Recent developments in the reuse of agricultural residues/resources have led to environmental sustainability and cleaner technology emphasizing the utilisation of natural resources. Novel approaches to sustainable and energy conservations inter-relates the scientific and practical applications employed in engineering solutions. The increasing importance of biomass had led to an acute need for mitigating global sustainable problems. In the third world economics, Rice Husk (RH) collected from rice milling industry is considered as one of the abundant and invaluable agro-based residues. A focus on industrial food production and its sustainability is due to the generation of huge quantity of RH. The improper handling and disposal management of RH has resulted in environmental and population health risk, due to its large space occupancy and leaching. The effective utilization and study of rice husk in various industrial applications such as construction industry, energy production, water purification and soil stabilization have shown acceptable results. This review discusses the current research works focussing on the suitability of RH and its ash over a wide field of applications. Silica being the dominant content in RH and Rice Husk Ash (RHA) has attracted interest among the researchers to develop it into high strength composite materials, porous nanomaterials, a precursor of renewable energy and soil stabilising biochars. Replacement of fine aggregates with RHA has improved the strength and durability of the concrete. The RHA is also developed into an adsorbent and coagulant in water purification. The binding between the ions present in impure water and highly reactive silica bond enhances the removal efficiencies of metal ions in water treatments. Very few researches are carried out using RH compared with the pyrolyzed RHA as an alternative. This paper highlights the various field of RH applications and suggests composting of RH with nitrogen-rich garden waste to obtain an enriched soil stabilizing product with high nutrient and organic value. This approach would restore RH in its the place of generation, thereby improving the economic value of the agricultural mass and sustainable way of living.

The present study aimed to develop the activated carbon from fruit waste like sapota peel and to optimize the condition of developed activated carbon for complete removal of lead ions from the desired concentration of a lead solution. The activated carbon was prepared from sapota peel by using sulphuric acid. The physicochemical characterization of the obtained activated carbon was done for various parameters along with analysis of crystal nature (XRD) and structural morphology (SEM). The optimum conditions for adsorption were studied by altering pH (2-10), agitation speed (50-250 revolution per minute), temperature (10-60°C), adsorbent dose (0.02-0.14 g) and contact time (30-240 minutes). The optimized conditions necessary for complete removal of lead ions by the prepared adsorbent were pH - 5.5, agitation speed - 200 revolutions per minute, temperature - 60°C, time - 3 hours and adsorbent dose - 0.12 g. This study can be further helpful in designing the process of wastewater treatment for the removal of toxic metals from water particularly lead by adsorption.

The online spectrophotometric technique was adopted to monitor the degradation of simulated Acid Light Yellow 2G (ALY 2G) solution with the Fenton oxidation process, and the kinetic process was also discussed. The effects of the initial concentration of H2O2 and Fe2SO4, pH value, and initial dye concentration on the degradation process were studied. The results showed that the ALY 2G can be degraded by Fenton oxidation, and the colour removal rate of Acid Light Yellow 2G was 94.66% after 300 s when the concentration of simulated wastewater was 20 mg/L, the dosage of Fe2+ was 0.1 mmol/L, the dosage of H2O2 was 0.6 mmol/L, and the pH was 3. The degradation process was divided into two stages: the first stage, the degradation rate is very fast; in the second stage, with the extension of reaction time, the increase of decolourization rate decreases. The first stage of the reaction accords with the first-order kinetics, and the reaction rate constant Kap is 0.04824 s-1. The intrinsic reaction rate constant of ALY 2G and hydroxyl in aqueous solution in the Fenton oxidation method is 0.55 ×109 M-1s-1.

