Pilot-scale studies of combined clarification, filtration, and ultraviolet radiation systems for disinfection of secondary municipal wastewater effluent

Disinfection of municipal wastewater effluent was evaluated using three alternatives, including: (1) low-pressure (LP)+medium-pressure (MP) UV lamps; (2) clarifier+LP+MP; and (3) pressurized sand filter+ LP+MP. Total coliform (TC), fecal coliform (FC), fecal Streptococcus (FS), TSS, several physicochemical parameters, absorbtivity and UV transmittance (UVT; ) were tested. The UVT for secondary, clarified and filtered effluents were 3.5, 34 and 50, respectively. A 15 photo-reactivation in secondary effluent disinfected by LP lamp was observed, while it was limited to 0.03 by the MP lamp after filtration. Filtration to a surface overflow rate (SOR) of 1050 L/m2h, followed by MP irradiation at a dose of 230 mW s/cm2 was an effective alternative to reduce the TC, FC, and FS in the disinfected secondary effluent. Filtration+MP lamp met the standards of 1000 TC and 400 FC/100 mL for effluent discharge to receiving waters. This process can also inactivate FS, effecting a 6-log reduction. Among the evaluated alternatives, none of the other treatment systems performed as well as the pressurized sand filter+MP lamp, making this the best combination for post-treatment and disinfection of secondary effluent from a well-run wastewater treatment plant. © 2010 Elsevier B.V. All rights reserved

The effects of incubation period and temperature on the Hydrogen sulphide (H2S) technique for detection of faecal contamination in water

A total of 171 water samples from 3 sources were analyzed for the presence of faecal contamination by standard MPN, P/A, EC-M and H2S techniques at different temperatures and incubation times. Analysis of water samples by H2S technique showed that the incubation period of H2S bottles is highly dependent on temperature and concentration of faecal coliform bacteria. Incubation temperature was changed from 22 to 45°C. At higher temperatures (45°C) the bottles turned to black after a 6 h incubation period. Correlation of H2S technique with P/A and MPN techniques were 75.4 and 71%, respectively. Furthermore, the P/A technique showed a correlation of 60.9% with standard MPN technique. In relation to the faecal coliform and by using EC-M technique, we obtained a correlation percentage of 65.1, 56 and 62.3% for standard MPN, H2S and P/A techniques, respectively. This study indicated that incubation period and temperature had significant effects (P = 0.05) on the efficiency of H2S technique. The times when H2S bottles take to turn black is dependent on the number of faecal bacteria, an indicator of the risk that pathogenic organisms are present. Based on the results obtained in this study, we concluded that H2S technique is a reliable method that can be used as an alternative for indication of faecal contamination and drinking water quality surveillance. By using this technique at high t emperatures, rapid screening of large number of water samples in a short period can be profitable especially when the number of drinking water sources is high

Innovative anaerobic upflow sludge blanket filtration combined bioreactor for nitrogen removal from municipal wastewater

In this research, a novel laboratory scale anaerobic/upflow sludge blanket filtration combined bioreactor was designed and operated to improve the efficiency of the upflow sludge blanket filtration process for the simultaneous removal of phosphorus and nitrogen from wastewater. The anaerobic/upflow sludge blanket filtration technique was developed by adding an anaerobic reactor to its influent and operated by varying the main process parameters in order to gain the optimum conditions. The results showed that biological removal efficiency of nitrogen and preservation of sludge blanket strongly depend on wastewater characteristics, hydraulic retention time, sludge age and process controlling parameters. The combined bioreactor performed a total nitrogen removal efficiency of 96.6 % with the sludge age of 25 days, total hydraulic retention time of 24 h and optimum "chemical oxygen demand/nitrogen/phosphorus" ratio of 100/5/1. This ratio also improved the compaction quality of sludge blanket in the upflow sludge blanket filtration clarifier. The average specific nitrification and denitrification rates occurred during the process can be expressed as 4.43 mg NOx-N produced/g VSS.d and 5.50 mg NOx-N removed/g VSS.d at the optimum ratio, respectively. To avoid sludge rising due to denitrification process, the optimum total hydraulic retention time of 16 to 24 h was achieved based on the effluent quality. This study suggested that the anaerobic/upflow sludge blanket filtration bioreactor at the optimum operational conditions can be an effective process for removal of nutrients from municipal wastewater

