All household wastewater from pipes connected to urban homes, businesses and schools goes to a wastewater treatment plant. (A small percentage of people have composting toilets and alternative greywater systems.)
Once we have used water, it must be treated before being returned to the environment. Like water treatment for supply, this process has a cost, and the more water we use in our houses, schools and businesses, the more water there is to treat.
In rural areas, household wastewater is treated in wastewater treatment systems and septic tanks and disposal fields in the soil.
Wastewater must be treated to reduce bacteria, nutrients such as phosphate in faeces and detergents and nitrogen in urine. Nutrients increase the growth of plants in waterways, and this can lead to eutrophication.
There are a number of conservation measures that we can take in our schools, businesses and homes to help reduce the amount of wastewater.
There are many different types of wastewater, especially in the Waikato region. For example, we have geothermal wastewater from our geothermal power stations, and that wastewater is hot and full of heavy metals. So if you put that into a river, it impacts it. The other main source of wastewater in this region is sewage or effluent. That is treated, but it has an impact as well by increasing nutrients, sediment and bacteria in our waterways.
So a lot of our wastewater or sewage discharge companies have permits called resource consents that require them to treat the water, and every year, the technology gets better and better at treating our wastewater. For example, a lot of the wastewater treatment plants now discharge zero bacteria, and technology is improving to remove nutrients such as nitrogen and phosphorus.
Dr Eloise Ryan
Waikato Regional Council
Footage of Ngatamariki Power Station, Chris Sisarich
This video has been developed in partnership with the Waikato Regional Council as part of the Rivers and Us resource.