BIOSOLIDS AND RESOURCE RECOVERY PROGRAM
Biosolids and resource recovery are of significant interest to the water industry. The effective management of biosolids is a pressing issue as the current system in place (stockpiling) is labour intensive, occupies a large land area and risks polluting land and water tables with heavy metals and nutrients. Urban sprawl is increasing both the pressure on land use and the amount of biosolids produced, thus a cost effective, efficient and environmentally friendly management plan for biosolids is desired by water corporations. Similarly, a more efficient and low energy resource recovery system is also a main industry focus. A range of potential projects are being considered for application in these areas. Christine Grundy from Coliban Water is the program leader.
Current Projects
Nutrient Removal/Recovery Project
Background
The current waste water nutrient removal process is responsible for significant chemical, energy and maintenance cost issues at waste water treatment plants (WWTPs) with anaerobic digestion. Researchers from Victoria University (VU) have developed new techniques to enhance Nitrogen (N) and Phosphorous (P) capture, with the intention of improving water treatment efficiency, reducing energy consumption and enriching the nutrient content of biosolids.
Description of trial
Central Highlands Water (CHW) aims to conduct an 8-week trial of VU’s innovative nutrient capture process at the Ballarat South Waste Water Treatment Plant.
Currently, P is recovered by dosing the belt press filtrate with lime to cause precipitation. The filtrate is returned to the head of works, where denitrification requires aeration by blowers to create nitrates that can be digested by microbes. The blowers consume large amounts of electricity. VU’s technology is designed to capture and recover the N and P within the biosolid stream before it is returned to the head of works.
There are two options for the trial of VU’s technology:
1. Recover P as calcium phosphate, using the existing lime dosing process, then extract N as concentrated ammonium.
2. Recover all P and some N by dosing with magnesium (in place of lime) to create struvite (a crystalline mineral), and then capture the remaining N as ammonium.
In both cases, the captured N and P would be added to the plant’s biosolids output to create a more nutrient-rich product.
The main benefits anticipated from using VU’s technology are improved efficiency, reduced energy consumption and emissions, and recovery of valuable resources.
Performance targets for the trial include:
· Reduce energy consumption and emissions by 40%
· Recover N as ammonium at 0.84t/ML (zero is currently recovered), and
· Recover P as struvite at 0.06t/ML (zero is currently recovered).
Current status of trial
Both approaches achieved removals of P and N of >90% when trialled separately. The vacuum membrane distillation (VMD) demonstrated electrical cost savings for N removal. The crystalliser demonstrated > 90% P removal along with >30% N removal. This is a promising technology that appears ready for adoption with some civil and electrical and mechanical modifications to the current plant at the Ballarat South Waste Water Treatment Plant. The technology could also be adopted by other Victorian Water Authorities.
Both the crystalliser for P and N removal and the VMD for N recovery are technically feasible and are alternatives to current nutrient removal practice. However further tests, cost analysis and engineering designs are recommended for scaling up to full scale operations.
Central Highlands Water is not in position to progress the project any further due to alternative priorities, while Melbourne Water found that the process is not cost effective for large systems due to poor scaling. However, North East Water are0- currently investigating a high level business case.
Executive summary
If you require more information about this project, please email program lead Christine Grundy or Fawzi Saldin. Christine can be reached at Christine.Grundy@coliban.com.au, Fawzi at tfawzi.saldin@chw.net.au.
Biosolids to Biochar Project
Background
This South East Water led project has been designed to tackle the shortcomings of biosolids management. This project will aim to demonstrate how a novel PYROCO technology can convert biosolids (sewage sludge from wastewater) into biochar, thereby reducing stock pile volumes, management costs and producing value-added materials.
Description of trial
Managed by an experienced team of engineers, scientists, social scientists and economists, this project will see a 75 kg/hr PYROCO pilot-plant designed, constructed and commissioned, with an aim to reduce spatial footprint by 40-60%. The goal is to validate the social and commercial viability of the technology by showcasing how it provides a low emission and low cost solution by offering 80-85% reduction in energy and 30-40% reduction in capital and operating costs compared to existing technologies. Working closely with industry, this project will aim to reduce biosolids management costs by 30-35%. Other members of the team are RMIT and Yarra Valley Water.
The project focuses on the development of novel mobile (containerised) pyrolysis technology with an aim to produce homogeneous and high surface area biochar from biosolids feedstock from South East Water’s Mt Martha and Boneo solar dryer sheds. The technology is expected to provide the following advantages:
40-60% reduction in the biosolids volume
100% destruction of pathogens and micro-plastics
Production of slow phospohorous release homogeneous biochar with high surface areas, cation exchange capacity and pH.
Immobilisation of heavyt metals and possibly PFAS in biochar
Mobile unit allows operational flexibility
Current status of trial
Semi-pilot scale trials confirmed the results obtained from lab-and bench-scale designs and encouraged the project team to design pilot scale plant.
Next steps
The plant will be moved from Newcastle to Victoria, either to Mt. Martha or RMIT Bundoora campus.
A pilot plant will be built and operated at South East Water’s Mt. Martha treatment plant by March 2020 on a trial basis.
Upon successful completion of trials at South East Water’s Mt Martha treatment plant, the pilot plant will be tweaked to consider additional feed material opportunities.
The pilot plant aims to prove that the process has the ability to
Produce biochar from solar dryer shed biosolids from South East Water’s Mt Martha and Boneo treatment plants (around 50 solids),
Eliminate contaminates such as microplastics and hopefully PFAS through higher operating temperatures.
A second aligned project to investigate alum sludge is being initiated. RMIT are awaiting are awaiting written confirmation of agreement for the appointment of a PhD student, who will investigate the feasibility of pyrolysis/co-pyrolysis on biosolids and alum sludge.
Innovative use of biosolids to overcome subsoil constraints in the grain industry
The project is a collaboration between Victoria University, Grain Research Development Corporation (GRDC) and IWN. Support and collaboration from Central Highland Water was greatly appreciated.
The success of the project will help to demonstrate the use of biosolids across the Australian grain industry to improve subsoil constraints by subsoil incorporation of biosolids. Two trials were successfully established at Central Highlands Water and Barwon Water catchments – Ballan and Balliang.
Field trials were successfully established at Yaloak Estate in Ballan and Sharkey’s Farm in Balliang. Results obtained to date from these two trial sites are very promising, and consortium members strongly believe it is vital to continue these trials in order to obtain further data related to temporal changes in soil physiochemical and effects on crop quality after biosolid treatment. The project is seeking to extend the trail for the next three cropping seasons.