The major source of fresh water is rain, which ultimately streams down into oceans and rivers. This water is consumed by the human beings for various purposes. All the consuming channels of this water, such as domestic, industrial, agricultural etc. generate the wastewater. Furthermore, urbanization and population growth are also the prime contributors. The reason why this water is called wastewater is due to the presence of contaminants such as organic material, biological components and toxic compounds, hence they have adverse effect on human health. Conventionally, many of the inorganic materials have been used as coagulants to treat the wastewater as these compounds have the ability to alter the physico-chemical properties. The present paper reviews the polymeric coagulants used for wastewater treatment that are green, sustainable and efficient. Moreover, these natural polymeric coagulants are biodegradable, eco-friendly and without any adverse effects on human health.

In recent years, recycled aggregates from construction and demolition waste (CDW) have been widely accepted in construction sectors as the replacement of coarse aggregate in order to minimize the excessive use of natural resources. In this paper, an experimental investigation is carried out to observe the influence of low grade steel fiber reinforcements on the stress-strain behavior of concrete made with recycled and fresh brick aggregates. In addition, compressive strength by destructive and nondestructive tests, splitting tensile strength, and Young’s modulus are determined. Hooked end steel wires with 50 mm of length and an aspect ratio of 55.6 are used as fiber reinforcements in a volume fraction of 0% (control case), 0.50%, and 1.00% in concrete mixes. The same gradation of aggregates and water-cement ratio (w/c=0.44) were used to assess the effect of steel fiber in all these concrete mixes. All tests were conducted at 7, 14, and 28 days to perceive the effect of age on different mechanical properties. The experimental results show that around 10%～15% and 40%～60% increase in 28 days compressive strength and tensile strength of steel fiber reinforced concrete, respectively, compared to those of the control case. It is observed that the effect of addition of 1% fiber on the concrete compressive strength is little compared to that of 0.5% steel fiber addition. On the other hand, strain of concrete at failure of steel fiber reinforced concrete has increased almost twice compared to the control case. A simple analytical model is also proposed to generate the ascending portions of the stress-strain curve of concrete. There exists a good correlation between the experimental results and the analytical model. A relatively ductile failure is observed for the concrete made with low grade steel fibers.