ABSTRACT:The sorption of cadmium and humic acids from aqueous solutions using surface-modified nanozeolite A has been investigated under various examination conditions. The morphology of untreated and treated nanozeolite was studied under scanning electron microscope and transmission electron microscope. Isotherms of cadmium adsorption onto surfacemodified nanozeolite A were studied at different pH, solid to liquid ratio, adsorbate concentration and interaction time. Kinetic and equilibrium studies were conducted and the equilibrium data have been analyzed using Langmuir and Freundlich isotherm models. The study revealed that experimental results were in agreement with the Freundlich model. The Langmuir monolayer adsorption capacity was found to be 1666.67 g cadmium and 6.75 g humic acid per gram of modified nanozeolite A, which is higher than that of reported value for other zeolites. The sorption ability was enhanced by surface modification and reduction in size and enabled the zeolite to adsorb cadmium. The adsorption of cadmium and humic acid on nanozeolite was found to be the highest at pH 6 and 3, respectively. Results showed that solid to liquid ratio and pH are the most important factors for cadmium and humic acid removal, respectively. Effect of competitive ions was studied and results showed that there is no competition between cadmium and humic acid sorption and presence of these ions.

The occurrences of Cryptosporidium and Giardia in surface sources of drinking water in Tehran were monitored, using US EPA method 1623.1. The prevalence ratios (PR) of positive samples among other media (animal's stools, vegetables, and human's stools) were also estimated from literature data. The density of Giardia and Cryptosporidium in water samples were 0.129 ± 0.069 cysts/L and 0.005 ± 0.002 oocysts/L, respectively. Estimated PR in vegetables, animal stools, surface waters, and human stools were 6.65, 20.42, 21.05, and 4.28 % for Cryptosporidium and 6.46, 17.13, 73.68, and 15.65 % for Giardia, respectively. These reveal the importance of surface waters' and animal stools' roles in the prevalence of cryptosporidiosis and giardiasis in Tehran's population. Giardia's prevalence in untreated surface waters in Tehran was found 3.5 times as much as Cryptosporidium while this found 2.3 times on a global scale. Moreover, the prevalence of giardiasis to cryptosporidiosis infections in Tehran's human population was 3.65. These values could be a clue to attribute the infections to the occurrence of parasites in surface waters. Significant (p < 0.05) associations were observed between rainfalls and presence of Giardia (r = 0.62) and Cryptosporidium (r = 0.60) in surface waters. In autumn, rainfalls can increase the parasites occurrences in surface waters. Significant (p < 0.05) difference on the density of parasites was found between some seasons using Kruskal-Wallis and multiple comparison tests. A significant correlation (r = 0.86) between Giardia and Cryptosporidium densities also confirms the common sources of pollution in surface waters. Findings suggest that untreated surface waters in Tehran may be a potential route of human exposure to protozoan parasites.

During operation of most water treatment plants, spent filter backwash water (SFBW) is generated, which accounts about 2–10% of the total plant production. By increasing world population and water shortage in many countries, SFBW can be used as a permanent water source until the water treatment plant is working. This data article reports the practical method being used for water reuse from SFBW through different method including pre-sedimentation, coagulation and flocculation, second clarification, ultra filtration (UF) and returned settled SFBW to the beginning of water treatment plant (WTP). Also, two coagulants of polyaluminum ferric chloride (PAFCl) and ferric chloride (FeCl3) were investigated with respect to their performance on treated SFBW quality. Samples were collected from Isfahan's WTP in Iran during spring and summer season. The acquired data indicated that drinkable water can be produced form SFBW by applying hybrid coagulation-UF process (especially when PAFCl used as coagulant).

The amount of wastewater characteristics loading is one of the main parameters in the design of wastewater collection and treatment systems. The generation per capita per day (GPCD) of wastewater characteristics was estimated by analyzing the monthly data of nine wastewater treatment plants in Tehran, capital city of Iran. GPCD values were calculated from measured collected wastewater flow, the population and concentration data. The results indicated the values of 32.96 ± 1.91, 49.25 ± 2.49, 37.31 ± 2.44, 6.77 ± 0.53, 1.96 ± 0.11, 92.23 ± 5.68, 2.07 ± 0.39 and 128.96 ± 6.69 g/d.cap of GPCD for BOD5, COD, TSS, TKN, P, TDS, ON and TS, respectively, for Tehran’s wastewater. The per capita estimated for the wastewater production and treatment were determined to be 186.06 ± 7.85 and 136.72 ± 5.43 L/d.cap, respectively. It is estimated that about 504 m3/d and 346 m3/d of sludge, will be produced and waste as excrement raw sludge, respectively, in Tehran. Simple regression models were presented the relationships such as the change of collected and treated wastewater with population and changes of GPCD parameters with each other. It was revealed that the Tehran’s wastewater may be classified as highly degradable, but during recent decades its Biodegradability Index (BI) has been reduced up to 15%. The new suggested revised per capita parameters can be used for design purposes in Tehran, and possibly, in areas with similar characteristics, substituting the classical values obtained from foreign textbooks. These values could help in designing more accurate treatment systems and may lower the required capacity for the treatment of wastewater up to 40% in Tehran.

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