Download Reducing nutrients and salt from effluent

Reduction of nutrients and salt in
effluents for irrigation
Prepared by:
Raymond Mawson1
Nigel Goodman2
Tim Muster2
1
CSIRO Animal, Food and Health Sciences
2
CSIRO Land and Water
Date Published:
March 2015
Published by:
Australian Meat Processor Corporation
1
Acknowledgements
The project was undertaken by CSIRO and funded by the Australian Water Recycling Centre of Excellence
under the Commonwealth’s National Urban Water and Desalination Plan.
Further information: www.csiro.au and www.australianwaterrecycling.com.au
Disclaimer
This publication is published by the Australian Meat Processor Corporation Ltd ABN 67 082 373 448. Care is
taken to ensure the accuracy of the information contained in this publication. However, AMPC cannot accept
responsibility for the accuracy or completeness of the information or opinions contained in this publication.
No part of this work may be reproduced, copied, published, communicated or adapted in any form or by any
means (electronic or otherwise) without the express written permission of Australian Meat Processor
Corporation Ltd. All rights are expressly reserved. Requests for further authorisation should be directed to the
Company Secretary, AMPC, Suite 1, Level 5, 110 Walker Street Sydney NSW.
For further information please contact AMPC on 02 8908 5500 or [email protected]
2
Contents
Acknowledgements................................................................................................................................. 2
Contents .................................................................................................................................................. 3
Executive Summary................................................................................................................................. 4
1
Introduction .................................................................................................................................... 5
2
Irrigation.......................................................................................................................................... 6
3
Strategies for reducing the nitrogen load in effluent for irrigation ................................................ 7
3.1
Reducing the nitrogen load in the effluent stream ................. Error! Bookmark not defined.
3.2
Treating the effluent from anaerobic digestion ..................................................................... 9
3.3
Bio-conversion processes......................................................... Error! Bookmark not defined.
3.4
Phosphate removal - recovery .............................................................................................. 12
3.5
Salts management from Reverse Osmosis streams .............................................................. 14
4
Conclusions ................................................................................................................................... 17
5
References .................................................................................................................................... 18
3
Executive Summary
Meat industry effluents are distinct from effluents generated by other food industries and domestic
waste. Over the past half century, the industry has been successful in removing Biological Oxygen
Demand (BOD) and Chemical Oxygen Demand (COD) from its effluents, but there remains the vexed
issue of dealing with nonorganic nitrogenous materials and to a lesser extent phosphates, which
limit the capacity to use these treated effluents for irrigation or other disposal methods.
Internationally and within Australia there have been many limited scale studies of different
technologies to deal with high nitrogenous effluents.
There are several excellent reviews in public literature, including those prepared for AMPC and MLA
in the recent past on techniques for treating meat industry effluents. It is not the intention of this
position paper to repeat these reviews, but rather to extract information from them in a critical
manner, comment on how they may apply to current Australian meat industry practices and to
extrapolate from systems that have been researched and identify potential practical processes for
the future. It is assumed that the Australian meat industry will be aware of the pros and cons of
aerobic verses anaerobic treatments in their individual business contexts. Therefore this discussion
is not repeated here. This position paper establishes a framework for the further reduction of
nutrients in treatment effluents so that they can safely be used for irrigation purposes. The issue of
salts generated by reverse osmosis water treatments is also considered and in many instances it is
suggested that the salt water from these treatments could be usefully used as a processing aid in the
main effluent treatment processes.
Generally, wastes are well-managed by the Australian red meat industry. Solid wastes are
segregated from liquid waste; and in-plant segregation of solid and semi-solid wastes according to
the nature of the waste, allows disposal to external recycling, pet food manufacture, composting,
rendering, and conversion to fuel for energy generation. Wastewater is passed through primary
treatment processes to remove solids, oils, fats and greases followed by secondary treatment. In
many instances, anaerobic digestion occurs after primary treatment, and the treated effluent is
transferred to a local water authority for subsequent treatment. Where anaerobic treatment is
practiced, the treated effluent is often disposed of through irrigation.
This position paper assumes that methane will be harvested for in-factory energy substitution or
production. Biological processes are primarily explored with a view to their energy-efficiency,
potential in mitigating the emission of greenhouse gases, and control of the release of nutrients to
the environment. From the review based largely on available laboratory studies by various
international organisations, it is concluded that waste issues can be managed using low cost and
mostly biological means. These biological processes are being used to remove and potentially
recover nutrients, as well as the potential recovery of value-added products such as liquid and solid
biofuels, food products and specialty chemicals. Further studies and field trials are required to
validate these laboratory findings and adapted to suit the needs and practices of the Australian meat
industry.
