title: The plastic problem: Stormwater's role in polluting Lake Rotorua

authors: Kerebs, Aria

subjects: macroplastic

abstract: With the ever-increasing rate of plastic production, pollution of the aquatic environment is worsening. While microplastics (<5 mm), and marine plastic pollution are well studied, less is known about large plastic and its fate in freshwater systems. Large plastics include mesoplastics (5 mm – 2.5 cm) and macroplastics (>2.5 cm). This study aims to provide a baseline quantification of large plastics entering Lake Rotorua, focusing on the Rotorua city urban stormwater streams which are a known source of plastic entering the lake. A five-month sampling campaign collected large plastics from seven 50 m stream reaches across Rotorua city, including four sites along the longitudinal gradient of the Utuhina Stream (Headwater, Devon, Blomfield, and Depot Street sites) and three stream mouth sites (Waingaehe, Owhata Point, and Waiowhiro Stream). Sampled plastics were visually classified by polymer type to determine what plastics have been entering the lake, this was done using the New Zealand recycling and polymer guidelines. Results of the field campaign and plastic polymer classification were coupled with a systematic literature review of in situ plastic capturing devices and community initiatives to inform potential plastic reduction management options for Rotorua city. Devices were assessed against tailored suitability criteria (including Rotorua stormwater stream specific variables like channel depth and narrowness). The monthly sampling captured a total of nearly 6 kg of plastic, 30.2% (51 of 169 collected samples) of which was recyclable plastics (polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polypropylene (PP)). From the literature review, booms and boom-receptacles were the best suited devices for Rotorua streams; however, they are best paired with stormwater traps to increase effectiveness. Additionally, education on recycling procedures and the plastic lifecycle, increasing awareness, and implementation of community-led initiatives are management strategies that are best coupled with in-situ devices. The findings from this study provide a foundational understanding of large plastic in the Rotorua urban stormwater system.

text: The plastic problem: Stormwater's role in polluting Lake Rotorua With the ever-increasing rate of plastic production, pollution of the aquatic environment is worsening. While microplastics (<5 mm), and marine plastic pollution are well studied, less is known about large plastic and its fate in freshwater systems. Large plastics include mesoplastics (5 mm – 2.5 cm) and macroplastics (>2.5 cm). This study aims to provide a baseline quantification of large plastics entering Lake Rotorua, focusing on the Rotorua city urban stormwater streams which are a known source of plastic entering the lake. A five-month sampling campaign collected large plastics from seven 50 m stream reaches across Rotorua city, including four sites along the longitudinal gradient of the Utuhina Stream (Headwater, Devon, Blomfield, and Depot Street sites) and three stream mouth sites (Waingaehe, Owhata Point, and Waiowhiro Stream). Sampled plastics were visually classified by polymer type to determine what plastics have been entering the lake, this was done using the New Zealand recycling and polymer guidelines. Results of the field campaign and plastic polymer classification were coupled with a systematic literature review of in situ plastic capturing devices and community initiatives to inform potential plastic reduction management options for Rotorua city. Devices were assessed against tailored suitability criteria (including Rotorua stormwater stream specific variables like channel depth and narrowness). The monthly sampling captured a total of nearly 6 kg of plastic, 30.2% (51 of 169 collected samples) of which was recyclable plastics (polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polypropylene (PP)). From the literature review, booms and boom-receptacles were the best suited devices for Rotorua streams; however, they are best paired with stormwater traps to increase effectiveness. Additionally, education on recycling procedures and the plastic lifecycle, increasing awareness, and implementation of community-led initiatives are management strategies that are best coupled with in-situ devices. The findings from this study provide a foundational understanding of large plastic in the Rotorua urban stormwater system.

year: 2025

title: Pilot scale pyrolysis - determination of critical moisture content for sustainable organic waste pyrolysis

authors: Sichone, Kavwa

abstract: Economic feasibility of large scale organic waste pyrolysis was investigated for Inghams Enterprise (Waitoa) chicken dissolved air flotation sludge (DAF) and activated sludge (biosolids) from the Hamilton municipal waste water treatment plant. Processing data was obtained from pilot plant trials using the Lakeland Steel (Rotorua) continuous auger pyrolysis plant using feedstock at 15, 30, 45 and ~80% moisture contents. Economics were calculated based on estimated capital and operating costs of a large scale facility, revenue from selling char, savings from landfill diversion (including transportation and gate costs), energy savings by recycling syngas product and using waste heat for drying feedstock.
For DAF, 15% moisture content gave yields of 21% syngas, 27% char, and 52% oil (dry weight basis). 15% moisture content gave the best processing conditions based on handling properties and degree of autogenesis. The DAF case does not give a payback period due to low scale of operations.
For biosolids, 15% moisture content feedstock gave yields of 46% syngas, 31% char, and 21% oil (wet weight). Difficulties were found with plant blockages at 45% and 80% moisture contents. 15% moisture content gave the best processing conditions and the best economic performance with a payback time of 4.6 years for a facility that could process 11,000 tonnes per year.

text: Pilot scale pyrolysis - determination of critical moisture content for sustainable organic waste pyrolysis Economic feasibility of large scale organic waste pyrolysis was investigated for Inghams Enterprise (Waitoa) chicken dissolved air flotation sludge (DAF) and activated sludge (biosolids) from the Hamilton municipal waste water treatment plant. Processing data was obtained from pilot plant trials using the Lakeland Steel (Rotorua) continuous auger pyrolysis plant using feedstock at 15, 30, 45 and ~80% moisture contents. Economics were calculated based on estimated capital and operating costs of a large scale facility, revenue from selling char, savings from landfill diversion (including transportation and gate costs), energy savings by recycling syngas product and using waste heat for drying feedstock.
For DAF, 15% moisture content gave yields of 21% syngas, 27% char, and 52% oil (dry weight basis). 15% moisture content gave the best processing conditions based on handling properties and degree of autogenesis. The DAF case does not give a payback period due to low scale of operations.
For biosolids, 15% moisture content feedstock gave yields of 46% syngas, 31% char, and 21% oil (wet weight). Difficulties were found with plant blockages at 45% and 80% moisture contents. 15% moisture content gave the best processing conditions and the best economic performance with a payback time of 4.6 years for a facility that could process 11,000 tonnes per year.

year: 2012

title: The day ahead

authors: Webber, Warren

abstract: With a professional background in agriculture and veterinary science, and a decade of participation in water quality issues for the Rotorua Lakes catchments, Warren brings an intense personal, but non-vested interest, to issues of nutrient management on the land and in our waterways. Conference management (international and domestic) helps to pay the bills, but voluntary community interests take up much of his time. As an appointee to the Stakeholder Advisory Group (StAG) which considers land management and land use change policy issues on behalf of the Te Arawa Lakes Strategy Group, he is closely involved with the challenges of nutrient allocation and incentives for change.

text: The day ahead With a professional background in agriculture and veterinary science, and a decade of participation in water quality issues for the Rotorua Lakes catchments, Warren brings an intense personal, but non-vested interest, to issues of nutrient management on the land and in our waterways. Conference management (international and domestic) helps to pay the bills, but voluntary community interests take up much of his time. As an appointee to the Stakeholder Advisory Group (StAG) which considers land management and land use change policy issues on behalf of the Te Arawa Lakes Strategy Group, he is closely involved with the challenges of nutrient allocation and incentives for change.

year: 2013