BIO-TECH WASTE MANAGEMENT PTY LTD www.duckweed.com.au POTENTIAL FOR TREATMENT AND REUSE OF WASTEWATER “Turning wastewater into opportunity water”® Saline mine wastewater Sewage wastewater Agriculture/ BTWM Pty Ltd duckweed-based wastewater treatment Recycle water into BTWM treatment Store treated water for future Release treated water for externa Irrigat ion for agricul Commercial enterprises Domestic grey water Irrigat ion communi Harvest ed duckwee d plant High protein feed supplement - livestock and Feed-stock for conversion to bio-fuels eg Carbo n
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BIO-TECH WASTE MANAGEMENT PTY LTD
www.duckweed.com.au
POTENTIAL FOR TREATMENTAND REUSE OF WASTEWATER
“Turning wastewater into opportunity water”®
Saline mine wastewaterSewage wastewater
Agriculture/aquaculture wastewater
BTWM Pty Ltdduckweed-based
wastewater treatment system process
Recycle water into BTWM
treatment process
Store treated
water for future
use
Release treated
water for external
use
Irrigation for
agriculture
Commercial enterprises
Domestic grey water
applications
Irrigation community parklands
Harvested duckweed
plant matter
High protein feed supplement -livestock and aquaculture
Bio-Tech Waste Management (BTWM) was formed in 1993 and is widely recognised for the expertise and experience that the company has developed in the use of Lemnaceae (duckweed) as a unique, environmentally sound, low cost solution for the treatment of wastewater. The BTWM technology uses duckweed, a small floating aquatic plant, to remove nitrogen, phosphorus and excess mineral nutrients from urban and rural effluent, and wastewater produced as a by-product of industry or intensive livestock and aquaculture production.
In 2011, BTWM began working with a major mining company in Queensland to explore the potential for a BTWM system to remove salts from mine wastewater.
BTWM provides the following services:
Consulting advice to water authorities, councils, the mining industry, intensive animal production, aquaculture and food processing plants on using duckweed to treat effluent so that the treated wastewater can either be reused or safely discharged into the environment.
Design of the layout of the patented BTWM floating barrier system to suit individual pond sites. This ensures that each duckweed installation will work to its maximum efficiency.
Manufacture and installation of floating barriers on the site. Provide training for site operator in management and maintenance protocols to
ensure the health and efficiency of the duckweed system. Provide the BTWM remote controlled harvester, if required, and train the site
operator in its use. Provide an operations manual for the harvester. Work with the client to identify economic opportunities for reusing the
duckweed treated wastewater and marketing the harvested duckweed.
SEWAGE TREATMENT
For many rural communities in Australia, the availability of low-cost land has meant that a low-energy wastewater treatment process, like a maturation and oxidation pond system, can be a cost-effective alternative to the traditional mechanical wastewater treatment systems that consume large quantities of energy, chemicals and are expensive to maintain. Maturation ponds are commonly used in the final treatment process of effluent, but their efficiency can vary substantially, particularly when it comes to the removal of nutrients and algae. Odour production is another problem with some pond systems.
In recent years communities have become more aware of the real environmental cost of these basic systems – water is now recognised as a precious and precarious resource and the process of simply evaporating it is being seen as unsustainable. The fact that this water can be cleaned and at the same time produce an additional economic benefit has shifted the way communities view their ‘wastewater’. Treating the wastewater with a duckweed system not only allows the water to be re-used, it also provides the potential for income generation from the harvested plant material. In effect, turning a cost into an opportunity.
Bio-Tech Waste ManagementSmall towns and remote communities oxidation and maturation pond system
All material contained in this document is subject to the provis ions under the Copyright Act 1968 (as amended). No part of this document may bereproduced in any material form or transmitted to any other person without the express prior written permission of Bio-Tech Waste Management Pty Ltdexcept as permitted under the Copyright Act 1968 (as amended).
MID COAST WATER NSW
Mid Coast Water is the company responsible for the supply and maintenance of water and sewage services to the coastal region of NSW between Newcastle and Port Macquarie. Within this region there are two townships, Harrington and Coopernook where BTWM has installed duckweed based sewage treatment.
In 1999 MCW experienced problems with algal blooms in the sewage treatment maturation ponds, due to a combination of high temperatures and excess nutrients in the pond water. The algae reduced the operating efficiency of the sewage treatment system, consuming oxygen in the water and releasing toxins as it decayed. The effluent from the sewage treatment sites is normally used to irrigate nearby pastures but the presence of algae meant a risk to grazing stock, and the potential for algae to clog the reticulation and sprays in the effluent reuse system causing it to fail. Moreover, the effluent would not meet EPA reuse guidelines in terms of suspended solids and, if it needed to be released into the river during wet weather, effluent quality would be an issue.
