Activated sludge process

Ardern and Lockett described the activated sludge process in Manchester. It remains the dominant secondary wastewater treatment process worldwide.

Aqua Appia

The first Roman aqueduct. Rome eventually operated eleven, delivering water by gravity over distances up to 90 km, with distribution to public fountains, baths and some private supply.

Assyrian aqueducts

Sennacherib’s aqueduct at Jerwan carried water to Nineveh across a stone arch structure, several centuries before Roman aqueduct construction.

Cape Town Day Zero campaign

A major city halved its water consumption and avoided supply failure, establishing demand management as a first-order drought response.

Earliest known engineered water supply

Wells, drainage and bathing structures at Mohenjo-daro and Harappa in the Indus Valley — among the earliest planned urban water and sanitation systems known.

EU recast Drinking Water Directive

Introduced a risk-based approach across the whole supply chain and added parametric values for PFAS, bisphenol A and microplastics monitoring.

EU Urban Waste Water Treatment Directive

Required collection and treatment of urban wastewater across the EU, driving the largest programme of wastewater investment in European history.

EU Water Framework Directive

Shifted European water management to river basin planning with ecological status objectives, the most ambitious water law adopted anywhere.

First continuous drinking water chlorination

Middelkerke in Belgium began continuous chlorination; Jersey City followed in 1908, and the practice spread rapidly as typhoid rates collapsed wherever it was adopted.

First municipal sand filtration

Paisley, Scotland, installed the first treated public water supply using slow sand filtration, decades before the mechanism of waterborne disease was understood.

First WHO Guidelines for Drinking-water Quality

Established the international reference framework from which most national drinking water standards are derived.

Flint water crisis begins

A source change without corrosion control exposed a city to lead, and became the defining modern case of institutional failure in drinking water.

International Drinking Water Supply and Sanitation Decade

A UN decade-long programme that substantially expanded water and sanitation access in developing countries and established the global monitoring architecture that became the JMP.

John Snow and the Broad Street pump

Snow’s mapping of cholera deaths against water sources established waterborne transmission and founded epidemiology.

Milwaukee Cryptosporidium outbreak

Established that chlorination alone is not a sufficient barrier and reshaped filtration regulation.

Minamata disease identified

Methylmercury poisoning through contaminated fish established bioaccumulation as a central environmental health concept.

Practical reverse osmosis membrane

Loeb and Sourirajan developed the first asymmetric cellulose acetate membrane with useful flux, making reverse osmosis practical and eventually making seawater desalination economic.

Privatisation of the water industry in England and Wales

The ten regional water authorities were sold, creating the private regional monopoly structure regulated by Ofwat and the DWI — a model not replicated in Scotland, Wales or Northern Ireland.

Qanat systems

Persian qanats — gently sloping tunnels tapping groundwater and conveying it by gravity — spread across arid Asia, North Africa and Spain, and some remain in use today.

Sandoz chemical spill, Basel

Firefighting water carried agrochemicals into the Rhine, killing aquatic life for hundreds of kilometres and triggering the modern Rhine cooperation programme.

Singapore NEWater

Singapore began large-scale planned potable reuse, demonstrating that advanced treated wastewater can be returned to supply reliably and acceptably.

Sustainable Development Goal 6 adopted

Set global targets for universal safely managed water and sanitation by 2030, with a far stricter service definition than the Millennium Development Goals it replaced.

The 1976 UK drought

The most severe UK drought of the twentieth century. Standpipes were used, a Drought Act was passed, and a Minister for Drought appointed — all still the reference point for UK drought pla…

The Great Stink and Bazalgette’s sewers

London’s sewage crisis produced the intercepting sewer system that still underpins the city’s drainage.

UK Rivers Pollution Prevention Act

One of the earliest statutes anywhere to prohibit the discharge of sewage and industrial waste to watercourses.

UN recognises the human right to water and sanitation

General Assembly resolution 64/292 recognised access to safe drinking water and sanitation as a human right.

US Clean Water Act

Rebuilt US water pollution law around discharge permits and technology standards, and drove a transformation in the condition of American rivers.

US federal PFAS drinking water limits

The US EPA set the first enforceable national drinking water limits for PFAS, at 4 nanograms per litre for PFOA and PFOS — among the strictest chemical limits ever set for drinking water.

US Federal Water Pollution Control Act

The first major US federal water pollution statute, and the foundation later rebuilt as the Clean Water Act.

US Safe Drinking Water Act

Established federally enforceable drinking water standards in the United States for the first time.