Design of Water Treatment Systems for Beginners

Explore turbidity removal methods in water treatment, contrasting plain gravity sedimentation with chemically enhanced sedimentation using coagulation to remove suspended solids before filtration.

Explore design considerations for coagulation, flocculation, and clarification in water treatment, comparing inline and mechanical mixers (turbine, propeller, and badgered mixers) and detailing detention times, mixing speeds, and tank volumes.

Practice filtration basics: sediment filters remove sediments; carbon filters remove chlorine and some viruses and bacteria; smaller micron ratings remove finer particulates. Replace cartridge filters every four to six months.

Learn how water hardness, due to calcium and magnesium, is softened by ion-exchange resin that swaps hardness ions for sodium and requires periodic regeneration.

Size the system by calculating daily use from a two-day regeneration cycle and hardness in grains per gallon. Determine resin needs by dividing total grains by 30,000 per cubic foot.

Explore ferric iron removal by recognizing its insoluble precipitate, typically orange or red, and using simple filtration to remove sediments.

Remove ferrous iron from water by oxidizing it to ferric iron and precipitating it with manganese greensand, burn filters, or cartridge filtration, aided by calcite for pH and backwash.

Explore bacterial iron removal by targeting iron-bonded bacteria in wells and applying shock chlorination with around 200 mg/L, then learn basics of water chlorination.

Explore how reverse osmosis uses a semi-permeable membrane to remove salts, nitrates, arsenic, cadmium, phosphates, metals, bacteria, and organic chemicals, achieving up to 98 percent purification.

summarizes optimal chlorination: maintain pH 5.5-7.5 and at least 30 minutes contact, and compare gas chlorine, bleaching powder (33%), HTH (70%), and liquid sodium hypochlorite (1-5%).

Understand how the Ct value depends on residual chlorine concentration and contact time, and how temperature, pH, and turbidity influence disinfection against bacteria, viruses, and protozoa.

Calculate detention time from storage volume and flow, using 200 m3 and 5 m3/min, and estimate chlorine dosing from demand and residual with a 1% solution from 35% bleaching powder.

Ultraviolet disinfection offers a chemical-free method to inactivate bacteria and protozoa, including Cryptosporidium, with short contact times, but it lacks virus inactivation and relies on low turbidity and hardness.

Design a case study for a municipal water treatment system that treats 15 m3 per day using chlorination, multimedia filtration, carbon filtration, UV disinfection, and water softening.