Procedures for the treatment of raw water destined for human consumption (after Di Bernardo et al. 2002)
| Treatment phase . | Physical and chemical processes . | Reagents . | Advantages for the communities . | Disadvantages for the communities . |
|---|---|---|---|---|
| Preparation and polishing | Acidification | Hydrochloric acid Sulfuric acid | Chemistry of the processes are very well known; facilitates the subsequent processes; does not generate by-products | Expensive; risk of contamination with metals and other elements; requires knowledge of chemistry: dosing requires experience |
| Alkalization | Hydrated lime Sodium carbonate Sodium hydroxide | Chemistry of the process are very well known; facilitates the subsequent processes; does not generate by-products | Expensive; risk of contamination with metals and other elements; requires knowledge of chemistry: dosing requires experience | |
| Removal of particulate matter | Coagulation | Aluminum sulfate Polyaluminum chloride Ferric chlorine Chlorinated ferrous sulfate Ferric sulfate Tannate | Chemistry of the process are very well known; removes particulate substances efficiently | Expensive; risk of contamination with metals and other elements; generates significant amounts of sludge, contaminated with chemicals. Affected by the presence of organic acids; dosing requires experience; in acidic waters, reagent may dissolve in the produced water |
| Mechanical flocculation | Slow shaking – no reagents | Inexpensive; no risk of contamination; application does not require experience | Limited efficiency for removing particles; slow process, requires large installations for even mediocre production | |
| Chemical flocculation | Natural polymers: manioc, potato, arrowroot, maize Synthetic polymers | With natural polymers, inexpensive; accessible in the region; little risk of contamination | Deterioration of the polymers; generates large amounts of sludge; depending on the polymer, can attribute disagreeable taste to treated water; dosaging requires experience | |
| Sedimentation/filtration | Settling Sand filters | Inexpensive; no risk of contamination; application does not require experience | Slow process, requires large installations for even mediocre production; requires periodic maintenance | |
| Removal of contaminants | Adsorption | Activated charcoal Other adsorbents | Little risk of contamination of the produced water | Expensive; application requires experience; generates contaminated effluents |
| Disinfection | Chorination | Cl2 (gaseous or liquid) Sodium hypochlorite Calcium hypochlorite Chlorine dioxide | Fast and efficient; application does not require experience | Expensive; formation of THM; possible contamination with various elements |
| Ozonation | O3 | Fast and efficient | Expensive; releases O3 into the atmosphere; attributes disagreeable taste to water; ozonator requires maintenance | |
| Paracetic acid application | Paracetic acid | Fast and efficient | Expensive; may promote contamination, attributes disagreeable taste to water | |
| Solar disinfection | Long exposure to sunlight | Inexpensive; efficient; more healthful, with no application of reagents | Slow; requires constant maintenance to avoid algae; frequent replacement of UV-exposed materials |
| Treatment phase . | Physical and chemical processes . | Reagents . | Advantages for the communities . | Disadvantages for the communities . |
|---|---|---|---|---|
| Preparation and polishing | Acidification | Hydrochloric acid Sulfuric acid | Chemistry of the processes are very well known; facilitates the subsequent processes; does not generate by-products | Expensive; risk of contamination with metals and other elements; requires knowledge of chemistry: dosing requires experience |
| Alkalization | Hydrated lime Sodium carbonate Sodium hydroxide | Chemistry of the process are very well known; facilitates the subsequent processes; does not generate by-products | Expensive; risk of contamination with metals and other elements; requires knowledge of chemistry: dosing requires experience | |
| Removal of particulate matter | Coagulation | Aluminum sulfate Polyaluminum chloride Ferric chlorine Chlorinated ferrous sulfate Ferric sulfate Tannate | Chemistry of the process are very well known; removes particulate substances efficiently | Expensive; risk of contamination with metals and other elements; generates significant amounts of sludge, contaminated with chemicals. Affected by the presence of organic acids; dosing requires experience; in acidic waters, reagent may dissolve in the produced water |
| Mechanical flocculation | Slow shaking – no reagents | Inexpensive; no risk of contamination; application does not require experience | Limited efficiency for removing particles; slow process, requires large installations for even mediocre production | |
| Chemical flocculation | Natural polymers: manioc, potato, arrowroot, maize Synthetic polymers | With natural polymers, inexpensive; accessible in the region; little risk of contamination | Deterioration of the polymers; generates large amounts of sludge; depending on the polymer, can attribute disagreeable taste to treated water; dosaging requires experience | |
| Sedimentation/filtration | Settling Sand filters | Inexpensive; no risk of contamination; application does not require experience | Slow process, requires large installations for even mediocre production; requires periodic maintenance | |
| Removal of contaminants | Adsorption | Activated charcoal Other adsorbents | Little risk of contamination of the produced water | Expensive; application requires experience; generates contaminated effluents |
| Disinfection | Chorination | Cl2 (gaseous or liquid) Sodium hypochlorite Calcium hypochlorite Chlorine dioxide | Fast and efficient; application does not require experience | Expensive; formation of THM; possible contamination with various elements |
| Ozonation | O3 | Fast and efficient | Expensive; releases O3 into the atmosphere; attributes disagreeable taste to water; ozonator requires maintenance | |
| Paracetic acid application | Paracetic acid | Fast and efficient | Expensive; may promote contamination, attributes disagreeable taste to water | |
| Solar disinfection | Long exposure to sunlight | Inexpensive; efficient; more healthful, with no application of reagents | Slow; requires constant maintenance to avoid algae; frequent replacement of UV-exposed materials |
Note: Advantages and disadvantages are based on the characteristics of the riparian communities.