Guidance

Onsite Wastewater Wetlands in Maidstone Borough

Guidance for Developers on Cost Savings, Environmental Benefits & Planning Context

As Maidstone Borough continues to champion sustainable development and climate resilience, innovative approaches to wastewater management are becoming increasingly vital. On-site wastewater wetlands—also known as constructed wetlands—offer a nature-based solution that aligns with the Borough’s biodiversity and climate goals while delivering tangible benefits to developers.

This guidance outlines how integrating onsite wastewater wetlands into new developments can reduce infrastructure costs by minimising reliance on traditional sewer systems; Enhance environmental performance through natural filtration, habitat creation, and carbon sequestration; Support planning policy/guidance compliance by contributing to water quality mitigation, and biodiversity net gain.
Whether for rural developments, edge-of-settlement schemes, or larger mixed-use sites, this document provides practical insights into design considerations, regulatory alignment, and long-term maintenance. Developers are encouraged to explore this opportunity to deliver high-performing, low-impact wastewater solutions that benefit both communities and the environment.

1. Environmental Benefits

Nutrient Neutrality

Part of Maidstone Borough at Lenham falls within the River Stour catchment, where nutrient neutrality is a requirement for polluting developments as they can affect protected sites – at Stodmarsh (SAC/SPA/Ramsar).
Onsite wetlands can remove nitrogen and phosphorus from wastewater, helping developments meet Habitats Regulations Assessment (HRA) requirements.

Biodiversity Net Gain

Wetlands support amphibians, birds, and pollinators, and can contribute to Biodiversity Net Gain (BNG) targets.
They can be designed as multi-functional green infrastructure, enhancing landscape and ecological connectivity.

Climate Resilience

Onsite wastewater wetlands offer a robust, nature-based solution that enhances the climate resilience of new developments. By mimicking natural processes, these systems help developments adapt to and mitigate the impacts of climate change in the following ways:

• Flood Risk Reduction
• Constructed wetlands can retain and slowly release stormwater, reducing peak flows and downstream flooding. This is particularly valuable in areas prone to surface water flooding or where sewer capacity is limited.
• Drought Resilience
• Wetlands help recharge groundwater and maintain local water cycles, supporting water availability during dry periods. They can also be designed to reuse treated wastewater for irrigation or other non-potable uses, reducing pressure on mains supply.
• Temperature Regulation / Urban  Cooling
• Vegetated wetland systems provide cooling effects through evapotranspiration and shading, helping to mitigate urban heat island effects and improve microclimate conditions around developments.
• Carbon Sequestration
• Wetlands naturally capture and store carbon in plant biomass and soils, contributing to net-zero development goals. They also reduce emissions associated with energy-intensive conventional wastewater treatment.
• Biodiversity Enhancement
• By creating habitat for wetland species, these systems support ecological networks and contribute to biodiversity net gain requirements. Diverse ecosystems are more resilient to climate shocks and help buffer communities from environmental change.
• System Robustness
• Unlike mechanical systems, wetlands are less vulnerable to power outages and supply chain disruptions. Their passive operation and low maintenance requirements make them a reliable long-term solution in a changing climate.

2. Cost Savings

3. Integration with Existing Systems

Design Options

Subsurface Flow Wetlands: Ideal for compact sites; wastewater flows through gravel planted with reeds.
Surface Flow Wetlands: More visible and naturalistic; can double as landscape features.
Hybrid Systems: Combine vertical and horizontal flow for enhanced treatment.

Integration Points

SuDS: Wetlands can be co-located with Sustainable Drainage Systems.
Package Treatment Plants: Wetlands can polish effluent from small treatment units.
Greywater Reuse: Treated water can be reused for irrigation or flushing (subject to regulation).

4. Maintenance Requirements

5. Case Studies

Kent Downs National Landscape (Pilot)

Constructed wetland used to treat effluent from a small housing development.
Achieved over 70% nitrogen removal, enabling planning approval in a nutrient neutrality zone.

Hampshire – Nutrient Mitigation Scheme

Wetlands used as part of a strategic mitigation bank.
Developers purchase credits to offset nutrient loads; similar models could be explored in Maidstone.

6. Planning & Regulatory Context

Habitats Regulations Assessment (HRA) is required for polluting developments in the River Stour catchment at Lenham as they would feed into Stodmarsh which is a designated site of European importance.

Natural England supports onsite wetlands as valid mitigation if:

• Nutrient budgets are calculated.
• Wetland performance is evidenced.
• Long-term management is secured via planning conditions or legal agreements.

For more information and additional resources on incorporating Wastewater Wetlands into your development project, please visit the Constructed Wetlands Association website.

Guidance for New Developments: Achieving Highest Energy Efficiency Standards

1. Policy Context

New developments in the UK must comply with:

- Future Homes Standard (FHS): Mandatory from 2025, requiring new homes to be zero-carbon ready with 75–80% lower emissions than 2013 standards.

- Part L Building Regulations 2025: Updated to enforce stricter insulation, airtightness, and low-carbon heating systems.

- UK Net Zero Carbon Buildings Standard (UKNZCBS): Provides a science-based framework for verifying net-zero alignment using operational and embodied carbon metrics.

