A practical method was sought for removing the unacceptably high color and chlorine demand from the surface water source used at Kotzebue Air Force Site. Earlier laboratory tests of this water had indicated that treatment with 10 to 40 ppm chlorine would produce satisfactory water, with 95% color removal. Field tests were conducted at the site in 1962 and 1963. Treatment with 32 ppm chlorine reduced color from 70 cobalt units to 10-15 units in 24 days, with a final chlorine residual of 2 ppm. Treatment with 21 ppm chlorine reduced color to 20 units in 82 days, at which time the chlorine residual was zero and recoloration began. Although results of the field tests did not entirely agree with laboratory findings, the 32 ppm chlor:ine dose was found to be a satisfactory, simple and practical method of treatment. Reduction of chlorine residual to an acceptable level occurred within 24 days following treatment.
The U. S. Air Force has selected an Air Force Base located in interior arctic Alaska as the site for its first major sewage oxidation pond in Alaska. Through an Interservice Agreement with the Air Force, the Environmental Sanitation Section (ESS) of the Arctic Health Research Center (AHRC) has prepared design criteria for the construction of an experimental anaerobic pond followed in series by an aerobic pond for treating sewage from the Base. Because of the annual 6-month period of ice cover in this locale, the anaerobic pond has been designed large enough to store the entire winter sewage flow of 12 million gallons. During the summer months the stored sewage will be fed into the aerobic pond for a 10-day retention period with subsequent discharge. It is hypothesized that the almost continual summer sunlight will greatly increase algal action and satisfaction of Biological Oxygen Demand (BOD), resulting in adequate treatment with a shorter detention time and higher BOD loadings than are generally used. ESS will monitor the operation of the pond upon its completion to determine operating efficiencies, optimum loading and bacterial and chemical phenomena during the different seasons. Results of the study should permit establishment of more exact design criteria for future arctic sewage oxidation ponds.
BACKGROUND: We sought to summarize and critically appraise the literature on the epidemiology of infective endocarditis (IE) in the general population. METHODS: We retrieved population-based IE surveys by searching MEDLINE and EMBASE. Two reviewers independently extracted relevant data. We performed a metaregression to determine if temporal trends of IE characteristics exist. RESULTS: Fifteen population-based investigations with 2,371 IE cases from seven countries (Denmark, France, Italy, the Netherlands, Sweden, United Kingdom, and United States) from 1969 to 2000 were eligible. Different case definitions and procedures were used to capture all IE cases, including census of existing diagnoses, record-linkage system, and direct contact survey. In the unadjusted regression, there was a decline in the proportion of IE patients with underlying rheumatic heart disease (RHD; 12%; 95% confidence interval [CI], - 21 to - 3%; p = 0.01) and an increase in the proportion of patients undergoing valve surgery (9%; 95% CI, 3 to 16%) per decade. After adjusting for country, the decline in IE cases with underlying RHD became nonsignificant, but the proportions of IE patients undergoing valve surgery increased 7% per decade (95% CI, - 4 to 14%; p = 0.06), and those with underlying prosthetic valve increased 7% per decade (95% CI, - 1 to 16%; p = 0.07). There were no significant temporal trends in the causative organisms. CONCLUSION: Evidence from well-planned, representative IE epidemiologic surveys is scarce in many countries. Available studies suggest a changing distribution of underlying valvular heart disease in patients with IE and an increase in its surgical treatment.