Is Sludge Water Diluate Stream from Electrodialysis Suitable for Agricultural Purposes?

Abstract

Sludge water, a product of drainage of primary and activated sludge from the municipal wastewater treatment process, is rich in
nutrients, particularly nitrogen and phosphorus. Nitrogen and phosphorus are inorganic biogenic substances suitable for plant
nutrition. Sludge water can be treated via electrodialysis. This process leads to two products, one is a diluate stream (solution
less concentrated than the input, contains some nutrients) and the other is concentrate stream (solution in which nutrients are
concentrated against the input). There is abundant research in nitrogen and phosphorus recovery from the concentrate stream, for
example in the form of struvite used for fertilizing. However, little attention has been paid to the huge volumes of diluate stream.
The diluate stream can be used in agriculture as water suitable for irrigation, where the bonus of this product is a partial fertilizing
capacity. This way, wastewater can be used for irrigation and fertilizing having subjected the wastewater to agrochemical analyses.
An important condition for the use of sludge water or diluate stream for irrigation is the absence of heavy metals and toxic substances.
Still, if the water contains heavy metals, they can be removed with a relatively high success, for example by precipitation.
Using wastewaster as water for agricultural purposes for irrigation is one of the new options to find new secondary sources of water.
This theme is highly topical as it is important to reduce the consumption of quality water resources. These must primarily serve for
drinking purposes, and therefore it is necessary to search for alternative water resources.