Integrated Wastewater
Treatment and Aquaculture Production
by Martin S Kumar and Michael Sierp
May 2003
RIRDC Publication No 03/026 RIRDC
Project No SAR-16A
Eexecutive Summary
Intensive animal systems housing pigs, poultry, turkeys, dairy, feed
lot cattle and horses have caused an animal waste disposal problem in parts
of Australia. The efficient recycling and reuse of both nutrients and water
are likely to become essential requirements for these and other intensive
animal husbandry systems in the future, particularly given the focus on
ecologically sustainable development A proactive approach from the livestock
industry in dealing with its environmental issues and long term sustainability
has wide benefits including improvement in farm income, rural employment
and sustainability of the livestock industries.
The management of all wastes from a number of industries will also be
a platform for non fossil fuel energy production.
This project deals with the disposal of piggery effluent. The pig industry
is facing many challenges, with the major one being profitability. Factors
affecting profitability range from the price received for the product to
the high cost of inputs and increasing regulation on effluent and other
waste disposal. This regulation has become increasingly stringent in Europe
and Australia is now experiencing increasing government regulation on piggery
wastes. An example of this is the introduction of load-based licensing
in NSW where the producer will be charged for pollutants released into
the environment.
The main aim of the project is to obtain baseline information for the
development of integrated wastewater treatment model and to provide direct
input to the Urrbrae integrated treatment system for optimising its efficiency.
The experiments conducted in this project produced the following key information:
-
The optimum total nitrogen level to produce maximum algal biomass is about
100mg/l.
However, the nutrient depletion rate was greater in higher concentrations.
-
A retention time of eight days in summer and 14 days in winter will reduce
70-85% of the ammonia and about 50-60% of the soluble phosphorous content
from the digested wastewater. The retention time in algal ponds during
winter can be reduced by diluting the wastewater.
-
The digested wastewater did not contain any total and faecal coliform.
The properly digested wastewater appears to be safe from pathogens such
as coliform.
-
Both silver perch and rainbowfish can be cultured in wastewater with the
latter species more tolerant to high nutrient levels.
-
The duckweed and mussels along with fish could be used as an important
plants and animals for nutrient removal purpose. Duckweed is highly efficient
in removing ammonia from the wastewater.
Recommendations
-
The current expensive aerobic digester could be replaced with simple anaerobic
type that can produce biogas. The present system cannot be recommended
to farmers as it is expensive and complicated to operate. It also needs
to be modified to ensure manual operation if any breakdown in the electronic
system happens.
-
The high rate algal pond with heavy hydraulic paddle wheel can be replaced
with an extra two duckweed ponds. This will increase the efficiency of
ammonia removal and reduce the energy cost. Most importantly the system
is easier to operate.
-
The dilution of wastewater from the digester needs to be adjusted to a
concentration closer to 100mg/l nitrogen. This will optimise the efficiency
of the algal pond.
-
The flow rate in the algal and duckweed ponds needs to be adjusted to retain
water for the minimum period required during winter and summer. This will
enable proper biological treatment of water. The quality of the water going
into the fishpond will need to be maintained.
-
Mussels could be used in the fishpond with silver perch, rainbowfish and
aquatic plants.
The aquatic plants and mussels enhance the nutrient removal in the
fishpond. There is a need to undertake research to determine the optimum
density and combination of organisms to maximise the wastewater treatment.
-
Since most of the results were compiled from the microcosm and mesocosm
experiments, further pond level experiments are required to refine the
results.
-
The experiments conducted in this project were carried out in still water.
It is important to repeat the treatments in the flow-through system to
determine the levels more precisely
-
Further research is necessary to establish a commercial scale demonstration
system. The information from this pilot project should also be used to
establish a best practice commercial scale integrated farming system model
to treat intensive livestock industry waste (in particular piggery waste
utilisation).
Last updated: 8 May
2003
Copyright RIRDC
http://www.rirdc.gov.au/reports/Ras/03-026sum.html