Mid Coast Water contracted BTWM to install a duckweed based treatment system to control the algae and ensure the effluent released into the river or for irrigation met EPA discharge standards. To gauge the relative effectiveness of the duckweed treatment system, the first installation at Harrington was set up as a trial. One maturation pond was covered with a floating barrier grid and seeded with duckweed, while the other was retained as a control.
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The results clearly indicated that not only was the duckweed successful in controlling the algae, but it also treated the water to a quality better than that required by EPA standards for discharge.
At the conclusion of the trial period, the water quality in the duckweed treatment pond was compared with the control pond.
Normal biological growth in a sewage treatment process will remove 10-30% of the Phosphorus in the sewage, with the remainder being discharged in the effluent. Duckweed primarily uptakes orthophosphate, and absorbs other types of phosphate at various rates depending upon the relative concentrations. Duckweed has a lower growth limit compared with other pleustophytes and is able to compete effectively with algae for phosphorus in nitrogen poor waters. Nitrate results:Duckweed pond outlet: 0.4 mg/LControl pond outlet: 12.4 mg/L
Nitrate is found only in small amounts in domestic wastewater but in the effluent of nitrifying biological treatment plants, nitrate may be found in concentrations of up to 30mg/L. It is an essential nutrient for many photosynthetic autotrophs and in some cases has been identified as the growth-limiting nutrient. Duckweed uses the Nitrate as its growth nutrient at the Harrington sewage treatment site because of the low levels of TKN and NH3-N.
Nitrite is an intermediate oxidation state of nitrogen, both in the oxidation of ammonia to nitrate and in the reduction nitrate. Such oxidation and reduction may occur in wastewater treatment plants.
This coliform group of bacteria is part of the Total Coliform group, and is the principal indicator of contamination and the suitability of water for a variety of uses. Standard sewage treatment systems use maturation ponds as the means for disinfecting treated effluent, where the main instrument of disinfection is presumed to be UV light, although studies by the Dept of Land and Water Conservation have shown that a high level of disinfection is still achieved even with 100% shading over maturation ponds. Even though duckweed cover restricts light penetration, test results showed the faecal coliform level exiting the duckweed pond to be substantially lower than that of the control pond.
The analysis of suspended solids is important in measuring the control of biological and physical wastewater treatment processes and for assessing compliance with regulatory agency wastewater effluent discharge standards. The duckweed cover successfully controlled the algae growth by blocking sunlight and competing for nutrients.
The control pond was subsequently converted into a BTWM duckweed pond. The BTWM duckweed wastewater treatment systems installed for MCW have now been operating satisfactorily for over 11 years, with minimal maintenance required.
Suspended Solids And Faecal Coliforms ResultsHarrington STW
NORTHERN TERRITORY POWER AND WATER AUTHORITY
Power and Water Corporation, the authority responsible for the provision of water and energy services in the Northern Territory, recognised the potential of a duckweed based wastewater treatment system to up-take nutrients and eliminate algae from sewage maturation ponds, particularly given the favourable climatic conditions. In an efficiently functioning maturation pond system, the duckweed treated wastewater would also be suitable for reuse applications.
In 2008, Power and Water commissioned BTWM to set up a demonstration trial at Batchelor wastewater treatment plan, 100 kms south of Darwin. This project clearly demonstrated how quickly the duckweed plant can reproduce in warm, nutrient rich wastewater, and the effectiveness of the plant in eliminating algae. The demonstration trial also highlighted the importance of having properly designed ponds to ensure appropriate circulation of wastewater within the ponds.
When the duckweed cover was initially installed, the system did not function to optimum efficiency because the physical design of the pond meant that wastewater was short circuiting the process and moving through too quickly, providing insufficient detention time and allowing excessive sludge to form in the pond. BTWM addressed this problem by installing a baffle through the pond. After the baffle was installed the wastewater started to circulate and mix throughout the pond, enabling the duckweed to demonstrate its potential for up-taking nutrients and eliminating algae from the wastewater. At the conclusion of the trial, the improvement in water quality achieved by the BTWM duckweed system exceeded the levels stipulated by Power and Water Corporation for BOD by 63%, for COD by 48% and for Suspended Solids by 71%.
