RESUMO
Biofouling in membrane distillation (MD) has several repercussions, including reduced efficiency of the MD process and limiting membrane life. Additionally, the evaluation of MD biofouling using treated effluents from wastewater treatment plants remains an unexplored area. Thus, biofouling formation and development in a long term MD process (15 days) using treated effluent from a wastewater treatment plant was explored in this study. The results revealed that flux decline occurred in four phases: i) initial decline (0-1 d), ii) gradual decline (1-5 d), iii) progressive decline (5-10 d), and iv) rapid decline (10-15 d). Liquid Chromatography-Organic Carbon Detection (LC-OCD) analysis demonstrated that the treated effluent contained humic-like substances, which deposited on the membrane surface in phase 1. Whereas biopolymers development on the membrane surface in phase 2 and 3 was linked to biofouling. Microbial community analysis revealed that the initial colonisers were predominantly thermophilic bacteria, which were different from the microbial community of the treated effluent. The biofilm-forming bacteria included Schlegelella, Meiothermus, and Vulcaniibacterium. These microorganisms proliferate and release excessive extracellular polymeric substances (EPS), leading to the development of mature biofilm on membrane surface. This helped in the deposition of organics and inorganics from the bulk feed, which led to microbial community succession in phase 4 with the emergence of the Kallotenue genus. The results suggested that organic substances and microbial communities on membrane surface at different stages in a long-term MD process had a significant influence on MD performance for high-quality wastewater reuse.
RESUMO
Cost-effectiveness analysis is based on a simple formula. A dollar estimate of the total cost to conduct a program is divided by the number of people estimated to have been affected by it in terms of some intended outcome. The direct, total costs of most communication campaigns are usually available. Estimating the amount of effect that can be attributed to the communication alone, however is problematical in full-coverage, mass media campaigns where the randomized control group design is not feasible. Single-equation, multiple regression analysis controls for confounding variables but does not adequately address the issue of causal attribution. In this article, multivariate causal attribution (MCA) methods are applied to data from a sample survey of 1,516 married women in the Philippines to obtain a valid measure of the number of new adopters of modern contraceptives that can be causally attributed to a national mass media campaign and to calculate its cost-effectiveness. The MCA analysis uses structural equation modeling to test the causal pathways and to test for endogeneity, biprobit analysis to test for direct effects of the campaign and endogeneity, and propensity score matching to create a statistically equivalent, matched control group that approximates the results that would have been obtained from a randomized control group design. The MCA results support the conclusion that the observed, 6.4 percentage point increase in modern contraceptive use can be attributed to the national mass media campaign and to its indirect effects on attitudes toward contraceptives. This net increase represented 348,695 new adopters in the population of married women at a cost of U.S. $1.57 per new adopter.