Treatment Tanks Research Articles

Experimental study into the sedimentation process of solids of different origin

Sedimentation refers to the first stage of wastewater treatment from mechanical impurities. Its rate depends on the density and particle size of impurities, as well as the density and viscosity of dispersion medium. In industrial sedimentation tanks, particle settling can occur in laminar, transient or turbulent modes. Aim. To establish the criterion equations and their coefficients for sedimentation processes of sand, glass and polyamide granules. Sedimentation of sand particles of 0.001– 0.003 m, spherical glass particles with the diameter of 0.0025–0.004 m and polyamide granules with the volume-surface mean diameter of 0.0022–0.003 m was carried out in a measured glass cylinder filled with distilled water. Each solid particle was measured, then, it came into contact with the water surface by means of tweezers, and released, starting to settle to the bottom of the cylinder under the action of gravity. A stopwatch was used to time the particle passaging between the marks of the measured cylinder. Calculations were performed using dimensional analysis. According to the test results, the dependences of the Reynolds number on the Archimedes number were established for the sedimentation of sand particles and polyamide granules in the transient mode, while spherical glass particles in the turbulent mode. In addition, the criterion equations of the solid particles sedimentation in the liquid were derived. The coefficients for these equations were experimentally determined. The equations and coefficients obtained in the study can be used in the design of settling tanks for mechanical treatment of wastewater to remove sand, glass and polymer particles.

Diffusion behavior and environmental impact of odorants and TVOCs detected in a wastewater treatment plant for collaborative leachate treatment in Northwest China

Wastewater treatment plants (WWTPs) are major sources of volatile gaseous compounds, especially in mixed-source systems such as domestic wastewater and landfill leachate. This study aimed to investigate the emission behavior and environmental impact of gaseous substances, such as hydrogen sulfide (H2S), ammonia (NH3), carbon sulfide (CS2), and phosphine (PH3), at a WWTP in Northwest China. Odorants were detected in the air surrounding the grid room (XGS), biochemical treatment tank (SHC), secondary sedimentation tank (ECC), and sludge dewatering room (NTS). For comparison, the upwind boundary (O-SF) and downwind boundaries (O-XF) monitoring points were used, with odor concentrations ranging from 3.95 to 725.27 odor units. The concentration ranges of the odorant substances were 5.27–88.69, 5.61–71.96, 5.70–32.63, and 0.12–5.87 mg/m3 for H2S, NH3, CS2, and PH3, respectively. Meteorological factors such as temperature, relative humidity, and wind speed and direction substantially influence odorant emissions. The concentrations of various odorants and volatile organic compounds (VOCs) detected at the O-XF monitoring point were higher than those detected at the O-SF monitoring point, indicating that the wind intensified their diffusion toward the downwind plant boundary. The average odor intensities of odorant substances emitted from wastewater or sludge treatment equipment were 3.37, 5.09, 4.42, 2.00, and 3.82 for total VOCs, H2S, NH3, CS2, and PH3, respectively. Among them four, with downwind diffusion, only H2S presented olfactory and chronic toxicity risks based on Gaussian plume model calculations. The hazard index ranking across monitoring sites was XGS > NTS > SHC > ECC > O-XF > O-SF. These findings emphasize the urgent need for effective measures to control and mitigate gaseous pollutants emitted by collaborative WWTPS, thereby protecting environmental quality and public health.

