A comprehensive review on the coagulant recovery and reuse from drinking water treatment sludge

Re-utilization of drinking water treatment residuals (DWTR): a review focused on the adsorption of inorganic and organic contaminants in wastewater and soil

“…Most XRD analyses show that DWTRs are mainly made of non-crystalline (amorphous) mineral phases. 14 The general properties of DWTRs can vary largely with locations, seasons, and the nature of raw water but they all present common properties of surface such as Al-OH-, Fe-OH-, and Si-OH-type groups in variable proportions (Table S1 †) that can easily interact with dissolved metals, metalloids, and other substances, thus making them versatile adsorbents under various environmental conditions, which could be adapted to the nature of the solutions or systems to be treated. It is also important to consider the presence of natural organic matter that can play an important role in adsorbing inorganic and organic contaminants to complement the role of the main oxides of Fe, Al, and Si at various pH values as it has been demonstrated in a study on lake sediments.…”

“…The ion-exchange technique is simple and leads to safe recovery with low fowling but it does not allow high aluminum recovery and can produce acid wastes. 2,14,50 Yet, the utilization of chemicals such as sulfuric acid, different alkalis, or a more elaborated process to recover DWTR leads to increasing treatment costs. However, it is still important that the environmental advantages and cost benefits of less disposed waste over the years be considered and recovery processes be further applied and expanded.…”

“…[3][4][5] The most commonly used low-cost adsorbents include coal fly ash, 6,7 a large variety of biosorbents and cellulosic adsorbents coming from agriculture and aquaculture practices, 8,9 and, the focus of this review, drinking water treatment residuals (DWTR) also known as drinking water sludge, alum sludge or dewatered waterworks. [10][11][12][13][14][15][16] With the growing population, the need for the treatment and purification of water for drinking and direct consumption purposes is in continuous increase with many billions of cubic meters of water being required every year over the world. In general, treatments first require the removal of clay, colloidal particles, algae, humic substances, trace metals, and other contaminants possibly present in water.…”

“…3–5 The most commonly used low-cost adsorbents include coal fly ash, 6,7 a large variety of biosorbents and cellulosic adsorbents coming from agriculture and aquaculture practices, 8,9 and, the focus of this review, drinking water treatment residuals (DWTR) also known as drinking water sludge, alum sludge or dewatered waterworks. 10–16…”

“…One of them includes the recovery of coagulants using acid, alkaline, ion exchange, or filtration treatments for the removal of turbidity, and biological and chemical oxygen demand from wastewater. 14 It can also be used as a dewatering agent in sewage sludge due to the presence of aluminum hydroxide, to reduce the final volume of sludge to be treated. 11 Other studies report the addition of DWTR to produce cement, concrete, ceramics, and other materials such as bricks, blocks, and tiles.…”