The biosorption of Cd (II) ions from aqueous solutions by dried activated sludge was investigated as a function of initial pH, initial cadmium ion concentration, adsorbent mass, adsorbent particle size and temperature. Biosorption experiments were performed using activated sludge of the systems of wastewater refining of milk factory. The results showed that increasing the initial pH from 2 to 5.5 and the adsorbent mass from 0.5 g to 2 g increased the removal efficiency from 11% to 68% and 68% to 79% respectively. Increasing the adsorbent particle sizes from smaller than 0.063 mm to greater than 0.5 mm and the initial cadmium ion concentration from 15 ppm to 120 ppm decreased the removal efficiency from 77% to 67% and 80% to 54% respectively. The equilibrium data fitted both the Langmuir and Freundlich adsorption models, but the Freundlich isotherm was found to fit the experimental data slightly better than the Langmuir isotherm. The characteristic parameters for each isotherm have been determined. Maximum adsorption capacity (q0) was calculated at different temperatures (303, 318, and 333 K) 1.283, 1.581 and 1.726 mg/g, respectively. The dimensionless separation factor (RL) showed that the activated sludge of milk factory can be used for the removal of cadmium ions from aqueous solutions. The results (n, RL) represented good and favorable adsorption. Therefore, the activated sludge could remove Cd (II) ions effectively from aqueous solution.

Background: Using the sludge as fertilizer on farms is one of the options to dispose it, which due to its variety of pathogenic microorganisms, it may cause a wide range of bacterial and parasitic diseases in human and livestock. The purpose of this study is to investigate the feasibility of using dried sludge produced in municipal wastewater treatment processes to fertilize agricultural lands in accordance to the health and environmental standards.Methods: In this analytical-descriptive study, three sewage treatment plants of Chahar Mahal and bakhtiary province were selected as the sample plant, including Shahrekord, Farsan and Borujen due to their similarity in the weather condition and the treatment process. In order to investigate the sludge in its lowest and the highest rate of evaporation, in the freezing cold winter and burning hot summer respectively, two winters and two summers were selected as the timeframe. In this study, faecal coliform and total coliform were determined as the sludge microbial indexes and examined in accordance to the EPA standards.Findings: The findings of this study indicated that the mean value of faecal coliform for the three treatment plants in winter were 1.63 × 106, 1.93 × 106 and 1.98 × 106 respectively. Also in summer they were 4.51 × 106, 5.75 × 106, and 9.23 × 106 respectively.Conclusion: The evaluations of this study indicated that the biological sludge generated from the three treatment plants in the winter after drying off naturally were located in class B of the EPA standards.Thus, based on recommendations of the organization, such sludge can be used with regards to standard restrictions for agricultural purposes. However, the microbiological quality of the sludge in summer was lower than the U.S. EPA standards for Class B sludge, and thus is not applicable in agricultural use.

Nowadays, sewage sludge disposal is a great concern of wastewater treatment plants in both developed and developing countries. Land application of sewage sludge is still one of the most important disposal options in most countries. Although, land application of sludge allows the nutritional value of treated sludge to be used beneficially in agriculture, but pollutants and pathogenic organisms in sewage sludge can raise the health risk of human and animals. The aims of this study are 1) to investigate the applicability of dried sludge of Tehran WWTP's in agricultural activities according to U.S. EPA 40 CFR Part 503 regulations and, 2) to find a possible statistical relationship between parasite eggs, Fecal Coliform (FC) and Total Coliform (TC).Three wastewater treatment plants including "Shahrak-e-Gharb", "Shoosh and "Mahallati" were chosen in city of Tehran and the samples were collected during three seasons (fall, winter and spring (2006-7)). Parasite eggs, FC and TC of collected samples were examined using standard methods. The results showed that the average amounts of FC for sludge of Shahrak-e-gharb , Shoosh and Mahallati WWTP's were found to be 4.9 ×103, 3.7×103 and 1.21×104 MPN/g.DS, respectively. According to the data, the sludge of all these wastewater treatment plants is classified into Class B of EPA 40 CFR Part 503 regulations. Therefore, direct human exposure to Class B sludge would still pose a significant health risk and application of these sludges is restricted. In addition, strong statistical relationships were found between parasite eggs and Fecal Colifrom of the samples with the Pearson correlation factor of 0.989.

This study was conducted to investigate the removal of iron by dried biomass of activated sludge. Dried activated sludge, prepared as a powder, was tested as a sorbent for the removal of iron from aqueous solutions. The effects of various experimental parameters including initial iron concentration, mass of biomass and contact time were examined and optimal experimental conditions were obtained. The equilibrium time for iron adsorption onto biomass was determined as 150 min. The rate of iron removal was directly correlated to biomass amount and contact time. Increasing contact time from 0.5h to 2.5h resulted in 25% improvement in iron removal efficiency. When the weight of the biomass increased from 0.1g to 0.9 g, the iron removal efficiency increased from 62% to 95%. High initial iron concentration had an adverse effect on iron removal efficiency. Increasing initial iron concentration from 2 to 10 (mg/L) caused declining the iron removal efficiency from 70% to 56%. Freundlich, Langmuir, Dubinin-Radushkevich and Temkin isotherm models could describe the adsorption equilibrium of the iron onto the activated sludge. Meanwhile, Freundlich isotherm represented a better correlation compared to other isotherms (R2 > 0.999). Also Elovich kinetic models fits well with experimental data (R2>0.997).

