BOD and COD reduction using porous concrete pavements

Many places in the world suffer from a shortage in potable water because of the population growth, contamination of water supplies and the problems related with global warming issue. The contamination of drinking water is a considerable problem in the world. In this study, the possibility of using a Pervious Concrete Pavement (PCP) in wastewater clarification was studied. Twenty-four Portland cement mixtures were prepared and tested in order to estimate the effect of coarse aggregate size, water-to-cement ratio and cement content as well as the relationships between compressive strength, porosity, and permeability. Two gravel grades were used (G1 and G2), G1 includes the aggregate size between 4.75–9 mm, while the aggregate size between 9−19 mm was represented by G2. Three water cement ratios (W1 = 0.28, W2 = 0.30, W3 = 0.32) and four cement contents (C1 = 275, C2 = 300, C3 = 325 and C4 = 350 kg/m3) were used. The maximum compressive strength obtained in this study was 17.75 Mpa, which resulted from gravel size of G1 and the highest W/C ratio and cement content. The evaluation of water treatment properties of PCP involved pavement samples of 300 × 300 mm with three different thicknesses of 100, 150 and 200 mm that subjected to synthetic wastewater flow with volume of 5 L. Removal efficiencies of several pollutants such as the chemical oxygen demand (COD), biological oxygen demand (BOD) were inspected. The removal percentage of such pollutants increased with the increment of gravel size and pavement thickness. Maximum removal for COD and BOD were 54 % and 68 %, respectively, they were obtained using the aggregate size of G2, water cement ratio of W3 and pavement thickness of 20 cm. The modification in pollutants removal percentages can be done depending on the enhancement and refreshment of the bacterial growth by adding the required feed for the bacteria in wastewater in form of mineral salt solution MSM. The resulted removals due to this process also occurred when the large gravel size of G2, water cement ratio of 0.32 and pavement thickness of 20 cm were used, the removal percentages were increased in this case to be 61 % and 79 % for COD and BOD, respectively.