Wastewater treatment usually involves the removal of heavy metals and/or organic compounds from effluent. Regulating pH through the addition of acid/alkaline chemicals is an important part of any wastewater treatment system, as it allows the dissolved waste to be separated from the water during the treatment process.
Water consists of positively charged hydrogen ions and negatively charged hydroxide ions. In acidic (pH<7) water, high concentrations of positive hydrogen ions are present, while in neutral water, the concentrations of hydrogen and hydroxide ions are balanced. Alkaline (pH>7) water contains an excess of negative hydroxide ions.
PH regulation in wastewater treatment
By chemically adjusting the pH, we can remove heavy metals and other toxic metals from water. In most runoff or waste water, metals and other pollutants dissolve and do not settle out. If we raise the pH, or the amount of negative hydroxide ions, the positively charged metal ions will form bonds with the negatively charged hydroxide ions. This creates a dense, insoluble metal particle that can be precipitated out of the wastewater in a given time or filtered out using a filter press.
High pH and low pH water treatments
In acidic pH conditions, excess positive hydrogen and metal ions do not have any bond, float in the water, will not precipitate. At neutral pH, hydrogen ions combine with hydroxide ions to form water, while metal ions remain unchanged. At alkaline pH, excess hydroxide ions combine with metal ions to form metal hydroxide, which can be removed by filtration or precipitation.
Why control pH in wastewater?
In addition to the above treatments, the pH of the water can also be used to kill bacteria in the wastewater. Most organic matter and bacteria that we are familiar with and come into contact with every day are best suited to neutral or slightly alkaline environments. At acidic pH, excess hydrogen ions begin to form bonds with cells and break them down, slowing their growth or killing them completely. After the wastewater treatment cycle, the pH must be restored to neutral by using additional chemicals, otherwise it will continue to damage any living cells it touches.
Post time: Feb-24-2023