4
1 Introduction
There have been several excellent reviews on techniques for treating meat industry effluents both in
public literature and commissioned by AMPC and MLA. The intention of this position paper is to
extract information from them in a critical manner with respect to current Australian meat industry
practice. It will extrapolate from available research information and come up with potential practical
processes for the future. It is assumed that the Australian meat industry will be aware of the pros
and cons of aerobic vs. anaerobic treatments in their individual business contexts1. The purpose of
the position paper is to establish a framework for the further reduction of nutrients in treated
effluents so that they can safely be used for irrigation purposes without risk of toxic materials buildup which results in soil poisoning and the generation of greenhouse gasses.
The disposal of treated food industry effluents (including the meat industry) by irrigation is a
practice adopted internationally where there is suitable land availability and favourable climatic
conditions. However, particular attention has to be paid to the accumulation of toxic minerals and
excessively nitrifying the soil. An important issue for the Australian meat industry is the
management of gaseous nitrogenous material. Excess nitrogenous material, such as ammonia, is
toxic to plant life and soil microbiota, and nitrous oxide is detrimental as a green house gas.
Therefore, a key issue for the Australian meat industry is the reduction of the ammonia loading from
anaerobic treatment effluents so that it is safer for irrigation purposes.
Appropriate management of phosphorus (P) is also an increasing challenge for the industry. In some
cases, high P levels in treated wastewater can limit discharge or irrigation, but there are also
technologies available that can assist in the production of P-based fertilisers. It follows that there are
opportunities to better manage nitrogen (N) and P through source control, biological and physical
removal processes, all of which are discussed in this paper.
1
Aerobic and anaerobic refer to biological wastewater treatment methodologies which rely upon the
consumption of organics and nutrients to support microbial growth and metabolism, and water purification.
5
2 Irrigation
Irrigation of primary effluent after simple screening may appear to be economically attractive.
However, there are a range of complexities to consider relating to odour, vermin proliferation, soil
type, climate and environmental damage, and the release of pathogenic organisms into the
environment.
In nature, soil cycles between anaerobic conditions during periods of higher rainfall and immediately
post such an event, then shifts towards aerobic conditions as the soil begins to dry. The nitrogenous
materials within meat industry effluents contain high levels of proteins, which under anaerobic
conditions, lead to chemical and microbial conversion to soluble ammonium salts, and gaseous
ammonia, nitrous oxide and nitrogen (Figure 1). As the soil dries and becomes aerobic, the
nitrogenous materials are then microbially converted to nitrate. Nitrous oxide, a potent greenhouse
gas (298 times carbon dioxide equivialance) can be emitted during anaerobic periods by denitrifying
heterotrophic bacteria and by autotrophic nitrifying bacteria, mainly ammonia-oxidising bacteria. In
addition, emitted nitrous oxide will eventually migrate to the stratosphere at which point it becomes
converted to nitric oxide which in turn reacts with ozone to form nitric acid and depletes the
stratospheric ozone layer.
Source: http://www.regional.org.au/au/asssi/supersoil2004/s9/poster/1876_bhandralr.htm>
Figure 1. Summary of the irrigation – soil cycle.
If treated effluent is directly applied to land, pasteurising treatment to destroy remaining pathogens
will decrease human contact risks, and may also offer benefits in the reduction of odour. In this case,
the soil type and climatic conditions must be selected to allow for the rapid development of aerobic
conditions post irrigation. This will permit the nitrogenous compounds to be converted to nitrate
which can be taken up by growing plants. During dry conditions, the nitrate accumulated in the soil
6
can damage the root systems of surviving vegetation and potentially be carried into the subsoil as
soon as wet conditions return. If soils are overloaded with nitrogenous matter, there is potential to
limit the growth of soil organisms and to create a desert that is difficult to revegetate. Under
Australian conditions, unless the nutrient load can be reduced, large dispersal areas are required
with provision for backup/supplementary irrigation to maintain plant grown during low rainfall
periods.
3 Strategies for managing nutrient load in effluent for irrigation
Figure 2 provides a schematic of new technologies and their integration into existing wastewater
treatment processes.
Red
rendering
liquids
Dry
cleaning
slpps
Green
waste
Wet gut
Yard wash
Red
Washing
Carcass
Clean-up
Primary screening
D AF separation
Electrocoagulation
D AF separation
semi-solid
Biophosphate
recovery
Biochar
Solids
Anerobic lagoon
Rendering or
composting
Phospate recovery
Struvite
Aerobic treatment
Shortened Anammox
Fast reactor
Water recycling
Wetland
Extensive or
Constructed
Irrigation
Figure 2. Summary of all the technologies discussed illustrating how they would fit into a process
flow.
It is not anticipated that all the technologies would all be adopted, some are alternatives e.g. Fast
reactor aerobic treatment vs Shortened Anammox, Biophosphate biochar vs Struvite,
7
electrocoagulation to recyclable water vs conventional DAF then transfer into main stream
treatment.
