Quality of roof harvested rainwater from houses in Île-de-France area, France

International audienceBacteriological and physico-chemical water quality parameters were measured in rainwater from 10 harvesting tanks, belonging to two types of rainwater harvesting systems (outside tanks for garden watering and underground tanks for both outdoor and indoor uses) in Île-de-France area (France). The presence of fecal coliforms, enterococci, Pseudomonas spp., coliforms, total flora at 22°C and 36°C and total DAPI direct counts showed a microbiological contamination in water and sediment samples for both tank types. However, the harvested rainwater quality suited some existing water quality guidelines for different non-potable purposes (bathing water or reused wastewater). To our knowledge, the presence of microorganisms in sediment compartment in rainwater harvesting tank has been studied for the first time here. Results showed that the sediment could be a reservoir of re-contamination for some microbial species, which would survive in the sediment and may be resuspended in the water column. In parallel, physical-chemical parameters (temperature, turbidity, conductivity, pH and dissolved organic carbon) of collected rainwater were found in the ranges reported in the literature. Algal blooms, principally green algae, occurred in the outside tanks during spring and summer as shown by the high chlorophyll levels (the highest chlorophyll content reached 209.8 µg/L with a water pH of 9.37). Nitrate and phosphate concentrations in water samples were low (respectively less than 5 mg/L and 0.5 mg/L) but high enough to support the development of microorganisms and especially photosynthetic microorganisms in the outside tanks. The difficulty to evaluate the microbial quality of roof-harvested rainwater due to the lack of suitable quality standards is underlined. Depending on the usage of the harvested rainwater, some treatments may be needed to get a better microbial quality and direct measurements for pathogens may be also needed to establish whether or not such harvested rainwater is safe for different types of uses

Zinc Affects Differently Growth, Photosynthesis, Antioxidant Enzyme Activities and Phytochelatin Synthase Expression of Four Marine Diatoms

Zinc-supplementation (20 μM) effects on growth, photosynthesis, antioxidant enzyme activities (superoxide dismutase, ascorbate peroxidase, catalase), and the expression of phytochelatin synthase gene were investigated in four marine diatoms (Amphora acutiuscula, Nitzschia palea, Amphora coffeaeformis and Entomoneis paludosa). Zn-supplementation reduced the maximum cell density. A linear relationship was found between the evolution of gross photosynthesis and total chlorophyll content. The Zn treatment decreased the electron transport rate except in A. coffeaeformis and in E. paludosa at high irradiance. A linear relationship was found between the efficiency of light to evolve oxygen and the size of the light-harvesting antenna. The external carbonic anhydrase activity was stimulated in Zn-supplemented E. paludosa but was not correlated with an increase of photosynthesis. The total activity of the antioxidant enzymes did not display any clear increase except in ascorbate peroxidase activity in N. palea. The phytochelatin synthase gene was identified in the four diatoms, but its expression was only revealed in N. palea, without a clear difference between control and Zn-supplemented cells. Among the four species, A. paludosa was the most sensitive and A. coffeaeformis, the most tolerant. A. acutiuscula seemed to be under metal starvation, whereas, to survive, only N. palea developed several stress responses