Representatives of eight Waikato and Bay of Plenty councils recently took the opportunity to discuss current trends, issues and concerns around the treatment of sludge and biosolids at a workshop run by MWH at Hamilton City Council’s Pukete Wastewater Treatment Plant.
To assist with working through the issues and solutions, MWH experts Jim Bradley, Rainer Hoffmann and Bruce Petrik covered New Zealand and international trends, legislation and guidelines and the benefits of biosolids reuse. Discussions then followed on how well beneficial reuse is working in New Zealand, how we can improve performance, and what the drivers, roadblocks and opportunities are. Also addressed were the challenges in managing sludge and biosolids from smaller plants and the possibilities for regional approaches.
Over the years, a raft of regulations and guidelines published in Australia and New Zealand (particularly the Guidelines for the Safe Application of Biosolids to Land in New Zealand) have traversed procedures and practices. In 2010, MWH New Zealand’s Jim Bradley and Garrett Hall alongside an Australian team and Professor Stephen Smith from Imperial College, UK, were engaged by the Australian and New Zealand Biosolids Partnership to review and compare Australian and New Zealand biosolids guidelines, to identify and explain any differences, and make recommendations on improvements, including whether a more consistent regional approach is sensible.
Amongst the findings, a wide variation was discovered in the regulatory approaches adopted around both countries to deal with biosolids and sludge, while odour poses as one of the greatest threats to the long-term sustainable beneficial use of biosolids. The key outcomes of the resulting Australia and New Zealand Biosolids Partnership: Review of Biosolids Guidelines are 14 recommendations to achieve better biosolids beneficial reuse outcomes across Australasia.
International trends include the need for more holistic approaches, climate change considerations, biosolids partnerships becoming commonplace, the need for community involvement and consultation, energy considerations, the issue of odour management and the ongoing obstacle of the ‘Faecal Aversion Factor’ (or yuck factor). In the United States, reuse remains a key policy in the face of escalating costs, including the costs of disposal such as trucking to landfill, the potential energy use in a market of uncertain energy supply and power cost, a growing public awareness for sustainable development including renewable energy, and biosolids disposal.
Two international case studies provided some potential management approaches for similar situations in the Waikato and Bay of Plenty. In Hillsborough County, Florida, eight wastewater treatment plants needed to reduce haulage and disposal costs (haulage distances were over 100 kilometres each way and landfill disposal US$40 per wet ton), reduce the energy consumption in aerobic digesters, and sell biosolids products as fertiliser to the local farming industry. A biosolids master plan led to a centralised county-wide biosolids facility.
In Australia, Oxley Creek in Brisbane has built a centralised thermal hydrolysis and anaerobic digestion facility which is treating dewatered waste activated sludge from five wastewater treatment plants, more than doubling renewable energy production generated using the same technology at individual plants.
Positive outcomes from discussing common issues and potential collaborative solutions on managing sludge and biosolids at the summit include Western Bay of Plenty District Council promoting the topic at the NZ Water Managers Forum at the end of April.
For more information or to find out more about the recommended management approaches, contact Jim Bradley on 027 436 1195 or jim.w.bradley@mwhglobal.com, Rainer Hoffmann on 03 343 8783 or rainer.hoffmann@mwhglobal.com, or Bruce Petrik on bruce.petrik@mwhglobal.com