3.1 Nutrient source management
As noted in the work commissioned by the AMPC and other studies, the highest streams for nitrogen
loading are the initial red effluents from the kill and boning floor wash down, and drainage from the
raw material holding bins in the rendering department. The red effluent stream becomes very dilute
during wash down, while drainage from rendering remains highly concentrated. The green effluent
streams from gut washing and cleaning the stockyards is relatively low in nitrogen but higher in
phosphate.
Dry cleaning techniques for the initial kill floor and boning room clean-up, using wet vacuum
cleaners and/or scrupulous cleaning with a squeegee and collecting in bins, can reduce the load of
nitrogenous material that ends up in the liquid effluent. The material from this cleaning operation
may be disposed of either through rendering or by adding to the dry stream used for composting.
The concentrated nitrogenous stream from the rendering plant should be subjected to a separate
primary effluent treatment from the bulk effluent. In this way, much of the nitrogenous material
could be more efficiently recovered by flocculation and settling/flotation and subsequent disposal as
a solid waste either through rendering or through composting. The liquid would then enter the
mainstream process. For this material from rendering operations it may be appropriate to use
electro-coagulation and settling/flocculation rather than the conventional primary process. Whilst
more costly than the conventional process, the resulting effluent is clear and free of organic solids.
Due to the age, size and gradual expansion, some processing plants are difficult to modify to allow
for stream separation, however from a nutrient management perspective there is considerable
advantage in doing this. Rendering plants are usually co-located with the main processing operation
so there is often potential for segregating this effluent stream.
Source: http://www.wme.com.au/categories/water/august7_03.php>
Figure 3. Electro-coagulation in an Australian abattoir; processed wastewater leaving the electrocoagulation chamber (left), sludge separation (right).
8
3.2 Treating the effluent from anaerobic digestion
The large majority of waste streams generated by the meat industry utilise anaerobic digestion due
to the combined benefits of wastewater treatment, biogas production and minimising solid biomass.
Various strategies for the subsequent treatment of anaerobic digestion effluent are reported in the
literature. This ranges from the application of dissolved air flotation (which may be done in-vessel at
the end of batch digestion) to remove further solids, simple air treatments to convert ammonia to
nitrates, or may be sequentially treated through anoxic and aerobic zones (nitrification/ denitrifying)
to remove nitrogen compounds by conversion to nitrogen gas. Other approaches include ion
exchange and adsorption to remove the ammonium salts and air-stripping to removal ammonia gas.
Recent studies conducted for the AMPC and MLA looked at the segregation of waste streams to
facilitate phosphate recovery and also the use of a nitrification/denitrification finishing process for
anaerobic effluent to convert nitrite and nitrous nitrogen effluents into nitrogen.
Jensen & Batstone, 2012 suggested using aerobic treatment to treat green waste after phosphate
recovery by struvite process rather than feeding it back into the anaerobic digestion process. In the
case of nitrification/denitrification finishing, it was highlighted that the process would not work if
only anaerobic effluent was used and it was necessary to include a feed of volatile fatty acids derived
from a side fermentation process which they fed with red waste stream effluent. The study focussed
on the green waste for struvite recovery, but did not make the connection with the availability of a
green waste stream and its potential for providing a source of free fatty acids. Green wastes are
intrinsically high in volatile fatty acids by virtue of the digestive processes in the live animal and all
that would be required is to screen the solids from the stream to obtain a source of fatty acids to
combine into the denitrification process. The study also did not look at the simpler reduced forms of
the nitrification/denitrification process, which will be discussed later.
A number of aerobic treatment systems including ditches, trickling filters and intensive sequential
bioreactors could be used for aerobic finishing purposes. Aerobic treatments use either aerobic
microbes alone or aerobic microbes in combination with algae. Whenever aerobic microbes are used
alone the process is generally classified as an activated sludge process. There are a variety of
mechanical systems available for this purpose that require a significant amount of electrical energy
to drive pumps and mechanical aeration systems. At the end of the process there is a residual
"stabilised" microbial sludge that has to be disposed of. By using the process as a follow up to
anaerobic treatment, most of the carbon would have already been removed leaving only minimal
sludge volumes.
Alternatively, less energy-intensive aerobic lagoons that contain a combination of aerobic microbes
with algae may be used. The lagoons have to be shallow enough to enable the penetration of light to
the bottom of the lagoon. However, erratic loading can cause the lagoon to become anaerobic with
very smelly and messy consequences. An anaerobic treatment before the aerobic lagoon may help
maintain an even loading, but there is no literature evidence to support this contention. A method
used internationally by the food industry is the constructed wetland, which can be seen adjacent to
the Wyong, NSW food processing precinct. It is viewed by the public at large as an environmentally
friendly development and attracting kudos and environmental establishment funding to the
companies involved. The trees and shrubs growing in them can also be used to screen the processing
operations from public gaze. Constructed wetlands are in effect aerobic lagoons that recruit
9
microorganisms, algae and plants. Generally, they are best used following an intensive biological
pre-treatment to reduce carbon loading.