The modeling tank for the adsorption wastewater treatment by different charcoal

The modeling tank for the adsorption wastewater treatment by different charcoal

One-year old European perch (Perca fluviatilis)-specific in vitro digestion studies in special regard to feed optimization

The aim was to investigate the effect of water temperature on digestive enzyme activities of perch, to determine at which temperature their digestion process is more suitable. European perch (Perca fluviatilis) (1 year old, 50–60 g, 10 cm) were kept in recirculation system with the stocking density of 9 kg/m3 in 150 litre-sized-tanks, at 16°C, 18°C, 20°C, 22°C. Fish were kept for 1 week acclimatization, starved for 72 hours before feeding (crude protein: 45 %, crude fat: 16 %, crude fiber: 2.6 %; digestible energy: 18.5 MJ). Feeding was twice, with a 6 hours interval. There were 3 tanks for each proper temperature treatment; every tank contained 100 fish. 10 fish were moved out from all the tanks (30 fish per treatments). Stomach, intestine of fish was separated and their walls were washed with 1 ml of distilled water (pH 2.5), with 1 ml of 50 mM Tris-HCl, containing 0.5 M NaCl, 20 mM CaCl2 (pH 7.8), respectively, to retrieve gastric and intestinal digestive extracts. Extracts were used for pepsin, trypsin. total alkaline proteolytic, lipase, α-amylase activity tests. We have succeeded in developing protocol for gaining enzyme-containing extracts to monitor the realistic physiological conditions of perch based on enzyme activity measurements. The protocol was considered to be easy to implement and to provide sufficient enzyme extract to simulate subsequent in vitro digestion. The ambient temperature affected enzyme activities significantly: pepsin (40480.14; 69245.91; 79305.86; 40236.32 U/mg protein), trypsin – (7.77; 9.88; 11.12; 5.42 U/mg protein), total alkaline proteolytic - (1.47; 1.14; 1.25; 0.84 U/mg protein), lipase – (0.40; 1.16; 0.72; 0.76 U/mg protein) and α-amylase (0.29; 0.395; 0.98; 1.17 U/mg protein) activities, respectively at 16, 18, 20 and 22°C. Based on protease activities, 18–20°C was chosen to be the most appropriate rearing temperature, which contributes the most to the proper growth of the fish.

Effects of dietary supplementation with benthic diatom Amphora coffeaeformis on blood biochemistry, steroid hormone levels and seed production efficiency of Nile tilapia Oreochromis niloticus broodstock.

Aquafeed additive quality and quantity remain pivotal factors that constrain the sustainability and progress of aquaculture feed development. This study investigates the impact of incorporating the benthic diatom Amphora coffeaeformis into the diet of Nile tilapia (Oreochromis niloticus) broodstock, on the blood biochemistry, steroid hormone (SH) levels and seed production efficiency. Broodstock females displaying mature ovary indications were initially combined with males at a ratio of three females to one male. A total of 384 adult Nile tilapia (288 females and 96 males) were used, with 32 fish (24 females and eight males) assigned to each of 12 concrete tanks (8 m³; 2 m × 4 m × 1 m), with three replicate tanks for each dietary treatment, throughout a 14-day spawning cycle until egg harvest. Fish were fed one of four different dietary treatments: AM0% (control diet), and AM2%, AM4% and AM6% enriched with the diatom A. coffeaeformis at levels of 20, 40 and 60 g/kg of diet respectively. At the trial's conclusion, total protein, albumin, triglyceride and creatinine), SHs (follicle-stimulating hormone, luteinizing hormone, free testosterone, total testosterone, progesterone and prolactin) and seeds production efficiency of Nile tilapia improved significantly (p < 0.05) in alignment with the increment of A. coffeaeformis supplementation. The findings propose that including A. coffeaeformis at levels ranging from 4% to 6% could be effectively employed as a feed additive during the Nile tilapia broodstock's spawning season.