An assessment of heavy metal concentration in wild-captured Macrobrachium rosenbergii (giant freshwater prawns) from their natural habitat is important since it is susceptible to environmental pollution due to the rapid development and human activities along the Sarawak River. This study aimed to estimate the heavy metal contamination in muscles, exoskeletons and gills of the M. rosenbergii and to estimate the health risk assessment to human consumption. The concentration of heavy metals was analyzed by the flame atomic absorption spectrophotometer and the flow injection mercury system. The metal concentrations in prawns were detected in the following order: Hg < Cd < Co < Cu < Zn; in all body parts (P < 0.05), where a high concentration of metals was recorded in gills due to its function as the excretion site of contaminants from the body. A positive correlation of Co, Cu, and Zn in muscles and gills was observed with the increasing size of prawns. The human health risk assessment indicated a less potential adverse health effect of prawns for consumption from Sarawak River (hazard index values < 1). All samples contained metals below the Joint FAO/WHO Expert Committee on Food Additives (JECFA) permissible limit for human consumption (Cd < 2 mg/kg; Cu < 30 mg/kg; Zn < 150 mg/kg; Hg < 1 mg/kg). Therefore, M. rosenbergii from the Sarawak River were not contaminated enough to prevail high risk on human health, but regular monitoring is suggested for seasonal variability of heavy metals in M. rosenbergii for safeguarding human health.

Tank systems are essential for the agricultural growth and the livelihood of rural populations in India. Comprehending the multiple benefits from these traditional systems, tank rehabilitation has been one of the policy significances at the state level. The study was undertaken with the objective of assessing the impact of tank rehabilitation on cropped area, cropping pattern change, cost returns and income of farmers in a selected study village of south Tamil Nadu. The study was conducted on the basis of primary data obtained from 102 sample farmers belonging to “Pelasur” village of Thiruvannamalai district in south Tamil Nadu using a stratified sampling method. There was a significant difference in the cropped area, cropping intensity and irrigation intensity among the farmers before and after tank rehabilitation. It is found that there is an increase of 41.02 ha cultivated area and an increase in the net amount of Rs. 7,99,945. Many farmers shifted from paddy to sugarcane (cash crops) cultivation due to the availability of excess surface water in the tank and improved water table in their wells. Cropping intensity has been increased to 26% in the post-rehabilitation period. Thus, investment in tank rehabilitation shows a positive implication on marginal farmers and landless labours. Using SPSS, a paired-sample t-test is applied for analysing data collected from respondents.

In line with the 2015 Paris Agreement, the present study examines the efficiency of Iran’s electricity industry compared to world standards. In 2018, Iran is ranked second in the world in terms of direct subsidies to the electricity industry, while subsidies for fossil fuels as the main feedstock for power plants are also higher. The results of the study indicate that despite the privatization of the electric industry since 2005, centralized economic management and the provision of extensive direct and indirect subsidies have led to the expansion of inefficiencies in the production and consumption of electricity. Lack of cost-based pricing is a major factor in the production of inefficient units and the determination of electricity prices at very low levels (as a result of subsidies) is the main reason for the inefficient use of electricity in Iran. The undeniable role of fossil fuels in energy production has stabilized Iran’s second-largest power plant sector in CO2 emissions in the Middle East, and as a consequence of no noticeable changes in the energy production process, the carbon intensity index and carbon intensity for electricity consumption, have fluctuated slightly. However, the energy intensity and energy intensity for electricity consumption, unlike the developed countries, have shown an upward trend, indicating a decline in energy and electrical energy efficiency in the Iranian economy. The index of fundamental reforms in electricity production, exactly the reverse of the successes in Iceland, Switzerland, Norway, Sweden and Luxembourg, is less than 8%, which is against sustainable development goals. It is crucial to take advantage of countries’ successful experiences in electricity price reform and to address the four key components proposed.

Industrialization, urbanisation and agricultural development cause pollution in water bodies due to the discharge of wastewater directly or indirectly. The present study aims to assess the water quality of water bodies in and around A D Nagar, Badharghat, Dukli and Budhjungnagar Industrial Estates, West Tripura during pre-monsoon and post-monsoon in the year 2016 to 2018. Biological parameters namely DO, BOD, Total Coliform, Faecal Coliform and COD, Physico-chemical parameters namely pH, EC, TDS, Bicarbonates, Chlorides, Sulphates, Total Hardness, Calcium, Magnesium etc. and heavy metals were analysed using standard methods as prescribed by APHA. The analysed parameters were compared with the standards prescribed by BIS. The BOD values for all the water bodies were beyond the prescribed standard limit except the pond located at the southern side of Jutemill, Hapania (S-3) during pre-monsoon season. The Total Coliform values for water bodies located at the eastern and northern side of Badharghat Industrial Estate were beyond the prescribed standard limit. The seasonal variations of water quality have also been observed. Water Quality Index values reflected that the 75% of surface water samples were of poor quality and 25% were of good quality in both the season. Correlation study revealed that positive and significant correlations between the pairs of selected parameters in surface water samples were observed. This study reveals that the surface water of these water bodies needs proper treatment before consumption and it also needs to be protected from the domestic as well as industrial contamination.