Source: http://www.woodlotsandwetlands.com.au/wastewater.htm>
Figure 4. Extensive wetlands.
More intensive constructed wetlands involve lined areas and are built up from graded sands
inoculated with appropriate wetland micro flora that support the growth of selected reeds.
Source: http://www.permaculturenews.org/images/how-reed-bed.jpg
Figure 5. Intensive constructed wetlands. Note: this is a cross-flow system, up-flow and down-flow
systems offer more even distribution of feed, but are often operated as a series of beds.
10
Source: http://en.wikipedia.org/wiki/Constructed_wetland>
Figure 6. Intensive constructed wetland new reed bed ready to go (left) the same reed bed 2 years
later (right).
In the context of the meat industry, as long as the effluent is disbursed evenly throughout the
wetland and there is no shock loading of any nitrogenous material, they can be an effective way of
denitrifying anaerobic treatment effluent. In Australia, the limitation is that wetlands tend to have
cyclical viability due to climatic factors. They may still be a useful technology if there is a
supplementary source of water that can be used to maintain them during dry periods.
Recently, alternative technologies have been developed to manage the high ammonia
concentrations in anaerobic digester effluent. In particular, the anaerobic ammonium oxidation
(Anammox) biological conversion process, where ammonium is oxidised under anoxic conditions by
Planctomycetes bacteria to nitrogen gas, consuming nitrite as electron acceptor. As opposed to
denitrifying bacteria, the Anammox bacteria grow using carbonate or carbon dioxide as the carbon
source. The main product from the Anammox process is nitrogen gas, but approximately 10% of the
nitrogen feed is converted to nitrate which inhibits the process and research to convert this back
into nitrite is underway. Compared to a conventional two-step biological nitrogen removal via
nitrification and denitrification (Anammox), the advantages of technology based on shortcut (partial)
nitrification followed by denitrification of nitrite include: lower carbon requirement, lower oxygen
requirement in nitrification, low nitrous oxide emission and even less biomass production. The lower
“chemical oxygen demand” requirement by this pathway makes nitrogen removal from low carbon
to nitrogen ratio effluent feasible. Additionally, nitrite denitrification rates are 1.5-2 times faster
than nitrate denitrification rates. The Anammox process is ideally suited for the treatment of
ammonia-rich wastewater streams and has been successfully applied at the laboratory scale, pilot
scale and at full scale internationally. The limitations of Anammox systems include very slow growth
rates and yields, and hence efficient biomass retention and long start-up times are necessary. The
Anammox bacteria are also very sensitive to various environmental factors. Elevated oxygen,
excessive nitrite and phosphate concentrations inhibit Anammox completely but reversibly.
Anammox bacteria are also very sensitive to the presence of some organic carbon sources, such as
methanol, which can completely and irreversibly inhibit the Anammox process.
Practically, it should be feasible to include the shortened form of the process as an anoxic zone at
the discharge end of an anaerobic lagoon fed with carbon dioxide scrubbed from methane collection
at the feed end of the lagoon. The nitrogen gas from the anoxic zone would be vented to
11
atmosphere. Field studies at a test site and further development would be required to make this
integration become a reality. On the face of it, this should be an attractive process for a post
anaerobic lagoon treatment, however, there are several technical issues to be overcome.
Operationally, it will be necessary to carefully manage the growth and sustained survival of the
micro-organisms involved and field studies are needed to inform how this is achieved in a lagoon
environment and whether, for management reasons, the process can be done at the exit end of an
anaerobic lagoon or in a secondary post treatment lagoon. The Anammox process is currently being
trailed in Australia by a number of researchers including University of Queensland, South Australian
Water, Commonwealth Science and Industrial Research Organisation and others. These studies are
typically focused on highly concentrated ammonia side streams from anaerobic digesters with high
organic loadings, but it is only a matter of time before the technology is extended to treat more
dilute ammonia streams with varied composition and temperature dependencies.
An alternative to Anammox and nitrification/denitrification is the nitritation/denitritation pathway
(sometimes referred to as nitrite shunt). This process, which is somewhat a hybrid between
traditional methods and Anammox, is reliant upon ammonia oxidation to nitrite (by Nitrosomonas
bacteria) and then subsequent denitritation by heterotrophic bacteria under anoxic conditions.
Aside from biological treatment, the principal physical and chemical processes used for nitrogen
removal are air stripping, breakpoint chlorination, and selective ion exchange. Where hydrogen
sulphide is an issue, chemical intervention is required. These techniques have not been used
extensively due to cost, inconsistent performance, and operating and maintenance problems. The
removal of N as ammonia is also possible through the use of vacuum-stripping technologies; but
typically is not cost-effective compared to biological N removal. While air stripping using compressed
air is restricted by cost, there are efforts to develop less intensive techniques such as natural
convection airflow over thin film effluent flows, and membranes that allow the passage of ammonia.
