Simultaneous remediation of nutrients from liquid anaerobic digestate and municipal wastewater by the microalga Scenedesmus sp. AMDD grown in continuous chemostats.

AIMS: The primary aim of this study was to investigate the capacity of a microalga, Scenedesmus sp. AMDD, to remediate nutrients from municipal wastewater, either as the sole nutrient source or after blending with wastewater obtained from the anaerobic digestion of swine manure. A complimentary aim was to study and define the effects of these wastewaters on microalgal growth, biomass productivity and composition which have important implications for a commercial biofuels production system. METHODS AND RESULTS: A microalga, Scenedesmus sp. AMDD, was grown in continuous chemostats in municipal wastewater or wastewater supplemented with 1·6× or 2·4× higher levels of nitrogen (N) obtained through supplementation with anaerobic digestates. Biomass productivity increased with increasing nutrient supplementation, but was limited by light at high cell densities. Cellular quotas of carbon (C), nitrogen and phosphorus (P) all increased in direct proportion to their concentrations in the combined wastewaters. At higher cell densities, total carbohydrate decreased while protein increased. Fatty acid content remained relatively constant. Under high nutrient levels, the fatty acid profiles contained a higher concentration of polyunsaturated fatty acids at the expense of monounsaturated fatty acids. Chlorophyll a was 2·5 times greater in the treatment of greatest nutrient supplementation compared to the treatment with the least. Ammonium (NH4(+)) and phosphate (PO4(3-)) were completely removed by algal growth in all treatments and with maximal removal rates of 41·2 mg N l(-1) d(-1) and 6·7 mg P l(-1) d(-1) observed in wastewater amended with 2·4× higher N level. SIGNIFICANCE AND IMPACT OF THE STUDY: The study is the first to report stable, long-term continuous algal growth and productivity obtained by combining wastewaters of different sources. The study is supported by detailed analyses of the composition of the cultivated biomass and links composition to the nutrient and light availabilities in the cultures. Simultaneous remediation of these wastes by algal growth is discussed as a strategy for the valorization of the biomass.

Comparison of seven antibiotic treatments with no treatment for bacteriological efficacy against bovine mastitis pathogens.

Milk culture results were retrospectively reviewed from 9007 cases of subclinical mastitis affecting cows housed in dairy herds located in New York and northern Pennsylvania. Cases included in this analysis had at least one mastitis pathogen isolated from the initial milk sample, were recultured within 1 mo, had permanent cow identification, and had records of whether mastitis was treated with an antibiotic or no treatment at all. Overall bacteriological cure rate for 21 mastitis pathogens was 68% (6097 of 9007). Antibiotic treated cases had a higher cure rate (75%) than did untreated cases (65%). Antibiotic treatments that significantly differed from the untreated cure rate of 65% were amoxicillin (82%), erythromycin (76%), cloxacillin (73%), and pirlimycin (44%). Cure rates for antibiotic treatments with cephapirin, hetacillin, or penicillin did not differ from the untreated cure rate. Agents for which some antibiotics were associated with increased cure rates compared with no treatment were Streptococcus agalactiae, streptococci other than Strep. agalactiae, and coagulase-negative staphylococci. The antibiotic most commonly associated with higher cure rates was amoxicillin. Most of the 21 mastitis agents showed no difference in bacteriologic cure rates between any of the 7 antibiotic treatments and no treatment.