In this study, the applicability of electrocoagulation using iron electrodes in real dyeing wastewater treatment was assessed based on pollutants removal efficiency, sludge generation, energy consumption and operation cost in practice. The effects of current density, pH, conductivity, and reaction time on treatment performance were evaluated. The operation cost of electrocoagulation was calculated including the energy cost, the iron plate cost, generated sludge treatment cost, and added substances cost. The results indicated that the colour, CODcr and TSS removal efficiencies were high and quite stable with short reaction time (reached 92.07 ± 1.21%, 65.7 ± 1.47%, and 89.8 ± 1.2%, respectively, with only 15 min). Average sludge generation, specific energy consumption, and operation cost were determined respectively as 0.645±0.0543 kg/m3, 1.182 kWh/m3 and 0.517 USD/m3. Coagulation-flocculation using FeSO4 was performed as a control experiment as well. Compared to coagulation-flocculation, electrocoagulation has the same removal efficiency but has less generated sludge (only 50%) and little to no added chemicals. Therefore, the operating cost was quite less than the others, with only 0.517 USD/m3 instead of 1.99 USD/m3 (equal to 1/3.5).

Water resource ecological safety is a key factor in regional economic and social development. The comprehensive evaluation of water resource ecological safety is an important precondition for realizing regional sustainable development with the increasingly serious water ecological crisis. Zhoushan City of China was taken as an example, and the pressure–state–response model (PSR) was used to evaluate the ecological safety status of regional water resources, improve deficiencies in the existing evaluation index system and evaluation method effectively, and put forward three evaluation subsets (18 evaluation indexes). An evaluation index system was established based on these indexes to evaluate the water resource ecological safety. Combined weights of indexes were calculated using the analytic hierarchy process (AHP) and entropy weight method, and water-resource ecological safety indexes were used to evaluate the water-resource ecological safety status in Zhoushan City during 2010–2019. Results show that the water-resource ecological safety level in Zhoushan City during 2010–2019 presents a rising trend and transformed from a serious warning state into a medium warning state as well as a relatively safe state and safe state. This transformation indicates that the ecological safety status in Zhoushan City gradually improves. The comprehensive evaluation value is the minimum (0.15) under the serious warning state in 2013 and the maximum (0.85) under the safe state in 2019. Ammonia nitrogen and chemical oxygen demand (COD) emissions in industrial wastewater, total water supply throughout the year, and governance area of water and soil loss are the main factors that influence the water resource ecological safety in the city. The ecological safety level of regional water resources can be effectively elevated through key measures, such as increasing the water resource supply throughout the year, reducing the application of pesticides and chemical fertilizers, and reducing the discharge of pollutants, including COD and ammonia nitrogen in industrial wastewater. The water resource ecological safety evaluation model based on the PSR model and AHP–entropy weight method that demonstrates a certain application value can provide a novel idea and method to support the ecological safety evaluation of regional water resources.

The possibility of replacing the inorganic medium with tropical organic fruit waste medium as a nutrient supplement was evaluated for the cultivation of Chlorella vulgaris and Haematococcus pluvialis in this study. Various concentrations of tropical fruit waste medium such as papaya, pineapple and mango were prepared to cultivate microalgae of C. vulgaris and H. pluvialis. The biomass concentration, productivity and specific growth rate were determined and compared with those grown in a fully inorganic medium. For C. vulgaris, the use of a 20% tropical fruit waste medium was found to yield higher biomass concentration (4.133-4.533 g/L) compared with cultivation in a fully inorganic medium (3.400 g/L). For H. pluvialis, the use of a 10% mango waste medium was found to yield a similar biomass concentration compared with cultivation in a fully inorganic medium (3.400 g/L). These results unveiled the potential of utilizing with tropical organic fruit waste medium as an effective strategy to reduce the cultivation cost of microalgae and treat the tropical fruit waste prior to discharge to the environment.