The bulk of methane harvesting would be done as part of the digestion process, however, the air
stripping process can not only remove ammonia, nitrous gasses and carbon dioxide, but can also
recover any residual methane emanating from the treated effluent, which can be subsequently
delivered in the air feed to generators or boilers.
The sonochemical approach is another potentially attractive means to degassing the effluent. As for
other physico-chemical methods, the anaerobic effluent is the only necessary feed stream, however,
alkalinity must be increased to improve ammonia removal efficiency, which also adds to the cost of
treatment. The ultrasonic transducer operates at high frequency so there is no transducer wear.
However, whilst sonochemistry has been applied to other industrial waste streams it is not reported
as being used for this purpose.
Of all methods, biological treatments are typically the most cost-effective and AMPC has initiated
studies into the applicability of nitrification/denitrification, nitrite shunt and Anammox technology
to meat industry effluent streams.
3.3 Phosphate removal and recovery
Phosphorus appears in wastewater as orthophosphate, polyphosphate, and organically bound
phosphorus. Removal of phosphorus can be accomplished by biological, chemical and physical
methods. The removal of phosphorus from high-volume, low-concentration waste waters is usually
12
achieved via its assimilation into the cell biomass produced through processes focused on carbon
and nitrogen removal, but may also be removed through chemical precipitation with alum or ferric
chloride.
The accumulation of phosphorus into microbial mass is achieved through biological routes such as
phosphorus accumulating organisms which accumulate polyphosphate into their cells under aerobic
conditions, using uptake of volatile fatty acids as an energy source, and consuming either oxygen or
nitrate. In the treatment of high-volume wastewater, phosphorus uptake is enhanced by a short
anaerobic phase prior to an aerobic or anoxic (phosphate accumulation) phase. This process is
referred to as enhanced biological phosphorus removal (EBPR), which can reduce phosphorus levels
to as low as 0.2 mg/L. In Australian meat industry practice, wastewater could be drawn from the
feed end zone of the anaerobic lagoon fed with red effluent, then treated in an aerobic lagoon, fed
with green effluent, containing the phosphorus accumulating micro-organisms then returned to the
main anaerobic lagoon. The sludge containing excess phosphate from the aerobic lagoon is either
dewatered and treated to make bio-char or treated in a second anaerobic side lagoon to release the
phosphate. In effect, the process can be used to biologically pre-concentrate phosphate so that
chemical recovery is more efficient.
For situations where biological phosphorus removal cannot achieve the required effluent quality,
chemical precipitation is normally required. Iron, calcium, magnesium and aluminium salts can be
added at a variety of different points in the primary and secondary treatment process to induce the
precipitation of solid phosphate materials, which in turn lowers total dissolved solids, heavy metals
and to some extent, carbonaceous matter (as “biological oxygen demand”). Aluminium and ferric
ions provide good phosphorus removal in pH ranges of 6.3 – 7.0 and 5.3 – 7.0, respectively. The
relationship between phosphate levels achieved in wastewater and Aluminium and Ferric ion dosage
is logarithmic, meaning that it is a process of diminishing returns. Polyphosphates and organic
phosphorus are less easily removed than orthophosphate, so adding these salts after secondary
treatment (where organic P and polyphosphate are transformed into orthophosphate) usually
results in the best removal. By using calcium or magnesium salts, typically in the pH range of 7.5 9.0, the precipitated material can have greater bio-availability of P for uptake by plants. The
conversion of the recovered biomass into a phosphate rich bio-char with concurrent energy
harvesting is also a possibility. It is possible that in situations where artesian water is treated by
reverse osmosis that the salt stream rich in multivalient cations could be used to precipitate
phosphorus-rich sludge.
Biologically concentrated effluent high in phosphate lends itself well to be treated by the struvite
(magnesium ammonium phosphate) process to create a “green” phosphate fertilizer. This involves
the addition of alkalinity and a source of magnesium, causing the crystallisation of struvite.
Alternatively, calcium may be added to precipitate hydroxyapatite. Both of these approaches lead
to the recovery of phosphate that is more available (compared to common coagulants) as a nutrient
to support plant growth. Struvite manufacture has been commercially adopted in North America and
trials have been undertaken in Australia (including by AMPC) to demonstrate technical and
economic feasibility.
Phosphate may alternatively be physically adsorbed onto the surfaces of adsorbents, or
incorporated into the structure of ion-exchange materials using a range of materials. Adsorbent
13
materials are typically contained within packed columns and their adsorption capacity may be
replenished as for ion-exchange materials, by passing acid, alkali or saline solutions through the
column. A process with a similar outcome to the struvite process involves bulk adsorbent materials
such as calcium silicate hydrate, magnesia and hydrotalcites have been shown to adsorb up to
approximately 4% weight of phosphorus, which is almost half as much P as contained in typical
single superphosphate fertilizer (8-9% phosphorous). Such materials offer the ability of direct
incorporation with biosolids or independent application to agricultural soils. Magnetic separation
technologies (i.e. SIROFLOCTM) have also been developed such that nutrients bind with the magneticcontaining adsorbent/coagulant, and are then removed from the wastewater through the
application of a magnetic field. These adsorbents are typically based upon iron compounds
(magnetite, zirconium ferrite). These technologies are utilised at full-scale; typically to treat
wastewaters where very low discharge limits need to be met (< 0.5 mg/L).
