Introduction

Coagulants have been used for thousands of years to ensure access to safe drinking water. Their large scale use for water treatment was however really trigged by the industrial revolution, when people moved from rural areas to the cities. Drinking and waste-water treatment became a necessity. Today, more than half of the world population lives in cities and 90% have access to safe drinking water, most of it thanks to coagulants. However, still 30% of the world population is without improved sanitation facility.

When mankind established in communities, it was in places where there was easy access to water. It was also important that the water tasted and smelled good, which was considered to be a proof that the water was of good quality.

2000 B.C. in India and parts of China, the Hindus devised the first recorded drinking water standards, including methods such as boiling water, expose it to sunlight, use of charcoal and filtering. If the water was turbid, it contained particles that could give unpleasant taste and odour to the water. As there was no knowledge about the presence of microorganisms in the water, only the aesthetic properties constituted the quality criteria.

1500 B.C. the Egyptians started to use aluminium sulphate to flocculate and coagulate impurities to larger particles, which could then be separated by sedimentation or filtration, the same technology that we use today to purify drinking water and to treat wastewater. Pictures of this purification technique were found on the wall of the tomb of Amenophis II and Ramses II. The products and technology have of course been refined, but the mechanisms are the same.

500 B.C. Hippocrates invented the practice of sieving water, and obtained the first bag filter, which was called the ‘Hippocratic sleeve’. The main purpose of the bag was to trap sediments that caused bad tastes or odours.

300-200 B.C., Rome built its first aqueducts. Archimedes invented his water screw. 

500-1500, during the Middle Ages water supply was no longer as sophisticated as before. These centuries where also known as the Dark Ages, because of a lack of scientific innovations and experiments. The future for water treatment was uncertain. We however find some evidence of aluminium sulphate trade all over Europe and the Ottoman Empire during all this period.

1700- 1900 In fact, it is really during the 18th century that effective methods to purify and conduct water at a large scale were built (i.e. filtration systems, pipe networks, etc.). Quite logically, the use of coagulants started to boom at that period, with recorded use of aluminium sulphate in England in 1797, in France by the 1820’s and in the United States in 1885. At the beginning of 1890s, the United started building the so called rapid sand filters, which worked even more effectively by adding coagulants and letting the formed flocks settle before filtering.

Drinking water

shutterstock 36499666Just like air, water can be contaminated by numerous types of pollution. For centuries, humans unknowingly contaminated sources of drinking water with raw sewage, which led to diseases such as cholera and typhoid. With the increase of population in the cities due to the industrialisation, a number of pandemic cholera outbreaks occurred that cost hundreds of thousands of human lives. The origin of the infection was unknown, and thus the disease spread without restraint. In the summer of 1854 there was a cholera epidemic outbreak in London. This outbreak is best known for the physician John Snow's study of the outbreak and his discovery that contaminated water, not air, spread cholera. This discovery came to influence public health and the construction of improved water sanitation facilities.

Thankfully, today more than 90% of the world population has access to safe drinking water, with enormous progress accomplished over the last 50 years. Coagulants are used in all the countries on earth and strongly participate to that improvement.

 

Waste water

The industrial revolution, bringing together millions of people in cities, made the sanitation of drinking water necessary. Quite logically, once the problem of drinking water had been solved, the waste waters of big cities appeared as a major new issue. The first sewage treatment plants were built in the 19th century, and they were only designed to separate organic material using biological methods.

In 1911 for the first time aluminium and iron based coagulants were added in order to reduce the phosphorus content, with very good results and less sludge formation compared to using lime. Until the 1950s the removal of phosphorus was not a high priority, but in the late 1960s and beginning of 1970s people begun to recognise the large contribution of phosphorus to eutrophication. At that time Scandinavia and especially Sweden introduced phosphorus removal on all major sewage works. This effort gave very big improvements in aquatic environment along the coasts and in the lakes and streams. Nowadays the water quality in lakes has improved a lot and it is close to drinking water standards.

 

The evolution of consciousness and regulations

Eventually, starting 1914 drinking water standards were implemented for drinking water supplies in public traffic, based on coliform growth. It would take until the 1940s before drinking water standards applied to municipal drinking water. In 1972, the Clean Water Act was passed in the United States. In 1974 the Safe Drinking Water Act (SDWA) was formulated. The general principle in the developed world now was that every person had the right to safe drinking water.

In October 1972, The Paris Summit meeting took place. The Heads of State or Government of the six founding members of the European Community (Belgium, France, Germany, Italy, Luxembourg, the Netherlands) and the three countries which would join the EC the following year (Denmark, Ireland and the United Kingdom) gathered in Paris. This summit may be regarded as the beginning of a comprehensive environmental policy that would apply within the EU Member States.

In 1991 the Urban Waste Water Treatment Directive was adopted. Its objective is to protect the environment from the adverse effects of urban waste water discharges and discharges from certain industrial sectors. It was followed in 1998 by the Drinking Water Directive (98/83/EC), which concerns the quality of water intended for human consumption. Its objective is to protect human health from adverse effects of any contamination of water intended for human consumption by ensuring that it is wholesome and clean. Two years later, in 2000, the European Union Water Framework Directive (2000/60/EC) concerning water resources management -which commits European Union member states to achieve good quantity and quantitative status of all bodies- was implemented.

On 28 July 2010, the United Nations General Assembly recognized the human right to water and sanitation. It also acknowledged that clean drinking water and sanitation are essential to the realization of all human rights. Access to safe water and adequate sanitation services have proven to be among the most efficient ways of improving human health.

Today

The UN Sustainable Development Goals formulated in 2015 include targets on access to water supply and sanitation at a global level.