Drinking water from Chinese rivers: challenges of clarification

Despite an age-old preference in China to use spring or well water as drinking water, turbid waters from large rivers (Huanghe, Changjiang, Zhujiang, Hanjiang) have to be used for this purpose by the less privileged. Landslides and an increase in sediment loads in rivers are affected by population growth and deforestation. Clarification is required for shorter periods or throughout the year. Traditional clarifiers have been recorded since the 2nd century AD. Gelatinous and mucilaginous materials acting as adsorbents and coagulants of various efficiencies are identified and assessed. Some active substances are also known elsewhere. Certain materials contain toxic substances. Apricot kernels were later also used as a coagulant for turbid Nile water. Alum, also detected as a clarifier by humble Chinese, was chosen by engineers worldwide for use as a coagulant in waterworks. The need for clarified river water increases. Modern Chinese waterworks use aluminium polymers of their own production. Assistance is required for rural people in poor, remote counties without access to public water supplies. Primary school teachers could learn to monitor, in their communities, semi-quantitative clarification at the household level according to simplified water coagulation worked out for Moringa seeds.