The protection of the environment and pollution control are issues of paramount importance. Researchers today are engrossed in mitigating the harmful impacts of petroleum waste on the environment. Lubricating oils, which are essential for the smooth operation of engines, are often disposed of improperly after completing their life. In the experimental work presented in this paper, deteriorated engine oil was regenerated using the acid treatment method and was reused in the engine. The comparison of the properties of reused oil, the engine’s performance, and the emissions from the engine are presented. The reuse of regenerated oil, the evaluation of performance, and emissions establish the usefulness of the regeneration of waste lubricating oil. For the used oil, total acid number (TAN), specific gravity, flash point, ash content, and kinematic viscosity changed by 60.7%, 6.7%, 4.4%, 96%, and 15.5%, respectively, compared with fresh oil. The regeneration partially restored all the lost lubricating oil properties. The performance parameters, brake power (BP), brake specific fuel consumption (BSFC), and exhaust gas temperature (EGT) improved with regenerated oil in use compared with used oil. The emissions CO and NO_X contents for acid-treated oil were 9.7% and 17.3% less in comparison with used oil, respectively. Thus, regenerated oil showed improved performance and oil properties along with significantly reduced emissions when employed in an SI engine.

This study was carried out to evaluate the suitability of polyethylene foam as disc material for rotating biological contactors (RBC). Effect on DO levels due to change in RPM and submergence was also investigated. For this purpose, a pilot-scale model of RBC was constructed. The model was operated at 3, 5 and 7 RPM with varying submergence of discs, i.e. 30, 40, 50, 60 and 70%. Domestic sewage was used to run the model. Different parameters like pH, DO, total suspended solids (TSS), BOD and COD were monitored for the influent and effluent of pilot-scale RBC under varying operating conditions. Optimum values of submergence and RPM were found to be 40% and 5 RPM, respectively. BOD and COD removal, under optimum conditions, were 85.7 and 67.6%, respectively. The effluent concentrations for BOD and COD, under optimum conditions, were 42 and 124 mg/L, respectively, meeting the national effluent standards, with DO level of 4.6 mg/L. New disc material used costs US$ 0.38, while conventionally used material, i.e. polystyrene costs US$ 1.91 per square metre. Due to lesser weight energy consumption of newly proposed material is 26 kWh/m³/year while for Polystyrene it is 96.6 kWh/m³/year, no wear and tear of material was found after a continuous run of 90 d. Analysis of variance showed that submergence has more dominant role in raising DO levels as compared to RPM.

This paper evaluates the feasibility of bioethanol production from onion waste by Saccharomyces cerevisiae and Pichia pastoris and their novel co-culture through fermentation. The process parameters were optimized for each strain and their combination to observe the synergistic effect of co-fermentation. A dinitro salicylic acid (DNS) test was conducted to study the reducing sugar content of samples at different time intervals. Fourier transform infrared (FTIR) spectroscopic analysis was used to compare results for functional groups of samples before and after fermentation, and gas chromatography with flame ionization detection (GC-FID) analysis was performed to measure the bioethanol concentration obtained at different combinations of pH (5, 5.5, 6), temperature (20 °C, 30 °C, 40 °C), and time (24–110 h). The maximum bioethanol concentration was achieved through a monoculture of Saccharomyces cerevisiae, i.e., 30.56 g/L. The ethanol productivity was determined based on the ethanol concentration and fermentation time ratio. The energy content was determined using the obtained ethanol value and the specific energy content of ethanol, i.e., 30 kJ/g. The productivity and energy of bioethanol obtained at this maximum concentration were 0.355 g/L h and 916.8 kJ/L, respectively, after 86 h of fermentation at 30 °C and pH 5. Pichia pastoris produced a maximum of 21.06 g/L bioethanol concentration with bioethanol productivity and energy of 0.264 g/L h and 631.8 kJ/L, respectively, after 72 h of fermentation at 30 °C and pH 5. The coculture fermentation resulted in 22.72 g/L of bioethanol concentration with bioethanol productivity and energy of 0.264 g/L h and 681.6 kJ/L, respectively, after 86 h of fermentation at 30 °C and pH 5. The results of reducing sugars also supported the same conclusion that monoculture fermentation using Saccharomyces cerevisiae was the most effective for bioethanol production compared to Pichia pastoris and co-culture fermentation.

Despite the reported occurrence of several disinfection by-products (DBPs) in swimming pools, it is challenging to identify important DBP species due to strewn and conflicting information about their occurrence and importance in the literature. There is a need to provide clear direction and decisive information to support regulators' and pool facilities' efforts to control DBPs. In this review, alongside providing detailed occurrence data, we have developed a novel prioritization approach to classify DBPs as Tier-1 (critical priority), Tier-2 (medium priority), and Tier-3 (low-priority) DBPs in chlorinated indoor swimming pools (ISPs). After compiling an exhaustive database of published literature on chlorinated ISPs, DBP species were evaluated on a defined scoring system based on their occurrence (concentration levels and reported frequency) and toxicity. The normalized aggregated scores from these criteria were used to prioritize the DBPs. The DBPs identified as Tier-1 species with the highest occurrence and potential toxicity include Trichloromethane (TCM), Trichloroacetic acid (TCAA), and Dichloroacetic acid (DCAA). Respectively, ten DBP species were identified in Tier-2 and fifteen in Tier-3. Implications of the prioritization results for regulatory agencies, pool facilities, and researchers have been provided. Furthermore, a comparative analysis of the available studies, that described the correlation of water quality and pool operational factors with Tier-1 DBPs, was carried out. The identified critical factors include the number of swimmers, free residual chlorine, disinfection methods, total organic carbon (TOC), and temperature. These factors can be used to control the formation of DBPs and reduce the associated risk, especially for Tier-1 species.