Applicability of Nickel-Based Catalytic Systems for Hydrodehalogenation of Recalcitrant Halogenated Aromatic Compounds

This review summarizes recent applications of nickel as a nonprecious metal catalyst in hydrodehalogenation (HDH) reactions of halogenated aromatic compounds (Ar–Xs). Nickel-based HDH catalysts were developed for reductive treatment of both waste containing concentrated Ar–Xs (mainly polychlorinated benzenes) and for wastewater contaminated with Ar–Xs. Ni-catalyzed HDH enables the production of corresponding nonhalogenated aromatic products (Ar–Hs), which are principally further applicable/recyclable and/or Ar–Hs, which are much more biodegradable and can be mineralized during aerobic wastewater treatment. Developed HDH methods enable the utilization of both gaseous hydrogen via the direct HDH process or other chemical reductants as a source of hydrogen utilized in the transfer of the hydrodehalogenation process. This review highlights recent and major developments in Ni-catalyzed hydrodehalogenation topic since 1990.

A Review on the Methods of Industrial Waste Water Treatment

Nowadays environmental pollution is a great threat to us. Water resources are mostly polluted by industrial wastes. Among all other pollutions, water pollution is one of the most vital pollution caused by different sources like industrial, domestic, sewage, hazardous waste, municipal waste, medical waste, manufacturing waste, etc. Public concern over the impact of wastewater has increased. There are several methods for the treatment of wastewater. Among them, techniques like coagulation, adsorption, activated sludge are prominent. The use of aerobic wastewater treatment as a reductive medium is receiving attention for its low cost of operation and low cost of maintenance. The uses of low-cost adsorbents are also effective in wastewater treatment. The aerobic wastewater is effective in degrading the contaminants. There are different electrolytic techniques as well for wastewater treatment. This paper reviews the possible techniques available for the treatment of wastewater to remove contaminants such as halogenated hydrocarbon compounds, heavy metals, dyes, pigments etc. from the wastewater.

Microalgae cultivation in wastewater effluent from tilapia culture pond for enhanced bioethanol production

The large number of wastewaters are generated because of the various production processes. Vegetable and fish processing can be considered an important industry for wastewater generation. The essential method for completing this waste is to digest the organic matter using anaerobic digestion followed by aerobic wastewater treatment processes; however, wastewater from tilapia culture pond retains considerable quantities of inorganic substances, particularly nutrients like nitrogen and phosphorus. The optimal conditions for cultivating Chlorella vulgaris from wastewater treatment effluent from tilapia culture pond were investigated in this study. The appropriate conditions were found to be 10% initial stock suspension, 20 cm depth, and 12 days of culture conditions. C. vulgaris had an optical density of 0.649, a cell density of 17.68 × 105 cells/mL, and biomass of 0.376 ± 94.21 mg/L after cultivation. Discharged wastewater from the fishpond was utilized for the improved growth of microalgae and obtained biomass was used for bioethanol production. This study verified that fishpond wastewater is the best source of nutrients for algal mass production and biofuel applications.

Nitrous oxide emissions during microalgae-based wastewater treatment: current state of the art and implication for greenhouse gases budgeting

Microalgae can synthesise the ozone depleting pollutant and greenhouse gas nitrous oxide (N2O). Consequently, significant N2O emissions have been recorded during real wastewater treatment in high rate algal ponds (HRAPs). While data scarcity and variability prevent meaningful assessment, the magnitude reported (0.13–0.57% of the influent nitrogen load) is within the range reported by the Intergovernmental Panel on Climate Change (IPCC) for direct N2O emissions during centralised aerobic wastewater treatment (0.016–4.5% of the influent nitrogen load). Critically, the ability of microalgae to synthesise N2O challenges the IPCC's broad view that bacterial denitrification and nitrification are the only major cause of N2O emissions from wastewater plants and aquatic environments receiving nitrogen from wastewater effluents. Significant N2O emissions have indeed been repeatedly detected from eutrophic water bodies and wastewater discharge contributes to eutrophication via the release of nitrogen and phosphorus. Considering the complex interplays between nitrogen and phosphorus supply, microalgal growth, and microalgal N2O synthesis, further research must urgently seek to better quantify N2O emissions from microalgae-based wastewater systems and eutrophic ecosystems receiving wastewater. This future research will ultimately improve the prediction of N2O emissions from wastewater treatment in national inventories and may therefore affect the prioritisation of mitigation strategies.