3.4 Salts management from Reverse Osmosis streams
Reverse osmosis (RO) is used throughout Australian industry to improve feed water quality for
production facilities (i.e. those sourcing water from saline artesian bores), to enable water recycling
to potable standard onsite, or to manage salt loadings in irrigation water. The brine produced from
the use of RO can be difficult to dispose of.
Several disposal techniques of brine concentrate are practiced worldwide. These include direct
surface water discharge, discharge to a sewage treatment plant, deep well disposal, land application,
evaporation ponds, brine concentrators, and mixing with the cooling water or treated effluents
before surface discharge. Discharge to surface water may not be attractive due to the lack of
perennial stream flow with sufficient carrying capacity to assimilate the contaminants present in the
concentrate. Deep well injection into aquifers may be feasible, depending on the geological
conditions of the area, but unlikely in many parts of Australia. Similarly, land application/irrigation
can be infeasible due to the soil accumulation of unacceptably high salt concentrations.
Opportunities to reuse Reverse Osmosis brine depend on a number of factors including the final
wastewater treatment processes, land and transport availability. In Australian practice, the water
recovery rate for Reverse Osmosis desalination varies between 35% and 85% depending on the
quality of the feed water, the quality of the produced water, the pre-treatment method and cleaning
procedures and chemicals used. This implies that the brine stream can be as much as 65% of the
feed water. In this instance some attention should be given to the operation of the reverse osmosis
system as this is extraordinarily high, unless this mode of operation is intentional to facilitate water
reuse. The brine stream generated can be many times more concentrated (60,000 mg/L total
dissolved solids) than the feed water (1500 – 10,000 mg/L) and therefore requires careful
management. Reuse options without salt removal treatment are for plant wash-down purposes,
with the brine eventually going to effluent treatment processes. The down side of this practice
includes potential plant corrosion.
Technological solutions can free up a significant amount of water, however at some cost. These
include: Forward Osmosis, Vacuum Membrane Distillation (VMD), Reverse Osmosis – Nanofiltration
(RO-NF) integration, Electrodialysis with Bipolar Membranes, Electrodialysis (ED) and Electrodialysis
14
Reversal (EDR) as well as others. The following discussion focuses on technologies that may be of
interest in the Australian meat industry context.
Electrodialysis is a process that uses an electrical current to remove salt ions from a solution. It is
based on the property that salts in solution are dissociated into positively and negatively charged
ions. Ions are separated from solution by passing a direct current between a cathode and an anode
while passing water containing the ions across alternating pairs of cation-transfer and anion-transfer
membranes. The result is the production of a demineralised product stream (from which ions have
migrated) and a concentrate stream (to which ions have migrated). Electrodialysis Reversal is a
variant of Electodialysis in which the cathode and anode positions are alternated several times per
hour (polarity reversal). Polarity reversal assists in the control of membrane fouling and allows
operation at higher feed water recovery with less scale control chemicals. It should be noted that
unlike other membrane processes used in drinking water and reuse, water does not flow through
the Electrodialysis Reversal membranes, only ions.
Solar energy powered mechanical evaporation/separation systems or solar evaporation ponds. If the
artesian water contains significant amounts of iron or other valued metal salts they may find use as
bulk coagulants, or aids to other industrial processes.
It follows that blending reverse osmosis concentrate with treated effluent from a meat processing
plant can be practiced to mitigate the impact of the high “total dissolved solids” (or other specific
solute) concentrate using the blending capacity of a lower- “total dissolved solids” stream. The likely
presence of multivalent cations will facilitate flocculation for removal of phosphate from the effluent
stream particularly if there has been pre-concentration of the reverse osmosis stream.
Implementation of this technique for Reverse Osmosis water disposal is simple because no new
equipment is needed. Only few pipelines have to be modified and so the implementation issues are
minimal. However, this approach may render phosphate solids unsuitable as a fertilizing material
due to a high salt content.
Conventional Reverse Osmosis systems are subject to scaling by sparingly soluble salts and high
concentrations of dissolved organic and colloidal matter. Vibratory Shear Enhanced Process (VSEP), a
patented process of New Logic, was developed to reduce polarization of suspended colloids and
sparingly soluble salts on the membrane surface by introducing shear to the membrane surface
through vibration. Shear waves produced on the membrane surface keep the colloidal material in
suspension, thereby minimizing fouling and prevent precipitating salts from accumulating on the
membrane surface as scales. As a result, high throughput and water recoveries above that of a
conventional membrane system can be achieved. This technology is in international commercial use.
