Effect of Temperature on Algal Removal by Alum Coagulation

Questions about the effect of temperature on algal cell coagulation and the relationships between algae removal and temperature, alum dosage, paddle speed, flocculation time, and settling time are answered. The investigations consisted of two series of tests: Studies on algae cultured under laboratory control, and algae in wastewater stabilization ponds. The jar-test technique was used for the coagulation of algal suspensions by alum. Coagulation of algae is caused mainly by the insoluble flocs of aluminum hydroxide. Other aluminum species also have coagulative properties but are far less effective. The destabilization of algal colloids results from enmeshment within the hydroxide precipitates, or by adsorption of coagulant species. Neutralization of the pH-dependent charges of algal cells is not necessary for coagulation, but does aid coagulation. Analyses of variance of the variables and their interactions showed significantly the effect of all variables ad most of their interactions. Step-wise multiple regression technique was used for the development of mathematical models for the estimation of algal removal. Increased temperatures adversely affected the percentage removal of algal cells by alum coagulation. The effect of temperature on the removal of algae grown in the wastewater stabilization pond effluent was more pronounced than that found for the algae cultured in the laboratory. Alum was effective in removing algae from Logan wastewater stabilization ponds. However, high alum dosages are required which may not be justified economically. It also was found that at low concentrations of algal cells the straight line portion of the Langmuir isotherm describes the removal of algae with alum

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries