-ground irrigation channels. Water flows from the macrophyte ponds into these areas. Plants take up excess nutrients which were missed by macrophytes. Residual algae are retained in the soil and become fertilizer.
- Underground channels are constructed of bamboo or plastic. Also, gravel beds or loosely joint clay pipes can be used. Much demineralized water leaches into soil or evaporates, while the rest leaves the facility through the outlet.
- Sometimes the final polishing area is used to raise ornamental fish in a low-pathogen environment. Examine this option with the local aquaculture expert and the consulting wastewater expert.
Photo: Looking up the outlet chute.Gravity and elevation are used to treat water and avoid pumping. If the watershed slopes below the outlet level , elevation is used for extra aeration in this shallow open channel. Petropolis, Brazil.
Outlet - This is normally a simple pipe running from the final polishing area into a channel or stream. However the pipe is constructed with a trap to prevent back-flow from the channel in the event of high water levels. It must also be established at the correct level to maintain the final polishing pond behind it. Usually a plastic pipe with siphon is used.
Photo: Water flow path: Enter oxygenation ponds (far upper right), flow beneath semi-circular wall (lower right) to shallow basin (center), into fish pond (left). Under-flow wall improves oxygenation entering the fish pond. A similar flow path is shown on site diagram page 27. Fences between ponds contain ducks which consume mosquito larvae. Ducks are resistant to pathogens. Petropolis, Brazil.
Livestock: Areas and structures
- This website does not show how to keep and raise livestock. This section only has details about areas/locations of livestock and some construction aspects.
- An essential livestock aspect of wastewater recycling is ducks which eat mosquito larvae at the edge of ponds. Ducks also reproduce on-site and provide contamination-free meat due to their high resistance to pathogens in most of the ponds. They also consume algae, provide nutrients for fish, and provide eggs.
- Construct low wire-mesh fences around each pond to keep the ducks contained and give extra guarantees against children falling into ponds if they get into the site accidentally. Ducks prefer small houses to nest and offer some protection from torrential rain. These structures are easily constructed
- The poultry area of the pond is fenced down to the bottom of the fish pond so that the bird's waste are not directly consumed by the fish, but mineralized first to allow for more feed production, algae, phyto- and zoo-plankton etc., for the fish. Also, this reduces losses of small fish consumed by birds
- Confined pigs are optionally used to provide meat and also manure for biogas. The piggery needs to have a concrete floor so manure could be flushed into drains which lead to the biodigester. It should also have an area outside the confining walls so that pigs could get sunlight. Raising pigs and determining the optimal number to keep on site requires special expertise of an integrated farming expert. Too many pigs overload ponds and defeat the treatment aspects of the facility. Piggeries, digesters and algae ponds together form a unit which must be sized correctly.
- It may be decided to have other livestock on the site. This depends on local conditions. Consultations are required with local agronomy consultants for construction requirements.
- In any case, wastes of these other livestock must be mineralized - either in the biogas digester or the ponds - and used in the nutrient cycle on the facility.