Enhancement of sunlight irradiation for wastewater disinfection by mixing with seawater

There is a need for developing a simple and easy-to-maintain disinfection technique for sewage treatment for use in developing countries and disaster-affected areas. We propose a novel disinfection technology that inactivates bacteria in wastewater via sunlight irradiation under high salt concentration by mixing with seawater. The disinfection efficiency of the proposed method was quantitatively evaluated and examined using fecal indicator bacteria. When the salinity in wastewater was adjusted to 30 practical salinity units by mixing with seawater, the constant of inactivation irradiation energy Ks (m2/MJ) was 1.6–2.2-fold greater than that without seawater for total coliforms and Escherichia coli. By contrast, although enterococci were inactivated by sunlight irradiation, an increase in salinity did not enhance disinfection. On setting the irradiation energy of sunlight to 5.5 MJ/m2, >99% of the fecal indicator bacteria were inactivated. Finally, we examined the relationship between the attenuation of irradiance and water depth and accordingly proposed a design of a treatment system wherein wastewater and seawater were adequately mixed and passed via a disinfection tank under the natural flow with sunlight irradiation.

A Strategy to Revalue a Wood Waste for Simultaneous Cadmium Removal and Wastewater Disinfection

In this investigation, the possibility of wood waste (hardwoods such as oaks’ and alternatives’ staves from Balkan cooperage) revalorization for simultaneous cadmium removal and wastewater disinfection was examined. All samples were characterized in terms of their crystallinity index and crystallite size, amount of functional groups, and surface chemistry (determined by ATR-FTIR) as well as antibacterial activity. Mulberry is characterized by the lowest crystallinity index which can be ascribed to the highest crystallite size disabling crystallite denser packaging, while myrobalan plum has about 23% lower crystallite size that enables crystallite better packaging, thus resulting in a 42.4% higher crystallinity index compared to the mulberry. All oaks have a significantly higher amount of carboxyl groups compared to the alternatives (0.23-0.28 vs. 0.12-0.19 mmol/g). The adsorption experiments revealed that with increasing the initial cadmium concentration from 15 up to 55 mg/g, samples’ adsorption capacity increases by 89-220%. The equilibrium data fit well with the Langmuir isotherm model implying monolayer coverage of cadmium ions over a homogeneous wood surface. The relationship between the samples’ maximum adsorption capacities (ranged from 5.726 to 12.618 mg/g), their crystallinity index, and crystallite size was established. According to ATR-FTIR spectra, aldehyde, carboxyl, hydroxyl, and phenyl groups present on the wood waste surface are involved in Cd2+ adsorption which proceeds via the interplay of the complexation, cation-π interactions, and ion-exchange mechanisms. Mulberry and myrobalan plum showed about 89% and 80% of the total uptake capacity of cadmium within 60 min, while the equilibrium was attained after 240 min of contact time. Good compliance with pseudo-second kinetic order indicated that cadmium adsorption was mediated by chemical forces. Thermodynamic parameters revealed the spontaneous and exothermic character of cadmium ion adsorption onto mulberry and myrobalan plum. All studied samples provide maximum bacterial reduction (>99%) for E. coli and S. aureus. Wood waste from Balkan cooperage can be successfully used for simultaneous cadmium removal and wastewater disinfection.

Molecular Characterization And Ecotoxicological Evaluation of The Natural Dye Madder And Its Chlorinated Products

There has been increased interest in the use of natural dyes for textile coloration as alternatives to synthetic dyes, due to the general belief that natural dyes are more environmentally friendly. However, natural dyes have poor affinity for textiles, which can lead to high dye levels in the resultant wastewater. While chlorine treatment has proven to be effective for dye wastewater disinfection and decolorization, this process can also lead to the formation of more toxic degradation products for certain synthetic dyes. On the other hand, little information is available regarding the ecotoxicity of natural dyes and their chlorination products. To advance knowledge in this area, madder was selected due to its historical importance and wide application in the textile industry. Specifically, we sought to characterize the chlorine-induced degradation products of an aqueous madder solution and to assess their ecotoxicity. The main component of the present madder sample was Alizarin (89.8%). Chlorination led to complete decolorization, and 2-hydroxynaphthalene-1,4-dione and phthalic anhydride were identified as key degradation products. Chlorination of madder decreased toxicity to Daphnia similis (microcrustacean) 10-fold and removed the toxicity to Raphidocellis subcapitata (algae), when compared to the parent dye.