Recap and Glossary
- Untreated water can contain high levels of undissolved solids. When these solids are small enough, they can make the water turbid (cloudy).
- Turbidity is caused by colloids in water. Colloids are suspended solids.
- Colloids are held in suspension by an arrangement of positive and negatively charged ions that adsorb onto their surface. The anions on the outside of the colloid create a negative charge that acts as a repulsive force to other colloids.
- When water is treated, flocculants such as alum can be added. The alum introduces new cations into the water that are positively charged.
- Flocculants cause the colloids to come together (to flocculate). Then they become too heavy to remain suspended, so they sink to the bottom.
- Water is filtered through sediment filters and is finally put through a disinfection process that involves chlorine or chloramine (chlorine plus ammonia).
- These chemicals need to be removed before we brew our coffee.
- Chemical contaminants from agriculture, such as nitrates, can cause the growth of unwanted organic matter in waterways. These can cause a buildup of organic slime in our coffee equipment. These contaminants must be removed through filtration before we brew our coffee.
- Excessive salt dissolved into water can accelerate corrosion by increasing the electrical conductivity of water.
- When rust spots occur in a boiler, these weak spots take the role of an anode — they give up electrons.
- When rust occurs, the anode becomes gradually thinner as electrons are removed from the rust spot and are transported to the cathode (a piece of metal that is happy to accept the electrons).
Anode A electrode (or weak part of a boiler that serves as an electrode) which allows electrical current to enter a system.