RP2008: Wastewater Biosolids

RP3008: Journal Article: Eco-Acupuncture: designing and facilitating pathways for urban transformation, for a resilient low carbon future

The implications of climate change and the end of the fossil fuel era suggest that we are entering a period of major, transformative, change requiring the restructure of the most fundamental systems for urban living. But rapid structural change is hard to negotiate within existing communities.

In Melbourne Australia, a research unit known as the Victorian Eco-Innovation Lab (VEIL) has developed a unique process to co-create visions for a 25 year horizon for specific urban communities in response to climate change. The need to bring that process from vision to intervention, to catalyse rapid transformation of an existing urban environment, has produced a new program – Eco-Acupuncture – for work with local precincts in metropolitan Melbourne and regional communities. Eco-Acupuncture focuses on multiple small interventions in an existing urban precinct that can shift the community's ideas of what is permissible, desirable and possible and provide transformation points for a new trajectory of development to a resilient low-carbon future.

The paper describes the context and evolution of the program and the framework developed to deliver new locally specific starting points for urban transformation, a process involving academic researchers and designers, a shifting network of professional designers, many hundreds of design masters students, representatives of local government, business and the wider community.

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RP2008: Journal Article: Sulfur flows and biosolids processing: using Material Flux Analysis (MFA) principles at wastewater treatment plants

High flows of sulfur through wastewater treatment plants (WWTPs) may cause noxious gaseous emissions, corrosion of infrastructure, inhibit wastewater microbial communities, or contribute to acid rain if the biosolids or biogas is combusted. Yet, sulfur is an important agricultural nutrient and the direct application of biosolids to soils enables its beneficial re-use. Flows of sulfur throughout the biosolids processing of six WWTPs were investigated to identify how they were affected by biosolids processing configurations. The process of tracking sulfur flows through the sites also identified limitations in data availability and quality, highlighting future requirements for tracking substance flows.

One site was investigated in more detail showing sulfur speciation throughout the plant and tracking sulfur flows in odour control systems in order to quantify outflows to air, land and ocean sinks. While the majority of sulfur from WWTPs is removed as sulfate in the secondary effluent, the sulfur content of biosolids is valuable as it can be directly returned to soils to combat the potential sulfur deficiencies. Biosolids processing configurations, which focus on maximising solids recovery, through high efficiency separation techniques in primary sedimentation tanks, thickeners and dewatering centrifuges retain more sulfur in the biosolids. However, variations in sulfur loads and concentrations entering the WWTPs affect sulfur recovery in the biosolids, suggesting industrial emitters, and chemical dosing of iron salts are responsible for differences in recovery between sites.

Read the full article here: https://doi.org/10.1016/j.jenvman.2017.04.056

RP2008: Journal Article: Towards a comprehensive greenhouse gas emissions inventory for biosolids

Effective handling and treatment of the solids fraction from advanced wastewater treatment operations carries a substantial burden for water utilities relative to the total economic and environmental impacts from modern day wastewater treatment. While good process-level data for a range of wastewater treatment operations are becoming more readily available, there remains a dearth of high quality operational data for solids line processes in particular.

This study seeks to address this data gap by presenting a suite of high quality, process-level life cycle inventory data covering a range of solids line wastewater treatment processes, extending from primary treatment through to biosolids reuse in agriculture. Within the study, the impacts of secondary treatment technology and key parameters such as sludge retention time, activated sludge age and primary-to-waste activated sludge ratio (PS:WAS) on the life cycle inventory data of solids processing trains for five model wastewater treatment plant configurations are presented. BioWin® models are calibrated with real operational plant data and estimated electricity consumption values were reconciled against overall plant energy consumption.

The concept of “representative crop” is also introduced in order to reduce the uncertainty associated with nitrous oxide emissions and soil carbon sequestration offsets under biosolids land application scenarios. Results indicate that both the treatment plant biogas electricity offset and the soil carbon sequestration offset from land-applied biosolids, represent the main greenhouse gas mitigation opportunities. In contrast, fertiliser offsets are of relatively minor importance in terms of the overall life cycle emissions impacts. Results also show that fugitive methane emissions at the plant, as well as nitrous oxide emissions both at the plant and following agricultural application of biosolids, are significant contributors to the overall greenhouse gas balance and combined are higher than emissions associated with transportation. Sensitivity analyses for key parameters including digester PS:WAS and sludge retention time, and assumed biosolids nitrogen content and agricultural availability also provide additional robustness and comprehensiveness to our inventory data and will facilitate more customised user analyses.

