RIRT

The use of electron beam to disinfect sewage water is gaining importance. The current problem on
environmental health in relation to water pollution insists for the safe disposal of sewage water. In
general, sewage water comprises of heterogeneous organic based chemicals as well as pathogens. EB
(electron beam) treatment of the wastewater was found to be very effective in reducing the pathogens
as well as organic load. EB dose of 1.5 kGy was sufficient for complete elimination of total coli forms.
The experimental results elucidated that the reduction of biological oxygen demand (BOD) (30.38 and
51.7%) in both inlet and outlet sewage samples. Similarly, reduction of chemical oxygen demand (COD)
was observed (37.54 and 52.32%) both sewage samples with respect to increasing of irradiation doses
(0.45 to 6 kGy). The present study demonstrated the potential of ionizing radiation for disinfection of
sewage and to increase the water quality of the wastewater by decreasing BOD and COD. So, the
irradiation sewage water can find its application either in agriculture for irrigation or in industry sector
for cooling purpose or in both the sectors.

First time in India, a study was aimed to establish a base- line data for electron beam
radiation dose level needed to disinfect and also improve the water quality of sewage water
for possible reuse in irrigation, industries as well as a few domestic purposes. Raw and
secondary treated sewage water samples, which were rich with microorganisms from Navi
Mumbai municipal sewage plant were irradiated with electron beam accelerator at doses of
0.45, 0.75, 1.5, 3.0, 4.5, 6.0, 7.5, 9.0 and 10.5 kGy. Electron Beam irradiation treatment of
the wastewater was found to be very effective in reducing the pathogenic load. Electron
Beam (EB) dose of 1.5 kGy was sufficient for complete elimination of total coli forms
whereas Cryptococcus laurentii, Aspergillus fumigatus and Absidia sp. were killed
by10.0 kGy and no larvae of helminthes (Ascaris lumbricoides) were recovered at the
dose ≥ 1.5 kGy. The experimental findings obtained highlighted the potential of this
technology for disinfection of wastewater.

Radiation induced effects on poly (p-sodium styrene sulphonate) (PSSS) of two molecular weights, namely 10 6 and 70,000 in aqueous solution have been investigated by steady state and pulse radiolysis (PR) techniques. The reactions of primary radicals of water radiolysis such as OH radical, e aq À , H atom, some oxidizing radicals like N 3 , Cl À 2 and SO À 4 and reducing species like CO À 2 with PSSS have been investigated. The results indicate that the reactivity of these species towards PSSS is a function of molecular weight of PSSS. The absorption spectra of transient species produced when dilute aqueous solutions of PSSS of different molecular weights are subjected to pulse radiolysis have been compared. Rate constants for the reaction of OH radical and H atom with PSSS have been evaluated both by competition kinetics method and by direct observation of build up of transient species. The results indicate that OH radical and H atom react with PSSS in different ways. Near neutral pH, the OH radical reacts with substituted pendant aromatic ring of the PSSS to form an adduct, with a rate constant of 5.5 Â 10 8 and 1.1 Â 10 9 dm 3 mol À1 s À1 for PSSS of molecular weights 10 6 and 70,000, respectively. H atom on the other hand abstracts H atom from the PSSS backbone as well as forms an adduct by reacting with aromatic ring. The rate constant values for reaction of aqueous electron with PSSS were found to be 5 Â 10 7 dm 3 mol À1 s À1 (M w =10 6 ) and 2.2 Â 10 8 dm 3 mol À1 s À1 (M w ¼ 70; 000). The anion formed did not transfer electron to methyl viologen in the pH range of 6-10.5. The viscosity of the aqueous PSSS solution decreases with irradiation, up to doses of 1000 kGy indicating degradation of PSSS in this dose range. The PSSS of higher molecular weight is more prone to degradation. The chain scission is a function of dose rate, concentration of polymer and ambient of irradiation. At doses beyond $2500 kGy there is a sharp increase in viscosity of the PSSS solutions till the solutions set to a soft, sticky gel mass. The gelation dose (D gel ) is a function of molecular weight of the polymer and initial polymer concentration. In the presence of crosslinking agent like N,N-methylene bis acrylamide, the gelation was faster for PSSS of higher molecular weight. Gelation was most efficient for 20% (w/w) polymer concentration. #