Wastewater is used water. It includes substances such as human waste, food scraps, oils, soaps and chemicals. In homes, this includes water from sinks, showers, bathtubs, toilets, washing machines and dishwashers.
What is wastewater?
If the term ‘wastewater treatment’ sounds confusing, you might think of it as ‘sewage treatment’. Much of the water that people, industries and business use need to undergo treatment before we can release it back to the environment.
Nature has an amazing ability to handle small amounts of water wastes and pollution but it would be overwhelming if we did not treat the billions of litres of wastewater and sewage produced every day. Treatment plants reduce pollutants in wastewater to a level nature can handle.
Wastewater also includes storm runoff. Although some people assume that the rain that runs down the street during a storm is fairly clean, it is not. Harmful substances that wash off roads, parking lots and rooftops can harm our rivers and lakes.
Why treat wastewater?
Treating wastewater is a matter of carrying for our environment and for our own health. There are a lot of good reasons why keeping our water clean is important.
FISHERIES: Clean water is critical to plants and animals that live in water. This is important to the fishing industry, sport fishing enthusiasts and future generations.
WILDLIFE HABITATS: Our rivers and ocean waters teem with life that depends on shoreline, beaches and marshes. They are critical habitats for hundreds of species of fish and other aquatic life. Migratory water birds use the areas for resting and feeding.
RECREATION AND QUALITY OF LIFE: Water is a great playground for us all. The scenic and recreational values of our waters are reasons many people choose to live where they do. Visitors enjoy water activities such as swimming, fishing, boating and picnicking.
HEALTH CONCERNS: If it is not properly cleaned, water can carry disease. Since we live, work and play so close to water, harmful bacteria have to be removed to make water safe.
Effects of wastewater pollutants
If we don’t properly treat wastewater, it can have a negative impact on the environment and our health.
- Decaying organic matter and debris can use up the dissolved oxygen in a lake so fish and other aquatic biotas cannot survive;
- Excessive nutrients, such as phosphorus and nitrogen (including ammonia), can cause eutrophication or over-fertilization of receiving waters, which can be toxic to aquatic organisms, promote excessive plant growth, reduce available oxygen, harm spawning grounds, alter habitat and lead to a decline in certain species;
- Chlorine compounds and inorganic chloramines can be toxic to aquatic invertebrates, algae and fish;
- Bacteria, viruses and disease-causing pathogens can pollute beaches and contaminate shellfish populations, leading to restrictions on human recreation, drinking water consumption and shellfish consumption;
- Metals, such as mercury, lead, cadmium, chromium and arsenic can have acute and chronic toxic effects on species;
- Other substances such as some pharmaceutical and personal care products, primarily entering the environment in wastewater effluents, may also pose threats to human health, aquatic life and wildlife.
The major aim of wastewater treatment is to remove as much of the suspended solids as possible before the remaining water (effluent) goes back to the environment. As solid material decays, it uses up oxygen, which plants and animals living in the water need.
“Primary treatment” removes about 60 per cent of suspended solids from wastewater. This treatment also involves aerating (stirring up) the wastewater, to put oxygen back in. Secondary treatment removes at least 85 per cent of suspended solids.
Thanks for taking the time to read our blog post about wastewater treatment. Do you want to study abroad in Spain? Take a look at our Water engineering study programme and feel free to talk to our counsellor for more information.