Read the full article here: http://dx.doi.org/10.1016/j.watres.2016.03.059

RP2008: Journal paper: Investigation of non-community stakeholders regarding community engagement and environmental malodour

Research into industry-community relationships have focused almost exclusively on the ways in which communities responds to actions from industries. This has led to a paucity of understanding with regards to how community engagement and malodour amelioration practices have been adopted by industry personnel, as well as the attitudes and beliefs of non-community stakeholders in general. I

n this study, a survey to water industry personnel was distributed to three Australian water utilities in South-Eastern Australia and a semi-structured interview process was carried out with plant managers at six wastewater treatment plants.

It was observed that best practice has not yet been established with regards to community engagement and odour amelioration, and that water industry personnel in general had a poor understanding of these concepts. Recommendations for how this situation could be improved, and how non-community stakeholders investigated, are discussed.

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RP2008: Journal paper: Survey of the effect of odour impact on communities

In the context of environmental malodour, surveys are valuable as they allow for the relatively detailed analysis of multiple factors pertaining to odour perception and subsequent reaction. However, the causes for an individual to experience odour impact while a neighbour will not are still not understood.

The goal of this current survey design was to consolidate varying research paths for surveys within the environmental odour research space. This survey investigated the area of effect for wastewater treatment plants by using stratified random sampling techniques that radiated from the industrial areas. Additionally, it provided a “non-alerted” response to environmental malodour that represents a step forward for ecological validity.

The researchers found a small number of items relating to odour annoyance and home ownership that can be used in order to predict odour impact for individual community members. However, they also did not find any relationship with odour impact and perceived control. This survey design and analysis reconciles the varied approaches towards community surveys administered in prior literature, as well as providing information to improve future community engagement policies.

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RP2008: Journal paper: Unrepresented community odour impact: Improving engagement strategies

Complaints for odour causing industry continue to increase in numeracy and severity. One assessment approach using Gas Chromatography–Mass Spectrometry/Olfactometry (GC–MS/O), was used primarily to identify priority odourants within a standardised panel.

The researchers investigated the variation of response between participants of average and high olfactory sensitivity, and discovered that current GC–MS/O methodologies did not represent the entirety of community odour impact. Based on these results they constructed a Biosolids Processing Odour Wheel followed by a Community Odour Wheel for use by untrained community members and site operators.

By using the information gathered from this research, as well as odour testing workshops for a wastewater treatment plant's staff and community surrounding the facility, the researchers established a communicative system, which was subsequently incorporated into an online dynamic odour observation platform. This platform provides the WWTP with meaningful information from the community, as well as a common language for which to discuss environmental malodour with all stakeholders.

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RP2008: Journal paper: The impact of malodour on communities: A review of assessment techniques

Malodours remain the biggest source of complaints regarding environmental issues. This factor is likely to increase, as the urban development steadily encroaches into areas that have malodourous emitting industries (such as wastewater and waste management operations and intensive livestock practices), and has the potential to be both time and fiscally expensive.

Despite the enormous amount of research involved in odour detection and abatement, as well as the creation of several distinct methodologies, there has yet been no definitive procedure to evaluate odour impact on communities, as well as community response. This paper is a review of the current methods that explore this problem, as well as a précis of this research field's goals and challenges.

The first aim of this review is to illustrate the dichotomy between regulatory-established procedures, such as panellist testing, and methods that are centred around producing a more comprehensive explanation of factors that influence an odour's impact on a community or individual. In that regard, we have addressed several predominant paradigms of inquiry for this field: analytical methods, panellist testing, qualitative research, and survey methods, with associated variants.

Secondly, the challenges of measuring and monitoring community impact are discussed. While the quantification of odorants is crucial to appreciating impact, individual-based modifiers of perception have an enormous scope for which to shape the effect of those odours. Perceptual differences are also likely the most dominant variables that influence the elicited behaviour of individuals who have experienced malodour exposure.

