Water treatment without grid electricity
A crank or pedal powers the UV lamp in this water-treatment prototype. I am working with the research group to consider where it might be useful after displacement. The starting point is their 2026 study in ACS Nano; the next questions concern the water people use and how they would operate the device.
Project notes by Jerry Zou. The study and laboratory demonstration are the research group’s work; my contribution is described below.
Water supply and water treatment
UNHCR’s 2024 WASH report covered 104 settlements in 17 countries, serving 3.2 million people. Reported daily water provision averaged 18 liters per person, and 69 percent of reporting sites fell below minimum standards. UNHCR’s monitoring report provides the full scope.
A family needs enough water, and that water needs to be safe. The two problems overlap, but a treatment device cannot make up for a dry well or a broken delivery system. TEHG-UV disinfects water already available to the user.
Existing treatments offer different ways to address microbial contamination. Their usefulness depends on the water source, the resources available, and how people will store treated water.
Chlorination works at household and larger scales. It needs suitable dosing and a supply of disinfectant; its residual can help protect water during storage. Boiling inactivates disease-causing organisms but requires heat, cooling time, and safe handling.
Solar disinfection uses clear containers and suitable sunlight. Cloud cover increases the exposure needed, while water clarity and local weather affect whether the method is practical.
At Dabat Bosin in Sudan, UNHCR reported just four liters per person per day in 2024, against a post-emergency standard of 20 liters. Those needs include more than drinking. Disinfecting a ten-liter batch would not meet a household’s full daily water requirements.
For a country-level view, see WHO/UNICEF drinking-water data, presented by Our World in Data. The 2025 data release covers 2000–2024. National estimates provide context; conditions in individual settlements require local evidence.
How the device works
Xingwei Wang and colleagues combine two generators to power a UV lamp. The engineering problem is that starting the lamp and keeping it running require different electrical outputs. Their hybrid system changes its electrical behavior to accommodate both stages.
A crank or pedal drives a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG). Contact and separation between materials produces charge in the TENG; electromagnetic induction produces current in the EMG.
The TENG supplies high voltage useful for starting the lamp. The EMG supplies the current needed to sustain operation. Combining them allows the system to respond to the lamp’s changing impedance without drawing operating power from the grid.
The lamp’s radiation inactivates microorganisms. The paper reports an eight-log reduction under laboratory test conditions. That describes a measured reduction in the tested organisms, not proof that any source water becomes safe or that the device has a WHO product rating.
The study reports treatment of two liters in 25 minutes with hand-cranking and ten liters in 15 minutes with pedaling. In smaller tests, 500-milliliter samples deliberately contaminated with E. coli, B. subtilis or MS2 bacteriophage reached an eight-log reduction within five minutes at 80 rpm. The supporting information reports five replicates. These tests establish performance in specified conditions, rather than across every water source.
The authors estimate a levelized cost of $8.57 per person per year, using fabrication costs and assumed component lifetimes. It is not a retail price or a measured cost of deployment in a refugee settlement.
Before a field trial
The researchers designed TEHG-UV for households in regions with limited electrical infrastructure. Applying it to displacement is the question behind this project. A useful starting point is a household with accessible water, a microbial-treatment need, and unreliable power. Where water itself is unavailable, a different intervention is needed.
Human motion supplies electricity during use, reducing dependence on charging or fuel for treatment. The two configurations offer a basis for testing how the device fits into everyday water collection and storage. Conversations with water-service staff and prospective users would establish whether these features address a problem they face.
Water quality would shape any trial. UV does not remove chemical contaminants or heavy metals. Cloudy water may need pretreatment, and treatment for chemical contamination must address the substances present.
Physical effort, cleaning and protected storage also need assessment. UV leaves no continuing disinfectant residual, while the mercury lamp requires a workable plan for breakage, replacement and disposal. The study does not establish sustained performance in displacement settings.
Other treatment methods
This comparison describes operating requirements, rather than ranking methods by a single efficacy score. Performance depends on the particular device, dose, water quality, and use conditions.
| Method | What it needs | Practical consideration |
|---|---|---|
| TEHG-UV | Mechanical effort, lamp and working generator | Laboratory prototype; field use and upkeep need evaluation |
| Chlorination | Disinfectant, suitable dose and contact time | Residual can protect stored water; effectiveness varies by organism |
| Boiling | Heat and a suitable vessel | Cooling, safe handling and clean storage |
| Solar disinfection | Suitable bottles, clear water and sunlight | Weather and exposure time affect use |
| Portable electric UV | Power, including batteries in some devices | Water clarity, treatment dose and charging or replacement power |
WHO’s household-treatment evaluation uses separate criteria for bacteria, viruses and protozoa. A laboratory result for selected organisms does not establish a WHO classification.
The research group and my role
This page grows from an ongoing collaboration with the group behind the technology. Xingwei Wang is first author of the study, conducted at Tsinghua University’s State Key Laboratory of Regional Environment and Sustainability. Co-corresponding author Prof. Zhiguo Yuan of City University of Hong Kong is a member of FIRST’s Management Committee.
FIRST — Fostering Innovation for Resilience and Sustainable Transformation — is led by City University of Hong Kong and endorsed by UNESCO under the International Decade of Sciences for Sustainable Development. The affiliations shown here identify the research and programme context.
The research group developed the device and carried out the experiments. I am looking at its possible relevance to displacement and explaining the research to humanitarian organizations. A next step I want to develop is a short technical note for water-service staff, followed by discussion of a specific water problem and whether the device fits. Any field trial would need to be designed with researchers, local staff and prospective users.
Work with water access?
I would like to hear how water is collected and treated where you work, and which problems take the most time to solve. That would help establish whether this device is worth assessing in your setting.