The pH levels of the water exiting the pond were in the range of 6.7 to 7.8, ideal for good duckweed growth, and the E.coli levels are in the range of 300 to 700 parts per 100 mL, making the water ideal for reuse applications in agriculture or for irrigating sporting fields or open public spaces.
ALGAE CONTROL
The ability of a duckweed cover over a pond to eliminate algae has proven to be attractive to both crop irrigators, and managers of wetland sites.
South Australia is possibly the state most vulnerable to the impact of drought as its water supply is heavily dependent on the Murray Darling River system. Not surprisingly, this state is leading the way in reusing treated wastewater for agriculture purposes. The Adelaide sewage treatment plant at Bolivar treats the city’s effluent to a level that allows the wastewater to be piped to a large number of vineyards and vegetable growers in the greater Adelaide region. All of the users have on-site dams to hold the wastewater for several days before it is processed through elaborate filtration systems and then on to the drip irrigation system.
BTWM worked with a large vineyard in Virginia, a suburb of Adelaide, that was experiencing algal problems in its holding dam. The algal problem was so severe that it was causing major problems for the filtration plant and was disrupting the water getting to the vines at crucial summer growing periods. BTWM installed a duckweed system on the holding pond, which eliminated the algae and resulted in major savings for the vineyard by significantly reducing the operation of the filtration plant, and also by reducing the amount of wastewater lost through evaporation, which was significant during the hot summer months.
In 2011, BTWM installed a similar system at a wetlands restoration site in Meeinyan in Victoria, where again the objective was to stop the algae that develops in nutrient rich ponds flowing in to the wetland and contaminating the restored site.
Bio-Tech Waste ManagementDuckweed applications at vineyards and selected crop production
All material contained in this document is subject to the provis ions under the Copyright Act 1968 (as amended). No part of this document may be reproduced inany material form or transmitted to any other person without the express prior written permission of Bio-Tech Waste Management Pty Ltd except as permittedunder the Copyright Act 1968 (as amended).
ADDING VALUE
These installations used the duckweed system to treat the wastewater but did not take the next step forward by taking advantage of the plant’s economic value.
Interest in duckweed as a crop has increased recently due to the rapidly escalating price of protein, along with the realisation that duckweed can extract unwanted minerals such as nitrogen, phosphorus, potassium, aluminium, iron, magnesium and sodium from wastewater. Duckweed needs to be managed, protected from wind, maintained at an optimal density by judicious and regular harvesting and fertilised to balance nutrient concentrations in water to obtain optimal growth rates. When effectively managed in this way, duckweed yields up to 100 tonne dry matter/ha/year containing up to 45% crude protein, 5% fat and a highly digestible dry matter.
Duckweed protein (35-45%) has higher concentrations of the essential amino acids, lysine and methionine than most plant proteins. It also has high concentrations of trace minerals and pigments, and zanthophyll that makes duckweed meal an especially valuable supplement for poultry, fish and other animal feeds.
With duckweed being approximately 94% water, drying of the plant is required when it is used in a pre-mix application, either as a dried plant material or incorporated into pellets. The drying trials that we undertook with University of New England emphasised the significant time and cost savings that could be realised if the harvested duckweed could be feed as a fresh plant. This is possible where the duckweed is cultivated on wastewater at a farm, such as a piggery, dairy, beef cattle feedlots or on aquaculture farms.
AQUACULTURE
The Australian fish farming sector is under pressure from a lack of fresh water to maintain pond levels, and the increasing cost of feed. Fish, prawns and red claw ponds all generate significant levels of ammonia, which if not strictly controlled, will kill all the living creatures in the pond. The most common method of controlling the ammonia level is to constantly add fresh water to the aquaculture ponds.
The Bribie Island Aquaculture Research Centre in Queensland, in conjunction with BTWM, has conducted trials of removing the ammonia from the aquaculture pond by passing the water through a duckweed pond. The duckweed uses the ammonia in the circulation pond as a growth nutrient and reduces the ammonia level to a range that allows the water to be circulated back through the fish, prawn and red claw pond. The duckweed cover in the circulation pond also reduces the amount of water lost to evaporation.
The duckweed can be harvested and fed either fresh to selected species of fish such as tilapia or jade perch, or dried and pelletised and fed to most other species of fish, prawns and red claws.