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RP2008: Journal paper: Sewer catchment effects on wastewater and biosolids odour management

The composition of wastewater in sewer catchments is known to affect the performance of wastewater treatment plants (WWTPs). However, there is limited knowledge as to how catchment characteristics, such as types of catchment industries, impact odour emissions from downstream sludge processing and biosolids management.

Odorous emissions from biosolids processing at WWTPs can represent a significant community impact when the local population is exposed to odours. The main odorants emitted from biosolids are volatile sulfur compounds (VSCs), however, volatile organic compounds (VOCs) in emissions may also be perceptable after the removal of VSCs in odour abatement systems.

Types of compounds present in emissions throughout biosolids processing at five WWTPs of varying sizes and levels of treatment (primary only and primary and secondary) were analysed. The ratio of total VSCs to VOCs in emissions, and the sensorial importance of each class varied between the sites. As a number of the VOCs in emissions were of industrial origin, this variation is likely dependent on industrial flows into the upstream sewer catchment.

The impact of different emission compositions on both activated carbon and biologically based odour abatement systems were discussed.

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RP2008: Journal paper: Framework for the use of odour wheels to manage odours throughout wastewater biosolids processing

Odorous emissions from wastewater biosolids processing can cause nuisance impacts to the surrounding community. 

Odour Wheels are an effective tool for environmental odour management, but have yet to be provided for wastewater biosolids processing. Emissions throughout the biosolids processing from eight wastewater treatment plants, each with different unit operation configurations, were surveyed to identify odorants present and their olfactory properties.

Chemical and olfactory methods identified a range of odorants and odours emitted throughout biosolids processing. Within the biosolids processing locations studied Sulfur type odours, described as rotten eggs or cabbage, were typically encountered. However, there was also a varying presence of Rancid/putrid and Faecal/manure type odours.

Odour Wheels were generated to communicate both the olfactory and chemical components of emissions which were measured throughout biosolids processing. Examples based on the operation of the eight wastewater treatment plants were used to demonstrate how the Odour Wheels can be used as an onsite odour management aid.

This paper published in Science of the Total Environment demonstrates how Odour Wheels can be prepared using chemical and olfactory measurements and then used to communicate olfactory properties, as well as identify the causes of nuisance emissions throughout biosolids processing at wastewater treatment plants. The linking of odours and odorants to process conditions throughout biosolids processing facilitates effective abatement and management practices.

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RP2008: Journal paper: Odorous volatile organic compound (VOC) emissions from ageing anaerobically stabilised biosolids

Opportunities for the beneficial re-use of biosolids are limited by nuisance odour emissions. Volatile organic compounds (VOCs) from anaerobically stabilised biosolids were measured to identify compounds that could contribute to the overall odour character of nuisance emissions. Flux hood sampling and chemical analysis were used to identify VOCs emitted from biosolids as they were stored in ambient conditions.

Compounds emitted varied as the biosolid cakes were stored for a period of 50 days. VOCs detected in the biosolids are likely to occur from catchment sources as well as abiotic and biotic generation in the wastewater processing and the biosolids as they are stored. Odour activity values (OAVs) were used to compare odorants. Trimethylamine was the only VOC detected that exceeded the sulfur compounds in terms of OAVs. Other compounds such as limonene, ethyl methyl benzene and acetic acid were detected at concentrations exceeding their olfactory detection limits, however at lower OAVs than sulfur compounds.

The objectives for this study reported in Water Science & Technology  were to identify VOCs associated with anaerobically stabilised biosolids, map emissions as the biosolids are stored and to identify sensorially relevant VOCs that have the potential to contribute to nuisance emissions from the biosolids at wastewater treatment plants.

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RP2008: Journal paper: Distribution and sensorial relevance of volatile organic compounds emitted throughout wastewater biosolids processing

A diverse range of volatile organic compounds (VOCs) are emitted from wastewater biosolids processing. Odorous emissions are predominately made up of volatile sulfur compounds (VSCs) which are typically the only odorants measured. However, a range of VOCs are known to contribute to malodours yet previous studies often overlook the contribution of VOCs in comparison with VSCs.

