PWT
Pacific Waste Technologies
PTY LTD
"Sanitation Solutions"
How it Works
Envirocheck Enterprises
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Summary of The Hybrid Toilet Processes
1. Waste Delivery
Waste is delivered via a NonFlush or MicroFlush toilet pedestal.
2. Preliminary treatment
The waste enters a water filled primary tank. It includes significant amounts of suspended solids. Faecal matter and paper are broken down by a combination of dissolution and metabolic actions of a wide variety of aerobic and anaerobic bacteria, which contain cellulytic enzymes.
Since no mixing takes place one would expect a steady gradient of an oxic zone (at the surface of the primary tank), which is gradually being depleted into an anoxic zone (at the bottom of the primary tank). A significant stable population of ammonia and nitrite oxidizers (nitrifyers) may develop in the upper layers.
Aeration is provided via standard rotary ventilation. The accumulation of sludge settling to the bottom will foster the growth of anaerobes such as the methanogenic bacteria and denitrifyers in the lower layers.
The anaerobic digestion of wastes can be considered a two-step process. First, the complex organic materials including, paper, faecal matter and microbial biomass are depolymerised and converted to fatty acids, carbon dioxide and hydrogen.
A large variety of non-methanogenic bacteria, obligate or facultative anaerobic bacteria participate in this process. In the next step, methane is generated either by the direct reduction of methyl groups to methane, or by the reduction of carbon dioxide, either by molecular hydrogen, or by other reduced fermentation products such as fatty acids, ethanol, carbon monoxide.
Anaerobic processes are generally slow and highly dependent on pH (optimum 6-8) and temperature (optimum 30-37C). However, even under suboptimal conditions the anaerobic processes generally continue, although much slower. The given retention time of sludge in the hybrid toilet system is 4-7 years allowing for substantial digestion and reduction of sludge volumes.
Continued
3. Separation Chamber
Gas production (methane, carbon dioxide and small traces of nitrogen, hydrogen, hydrogen sulphide) will cause some sludge to rise. The suspended solids are separated from the liquid by passing the sewage through a separation chamber.
The separation chamber allows liquid to pass to the secondary treatment tank without transfer of solids, this is eliminated by the slots in the side of the twin separation chamber.
4. Secondary Tank
In a simple sewage treatment process, micro-organisms are encouraged to grow on plastic pipe media through which the overflow from the primary tank is channelled through a series of baffles. The large surface area of the plastic medium provides a suitable substrate for the growth of biofilm, which consists exo-polymers generated by a wide range of bacteria which include Zooglea species amongst others.
This biofilm forms the main matrix, which accommodates a heterogenous community of bacteria, fungi, protozoans, nematodes and rotifers. This community feeds on other bacteria matter (eg. Faecal bacteria) and absorbs and mineralises the dissolved organic nutrients in the sewage further reducing the biochemical oxygen demand in the sewage.
Aeration is provided passively through tank ventilation and surface-overflow. A retention period of up to 135 days provides ample time for mineralisation (dependent on temperature and pH).
5. Disposal
The treated effluent is discharged from the Secondary treatment tank to ground or to a holding tank (for removal). If discharged to ground, adequate drainage and preparation of the discharge zone should be selected similar to those of septic tanks.
Although substantially reduced in potential pollutants, additional improvement of the effluent quality occurs especially in well drained, sandy soils or polishing (grass/reed) beds through which the sewage is trickled. The micro-organisms, which need oxygen to thrive, feed on the remaining nutrients in the sewage and purify the water in similar fashion to a percolating filter.
Michael ten Lohuis (Ph.D., BscHons, MASM)
184 Vickers Rd Condon QLD 4815
NATA Endorsed Report