JWSS - Journal of Water and Soil Science

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The black dot disease of potato is a fungal disease caused by Colletotrichum coccodes (syn. C. atramentarium) that produces accervuli on infected underground plant parts which appear as black dots. The disease appears at the flowering stage and develops up to the season end. The survey on black dot disease of potato in two successive years indicated that the infection percentage is 39.86 in Feraydan (Isfahan), one of the most important potato production regions in Iran. Studies on usual cropping patterns with, potato including, wheat alfa-alfa, barley and fallow showed that in terms of disease infection, one year rotation with fallow reduced the disease severity almost to half compared with control and other cropping patterns. Biological seed and soil treatment, with Trichoderma harzianum in various spores density reduced the disease in various degrees significantly and increased the potato plant growth factors including the number of stems, foliage fresh and dry weights, and also the yields in cases of spore applications, depending upon the type and application dosage. Comparative susceptibility assessments of 24 commercial potato varieties to the black dot disease indicated that the variety Desiree was the least concerned in terms of infection, followed by Scort ,Casser, Casmos, Carlita and Moren , where as Marijke, Cosima and Monalisa were highly infected in comparison to other tested verities and the rests of varieties were scored within these two ranges.

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In recent years, due to the overpopulation, serious water shortages, and need to consume more water, the use of wastewater treatment plant has attracted lots of attention. When the pollution load is not high, biofilm reactors are commonly used for the purpose. In this study, the porous concrete as a bed biofilm in reducing pollution load of wastewater was investigated. In order to evaluate porous concrete, basic mix designs were selected according to regulations ACI211.3R. To increase the specific surface area of concrete for biofilm growth, fine particles were added to the basic mix in three stages with each stage 10% by weight of coarse particles. Experimental design was a randomized complete block. A rectangular channel (with the cross section 20×30 cm2) and 8 meters in length was constructed near the wastewater treatment plant of Isfahan University of Technology. Then, the concrete blocks were made, put on the channel and biofilm processing operations were conducted on the pores of porous concrete cubes. Qualitative tests for BOD, COD, TSS and total coliform of samples from wastewater inflow and outflow were performed. Results showed that the removal of these parameters increased by adding fine particles. The average removal rates of BOD, COD, TSS and total coliform for the first mix design (1400 kg per cubic meter of coarse particle and without fine sand) were 25%, 33%, 45% and 37%, respectively. Similarly, the average removal rates of BOD, COD, TSS and total coliform for the fourth mix (1400 kg per cubic meter of coarse particle and 420 kg per cubic meter of fine sand) were 36%, 40%, 57% and 81%, respectively. It could be concluded that porous concrete can be used as a bed biofilm, and the third mix design (1400 kg per cubic meter of coarse particle and 280 kg per cubic meter of fine sand) was the best mix design.

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In this paper, the efficiency of four hybrid horizontal-vertical subsurface constructed wetlands which have been built for the tertiary treatment of Isfahan North Wastewater Treatment Facility and removal of organic matters was evaluated. In these constructed wetlands three plants including Phragmites australis, Typha latifolia and Arundo donax were planted and one unit left unplanted. The results of 12 months of sampling showed that the type of vegetation has no significant influence on the organic matter removal in the subsurface constructed wetlands, although the removal efficiencies in the planted constructed wetlands were more than unplanted control one. The COD and BOD₅ removal efficiency in the constructed wetlands changes between 77% to 83% and 84% to 86%, respectively, during the operation period. The results of this research also showed that the organic matter removal was dependent on the influent organics nature and biodegradability. The first order model constants were calibrated in different wetlands for designing main projects. The organic concentration in the wetland effluents met the Iranian regulation limits for different reuse applications that shows the constructed wetland is a suitable technology for wastewater treatment in Iran.