rate: rate is similar to speed, but is used to talk about how often something happens, rather than speed of movement.
investment: People often say, “if you want to make money, you have to spend money.” This is the idea of investment.
environmental protection laws: Laws that control pollution or other damage to the environment are called environmental protection laws.
effluent: Effluent is chemical waste from industry. On farms, this is usually sewerage from animals, and also chemicals used in farming.
digest: When you eat something, your stomach digests it so that you can use the food to get energy and other good things.