Accelerating the Concentration of Water Treatment Residue

This Innovation Exchange challenge, delivered by Innovate UK KTN through the Global Alliance Africa project, is supporting Rand Water to identify innovative solutions to accelerate the concentration of Water Treatment Residue (WTR). The current drying times for WTR range from 30-45 days to increase solid matter from the initial 16-20% to 75-100%. Rand Water is seeking innovative solutions to lessen the drying times required to improve operational efficiencies.


Challenge opens


Challenge closes



Successful applicants will be given the opportunity to pitch their solution to Rand Water. The winning applicant, as selected by Rand Water, will get the opportunity to collaborate with them on a trial project. Up to GBP 25,000 seed funding is available to the successful finalist/s for this collaboration.

The Challenge

Rand Water is actively looking for solutions which can rapidly and effectively remove water from Water Treatment Residue at their treatment facility.

Solutions are invited from, but not limited to, the following sectors:

  • Agricultural sector
  • Engineering and Design
  • Chemical Sector
  • Construction & Infrastructure
  • Materials
  • Mining


Rand Water, the largest water utility company in Africa, is based in South Africa and supplies drinking water to the Gauteng province and other areas of the country. They process and purify large volumes of water. 

Rand Water Institute has focus areas for its innovation and R&D activities. One of these priorities is to utilize Circular economy thinking to encompass sludge beneficiation, waste beneficiation, water security and resiliency, and water reuse.

Disposal of Water Treatment Residue (WTR) is a universal problem with growing environmental awareness and subsequent legislative requirements. Rand Water’s situation is unique in that the nature of the raw water, the treatment process used and the significant volumes of water being processed results in the production of a very large mass of WTR. 

The  WTR, created at Zuikerbosch and Vereeniging water treatment works is combined at Zuikerbosch and dried at the nearby facility of Panfontein. This is dried in stages, coming in at c. 1-2% solids, which is increased to 16-20% solids using gravity thickeners, and then sprayed into large earth beds where moisture both percolates and evaporates, leaving 75-100% dry matter. This ongoing process produces about 500-600 tonnes of residue per day (expressed as dry material). Due to the nature of the process (waste streams are combined from 2 different plants plus natural variations) this residue has variable compositions of primarily inorganic and lesser organic constituents.

The drying facilities are close to capacity and sustainable innovative solutions with minimal environmental impact for the dewatering process are needed. Rand Water is particularly interested in solutions which address circularity, water security and resilience, and water reuse. 

Panfontein is permitted as a hazardous waste disposal site, with conditions of the permit that any disposal options are to be approved by relevant authorities. Previously, Rand Water’s WTR was approved for use as a ground improvement agent only. The vast bulk of WTR remains in the drying bed, and subsequent layers are added until the beds have reached capacity. The storage and logistical requirements of the facility require various logistical operations to be undertaken, e.g.: shifting to other locations if needed.

Panfontein is road accessible with mostly dirt roads within the site. There are 90 drying beds in total ranging in area from  2-3 hectares each with 1.5-4.0 m high sides. 

Rand Water is looking for innovative solutions, which are sustainable and environmentally friendly, to accelerate the WTR drying process and preferably allow for recovery of water for reuse. These solutions may create an intervention at any stage of the treatment process prior to sedimentation, or at the Panfontein disposal site itself.

This challenge has both technical and commercial aspects. Primary drivers for this pilot project include: 

  • Management and disposal of WTR
  • Environmental compliance
  • Cost effective and economically viable solution

There is a pilot project for beneficiation/valorisation of WTR running concurrently. This aims to create new products and services that generate commercial value. Success with this dewatering challenge will also facilitate the progress of the valorisation project. 

Technical Information: 

Panfontein Water Treatment Process Stages


Water Treatment Residue Production


Composition of Rand Water’s WTR

Rand Water’s WTR (sludge from the potable water treatment process) is primarily composed of aluminosilicate (clay) material which makes up the bulk of the suspended matter in the source water. The moisture content of WTR in the drying beds will be 80-84% initially to 0-25% when dried. On average 500-600 tonnes dry WTR is accumulated per day. It’s overall composition includes:

  • Clay and fine particulates
  • Organic matter
  • Inorganic particulates
  • Algae, bacteria and other biological organisms
  • Added chemical treatments

Samples are available to iX challenge applicants upon request (to request please contact

Macro Chemical Composition of WTR


* The loss on ignition component typically includes residual water, carbonates, synthetic coagulation chemicals and natural organic matter present in the source water.


Some elements in the WTR may be considered harmful or undesirable for certain applications.  Maximum and average concentrations of selected elements are provided in the table below.