Applied appropriately, ultrasound can achieve the same effect. By using technologies such as these,
it should be possible to concentrate artesian water waste streams by reverse osmosis to a greater
extent than is sometimes practiced in the Australian meat industry.
Enhanced membrane systems involve the use of a nonconventional reverse osmosis system to
permit operation at higher recovery and at higher flux. One example of an enhanced membrane
system is the patented High-Efficiency Reverse Osmosis (HERO™) system. This process uses ionexchange softening to pre-treat the conventional reverse osmosis concentrate to reduce its scaling
potential, followed by the high-pH operation of a three-stage reverse osmosis system using standard
15
spiral wound reverse osmosis elements. Caustic is added to raise the pH to approximately 11 to
retard silica scaling and bio-fouling. Historically, the HERO™ process has been applied for industrial
use, for example, to treat cooling tower blowdown as a part of a zero liquid discharge treatment
system. It is probably not attractive for artesian water reverse osmosis effluent treatment due to
the large volumes treated.
16
4 Conclusions
With respect to treating nutrients efficiently, source separation is very important.
Under the conditions that the Australian meat industry operates in, there are opportunities for postdigestion improvements for both reactor and lagoon systems based upon energy-efficient biological
treatment. Further effort will potentially be required to adopt and modify some of these
technologies to suit lagoon based systems. It is anticipated that the result of using such systems
would be an effluent largely devoid of nitrogenous matter and phosphate, suitable for continuous
irrigation purposes. Furthermore, the emissions of greenhouse gasses would be largely eliminated.
To enable water recycling based upon Reverse Osmosis and Electrodialysis, levels of “biological
oxygen demand”, “total dissolved solids” and phosphate need to be significantly reduced to enable
efficient operation.
It is expected that many Reverse Osmosis effluents can be usefully used within the waste treatment
systems to facilitate phosphate or protein removal depending on whether they are applied to the
anaerobic effluent or prior to primary treatment. This approach may however limit effective
phosphorus recovery for fertilising purposes.
17
5 References
Asselin, M., Drogui, P., Benmoussa, H., & Blais, J.F. 2008. Effectiveness of electrocoagulation process
in removing organic compounds from slaughterhouse wastewater using monopolar and bipolar
electrolytic cells. Chemosphere, 72, (11) 1727-1733 available from: WOS:000258901300016
Badruzzaman, M., Oppenheimer, J., Adham, S., & Kumar, M. 2009. Innovative beneficial reuse of
reverse osmosis concentrate using bipolar membrane electrodialysis and electrochlorination
processes. Journal of Membrane Science, 326, (2) 392-399 available from: WOS:000263006500018
Balasubramanian, P. 2013. A brief review on best available technologies for reject water (brine)
management in industries. International Journal of Environmental Sciences, 3, (6) 2010-2018
available from: CABI:20133321026
Batstone, D.J. & Virdis, B. 2014. The role of anaerobic digestion in the emerging energy economy.
Current Opinion in Biotechnology, 27, (0) 142-149 available from:
http://www.sciencedirect.com/science/article/pii/S0958166914000263
Bosko, M., Rodrigues, M., Ferreira, J.Z., Miro, E., & Bernardes, A. 2014. Nitrate reduction of brines
from water desalination plants by membrane electrolysis. Journal of Membrane Science, 451, 276284 available from: WOS:000327892900030
Burn, S., Muster, T., Kaksonen A., & Tjandraatmadja, G. 2013. Resource recovery from wastewater:A
research agenda. Report prepare for Water Environment Research Foundation, 635 Slaters Lane,
Suite G-110, Alexandria, VA 22314-1177
Carreau, R., VanAcker, S., VanderZaag, A.C., Madani, A., Drizo, A., Jamieson, R., & Gordon, R.J. 2012.
Evaluation of A Surface Flow Constructed Wetland Treating Abattoir Wastewater. Applied
Engineering in Agriculture, 28, (5) 757-766 available from: WOS:000310492600015
de Sena, R.F., Moreira, R.F.P.M., & Jose, H.J. 2008. Comparison of coagulants and coagulation aids
for treatment of meat processing wastewater by column flotation. Bioresource Technology, 99, (17)
8221-8225 available from: WOS:000258738700048
GHD Pty Ltd. 2002. Assessments of Contaminants in Waste Solids from Meat Processing Wastewater
Streams. PRENV.023a. Meat & livestock Australia, Locked Bag 991, North Sydney NSW 2059.
