Eco-innovations and sustainability in solid waste management: An indian upfront in technological, organizational, start-ups and financial framework

Technological interventions and eco-innovative solutions are necessary to cope with the adverse environmental impacts of waste accumulation. The notion to consider "waste as a resource and recycling of the same for getting the value of the waste" has truly transformed the approach towards solid waste management (SWM). Technological eco-innovations rely on the automation of waste segregation, collection, route optimization, digital apps for creating communication (enhanced efficiency by 40-85%) and treatment technologies. The regulatory framework with amendments in rules, new policies, schemes, smart city missions are responsible for the implementation of "Tech-innovations" at the ground level and has shown societal benefits. India has significantly shown progress in sustainable development goals (SDGs) score from 50.93 to 60.23 (year 2000-2019). The innovative and sustainable waste management practices in India have increased contribution to renewable energy (approx. 2554 MW/annum), 15-billion-USD business opportunity by the circular economy, 25-30% resale profit from processed E-waste, increased co-operative collaborations, trailblazing start-ups, improved SDG 3,7,8,9,11,12,13, improved market for green products and services, brilliant institutional and regional innovations addressing the issue of climate change. The present article critically reviews the exemplary eco-innovations (technological and non-technological) including resource recovery and viable technologies for SWM in India. The review also illustrates the lacunae (in awareness, bioproducts adoption and advanced technologies), recommendations based on findings and future research areas. The paper can also assist researchers, entrepreneurs and the policy makers for improving the status of SWM in India as well as other developing countries with the same societal and economic status.

Traffic noise prediction model of an Indian road: an increased scenario of vehicles and honking

Noise is considered as an underrated and underemphasized pollutant in contrast to other pollutants of the environment. Due to the non-acute response of health effects, people are not vigilant towards consequences regarding noise pollution. The expansion of the transportation industry is contributing towards the increment in the public and private vehicular volume which causes an increment in noise pollution. For evaluation of respective scenario, the research study has been conducted on one of the minor roads of Nagpur, India; for 2 years, viz., 2012 and 2019. The study concludes an increment of 5-6 dB(A) in noise level, 4-6 times in honking, and 1.7 times in traffic volume. The study confirms increment in sound pressure by 65.9% and 81.9% for the year 2012 and 2019 during morning and evening sessions, respectively. Noise prediction model has also been developed for the abovementioned years, using multiple regression analysis, considering traffic volume, honking, and speed against noise equivalent level. Honking has been further characterized into honk by light and medium category vehicles as acoustical properties of horns vary with respect to category of vehicle and introduced into the noise prediction model. Noise prediction model for 2019 has predicted the noise level in a range of - 1.7 to + 1.4 dB (Leq) with 84% of observations in the range of - 1 to + 1 dB (Leq), when compared with observed Leq on the field. For proper management of noise pollution, a noise prediction model is essentially needed so that the noise level can be anticipated, and accordingly, measures can be outlined and executed. This increased noise level has serious impacts on human hearing capacity and overall health. Accordingly, noise mitigation preventive measures are recommended to control traffic noise in the urban environment.

Hydrodynamic cavitation using vortex diode: An efficient approach for elimination of pathogenic bacteria from water

The present study successfully demonstrates greener methodology of hydrodynamic cavitation using rotational flows for disinfection of water. Disinfection of two model microbial strains-gram- negative (Escherichia coli) and gram-positive (Staphylococcus aureus) using vortex diode was evaluated. The removal efficacy was quantified for two different cavitation reactors. Practically complete elimination of E. coli was achieved (99%) after 1 h of cavitation at a pressure drop of only 0.5 bar. However, elimination of S. aureus using vortex diode was observed to be lower in comparison to the removal of E. coli and only 60% disinfection could be achieved under similar conditions, which can be subsequently enhanced up to 98% by increasing pressure drop. The results were compared with another cavitating device that employs linear flow for cavitation, orifice. The reactor geometry has significant impact on the disinfection process and orifice was found to require significantly higher pressure drop (10 bar) conditions for disinfection and for eliminating gram-positive bacteria with high efficiency. A plausible mechanism for disinfection was proposed to elucidate the role of cavitation in cell destruction leading to death of cells through the rupture of cell wall, oxidative damage and possible DNA denaturation. Also, a cavitation model using per pass disinfection was developed that can provide meaningful physical description of the disinfection process as against the conventional first order reaction rate model. This study would provide meaningful insight into cavitation process based on hydrodynamic cavitation for the destruction of both gram-negative and gram-positive bacteria from various water sources, including industrial wastewaters.

Experimental models for defluoridation

The effect of some parameters such as the flow rate, initial solute concentration and column bed depth on fluoride removal by fishbone charcoal in a fixed bed column and continuous flow operation was investigated. The useful (or effective) treated effluent volume (corresponding to the desired breakthrough concentration of 1.0 mg/L of fluoride, in this study) is found to be a function of the flow rate, initial solute concentration and column bed depth. The useful treated effluent volume decreased with an increase in the flow rate and initial fluoride concentration but it increased with the column bed depth. Empirical relationships have been developed to predict the stated useful treated effluent volume for the known values of flow rate, column bed depth and initial fluoride concentration for the observed test conditions. The relationships evolved manifest high correlation coefficients.

Applicability of alkaline method to alum recovery from waste stabilization pond sludge

In this paper, the results of laboratory experiments carried out for the recovery of alum from the sludge obtained from the tertiary treatment of effluent collected from waste stabilization pond have been discussed. The effluent had suspended colloidal impurities. The laboratory test results revealed that at pH 12.0, alum recovery of 79.90% was obtained which made the recovery of alum from sludge practically feasible and economically viable option.

Applicability of liquid ion exchange to alum recovery from waste stabilization pond sludge

This paper reports the evaluation of the tertiary application of relatively low doses of alum for improving the overall performance and reliability of existing wastewater treatment plants. With this type of system, the additional capability for phosphorus removal is imbibed by simply altering the chemical dose. The study was conducted on wastewater from a Stabilization pond having capacity of 54 mld, which was treating municipal wastewater from Ujjain city. The wastewater had suspended colloidal impurities.