2. Design Principles for Maximum Energy Efficiency

Fabric-First Approach

- High-performance insulation: Walls, roofs, floors must meet lower U-values (e.g., windows ≤ 1.2 W/m²K). [norrsken.co.uk]
- Airtight construction: Max air permeability target of 8 m³/(h·m²) at 50 Pa. [enevo.co.uk]
- Thermal bridging minimisation: Use thermal modelling to eliminate cold spots.

Passive Design Strategies

- Optimal building orientation for solar gain.
- Natural ventilation and daylighting to reduce HVAC and lighting loads.
- Shading devices and green roofs to mitigate overheating.

Low Carbon Technologies

- Heat pumps (air/ground source) instead of gas boilers.
- Solar PV systems with battery storage.
- Mechanical Ventilation with Heat Recovery (MVHR) for indoor air quality and energy recovery.

3. Compliance & Verification

Energy Performance Assessment

- Use SAP 10 methodology for dwellings and SBEM for non-domestic buildings.
- Conduct TM54 operational energy assessments to compare predicted vs actual performance. [cca-ltd.uk.com]

Evidence Requirements

- Submit digital photographic evidence during construction to prove compliance. [ukproperty...news.co.uk]
- Post-construction testing: airtightness, EPC ratings, and renewable energy generation.

Certification

- BREEAM for commercial buildings.
- UKNZCBS verification for net-zero alignment (pilot version available). [nzcbuildings.co.uk]

4. Best Practices for Developers

-Start early: Integrate energy strategy at concept design stage.
-Engage sustainability consultants: For energy modelling, overheating analysis, and compliance support.
-Use modern methods of construction (MMC): Prefabrication and modular systems improve quality and reduce waste.
-Select sustainable materials: Low-carbon concrete, recycled steel, FSC-certified timber.

5. Resources & Further Reading

-Future Homes Standard Guide – CCA Environmental
-Part L 2025 Overview – UK Property Market News 
-UK Net Zero Carbon Buildings Standard – CIBSE

Guidance for Property Owners: Renewable Energy Installation & Shared Purchasing Schemes

1. Why Invest in Renewables?

- Comply with upcoming legislation (see Section 2)
- Reduce energy bills for tenants and communal areas
- Increase property value and tenant appeal
- Support Maidstone’s Biodiversity & Climate Strategy
- Access grants and shared purchasing discounts

2. Upcoming Energy Efficiency Legislation

The UK Government is tightening energy efficiency standards for rental properties:

- Minimum EPC rating will rise to C
- From 2028: Required for new tenancies
- By 2030: Required for all tenancies
- New EPC metrics (from 2026) will assess:
-Fabric performance (insulation, glazing)
-Heating system efficiency
-Smart readiness (e.g. battery storage, smart meters)
-Cost cap: £15,000 per property (with possible exemptions)

Landlords should begin upgrades early to avoid fines (up to £30,000) and benefit from available grants.

3. Renewable Energy Options

a. Solar PV Panels
Generate electricity for communal or individual use.

b. Solar Thermal Panels
Provide hot water, reducing reliance on gas/electricity.

c. Heat Pumps (Air/Ground Source)
Efficient heating and cooling.

d. Battery Storage
Store excess solar energy for later use.

e. EV Charging Points
Future-proof your property for electric vehicle uptake.

4. Shared Purchasing Schemes

Solar Together

-Council-backed group-buying scheme for solar panels and battery storage
-Open to landlords, homeowners, and small businesses
-Reverse auction ensures competitive pricing
-No obligation after registration

Community Energy

-Community-owned solar projects across Kent
-Offers investment opportunities and grants
-Profits reinvested in local sustainability initiatives

5. Past Events

Green Homes Bearsted

Green Homes Bearsted
📅 Date: Friday, 18 October 2025
📍 Location: Bearsted Parish, The Memorial Hall, ME14 4DB
🎯 Focus: Home energy efficiency, renewable technologies, and grants

Please subscribe to the Biodiversity & Climate Change newsletter (link on top right) to receive notifications of upcoming events.

6. Landlord Networks & Support

Maidstone Borough Council Landlord Forum

-In partnership with the NRLA
-Offers updates, training, and networking

Kent Property Meet

- Monthly networking event for landlords, investors, and developers
-Held at Mercure Great Danes Hotel, Maidstone

7. Funding & Grants

When funding becomes available, we will share information to promote any live campaigns. These might include:

-Boiler Upgrade Scheme
-Great British Insulation Scheme
-Kent Community Energy Grants
-Solar Together Discounts

Please subscribe to the Biodiversity & Climate Change newsletter (link on top right) to receive notifications of available grants and funding.

8. Next Steps

✅ Assess your property’s EPC rating
✅ Register for Solar Together or Kent Community Energy
✅ Attend Green Homes Bearsted on Oct 18
✅ Join a landlord group
✅ Begin budgeting and planning for 2028–2030 EPC upgrades

9. Cost of Living - Video Series

We spoke to the voluntary community sector, and polled their staff on what barriers were for our most vulnerable residents when it came to engaging with sustainability campaigns. They suggested a series of educational explainer videos, to help demonstrate  how to improve the cost of living by adopting tips at home. The following series was produced as a result, and alongside our ecohub and extending into winter via our distribution partners, we have given away over £5,000 in products to help with cost of living for our most vulnerable residents at home.

1. Wool drier balls https://www.facebook.com/watch/?v=1276680514479589