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.

This lecture demonstrates designing a coagulation and flocculation system for a water treatment plant, including peak flow calculations, alum dosing at 40 mg/L with 10% concentration, and 15-minute clarifier detention.

Explore cartridge filtration for small to medium systems, using in-line 10–20 inch housings with sediment filters at multiple microns and carbon filters to remove particles and chlorine.

Explore multimedia filtration, the most common water filtration method for high contamination and flows, featuring three media layers—anthracite, sand, and garnet—plus backwash cycles and vessel options.

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.

Explore whole-house softener components, including the resin bead vessel that exchanges calcium and magnesium for sodium, the control, and the brine solution used to regenerate the resin.

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.

Learn to remove iodine from drinking water, note the 0.3 mg/L limit, and assess health risks, taste changes, and pipe issues while reviewing three iodine types.

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.

Explore pre-treatment before a reverse osmosis system, including chlorine removal with granulated activated carbon, water softening to reduce hardness and calcium/magnesium ions, and coagulation with filtration to prevent fouling.

Design a reverse osmosis system for medium to large scale projects using manufacturer software and key catalog terms, including feed flow, permeate flow, recovery, rejection, and salt passage.

Examine disinfection and safe storage of drinking water, comparing chlorination with UV, ozone, solar disinfection, and boiling, and showing how sedimentation and filtration lower pathogen load.

Use pre-chlorination to add chlorine before other treatments and storage to prevent sedimentation and biological growth in filters; post-chlorination after filtration maintains a 0.5–1.5 mg/L residual to keep water safe.

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%).

Explain chlorine demand and residual chlorine in water treatment, showing how chlorine reacts with organics and inorganics, leaving a residual 0.2–0.3 mg/L while dosing 1–5 mg/L by trial and error.

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.