The results from the Bribie Island study were of particular interest to the Queensland Dept of Primary Industry because fish production can be integrated with existing water treatment infrastructure without significant extra land requirements, and the Queensland climate is favourable to both duckweed growth and fish production. Such integration may contribute to cost recovery of the wastewater treatment process and, dedicated aquaculture operations can utilise a duckweed water treatment system to
Bio-Tech Waste ManagementAquaculture duckweed applications - fish, prawns, red claws
Fishponds generate high levels ofammonia, which kills the fish,prawns and red claws.
Water goes to a duckweed pond.Duckweed removes the ammonia asit is a growth nutrient for the plant.
Duckweed treated water returns tofish, prawn and red claw pond,which reduces the amount of freshwater required.
Duckweed harvested,can be fed to selectedspecies of fish (JadePerch) or dried andpelletised and fed tomost fish, prawns andred claws.
All material contained in this document is subject to the provis ions under the Copyright Act 1968 (as amended). No part of this document may bereproduced in any material form or transmitted to any other person without the express prior written permission of Bio-Tech Waste Management Pty Ltdexcept as permitted under the Copyright Act 1968 (as amended).
minimise the environmental impacts of the operation and improve profits by substituting duckweed for commercial diets.
The Burdekin trial identified a local aquaculture species, jade perch that may be reared on duckweed-supplemented diets. In that trial, jade perch were grown in-line of the municipal effluent stream, post tertiary treatment. The fish was feed only the fresh harvested duckweed and gained weight, with an average weight gain of 0.7g/day/fish over 102 days.
The greater potential for duckweed-based diets, however, is beyond only those aquaculture species that will consume it unprocessed. Large aquaculture industries in Queensland include barramundi and penaeid shrimp, but these species will not consume fresh plant matter, so the duckweed would need to be processed into a more suitable form. For crustaceans in particular, the abundance of carotenoids and pigments in duckweed can stimulate growth and improve colour.
If fish production is to take place in the final stage of an effluent stream, i.e. post duckweed water treatment, water quality parameters must be maintained within the tolerances of the cultured species. The effect of water quality will vary from species to species, and larval and juvenile stages may have lower tolerance levels than adult stages. Besides fish health, assured safety of the cultured stock for human consumption is critical. Low levels of water contamination may cause no obvious adverse effects but gradually accumulate in the fish to the point where it poses a potential health risk to human consumers.
In Australia, there are clear guidelines for water quality, and reference to these guidelines must be made to ascertain whether treated effluent meets these water quality criteria before an in-line aquaculture operation can be considered.
However, if these criteria are unable to be met, fish production is still feasible at adjacent sites where clean water is available, using duckweed harvested from the effluent stream as a food source. While public health considerations are still critical, the threat of transferring pathogens or other toxins from the effluent is greatly reduced by dilution. Further, the best quality duckweed (highest nutritional value) comes from the ‘farming’ zone of the duckweed treatment system. The predilection of duckweed in this zone to exclusively uptake growth nutrients over other contaminants, enables their safe utilization. In the Burdekin study semi-quantitative analyses of fresh harvested duckweed showed no residual elements from the effluent stream that were greater than toxicant guidelines proposed for aquaculture.
Duckweed plants, as a function of their surface area, accommodate attached pathogens from the wastewater. As such, pathogens will inevitably be harvested along with the crop. When fresh plants are fed to fish, dilution of pathogens will occur in the fishpond. Surviving pathogens consumed by fish will be digested in their guts. In instances where plants are processed and dried, desiccation will further destroy pathogens. While numerous studies have demonstrated the potential for large-scale fish production using effluent-grown duckweed, public assurance is paramount for wide acceptance of food cultured using by-products from the effluent treatment process.
ANIMAL FEED
BTWM, in partnership with the University of New England and with funding from the Rural Industries Research Development Council, (RIRDC) has conducted research into the value of duckweed as a feed supplement for ducks, chickens and sheep. The results were published by RIRDC in 1998. We conducted trials looking at the broader picture, where a duckweed wastewater treatment system was used to clean water generated from intensive animal production, and then harvested to provide a high value feed supplement.
Laying hens
Two trials were conducted with laying hens being fed diets that included varying percentages of duckweed.
Feed intake and production was excellent and no adverse clinical effects of the diets were evident. Birds ingested slightly more of the duckweed-containing diet, and produced slightly heavier eggs with attractive but darker yolks. The researchers concluded that duckweed is a useful protein, mineral and pigment source in diets for layers and it appears to contain no toxic or anti-nutritional factors.
Pekin Ducks
Two trials were conducted with 100 Pekin ducks being fed diets that compared commercial feed with diets that contained varying percentages of duckweed.
