Effects of the Combined Utilization of Ultrasonic/Hydrogen Peroxide on Excess Sludge Destruction

Excess sludge reduction has been a research hotspot for a long time. Ultrasonic treatment of excess sludge was an efficient and green pretreatment method, and also can be combined with the addition of oxidants. To improve the effect of ultrasound treatment on sludge destruction, hydrogen peroxide (H2O2) was added to examine the combined results in the current study. The effects of the ultrasound/hydrogen peroxide system on the release of sludge organic matter during the destruction process were studied. Single-factor experiments were carried out to determine the optimal operating conditions. With the initial pH of 11.0, H2O2 concentration of 0.5 mmol/L, initial sludge concentration of 17 g/L, and 15 min ultrasonic treatment, the maximum soluble chemical oxygen demand (ΔSCOD) in the sludge supernatant after destruction was achieved at 3662.78 ± 239.21 mg/L, with a disintegration degree of 28.61 ± 2.14%, sludge reduction rate of 19.47 ± 0.82%, and the change of mixture sludge concentration (ΔMLSS) of 3.31 ± 0.06 g/L. Meanwhile, the release of nitrogen and phosphorus were greatly improved. Under the optimal conditions, the release of total nitrogen (TN), ammonia nitrogen (NH3-N) and total phosphorus (TP) were 282.30 ± 24.06 mg/L, 25.68 ± 2.09 mg/L, and 105.69 ± 7.84 mg/L, respectively. The current work had provided solid evidence showing the addition of hydrogen peroxide can effectively strengthen the treatment effects of ultrasound on sludge destruction.

Enhancing the Economic Viability of Anaerobic Digestion by Exploiting the Whole Biomass of Mango Waste and Its Residues after Digestion

A significant expansion of anaerobic digestion (AD) processes would certainly result in a reduction in the current dependence on fossil fuels. The operational costs, the large amounts of digestate generated and the expenses of dealing with it and the volatility of the fuel indexes represent major environmental and economical challenges to the diffusion of AD. Increasing the bio-products of AD could possibly help in increasing its profitability and limit these challenges. This study investigates the influence of mango starch and seed coats on the biogas produced from mango waste. To overcome the environmental challenges, the digestate was tested and its bio-fertiliser potential proven. The study reached the conclusion that the effect of the starch on the AD biogas of mango waste is low while the effect of the seed coats is quite high. This finding supports further investigations to evaluate the effect of the production of mango starch and seed coat-based products on the profitability of AD. The highest energy balance achieved was 65% at 32 °C, 3.93 g-VS organic concentration and 37% sludge concentration, which yielded a maximum CH4 yield of 62.5%. This finding encourages the application of gate fees for accepting bio-waste, which may help in overcoming its economic challenges.

Optimum Organic Loading Rate in the Biomethanation of a Mixture of Cow Dungs and Poultry Droppings

The effect of varying the organic loading rate in the digester volume using a mixture of poultry droppings and cow dung as biomass was studied. The study was aimed at determining the optimum organic loading rates, which would produce the maximum volume of biogas from a mixture of poultry droppings and cow dung. The pH was maintained between 6.8 and 7.2. All other parameters affecting the production of gas were kept constant except the organic loading rate. The wastes, poultry droppings and cow dung was mixed in the ratio 60:40 and maintained at a sludge concentration of 700g/l. It was observed that biogas produced from the digester with the organic loading rate of 2.8 kg vs/m3/day gives the highest proportion of methane and the digester with organic loading rate of 3.2 kg vs/m3/day produced the highest proportion of carbon dioxide.

Toxicological Effects of Petroleum Refinery Sludge on the Terrestial Environment Using Bacteria and Earthworm as Bio Indicators

Aim: The aim of the study is to assess the sublethal (chronic) Ecotoxicological effects ofpetroleum refinery sludge pollution on the biota of the terrestrial environment using the effects on bacteria nitrogen transformation activity and growth rate of the soil fauna, Earthworm (Aporrectodea longa) as bioindicators. Place and Duration of Study: Department of Environmental Management and Toxicology, Federal University of Petroleum Resources, Effurun, between 2017 and 2018. Methodology: The OECD TG 216 (2000) test method was used to determine the chronic effects (% inhibition and EC50) of the petroleum sludge on the nitrogen transformation activity of Nitrobacter sp. in the soil, while the methods of Sandoval et al. [13] and OECD, 207 was used for the chronic effects of the sludge on the growth rate of the earthworms. Bioconcentration factor (BCF) of the sludge in the earthworms was also determined. Both tests were conducted for 28 days. Results from the test with multiple concentrations were analyzed using a regression model (ANOVA). EC5O was also determined using the Probit analytical software. Analyses weredone using ASTM methods. Results: Analysis of the Nigerian petroleum refinery sludge used for this research indicated that the sludge wasacidic with a pH value of 5.91and had a high TPH content of 340,000 mg/kg made mainly of between 10-40 carbon unit compounds. There was a progressive increase in the percentage (%) inhibition of the nitrogen transformation activitiesof the bacteria, from 18.0% (3125 mg/kg) to 79.30% (5000mg/kg) with increase in concentration and time. The effective concentration that decreased 50% (EC50) of the nitrogen transformation activity was 13761.059 mg/kg. The growth rate of the test earthworms decreased from 9.19x103 g/day (375 mg/kg) to 3.55x103 g/day (3000 mg/kg) for the test period. The BCF decreased from 5.168 (375 mg/kg) to 1.22 (3000 mg/kg) in the earthworms, while the EC50for the earthworms was 825.02mg/kg as the concentration of the sludge increased with time. Conclusion: The sludge inhibited the nitrogen transformation activity of Nitrobacter sp. because it exceeded the 25% inhibition limit for chemicals with the potential to cause chronic effects on soil microbial activities as specified in OECD TG 216. Similarly, the sludge reduced the growth rate of the earthworm progressively as the sludge concentration increased in relation to the control. Bioaccumulation factor also increased with increasing sludge concentration and time.

Analysis of Influencing Factors for Leaching of Acrylamide Monomer from Polyacrylamide-Based Flocculants Used in the Treatment of Sludge Dewatering

Acrylamide (AM) monomer is one of the harmful type substance, are commonly using to produce polyacrylamide (PAMs) flocculants for water treatment. Because of incomplete polymerization, the molecules of AM monomers also in exit marketable polymers. Therefore, discharge of AM from the usage of PAM based polymers flocculants in to environment. Currently study focus on, the AM leaching behaviour (emulsion and powder) polymer produced by two different production processes was studied with WTP sludge dewatering as the research object. The flocculants type's effects, Concentration of sludge and dosage on the discharge of AM residual monomer in sludge dewatering effluent were studied. The powder form flocculants results show, the regardless of the flocculants concentration and sludge concentration, the leaching concentration is not significant, but in the emulsion flocculants, the leaching concentration changes significantly. The Monomers of residual acrylamide be absorbed on the surface of sludge. Sludge concentration plays an active role in improving dehydration efficiency. Considering the trade-off between emulsion and powder polymer, the results of this study are related to the water treatment process.