Isosaari, P., Hermanowicz, S.W., & Rubin, Y. 2010. Sustainable Natural Systems for Treatment and
Disposal of Food Processing Wastewater. Critical Reviews in Environmental Science and Technology,
40, (7) 662-697 available from: WOS:000279633600002
Jensen, P., & Batstone, D. 2012. Energy and Nutrient analysis on Individual Waste Streams. Report#
A.ENV.0131 Meat & Livestock Australia Limited, Locked Bag 991, NORTH SYDNEY NSW 2059
Jensen, P. 2015. Nutrient recovery from paunch and covered anaerobic lagoon effluent. AMPC
Report 2013/4007.
Johns, M.R. 1995. Developments in wastewater treatment in the meat processing industry: A review.
Bioresource Technology, 54, (3) 203-216 available from:
http://www.sciencedirect.com/science/article/pii/0960852495001409
18
Kabdasli, I., Tunay, O., & Ozcan, P. 2009. Application of struvite precipitation coupled with biological
treatment to slaughterhouse wastewaters. Environmental Technology, 30, (10) 1095-1101 available
from: WOS:000269585200013
Kim, D.H. 2011. A review of desalting process techniques and economic analysis of the recovery of
salts from retentates. Desalination, 270, (1-3) 1-8 available from: WOS:000288583900001
Lemaire, R., Yuan, Z., Bernet, N., Marcos, M., Yilmaz, G., & Keller, J. 2009. A sequencing batch reactor
system for high-level biological nitrogen and phosphorus removal from abattoir wastewater.
Biodegradation, 20, (3) 339-350 available from: WOS:000265787500005
Logan, B.E. & Regan, J.M. 2006. Electricity-producing bacterial communities in microbial fuel cells.
Trends in Microbiology, 14, (12) 512-518 available from:
http://www.sciencedirect.com/science/article/pii/S0966842X06002460
Malvankar, N.S. & Lovley, D.R. 2014. Microbial nanowires for bioenergy applications. Current
Opinion in Biotechnology, 27, (0) 88-95 available from:
http://www.sciencedirect.com/science/article/pii/S0958166913007180
McCabe, B.K., Hamawand, I., Harris, P., Baillie, C., & Yusaf, T. 2014. A case study for biogas
generation from covered anaerobic ponds treating abattoir wastewater: Investigation of pond
performance and potential biogas production. Applied Energy, 114, 798-808 available from:
WOS:000330814100079
Mittal, G.S. 2006. Treatment of wastewater from abattoirs before land application - a review.
Bioresource Technology, 97, (9) 1119-1135 available from: WOS:000236661000005
National Water Quality Management Strategy publication 2005. “Australian Guidelines for Sewerage
Systems — Effluent Management”
O'Brien, C.A., Scholz, M., & McConnachie, G.L. 2005. Membrane bioreactors and constructed
wetlands for treatment of rendering plant wastewater. Water and Environment Journal, 19, (3) 189198 available from: WOS:000232075100006
Russell, J.M., Cooper, R.N., & Lindsey, S.B. 1993. Soil denitrification rates at wastewater irrigation
sites receiving primary-treated and anaerobically treated meat-processing effluent. Bioresource
Technology, 43, (1) 41-46 available from:
http://www.sciencedirect.com/science/article/pii/096085249390080U
Sun, S.P., Nacher, C.P.I., Merkey, B., Zhou, Q., Xia, S.Q., Yang, D.H., Sun, J.H., & Smets, B.F. 2010.
Effective Biological Nitrogen Removal Treatment Processes for Domestic Wastewaters with Low C/N
Ratios: A Review. Environmental Engineering Science, 27, (2) 111-126 available from:
WOS:000274527300001
Thayalakumaran, N., Bhamidimarri, R., & Bickers, P.O. 2003. Biological nutrient removal from meat
processing wastewater using a sequencing batch reactor. Water Science and Technology, 47, (10)
101-108 available from: WOS:000184016100014
Tian, G., Granato, T., Cox, A., Pietz, R., I, Carlson, C., & Abedin, Z. 2009. Soil Carbon Sequestration
Resulting from Long-Term Application of Biosolids for Land Reclamation. Journal of Environmental
Quality, 38, (1) 61-74 available from: WOS:000262483500009
19
Wang, Q., Jiang, G., Ye, L., Pijuan, M. & Yuan, Z. 2014. Heterotrophic denitrification plays an
important role in N2O production from nitritation reactors treating anaerobic sludge digestion liquor.
Water Research, 62, 202-210.
Yilmaz, G., Lemaire, R., Keller, J., & Yuan, Z. 2008. Simultaneous nitrification, denitrification, and
phosphorus removal from nutrient-rich industrial wastewater using granular sludge. Biotechnology
and Bioengineering, 100, (3) 529-541 available from: WOS:000255883600014
Zhang, Y., Desmidt, E., Van Looveren, A., Pinoy, L., Meesschaert, B., & Van der Bruggen, B. 2013.
Phosphate Separation and Recovery from Wastewater by Novel Electrodialysis. Environmental
Science & Technology, 47, (11) 5888-5895 available from: WOS:000320097400049
20