Waste lagoons move into the environmental risk management spotlight

Underperforming open industrial wastewater treatment lagoons are on the way out, according to an anaerobic technology advocate, as industry counts the cost of its pollution, odours, leakage, energy wastage and relative inefficiency in fixing the problems it set out to address.

Increasing carbon taxes, community activism and legislative awareness of environmental shortcomings are driving change that will see industry searching for better ways to reduce problems created by effluent from uncovered lagoons.

Food and beverage processors may be in the front line of change, along with primary processors, including meat and dairy processors, as well operators of any industrial manufacturing or processing plant that draws water from its surroundings and returns water to the environment.

“Open lagoon wastewater treatment systems were popular with industry for most of the 20th century because they were simple, cheap and easy to operate, allowing an ‘end of pipe’ solution to wastewater issues,” says wastewater treatment authority Michael Bambridge.

“However, these systems are now recognised for their environmental downsides, including their poor ability to control algae and suspended solids in warm weather and poor efficiency in removing pollution load.

“Besides emitting pollution to the air and feeding problems into groundwater and runoff - resulting in fish kills, algal blooms and bacterial contamination - open lagoons waste energy in processing and oxygenation, when better designs could use the waste to produce green energy,” says Bambridge, whose company, CST Wastewater Solutions, is one of Australia’s advocates of anaerobic technologies that generate green energy from waste. These cost-efficient and user-friendly technologies - as proven by Global Water Engineering in more than 75 industry plants worldwide - were most recently used in Australia to reduce the dependence of the $120 million Bluetongue brewery on fossil fuels and ultimately cut its overall energy needs by 15%.

“Leading companies, such as those in the partnership that built Bluetongue (Coca-Cola Amatil and SAB Miller), are acutely aware that industry has to provide a lead toward more efficient technologies that are globally sustainable.

“It is no longer satisfactory for companies to treat their wastewater lagoons as a dump into which they can pump process problems, as some have in the past. Such companies have to catch up with the future, before the future catches up with them and they are compelled to take expensive remedial action - or even close down, in the worst cases.

“As always, progressive prevention is better than a radical cure. Costs can be moderated and user-friendly technologies are available if a plant’s performance is audited and change is implemented early.”

Challenges facing industry in the treatment of its wastewater include:

• Many wastewater treatment and collection facilities built decades and generations ago are now old and worn, and require audits, further improvement or replacement to maintain their useful life. Also, some older facilities were sited long before groundwater issues were fully understood and pose near-term threats to the environment.
• The character, toxicity and quantity of contaminants presenting problems today are far more complex than those that presented challenges in the past, with pathogens, nutrients and highly publicised problems such as blue-green algae spilling into the environment and toxins building up over decades.
• Population growth is taxing reserves of shared community resources, such as clean water, clean air and land for urban development and sustainable agricultural uses. In a highly urbanised society such as Australia - and one which values and markets its clean/green credentials - conflict between land uses will grow without community-corporate partnerships to resolve issues.
• Environmental awareness has spread from being a fringe concern for activists to become a mainstream voting issue that spreads up from the level of individual communities confronting polluters, through to local, state and federal governments regulating for change.

“Far better for a company to take progressive action of its own volition now, as a responsible corporate member of the community, rather than to have change thrust upon it abruptly and expensively as a community recalcitrant that must be disciplined,” said Bambridge, who adds that good solutions do not have to be expensive and can be staged:

1. A satisfactory first step in many instances can be taken by covering lagoons and incorporating anaerobic processes with properly designed feed and recycle systems; steps which not only solve many odour emission problems, but also generate green energy in the form of captured methane that can be burned to power industrial processes or to generate electricity. The re-use of the captured methane as an energy source rather than flaring it reduces carbon emissions.
2. A second progressive step can involve the use of tanks to contain anaerobic and other processes, minimising land use, reducing plant footprints and providing high security against leaks and groundwater contamination. Anaerobic processes can also be more closely efficiently controlled in such close environments, optimising water purification and green energy production.
3. A third optimum stage can be the eventual incorporation of the most advanced anaerobic technologies into sealed tank environments, such as GWE’s Raptor treatment system for organic residues, for example, which can convert almost any organic residue or energy crop into biogas, valuable electricity or heat.

“The removal efficiency of GWE’s anaerobic wastewater treatment installations has been demonstrated globally to be as high as 90-95%, bringing the organic load down to regulatory discharge standards for some types of wastewater,” said Bambridge.

“For more heavily loaded wastewaters, relatively small extra post-treatment steps can further purify the effluent, meeting even the most stringent discharge regulations for water re-use.”

The Raptor technology - which stands for Rapid Transformation of Organic Residues - is a powerful liquid-state anaerobic digestion process that consists of enhanced pretreatment followed by multistep biological fermentation. Technologies such as this can be used on food wastes (such as market surplus, kitchen waste, off-specification fruit and vegetables, and excess crops), agroindustry wastes (starch and sugar pulps, vegetable or potato waste), industrial residues (spent grain, fruit processing waste and paper mill sludge) and energy crops, such as corn, various grasses and algae.

Anaerobic digestion facilities have been recognised by the United Nations Development program as one of the most useful decentralised sources of energy supply, as they are less capital-intensive than large power plants. They can also benefit local communities by providing local energy supplies and eliminate the need for large and often smelly, and environmentally challenging settling lagoons.

“It’s just sensible corporate risk management really for any company CEO or director to look at their options, to anticipate the problems lagoons may be creating now and certainly as we move into the future,” says Bambridge.