Support for Greywater Harvesting

EghtesadOnline: So long as water is sold at the present low rates, building owners will see no need to install greywater treatment systems, director of the Consumption Management Office at the National Water and Wastewater Engineering Company said.

News ID: ۷۴۷۹۰۷

20 July 2019

“Negotiations are underway with the Engineering Council of Iran to encourage builders to install such equipment. But the talks have not produced the desired results largely because the gadgets are costly,” Ali Seyedzadeh was quoted as saying by ISNA.

Seyedzadeh believes that the aversion to greywater recycling systems cannot be overcome unless builders are provided loans.

The concept has not become law in Iran as yet and that is why a subsidy program for households wanting to install greywater reuse systems should be initiated, he said. In Tokyo, greywater recycling is mandatory for buildings since 1997, according to Financial Tribune.

"The overriding positive environmental impact of greywater reuse is the reduction in demand for fresh water in regions fighting (a losing battle) drought," he noted, adding that saving fresh water not only will reduce water bills but also have a broader community benefit in reducing demand for water. Preservation of surface and underground water resources are other advantages of tapping into greywater.

Greywater is defined as any domestic wastewater produced, excluding sewage. The main difference between greywater and sewage (blackwater) is the organic loading. Sewage has a much larger organic loading compared to greywater. Greywater is captured from the household sources like sinks, hand-basins, showers, etc.

Good Use

With proper treatment, greywater can be put to good use. The uses range from toilet flushing to irrigation of plants. Treated greywater can be used to irrigate both food and non-food production units. Nutrients in greywater (phosphorus and nitrogen) are an excellent food source for plants.

Seyedzadeh went on to say that greywater accounts for 65% of urban sewage, a large proportion of which can be recycled. Experts argue against the use of high quality and costly potable water for purposes that do not require such high quality water, like irrigation.

By reusing greywater demand for expensive-to-treat potable water declines, he said.

It costs the government 25,000 rials (25 cents) to produce one cubic meter of water,  whereas consumers pay 40% of the total cost (10,000 rilas or 10 cents), which partly explains why people take the precious resource for granted.

Referring to the experience of other countries, he said  Japan treats at least 345,000 cubic meters of greywater a year, of which 230,000 cubic meters is used for urban green spaces.

The reuse of greywater is being increasingly practiced in a many countries, namely the US, Australia, Cyprus, the UK, Germany and Jordan.

Located in one of the world's most water-stressed regions, Iran suffers from low rainfall and excessive consumption plus high levels of water loss because of aging supply infrastructure and outdated irrigation practices.