Septic Tanks of the Future Allan Mason Scottish Water Sustainable - - PowerPoint PPT Presentation

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Sep 28, 2023 234 likes •549 views

Septic Tanks of the Future Allan Mason Scottish Water Sustainable Rural Communities - Household Water Usage B uilding and providing the assets, infrastructure and service that enable us to meet our needs now without jeopardising our ability to

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Septic Tanks of the Future

Allan Mason

Scottish Water

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Household Water Usage Sustainable Rural Communities -

Building and providing the assets, infrastructure and service that enable us to meet our needs now without jeopardising our ability to meet future needs. It is about building the consistent, upgradable assets that do not damage the environment and do not break the bank to implement.

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Scottish Water has over 1000 Septic Tanks for primary treatment in rural

locations.

The Future
Low sludge production or treatment locally
Energy generation
Able to incorporate food waste to increase energy generation
Able to manage surface water flows to provide local flood attenuation
Water Reuse

Background

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Challenges

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Household Water Usage

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Issues in Scotland

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Septic Tank of the Future

A Scottish Water & Cranfield University Collaboration Prof Bruce Jefferson Dr Gabriela Dotro Mr Gareth Brown

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Septic Tanks of the Future flowsheet

The aim of this project was to provide an outline design and cost estimates for the novel sewage treatment flowsheet

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Descriptive consents Septic Tank vs Anaerobic Pond

Descriptive consents

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Numeric consents Anaerobic Pond + Wetland vs SAF plant

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Adding value

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Highlights

Based on example 100 pe works

Sites with descriptive consents can be upgraded to an anaerobic pond to improve

effluent quality, improving the desludging interval and future proof.

Breakeven point is 3 to 7 years.
Transport carbon emissions savings of >80%
Relaxed consents and medium consents can be met with either AP+ VF wetland or

AP + aerated HF wetland

Both wetland flowsheets have similar WLC and are c. 70% lower CAPEX, OPEX

and WLC compared against the SAF

VF systems offer off-grid operation potential (lower WLC)
Operational carbon emissions savings of 88% and 98% for AHF and

Adding the tertiary SF system provides additional benefits without impacting WLC

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Results

Aerobic wetland air Anaerobic Pond Surface wetland

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Benchmarking against standard options Relaxed and medium consents

£50K £100K £150K £200K £250K £300K CAPEX OPEX WLC Cost AP + AHF AP + VF PT+SAF+HT

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Benchmarking against standard options Descriptive consents

£10K £20K £30K £40K £50K £60K 2 4 6 8 10 12 14 16 Whole life cost Desludging interval (years) Anaerobic Pond Septic Tank (6-month) Septic Tank (12-month)

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Impact on carbon emissions - Transport

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Operational carbon emissions

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Anaerobic ponds:
Impact of baffles on solids removal efficiency
Solids accumulation rates at low temperature wastewater
Treatment performance under flow variations
Biogas production rates and quality
Impact of biowaste addition on methane production and performance
Engaging with potential suppliers on design needed (GRP & soil)
Wetlands:
Performance with AP effluent
Impact of depth on AHF performance
Hydraulic limits with locally sourced materials
Configurations to achieve TN removal*
Passive alkalinity amendments*

Key uncertainties to resolve

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Doctorial Research - Aim

The overall aim of the project is to deliver a robust design approach for the novel flowsheet by resolving areas of uncertainty and risk.

1. Establishing the specific hydrolysis rate under low temperatures and assessing options to enhance it. 2. Establishment of the size and settling rate of particles within the pond and trial methods to increase the removal rate. 3. Establishment the benefit and impact of adding bio-waste to the pond. 4. Trial and determine the most appropriate configuration of wetland to meet different discharge consents. 5. Revise and adapt the initially proposed design standard

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Inclusion of Bio-wastes

Impact
How to include
Benefits and dis-benefits

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Integration in urban designs

Image from Molle (2017) at 6th Low Energy Wastewater Treatment Systems Conference, Cranfield University.

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Community perspectives on sustainable wastewater services for rural areas

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Gracey’s Journey

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Overall aim and individual objectives

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