Reuse of domestic sewage sludge to achieve a zero waste strategy & improve concrete strength & durability - A review
Sinqobile Vilakazi, Ednah K. Onyari, Onyeka Nkwonta, Joseph K. Bwapwa
Abstract
The sewage sludge generation from the wastewater treatment plant's primary, secondary & tertiary unit processes is greatly accumulating countrywide. This large quantity of sludge is related to the scarcity of dumping land/area, high population density and industrialization. Furthermore, the disposal & poor handling of sewage sludge has severe negative impacts to the environment. On the other hand, the use of the incineration method to dispose sludge mitigates only the sludge volumes. The remaining ash would still need to be disposed to the landfill, which is not economical. As a result, there is a need to develop long-term solutions to the problem of large volumes of sewage sludge produced by wastewater treatment plants. One of the found suitable solutions is to use the treated sewage sludge in the construction field to achieve a zero waste strategy. The current paper reviews the effects of sewage sludge on concrete strength and durability. Previous research suggests that depending on the nature of the sludge, the addition of sludge may reduce the mechanical strength of concrete. The mechanical strength of the concrete decreases significantly when 10% sludge is added in proportion to the amount of concrete, making it unsuitable for medium to high-strength reinforced concrete. However, some previously obtained results indicate that one possible area of application would be in the preparation of low-strength mass concrete that could be used as a filler for road bases and sub-bases with light traffic.