This study aims to evaluate how emissions are affected by different biosolids processing configurations, and if any non-sulfur VOCs should be included in odour measurement and management. Non-sulfur VOCs emitted from biosolids throughout six wastewater treatment plants in the Sydney, Australia region were measured at six locations on average twice each week over 2–3 weeks at each site. Variations in types of VOCs emitted throughout and between the sites were assigned to differences in WWTP processing configurations, plant operation and variations in industrial and municipal flows to the sewer network, referred to as sewer catchments.

The presence of VOCs is likely due to biotic generation as well as industrial or residential additions to the sewer network. The dewatered and stored biosolids samples had the highest levels of VOC emissions. Sensorially important odorants were p-cresol and butanoic acid, based on the frequency of detection and odour activity values. Other compounds with a high risk of nuisance impacts were trimethylamine, indole and phenol emitted from the dewatered and stored biosolids, and volatile fatty acids from the anaerobic digester inlet and outlet at one particular site.

The findings show that non-sulfur VOCs should be added to odorant monitoring campaigns at WWTPs. Identification of VOCs as sensorially important odorants opens opportunities for the more efficient management of nuisance odours, through targeted odour control or process improvement.

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RP2008: Journal paper: Review of the effects of wastewater biosolids stabilization processes on odor emissions

Odor emissions from biosolids limit opportunities for their beneficial reuse by land application. Odorous emissions are affected by the operation of stabilization processes via methods such as anaerobic digestion, aerobic digestion, alkaline treatment, thermal drying, or composting. Commonly used sampling and measurement methods for assessing odor emissions were identified and key odorants reported for biosolids produced using different stabilization methods.

Generally, dominant odorants from biosolids were volatile sulfur compounds; however other odorants such as trimethylamine, ammonia, indole, p-cresol and pinene may also be sensorially important in different types of stabilized biosolids. Therefore, initial studies should target a range of odorants potentially emitted at different sites. The use of sensory analysis, which was limited in many studies, coupled with analytical methods can be effectively used to characterize nuisance emissions.The processing of the biosolids both before and after stabilization was shown in many studies to affect the resultant biosolids odorous emissions.

These findings suggest that not only should the operational performance of biosolids processing before, during and after stabilization should be reported but that the biosolids management systems should consider the whole biosolids processing train, rather than just the operation of the chosen stabilization method.

Read the paper published in the Critical Reviews in Environmental Science and Technology

RP2008: Journal paper: Towards a comprehensive greenhouse gas emissions inventory for biosolids

Effective handling and treatment of the solids fraction from advanced wastewater treatment operations carries a substantial burden for water utilities relative to the total economic and environmental impacts from modern day wastewater treatment. While good process-level data for a range of wastewater treatment operations are becoming more readily available, there remains a dearth of high quality operational data for solids line processes in particular.

This study seeks to address this data gap by presenting a suite of high quality, process-level life cycle inventory data covering a range of solids line wastewater treatment processes, extending from primary treatment through to biosolids reuse in agriculture.

Within the study, the impacts of secondary treatment technology and key parameters such as sludge retention time, activated sludge age and primary-to-waste activated sludge ratio (PS:WAS) on the life cycle inventory data of solids processing trains for five model wastewater treatment plant configurations are presented. BioWin® models are calibrated with real operational plant data and estimated electricity consumption values were reconciled against overall plant energy consumption.

The concept of “representative crop” is also introduced in order to reduce the uncertainty associated with nitrous oxide emissions and soil carbon sequestration offsets under biosolids land application scenarios. Results indicate that both the treatment plant biogas electricity offset and the soil carbon sequestration offset from land-applied biosolids, represent the main greenhouse gas mitigation opportunities. In contrast, fertiliser offsets are of relatively minor importance in terms of the overall life cycle emissions impacts.

Results also show that fugitive methane emissions at the plant, as well as nitrous oxide emissions both at the plant and following agricultural application of biosolids, are significant contributors to the overall greenhouse gas balance and combined are higher than emissions associated with transportation. Sensitivity analyses for key parameters including digester PS:WAS and sludge retention time, and assumed biosolids nitrogen content and agricultural availability also provide additional robustness and comprehensiveness to our inventory data and will facilitate more customised user analyses.

Read the paper