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2. Digestion — Diverse bacterial populations continually degrade the organic solids that collect
in the scum and sludge layers. Soluble organic compounds and waste gases are the by-
products of the digestion processes.

3. Sludge/Scum Storage — Despite the microbial digestion there is always a net accumulation
of scum and sludge. The material that accumulates is predominantly in-organic or non-
biodegradable. This material is removed from the tanks periodically.

The liquid fraction of the sewage together with the soluble organic by-products of the digestion
process are then transferred to the subsequent treatment units. Innovative design of the tanks
and internals will ensure that no sludge or scum leaves the Primary tanks.

Balance/Aeration Compartment

Flow Balancing (or Equalisation) is used to minimise hydraulic surges to the treatment units.
When a surge or large influx of sewage enters the system, the Balance tank stores a portion of
the incorning liquid. This stored liquid is transferred to subsequent treatment units gradually.
Consequently, the hydraulic loading on the treatment units is more uniform. This improves the
performance of the Biofilter, Clarifier and Disinfection system ensuring a high quality effluent.

The Balance tank may be aerated to lift the oxygen concentration of the waste water.
This reduces the oxygen requirements of the aerobic Biofilter improving system performance.

Biofilter

The Biofilter (Biological Trickling Filter) is a bed of permeable media to which bacteria attach,
and through which the wastewater is trickled.

The primary treated effluent is transferred to a sprinkler system in the Biofilter which distributes
the effluent over the media. Organic material from the liquid is absorbed into a biological film
(Bioslime) attached to the media. The bacteria present within the Bioslime degrades the
organic material. As the slime layer grows it is sloughed off by the hydraulic flow over the
media.

Effluent drains from the Biofilter into a sub zone of the Clarifier. A significant portion of this
effluent is returned to the Biofiiter for polishing.

Clarifier Compartments

Effluent from the Biofilter is transferred to the Clarifer. Residual suspended solids and sloughed
bacterial matter from the Biofilter are removed from the waste water in the Clarifer, which also
acis as a recirculation tank for the Biofilter with effluent being returned to the Biofilter from the
Clarifer.

Matter that settles to the base of the Clarifier is returned (automatically on a daily basis) to the
Primary tank for storage and digestion,

Final Efiuent Compartment

The ireaiment process uses chlorine for disinfection. The treated effluent from the Clarifier is
discharged through an in-line chlorination unit into the final effluent compartment. The in-line
chiorination unit consists of a mixing box and open siatted holders which contain chlorine tablets
for disinfection of the effluent. The effluent is held in the final efftuent tank for a minimum of
thirty (30) minutes. This ensures sufficient chlorine contact time needed for high levels of
disinfection.

 

PETRAC LAND HOLDINGS P/L Noosa North Shore Eco-Tourism Portal September 2003
1.\7296-03\Report\FINAL REPORT ~ 18Sept03.doc Commercial in Confidence Page 12