A new method for measurement of sludge blanket height (SBH) based on image analysis is presented. The proposed method uses a histogram back-projection algorithm to distinguish between the settling sludge and supernatant and can be used with sludge possessing different coloring characteristics both in the sludge color and the color of supernatant produced. Individual pixels in the acquired image are compared with a histogram of a representative sludge region. Therefore, the proposed method relies neither on the assumed shape of light intensity profile nor on the dominant sludge or supernatant color. Batch sedimentation tests are presented for different initial sludge concentrations and different background colors to simulate different sludge characteristics. Parameters of a settling velocity function are estimated based on the obtained results. Additionally, an algorithm is proposed that enables the zone settling velocity (ZSV) to be estimated before the batch sedimentation test is completed.

Drug-abuse detection tests are becoming increasingly commonplace in patient care today and provide a rapid and effective method for identifying illicit substances. Occasionally, they may yield a positive result, indicating the presence of a substance, even though the individual has not consumed the suspected drug what sometimes can significantly impact both medical and legal decisions. The study outlines the substances that can lead to false-positive drug test results for amphetamines, cannabinoids, and benzodiazepines. The study’s findings have revealed pivotal insights for patients receiving chronic treatment and their primary care physicians. Notably, amphetamine assays appear to be most prone to cross-reactivity with other substances. The beta-blocker group of medications, confirmed by various studies to interfere with amphetamine assays, could pose a substantial challenge in drug screening given its widespread use. Efavirenz also warrants mention, as it frequently triggers positive results for both benzodiazepine and cannabinoid assays among its users. This research helps highlight new areas for further investigation and aims to guide clinicians in their daily practice, especially when interpreting questionable positive drug-abuse test results. This comprehensive review serves as a valuable resource for clinicians to navigate false-positive scenarios effectively and maintain the highest standard of patient care.