Wastewater sludge is categorized as hazardous waste material which must be stabilized and treated before disposal and reuse. Final disposal of sludge from treatment facilities usually involves some form of land disposal. However, sludge contains different type of pathogens and heavy metals which can causes pollution of surface and ground waters, soils and spread diseases if there is human exposure to the sludge. In this respect, U.S.EPA presented requirements for using and disposing of sludge.Thus, taking into account the potential risks caused by presence of heavy metals in sludge and for the control of processes of sludge treatment and disposal and also protect of environmental health and enhancement of public health level, specially for farmers and consumers of raw crops, needs sampling and characterization of sludge. In the present research concentration of 11 heavy metals and potentially toxic elements in dried sludge of Isfahan South and North and Shahinshahr wastewater treatment plants were determined using standard methods. Samples have been taken from dried sludge of treatment plants, and been measured after being prepared through atomic absorption apparatus and were compared with EPA enacted standards in regulation 40 CFR part 503. As well, fertilizer value parameters of sludge were measured and were compared with standards and guidelines. The results showed that the average concentration of above elements in all three treatment plants, not exceeded from EPA standards, however, regarding the accumulative property of these elements and lack of necessary protective effects of EPA standards, in using these sludges in the agricultural soils, the necessary caution and care should be taken, in other uses of sludges, however, there is no limitation.

Absorption of active dyes with Azo base (Active Red) is made by passing from dried active sludge. During performed tests, which was with changing of initial pH-gram of adsorbent matter -changing in shaker speed and initial dye concentration as well as investigation of kinetic changes and their effects on absorption rute show that equilibrium models follow from detailed equation of Freundlish & Longmuir well. the highest percent of absorption which obtained in these testes for the color of active red in concentration of 40 mg/lit is equal to 61.12% with absorbed gram 2.5 in pH=2. Adsorption stage of Azo dyes follows the second-degree kinetics and it was specified that the capacity of adsorption is relatively high. (pH<6) The high correlation coefficient, R>0.989, showed that this method is suitable.The adsorption method was used for absorbance of dyes the bucteries in the sludge were subject to growth, then it was dried for 24 hours fewer than 60o c.

Introduction: Given the interest in the use of low-cost adsorbent for the removal of heavy metals, the use of higher mud powder from dried sludge drying bed West Wastewater Treatment Plant is located in Ahwaz nickel metal uptake.Materials & methods: Batch experiment was carried out to prepare 100 ml of solution. Samples examined in this study with a synthetic standard solution of nickel were prepared. Adsorption efficiency in primary PH 2 to 8, 5 to 180 minutes of contact time, initial concentration of metal ions, 5, 10 and 50 milligrams per liter adsorbent dose, 0.1, 0.2, 0.5 and 1 mL and mixing speed of 100 rpm The minutes were reviewed. Pretreatment adsorbent comprises drying, grinding machines, and particle size sieve, 50 and 120.Findings: Based on the results of nickel adsorption process, the adsorption efficiency at a concentration of 5 milligrams per liter to 50.64%, and the rate of adsorption efficiency in pH 8, 24.13%, the absorption efficiency of the adsorbent dose 1 g/100mL equal to 30.63% and the adsorption efficiency at 120 minutes 21.59%. Freundlich adsorption isotherm obtained and fitted to the Langmuir model for nickel, respectively.Discussion & Conclusion: The dried, powdered sewage sludge as sorbent available for the removal of nickel from wastewater hasn, t a high efficiency.

Background: Nowadays, different methods are applied for the removal of heavy metals from the aqueous resources that the adsorption process is one of them. The chromium VI is one of the most prevalent contaminants which create serious difficulties; so, it should be removed from the contaminated waters by an effective method before being leaved into the environment. The present research investigated the use of dried powder of activated sludge of Kavirtire wastewater treatment plant as bio sorbent for removal of chromium (VI).Methods: In the present experimental study, the effects of pH, adsorbent dose, primary concentration of metal and contact time on the removal of chromium (VI) from the aqueous solutions were studied. Then, the equations of isotherm and adsorption kinetic were specified based on the optimal conditions. The absorbent features were analyzed by SEM and EDX techniques.Results: The maximum efficiency of the removal of chromium (VI) at pH 2, optimal dose of 5 g/L, contact time of 60 min and with primary concentration of 15 mg/L was reported 99.83 percent. The study of relation of the isotherm and kinetic in the reaction revealed that the process of adsorptions of chromium follows the Freundlich model (R2=0.90) and the pseudo- second order kinetic model (R2=1), respectively.Conclusions: The dried powder of activated sludge can be applied as a proper adsorbent for the removal of Chromium VI from the aqueous resources.