Bio-Tech Waste ManagementIntensive animal production
Water run off fromanimal sheds.
Wastewater pondwith duckweedcover.
Water returned tohosing down sheds.
Irrigation of crops.
Duckweed harvestedand used as feed foranimals.
Duckweedlowers BOD andeliminates algae.
All material contained in this document is subject to the provis ions under the Copyright Act 1968 (as amended). No part of this document may bereproduced in any material form or transmitted to any other person without the express prior written permission of Bio-Tech Waste Management Pty Ltdexcept as permitted under the Copyright Act 1968 (as amended).
Feed intake and egg production were recorded. Each bird ingested, on average, 0.5 - 0.6 kilos of fresh duckweed per day. Of the egg characteristics examined in both trials, only yolk colour differed between diets. Yolk colours were highly correlated with intake of duckweed, showing that duckweed has the ability to impart a rich golden colour to egg yolks.During the trial it was noted that the birds showed a strong preference for the fresh duckweed.
Merino Fine Wool Sheep.
The primary objective was to determine if the sheep would eat duckweed, and if they did, whether there was some benefit. The sheep were assigned to one of four dietary treatment groups using a random allocation technique. All of the sheep ate both dried and fresh duckweed and showed no adverse effect.
The trial confirmed that duckweed represents an alternative high protein supplement for sheep that are raised in a shed environment where the animal’s diet is crucial in producing either extra fine wool or lean body weight.
MINING INDUSTRY
Mining of coal and coal seam gas is a major industry in Australia. It is also a producer of vast reservoirs of contaminated water that cannot be re-used or released into the environment.
For the past 6 months, BTWM has been working with a major mining company on a trial to ascertain how effective a duckweed based water treatment system is for cleaning the mine wastewater. The results to date are promising and indicate that the plant can survive in highly saline water and can potentially remove the salts from this water to a level where it can be re-used or released. The system must be closely monitored and managed with regard to fertilising and harvesting, because the mine water, being saline and without significant nutrients is not naturally a quality medium in which to grow the plant. This project is currently on-going.
ENERGY
At BTWM we are in discussion with researchers who are engaged in developing new technologies for creating bio-fuels and electric power using duckweed as the primary feedstock. As these technologies come on stream we envisage building them in to a ‘whole of community’ model that makes use of the duckweed for its water treatment capacity while growing the plant as a crop to feed the technology to generate energy.
Our collaborators in this research include Professor Eric Lam, Rutgers University, N.J., USAProfessor Jay Cheng, North Carolina State University, N.C., USAProfessor Zhao Hai, Chinese Academy of Sciences, Chengdu, ChinaProfessor Lene Lange, University of Aalborg, Copenhagen, DenmarkA/Professor Aidyn Mouradov, RMIT, Melbourne, Australia
The case for using Duckweed (Lemnaceae)- a renewable and sustainable feedstock
for the production of bio-fuels.
A sustainable feedstock that does not compete for arable land or clean water. Low energy input to cultivation.
Rapid year round growth rate and wide habitat range. These features increase productivity while keeping the need to transport feedstock over long distance to a minimum.
Multi-purpose platform – additional existing uses for duckweed as a treatment for wastewater and animal feed supplement make it more economically viable and sustain its growth while R&D is being undertaken to optimise technology for efficient conversion.
Environmentally friendly - does not pose new challenges to the environment, actually alleviates existing environmental problems by cleaning wastewater.
Ease of biomass collection compared to other feedstock such as algae.
Simpler post-harvest processing compared to high lignin content feedstock options such as corn or switch grass.
Economic advantages in cultivation, transportation and conversion.
Research already well advanced in the integration of biology and engineering technologies required to optimise the parameters for duckweed biomass-to-fuel pipeline.
REPORTS AND RESEARCH
The following are accessible at www.duckweed.com.au
Leng, R.A., Stambolie, J.H. and Bell, R.E. (1995) Duckweed – a potential high-protein feed resource for domestic animals and fish. Livestock Research for Rural Development. 7(1):1-11
Bio-Tech Waste Management (1998) Duckweed: a potential high protein feed source for domestic animals and fish. RIRDC Publication No. 98/148
Bell, R.E. (2003) The application of a duckweed wastewater treatment system at the Harrington Sewage Treatment Works. Internal report to Mid Coast water
Willett, D. (2005) Duckweed-based wastewater treatment systems: design aspects and integrated reuse options for Queensland conditions. Department of Primary Industries and Fisheries, Queensland