Potentially Harmful Elements in WTR

*Manganese is also present and its values are included in the macro-chemical chart above


Some adjustments to existing infrastructure may be possible, eg: size of beds, type of pipes, etc. Please specify which aspects will require changes and how. The facility information available includes:

  • Facility size
  • Power available
  • Storage capacity
  • Soil type
  • Pipes
  • Drying bed size
  • Walls height

[current facility plans and technical details are available upon request]

Rewards & Benefits

  • Up to GBP 25,000 seed funding (subject to T&C)
  • Opportunity to pitch your solution to Rand Water
  • Collaboration/partnership with Rand Water
  • Access to Rand Water facilities (specific sites require prior security approvals)
  • Technical support and Mentorship from Rand Water team
  • Mentorship programme with Startup Discovery School (facilitated by KTN)
  • Access to materials, eg: Water Treatment Residue (Rand Water to provide relevant samples)
  • Sector expertise from KTN
  • Support in the development of a prototype or pilot 
  • Invitation to attend or present at KTN events
  • Investor introductions (if investment is required)
  • Application support for any Innovate UK or similar competitions that are relevant.

Functional Requirements

A solution would ideally provide the following:

  1. Increase the speed of concentration/dewatering of WTR (increasing solids from 16-20% to 75-100%)
  2. Solution must be scalable across all drying beds at facility (for solutions based at Panfontein)
  3. Cost effectiveness and economic viability
  4. Upstream focus is preferred so as to retain as much water as possible at the water treatment works before reaching Panfontein (thus reducing the scale of WTR volumes requiring processing downstream)
  5. Environmentally friendly operation enhancing consumer perceptions of sustainability
  6. Ideally improve, but at least meet minimum regulatory and statutory requirements,
  7. Technological maturity: preference for late stage solutions (TRL 7+) that have passed proof of concept stage, are in pilot, ready to commercialize or commercialized. However lower TRL ideas will also be considered.

Technical Requirements

  • Solution may be integrated with Rand Water’s existing system or may be a separate system alongside it.
  • Please detail any new infrastructure requirements for this solution
  • The existing pipelines are designed to transport sludge with less than 5% solids – so new transportation methods may be necessary also
  • Solution must be applicable in modular format, so it may be scaled progressively
  • Solution must reduce drying time of WTR by >50% from 30-45 days to range of 10-20 days
  • Solutions should estimate Iife cycle costing with a 20-year planning horizon

Operating Conditions

  • Solution must operate for 12 hours minimum (daytime)
  • Solution availability 24/7 would be preferable (day and night)
  • Solution should reduce typical drying time by at least 50% on average across the year
  • Solution must be able to operate in all seasons
  • Solution must be non-polluting 

Deployment Timescale

  • 16 Nov 2022 - Competition Launch 
  • 30 Nov 2022 – Information session/Q&A
  • 17 Feb 2023 - Deadline for applications
  • Mar 2023 - Selection and notification of finalists
  • Apr 2023 - Pitch day
  • Apr 2023 – Selection of Winner
  • May 2023 – Collaboration Discussions
  • Jun 2023 – Pilot programme activated

Cost Requirement & Market Opportunity

  • The solution process must be cost-effective for Rand Water in terms of ROI
  • The cost of investment and activity required in one bed must not exceed the value of any operational benefits
  • Innovator’s process will be scaled to all treatment facilities (eg: all drying beds at Panfontein if relevant) and costed/rewarded accordingly

Out of Scope

Solutions that are already being used when required include:

  • Pumping WTR into different areas of the facility
  • Loading and moving WTR using dumper trucks

These are useful for operational reasons but do not provide viable solutions for dewatering WTR

Eligibility & Assessment Criteria

Entrants to this competition must be:

  • Established businesses, startups, SMEs or individual entrepreneurs
  • Africa-based entrants, UK-based entrants and those from RoW are invited to apply.

Due Diligence requirements for seedfunding:

  • Applicants must ensure that receiving the £25k seed funding will not exceed the £315,000* state aid threshold under UK Minimal Financial Assistance regulations over the current and last 2 fiscal years [or *200,000 euros for applicants affected by EC de minimis regulations]
  • Further information will be required later relating to company policies, financial history and recent grant funding received.

Applications will be assessed on:

  • Relevance to the topic
  • Innovative nature of the subject
  • Coherence of the proposed business model
  • Feasibility/ economic viability
  • Development potential
  • Maturity of project/solution
  • Ability to launch project quickly/Ease of implementation
  • Price/quality ratio
  • Suitability for the South African Market

*Please ensure that you explain your idea clearly and concisely and add any useful attachments to support your application (eg: images, diagrams, prototypes, process, case studies, etc.) 

IP & Potential Commercial Route

  • Existing background IP associated with a potential solution will remain with Solution Provider(s). Where any new IP generation is envisaged, it will be subject to the mutual IP agreement of the Solution Provider(s) and Innovation Challenger.
  • Any commercial deployment of a transferred solution or newly developed solution, through licensing, joint venture, partnership or direct investment, will be subject to the commercial agreement between the Solution Provider(s) and Innovation Challenger.
  • Where necessary, a non-disclosure agreement (NDA) may be signed to uphold confidentiality in the engagement between the Solution Provider(s) and Innovation Challenger. (This would be expected to be after company selection, it is suggested that details of IP be not disclosed initially; focus on the outcomes of the technology proposed).
  • KTN do not take any share of IP ownership or enter into commercial ventures through the iX programme.