Perborates: The environmentally problematic bleaching agents

Boron (B) is widely distributed in nature and can be found in oceans, sedimentary rocks, and surface water and groundwater. Borates, boron-oxygen substances, are used extensively in industrial materials and end-use products. The extent and nature of their utilization determine the concentration of B discharged into water streams, lakes, or sewage water. Boron is taken up by plants and consumed by animals (aquatic and terrestrial). It is one of the essential microelements for crops, but only a narrow range separates deficiency from toxicity. Its availability to plants is affected by several factors, including soil solution pH, and soil texture, moisture, temperature, oxide content, carbonate content, and clay mineralogy. Boron toxicity to humans and animals has been only rarely reported. Its sorption and desorption from soil adsorption sites regulate the concentration of B in the soil solution. It is added to agricultural soils via the irrigation water. In arid and semiarid regions, the use of reclaimed wastewater for irrigation is on the rise, and it is expected to become the main irrigation water source. Therefore, B concentration could become a main limiting factor in wastewater recycling. During domestic, industrial, and agricultural use of freshwater, the concentrations of B increase. Sources are: human and animal excretions, detergents, laundry powders, paper mills, metal-coating processes, among others. Thus, recycling wastewater requires that special attention be paid to the prevention of B discharge into sewers.