[ survey on the effect of ultrasonic method on dewatering of bio sludge in wastewater treatment plant]

Background: Disintegration and dewatering of produced sludge during wastewater treatment is one of the main challenges in wastewater treatment process. The aim of this study is to investigate the efficiency of ultrasonic method on dewatering of bio sludge in wastewater treatment plant under different conditions and select the best conditions.

Materials and Methods: In the present study, sludge disintegration and sludge dewatering after undergoing different conditions of frequency [35 and 130 KHz] and detention time [3, 5, 10 and 30 min] were investigated and finally the changes of SCOD, CST and SRF were determined.

Results: The results illustrated that the maximum ability of dewatering was obtained at a detention time of 5 min and frequency of 35 KHz for ultrasonic. Under this conditions SCOD%, CST and SRF were achieved to 4.3%, 151 S and 2.1×1013 m/kg respectively.

Conclusion: According to the results, ultrasonic method significantly increases the sludge disintegration and improves the sludge dewatering.

Investigation of anaerobic fluidized bed reactor / aerobic moving bed bio reactor [AFBR / MMBR] system for treatment of currant wastewater

Anaerobic treatment methods are more suitable for the treatment of concentrated wastewater streams, offer lower operating costs, the production of usable biogas product. The aim of this study was to investigate the performance of an Anaerobic Fluidized Bed Reactor [AFBR] - Aerobic Moving Bed Bio Reactor [MBBR] in series arrangement to treat Currant wastewater. The bed materials of AFBR were cylindrical particles made of PVC with a diameter of 2-2.3 mm, particle density of 1250 kg/m[3]. The volume of all bed materials was 1.7 liter which expanded to 2.46 liters in fluidized situation. In MBBR, support media was composed of 1.5 liters Bee-Cell 2000 having porosity of 87% and specific surface area of 650m[2]/ m[3]. When system operated at 35 [degree sign] C, chemical oxygen demand [COD] removal efficiencies were achieved to 98% and 81.6% for organic loading rates [OLR] of 9.4 and 24.2 g COD/ l.d, and hydraulic retention times [HRT] of 48 and 18 h, in average COD concentration feeding of 18.4 g/l, respectively. The contribution of AFBR in total COD removal efficiency at an organic loading rate [OLR] of 9.4 g COD/ l.d was 95%, and gradually decreased to 76.5% in OLR of 24.2 g COD/ l.d. Also with increasing in organic loading rate the contribution of aerobic reactor in removing COD gradually decreased. In this system, the anaerobic reactor played the most important role in the removal of COD, and the aerobic MBBR was actually needed to polish the anaerobic treated wastewater

Biosorption of cadmium and copper ions from aqueous solution by chemically modified wheat straw

Increased environmental pollution caused by toxic metals is a great concern because of their carcinogenic, non-biodegradability and bio-accumulation properties. Cadmium [Cd] and copper [Cu] are two of the most common heavy metals in the environment. The objective of this study was to assess the effect of modified wheat straw promoted by sodium bicarbonate for removal of cadmium and copper from aqueous solution. Adsorption process was accomplished in a laboratory-scale batch with emphasis on the effect of various parameters such as pH, contact time, arsenic concentration and adsorbent dosage on adsorption efficiency. In order to understand the adsorption process, equilibrium isotherms were also determined. The results of this study showed that adsorption of the Cd and Cu was influenced by several parameters such as arsenic initial concentration, adsorbent dosage and solution pH. Maximum adsorption efficiency was achieved at a pH of 7. The adsorbed amount of metal ions increased with the initial concentration of the metals. Among the isotherm models tested, i.e., the Langmuir, Freundlich, and Dubinin Radushkevich, the adsorption equilibrium of both Cd and Cu was best described by the Langmuir and Freundlich models. Mean values of the free energies of adsorption [11.1 kJ mol-1 for Cd and11.4 kJ mol-1 for Cu] indicated that adsorption of Cd and Cu ions by wheat straw might follow a chemisorption mechanism. We concluded that adsorption by modified wheat straw is an efficient and reliable method for removal of Cd and Cu from aqueous solutions

