Water sludge: composition, properties, disposal in wastewater treatment (a review)

Summary

Advanced water treatment schemes are inevitably associated with water sludge generation, the volume of which becomes a separate problem that is comparable to the scale of the actual production of drinking water. In this regard, utilization of water sludge is considered today as a priority task in the research and development in this area. Based on the results of almost thirty years of studies, the main areas of potential use of water sludge have been identified; one of them being water and wastewater treatment. The results of numerous studies evidence the perspectiveness of using water sludge as an adsorbent of phosphates, arsenic, and also heavy metals: Cu, Cd, Cr, Co, Pb, Hg, Zn, Ni, V, Mo, Ga, and Se. Under the conditions of pilot tests, studies were conducted on the extraction of coagulants from water sludge, and on the direct use of water sludge as a coagulant, as well as on its use for enhancing excess activated sludge dewatering. Using water sludge in the foundation of bioengineering facilities, as well as a catalyst for the activation of persulfate and peroxomonosulfate in the destruction of organic micropollutants in the aquatic environment also made good results.

Key words

utilization , toxicity , catalyst , coagulants , water sludge , adsorbent

Water sludge: utilization in the production of construction materials and agriculture Alternative coagulants (a review)

Summary

Utilization of water sludge in significant amounts can be provided by using it in the production of construction materials and in agriculture. The use of water sludge in the construction industry can result in significant savings in traditional raw materials without compromising product quality. However, the supply of water sludge to the construction industry enterprises, has not been established so far, and the instability of its composition is posed as the main reason. At the same time, the results achieved evidence significant efforts made in this area. Based on the use of water sludge, technologies have been developed for the production of cement, building mortar, concrete, brick, roofing tiles, and ceramic products. Agricultural use of water sludge is considered as a most affordable and large-scale option of its disposal. The concentration of organics and heavy metals in water sludge is quite limited, which sets it apart from wastewater sludge and allows it being classified as safe. To date, in a number of countries many years of large-scale experiments have been conducted on the use of water sludge for adjusting the concentration of soluble phosphorus in soils; binding soluble forms of arsenic and chromium, and adjusting the concentration of trace elements. A radical solution to the problem of water sludge disposal should be associated with reducing its amount generated during water purification process. In this direction, studies are being conducted on alternative coagulants, primarily of plant origin. The results achieved made it possible to carry out pilot tests of using aqueous extract of Moringa oleifera oil-tree seeds as a coagulant in the purification of surface water.

Key words

ceramics , water sludge , brick manufacture , cement , building mortar , concrete , agriculture , soil amendment , alternative coagulants of plant origin , Moringa oleifera