Waste water mining is an important tool in addressing increasing community needs for the development of sustainable practices. One aspect of waste water mining is the recovery of water and materials from metropolitan sewage treatment plants. However, poor quality sewage frequently prevents reuse of sludge and water after treatment. Improving trade waste quality from non-residential sources would assist water authorities in ensuring the suitability of recoverable recycled water and sludge for reuse. Industries may also benefit from improvements in resource use and cost reductions associated with improving waste quality for disposal. This project identified best practice trade waste management options from the point of view of both waste treatment and cleaner initial production.
An international survey of wastewater dischargers and acceptors was undertaken, with the aim of understanding current examples of industry best practice. This includes clean production and pollution prevention practices as well as industrial pre-treatment of trade waste. The survey was initially conducted via email and widely circulated to water authorities, industry groups and individual sites in Australia, New Zealand, South Africa, the USA, Canada, Singapore, the UK, Ireland, Israel, parts of Europe, south east Asia and Latin America beginning in January, 2010. Response rates in the following year were low, so in January 2011 the survey was adapted to a phone format and run over two periods from January to February 2011 and June to September 2011 with a reduction in target nations to Australia, New Zealand, USA, Canada and Singapore using information from local EPA and other regulatory bodies. This led to a significant increase in response rates and allowed broad based conclusions to be drawn about a number of industries.
A total of 114 discharger surveys were received from Australia, USA, Canada, New Zealand and Malaysia, surpassing the original target of 100. The largest number of responses came from the food and beverage industry and allowed for more detailed analysis of this industry.
A report titled Best Practice Trade Waste Management addressed to water and manufacturing industry professionals was produced based on these results. A description of treatment processes and initial cost estimates are also included in this report.
A range of cleaner production practices were identified in each of the industries surveyed. Six concpets were found to stretch across all industries:
- Optimization of reaction and formulations
- Clean-in-Place optimization
- Changes in sanitizers and cleaning agents
- Diversion of high nutrient wastewaters
- Reduction of product losses and spillage
Best practice targets were developed across a range of industries including food and beverage, agrichemical production, pulp and paper manufacturing, container reconditioning and vehicle washing.
The final report provides assistance to both water authorities and industrial users to improve the quality of trade waste and reduce the cost both of production and of waste treatment. Improved quality in trade waste discharge leads to better quality in treated water and sludge and greater stability in waste water treatment processes creating overall better resource use efficiency and wider use of recycled water.