Nitrate removal from drinking water by point of use ion exchange

A laboratory study was conducted to investigate the ability of a special type of strongly basic resin MP500WS for the removal of nitrate from different waters. Two different types of Point-of-Use [POU] devices containing an identical resin were used. MP500WS known as macro porous was used in POU devices for removal of high concentrations of nitrate and sulfate ions from water. Sulfate and chloride ions are considered the most important interferences in the treatment process of nitrate by most anion exchange resins. The results obtained by treatment of water samples having different ranges of nitrate [20 to 150 mg/L], sulfate [50, 100 and 800 mg/L] and chloride [50 and 500 mg/L] have shown that the method was suitable for delivering water with NO[3] concentrations in less than its maximum contaminant level [MCL=45 mg/L] as long as the initial NO[3], SO[4] and CI concentration has remained in less than 150, 100 and 500 mg/L, respectively. For this purpose, POU systems that utilize a suitable tested resin may be considered as an economical and effective alternative to conventional systems. This study shows this strategy very effective for nitrate reduction to acceptable levels when macro porous type strongly basic resin is used as the resin

[Parasitological study on Lymnaea palustris and its ecological survey by GIS in Mazandaran province]

Lymnaea palustris was previously found in Mazandaran province but there was not any report about its parasitologic aspects. This study was conducted to finding ecological and Parasitological aspects of snail in Mazandaran province, North of Iran. In this descriptive study, more than 181 locations, were checked, in 36 locations, colonies of the snail were found and 490 snails were collected. After diagnosis of snails as Lymanea palustris, in laboratory, they were crushed and their probable cercaria was checked out by a dissecting microscope. Data were analyzed and processed by ArcGIS 9.2 and Microsoft Office 2003 for descriptive analysis. from 490 snails, 6 cases [1.22%] were infected with trematode larval stage. These cercariae were classified as echinostomaercaria. Optimum temperature for the snails was 15-19 degrees of celsius and optimum dissolved salt [TDS] was 200-400 ppm. Population of colonies were raised in autumn and winter but infected snails were seen in summer. This study could show the ecological pattern, distribution, and population dynamic of the snail. Also the existence of echinostomaercaria which is cercaria, generally belong to the Echinostoma sp, indicates veterinary and parasitological importance of local snails. It is probable these parasite, infect man also. More studies on definitive host and exact species of parasite are proposed

Ultrasonic technology effectiveness in fecal coliform disinfection of water

The sonolytic destruction of fecal coliforms is reported here. Ultrasonic energy at a frequency of 42 kHz was used to expose aqueous suspension of fecal coli forms to evaluate the germicidal efficacy of ultrasonic exposure. CavItation generated by ultrasonic can greatly enhance various chemical reactions, oxidize aqueous compounds, and disrupt micro-organisms. Controlled laboratory experiments have established the ability of these systems to destroy micro-organisms. Experiments were conducted using BRANSONIC ultrasonic cleaner and operating conditions. Histories of the contaminant concentration reductions and destruction of fecal coli forms were obtained from periodic sampling. The results using BRANSONIC system at 42 kHz for the microbial decontamination of water show that deactivation fecal coli forms dose occurs but not very rapidly. On the other hand, using this frequency it would appear that substantially more of the fecal colifom1s [99.95%] are inactivated in 90 minute

Investigation and evaluation of ultrasound reactor for reduction of fungi from sewage / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

The objective of the investigation was to study the application of ultrasound reactor technology (USRT) as a disinfectant for reduction of fungi from sewage effluent. Fungi are carbon heterotrophs that require preformed organic compounds as carbon sources. USRT is an attractive means to improve water quality because of the system simplicity and no production of toxic by-products. An ultrasound reactor produces strong cavitation in aqueous solution causing shock waves and reactive free radicals by the violent collapse of the cavitation bubble. These effects should contribute to the physical disruption of microbial structures and inactivation of organisms. There was significant reduction in fungal growth, with decreased fungal growth with increasing USRT. In this study, ultrasound irradiation at a frequency of 42 kHz was used to expose suspensions of fungi to evaluate the disinfection efficacy of the ultrasound reactor. Also, this study showed that in this system more than 99% reduction of sewage fungi was achieved after 60 min.