In the first stage of this study, the compound effects of sludge dry solid content and residual bulking agent type (paper, saw dust, straw) mixed with activated sludge (10, 15, and 20% dry solids) on volatile solids (V.S.) reduction were investigated using Eisenia foetida in pilot scale experiments with batches of fifty earthworms in each of the 10 experimental treatments over a period of 10 weeks. The maximum V.S. reduction was attained in the mixture of sludge and paper, with a D.S. of 15% (0.42 ±0.03 % day-1) while the minimum V.S. reduction was achieved in the mixture of sludge and straw, with a D.S. of 10% (0.26±0.01 % day-1). In the second stage, the survival of Eisenia foetida in the anaerobic sewage sludge was investigated. In the unmixed raw anaerobic sludge, all the earthworms died during the first 9 weeks of the study period due to acute toxicity. From week 10, however, their survival rate improved so that by week 12 when toxicity reduced to 25.40%, they completely survived. This is while in the mixture of anaerobic sludge with paper (D.S. 15%), 100% of the earthworms survived from week 8 after the volatile solids reduced to 20.42% and 17.40%.

Objective: In some part of Iran such Isfahan province some farmers tend to use the digested sludge as soil conditioner or fertilizer, and some of the mentioned sludge may content of pathogenic bacterial agents, such as Salmonella. The aim of the present study was therefore, to assess level of contamination by Salmonella products of which are used solely for agricultural purposes.Methods: Periodic sampling and counting of the level of Salmonella were according to the method presented by American Public Health Association (APHA) and the United State Environmental Protection Agency (EPA).Results: The results showed that the average number of Salmonella in the digested sludge of waste water treatment plant number 1 and Shahinshar, based of the most probable number were 24 and 11 per 4g dried sludge solids, respectively, and were higher than the standard 3 per 4g of dried sludge solids. Hence none of these two plants satisfied V.S. Government Environmental Protection Agency, for use of the sludge in agricultural works. The results taking from statistical analyese using Pearson's correlation coefficien showed that there was a meaningful relationship between the percentage of reduction of stabilized sludge (organic. materials) and Salmonella for plant number 1 (p=0.009 and r =0.9907) and Shahin-Shar digested sludge (p=0.001 and r=0.9885) .Conclusion: These results suggest the greater reduction of the volatile solids correlates with larger reduction in the level of Salmonella.

Anaerobic digestion, is microbial decomposition of organic materials in absence of oxygen, which results in production of methane and stable compounds. Anaerobic digestion technology has three phases: pre-treatment, digestion and post-treatment. Fermentation bacteria, hydrogen producer bacteria and methanogene bacteria, are the main three groups of metabolic micro-organisms for methanogenic fermentation. Anaerobic digestion in comparison with aerobic composting, is a net energy-producer. 500-1000 kwh energy per ton of wet waste is generated in anaerobic digestion process, while in aerobic composting, 500-750 kwh energy is consumed for treatment of each ton of wet waste. Methane yield is 0.2-0.5 Nm3 per kg volatile solids added in anaerobic digestion process. During this study, a 22 litre reactor was used for anaerobic digestion of putrescible solid wastes with high total solids (TS) content and 15-20days retention time. The reactor was heated by a hot-water coil inside it, therefore, internal temperature was kept in the range of 33-37°C.Resultsshow2500to 9400litre biogas generation per 1 m3. of reactor volume per day and more than 50%reduction in organic substances (as TS).

In this study, batch series of laboratory-scale anaerobic digesters at 35 and 55 ° C were used to investigate the production of biogas from dairy effluents and reduce its pollution. Dairy effluent sludge with ratios of zero, 10, 20, 30, 40 and 100% was used for inoculation. The interaction effect of sludge percentage and temperature at the level of one percent on the volumetric indices of biogas production was significant for the amount of initial volatile solids, volatile solids removed and chemical oxygen demand removed at the level of one percent. With increasing sludge percentage, the amount of biogas produced per initial volume increased for the removed COD but decreased for the initial volatile solids. The highest biogas production efficiency was obtained based on the removed volatile solids at thermophilic temperature and 40% sludge ratio, with the removal of 47.7% volatile solids and 266.5 ml per gram of removed volatile solids. According to the results, the amount of biogas production at mesophilic temperature, in lower proportions of added sludge, is more than the amount of gas produced at thermophilic temperature, and due to the low volume of sludge production in the dairy industry and higher energy consumption under thermophilic conditions, anaerobic digestion and biogas production are more favorable at 35 ° C. The results also showed that by anaerobic digestion of each m3 of dairy effluent, 20.83 MJ of heat energy can be produced.

Finite tight frames have many applications and some interesting physical interpretations. One of the important subjects in this area is the ways for constructing such frames. In this article we give a concrete method for constructing finite normalized frames using Platonic solids.