Update - New Pulp & Paper Wastewater Treatment Technologies from Forest Research
Forest Research provides a broad range of scientific and commercial resources to develop innovative solutions across the entire wood and wood processing value chain. In addition to helping enhance the economic sustainability of the sector, we recognise the importance of improving environmental sustainability. Waste management costs are typically viewed as substantial and mandatory burdens to the industry. Wherever possible, Forest Research is actively seeking to reduce these costs through incremental improvements in waste management practices and/or evolutionary and revolutionary enhancements of existing and novel waste treatment technologies.
The pulp and paper industry has historically been one of the world's largest consumers of freshwater resources and producers of wastewater discharges. These discharges have been the continuing focus of concern regarding their actual and potential environmental effects. Through a concerted environmental management investment strategy, involving implementation of both in-mill processing and external treatment best management practices, the industry has overcome many of these concerns. A multi-billion dollar investment by the international pulp and paper sector over the past 20 years has seen emissions of important waste constituents typically reduced by 80-90 percent. Environmental impacts, such as receiving water oxygen depletion, acute toxicity, and the formation of persistent chlorinated organic compounds, have been essentially eliminated through, for example, water cycle closure, use of non-chlorine-based bleaching processes, and the installation of effective secondary treatment systems.
The New Zealand pulp and paper industry has followed a comparable modernisation pathway and has similar waste management issues to those faced by other parts of the world. As such, it provides an ideal platform for Forest Research to build a robust end-user-focused treatment technology and environmental risk assessment research programme which is of both regional and international relevance. Two waste management processes under development by Forest Research highlight the potential for the New Zealand industry to overcome existing technology deadlocks and further improve its environmental performance.
Pulp and paper industry wastewaters are typically deficient in nitrogen and phosphorus and cannot be effectively treated using conventional biological treatment processes without the addition of supplementary nutrients, such as urea and phosphoric acid. Supplementation is a difficult step to manage efficiently, requiring extensive post-treatment monitoring and some degree of overdosing to ensure sufficient nutrient demand under all conditions. As a result treated wastewaters usually contain excess amounts of both nutrients, leading to potential impacts on the receiving waters such as eutrophication. Forest Research is developing an alternative biological treatment technology that overcomes this nutrient deficiency/excess paradox. Through the use of proprietary control systems, the process is able to select and utilise communities of nitrogen-fixing bacteria, which are able to extract and incorporate all required nitrogen from the atmosphere. In doing this, the process eliminates supplementation costs, which can be approximately 25 percent of total annual operating costs at a typical plant, and improves environmental performance through a substantial reduction in nutrient loadings in the final treated effluent.
Colour remains one of the more conspicuous properties of pulp and paper discharges. Besides the aesthetic changes in receiving water quality, high levels of colour in the wastewater can reduce light penetration and potentially affect benthic plant growth and habitat. The coloured material, formed from organic constituents dissolved from the wood during the pulp manufacturing process, is resistant to conventional biological treatment. Although physicochemical treatment processes are available to remove colour, they are unable to achieve this in an economically sustainable fashion. An advanced oxidative colour removal process, developed in collaboration with a North American research partner, has been demonstrated by Forest Research to be highly efficient in the removal of colour from targeted pulp and paper waste streams. Removal of over 50 percent in colour loadings has been achieved using relatively small quantities of oxidative catalysts. Whilst this technology is still some way from commercial application, it has significant potential to overcome a major environmental issue for the industry.
Overall, these innovative technologies form part of an ongoing Forest Research programme targeting environmentally sustainable waste management systems and technologies. Other aspects of the programme include the development of high temperature biokidneys for wastewater recycling, optimisation of existing treatment system performance, and environmental risk and toxicology studies directed towards the identification and mitigation of endocrine-disrupting effects. Bioconversion technologies are a growing focus of the programme. Here we are endeavouring to not only treat liquid and solid waste streams but also produce added-value products during the treatment process.
In this manner, we can begin to reconsider our current concepts of industry waste discharges as environmental problems and focus on their utilisation as high-value resources.
Contact: Trevor Stuthridge at Forest Research. Phone 07 343 5899; E-mail trevor.stuthridge@forestresearch.co.nz
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Dr Trevor Stuthridge Project Leader, Waste Management Systems and Technologies, Forest Research Trevor obtained his PhD in Environmental Chemistry from the University of Waikato. After completing post-doctorate fellowships in the US and Norway, he returned to New Zealand to work with Forest Research in 1993. His personal research interests are broad but include the fate and effects of recalcitrant organic pollutants, advanced treatment systems and novel technologies for the conversion of liquid and solid wastes to added-value biomaterials. |
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Amber Duncalfe
Editor - RM Update
Ministry of Agriculture and Forestry
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NEW ZEALAND
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