Evaluation of Color Changes in Sewage Sludge Ash Brick by Using Image Analysis Method

Abstract

Quantifying the surface color changes by digital image analysis to assess the quality of the sewage sludge brick is investigated. Relationships among the firing temperatures, percent weight of incinerated sludge ash added, and changes to red, green, and blue of the sludge bricks are studied. Indices, deduced from those relationships, while assessing the quality of the sludge brick are evaluated. This research involves testing the specimens of sludge brick under different firing temperatures, using a digital camera to capture images of the tested specimens and uploading them to the personal computer, and applying the “image color intensity analyzer” to the images in order to calculate the intensities of red, green, and blue. Among them, results show that red has the highest intensity, followed by green, then blue in RGB color space. Additionally, for HSI color space, hue (H) decreases, while saturation (S) increases with rising temperatures before 800°C. Thereafter, sudden increases and decreases occur for H and S at 1,000°C, respectively. It is suggested that a firing temperature of 800°C or higher is better in brickmaking.