THE EFFICIENCY OF YARN WOUND FILTERS IN GIARDIA CYSTS REMOVAL USING THE IMPROVED SUCROSE GRADIENT

Introduction. The protozoan parasite Giardia is one of the important biological cotaminants in water. lts presence in water has caused the outbreak of a number of epidemics in various part of the world including the United States. The major impediment in detecting this particular parasite is unavailability of suitable filters capable of removing it from water. Regarding the fact yarn wound filters (cartridge) used in removing Giardia under laboratory condition are currently difficult to obtain in Iran, attempts were made to design and manufacture the filters according to standards recommended in the literature.
 Methods. To determine the efficiency of filters manufactured in this way, a pilot system was established and parameters of concern were investigated. A given number of cysts were introduced in each case to the water in the pilot tank after being counted on the hemocytometer lamella After the entire tank water (at least 4001)had been pumped through the filters, the filter were removed from the pilot system to have their yarns separated and washed. The cysts recovered were then counted and compared with the original input cysts to determine the efficiency of the filters. Formation of sediments on filters due to suspended solids in water was a great impediment in counting the cysts hidden in the sediments. To overcome this difficulty, the method of floatation in sucrose was used to remove the hidden cysts from the sediments.
 Regarding the morphological characteristics of the cysts, the method was also studied in terms of the sucrose film concentration and the effects of centrifugal speed and duration on the removal of cysts from sediments.
 Results. The results indicated an efficiency of 80.69±5.85, which was ideal for a first experience in Iran. a level of 2.5 molar of Sucrose with a duration of 10 minutes for the centrifugation time at 2,000 rpm were considered to be optimum levels to yield a certainty of 95 percent and an efficiency of 89.95±4.25 .
 Discussion. The comparison of the efficiency obtained with those obtained across the world from the application of other techniques associated with this method indicated that this filter was advantages to similar filters, keeping in mind also that this filter can be used in field situations. It is essential to modify in each region the method of cyst removal from sediments using Sucrose gradient according to the particular morphological characteristics and density of cystes. The optimization of Sucrose gradient and the centrifugation duration and speed seems equally important

Survey on possibility of Disinfection of Isfahan North Wastewater Treatment Plant Effluent by Low and Medium Pressure Ultraviolet Systems in Pilot ScaleSystems in Pilot Scale

"n "n "nBackgrounds and Objectives:Today, due to health, environmental and economical problems, of chlorine application, UV radiation is better option than chlorine for disinfection of effluent. The aim of this study was disinfection of secondary effluent with UV radiation."nMaterials and Methods: Two types of UV disinfection system including low pressure (LP) and medium pressure (MP) was used to disinfection of Isfahan North Wastewater Treatment Plant (INWWTP) effluent without pretreatment. Single and combined lamps were operated to evaluate the removal of total and fecal coliforms (TC and FC), and fecal streptococcus (FS). TSS, iron, hardness, UV absorption and transmittance were analyzed in order to observe the fouling of the quartz sleeves. "nResults: After using LP lamp with dose of 161 mws/cm2, TC and FC content was declined to standard level (1000 TC, and 400 FC/100ml). In addition, disinfection with MP lamp was led to FS content of 400 MPN/100 mL. Combination of LP and MP, with dose of 460 mws/cm2 could be met the environmental requirements of TC & FC, and the FS count was reached to 400 MPN/100 mL with dose of 237 mws/cm2. Maximum photo-reactivation percentage of coliforms after LP and MP lamps were appeared 15 and 3 percent respectively, while it was not observed for FS."nConclusion: High fluctuation in secondary effluent quality of INWWTP mainly TSS concentration was caused to decline of the UVT value. Therefore, disinfection of effluent by LP, MP and even combined both systems are not applicable in conventional UV dose. Hence, using advanced process unit before UV disinfection system is necessary for removal of TSS