Comparison of the density and composition of bacteria and fungi in the air of anoxic and aeration tanks in the wastewater treatment plant

The bioaerosols from the wastewater treatment plant can be propagated into the air, affecting the health of residents, animals, and plants around the area. This study was conducted to evaluate the density and composition of bioaerosols (bacteria and fungi) in anoxic and aeration tanks of a domestic wastewater treatment plant. Bioaerosol samples were taken by the active method with SKC Biostage. The agar dishes were placed at a height of 1.5 m above the ground. After sample collection, the dishes were incubated at 37 ±1 °C for 24h-48h for bacteria and at 25 ±1 °C for 72h-120h for fungi. Then, these microorganisms were identified by 16S rRNA (16S Metabarcoding) method for bacteria and taxonomy method for fungi. The results showed that the density of bacteria and mold in the anoxic tank ranged from 233.2 ±7.8 to 339.2 ±13.9 CFU/m3 and 91.8 ±3.2 to 197.9 ±10.1 CFU/m3, respectively. Meanwhile, bacterial and mold densities of aeration tank ranged from 275.6 ±10.4 to 424.0 ±17.3 CFU/m3 and 176.7 ±5.8 to 254.4 ±12.1 CFU/m3, respectively. The density of bacteria and mold in the aeration tank is higher than in the anoxic tank. On the other hand, the 16S Metabarcoding analysis for the microbial diversity detects more than 100 species in two tanks, the predominant bacterial species are: Bacillus megaterium (B. megaterium), Bacillus cereus (B. cereus), Staphylococcus sciuri (S. sciuri) and two common fungi Aspergillus tamarii (A. tamarii), and Penicillium rubers (P. rubers). This preliminary survey in Viet Nam reveals the existence and diversity of bioaerosols in the air from the biological treatment tanks of the wastewater treatment plant.

Uncovering the reasons behind high-performing primary sedimentation tanks for municipal wastewater treatment: An in-depth analysis of key factors

The paper presents a long-term and extensive pilot-scale study on the primary settlement of municipal sewage to produce an in-depth understanding relating sedimentation efficiency to surface load, hydraulic retention time (HRT), sludge withdrawal time (SWT), temperature (T), and influent solid mass (TSSmass). Besides, primary sludge (PS) was subject to qualitative and quantitative analysis, intending to explore its potential utilization in various applications. These applications encompass enhanced energy and heat generation through conventional anaerobic digesters and the elevated production of volatile fatty acids (VFAs) in hydrolysis reactors, particularly within the context of biorefineries. TSSmass, T, and SWT were shown to be more important in controlling the removal of solids by primary sedimentation tank (PST) than other factors considered. This study introduces a mathematical model that can predict the PS volume based on factors like TSSmass, T, and SWT as a synthesis of the two disparate facets of the study. This model can immensely help maximize PS production quantitively and qualitatively, which can help elevate energy and VFAs production from PS via anaerobic digesters and hydrolysis reactors in conventional municipal WWTP and biorefineries, respectively. Therefore, this model can confidently be applied for calculating the required hopper volume in PST and ascertaining the optimal volume specifications for anaerobic digesters and hydrolysis reactors. Consequently, it leads to cost savings associated with eliminating under or over-designing. The results showed that by improving PST performance for TSS removal, more chemical oxygen demand (COD) would be available for biogas production in conventional municipal WWTPs (from 42 to 59 g (cap. d)−1). By shifting toward biorefineries, the potential to produce more biogas and VFAs, altering from around 40–50 g (cap. d)−1 and 6–12 gVFAs (cap. d)−1, respectively, will also be indicated.

Performance evaluation and application of host-specific Bacteroidales and mitochondrial DNA markers to identify sources of fecal contamination in river water in Japan

Microbial source tracking (MST) using host-specific Bacteroidales and mitochondrial DNA (mtDNA) markers is an efficient tool to identify the sources of fecal contamination in environmental water. This study evaluated and updated the previously reported performances of seven host-specific Bacteroidales markers (three human-, two cattle-, and two pig-specific). Additionally, the performance of a cattle-specific Bovine mtDNA and a pig-specific Swine mtDNA marker were evaluated and then applied to MST of river water samples collected in Yamanashi Prefecture, Japan. We collected 48 fecal-source samples, including raw sewage, secondary-treated sewage, an effluent of a domestic wastewater treatment tank, pig feces, pig wastewater, and cattle feces, which were quantitatively analyzed using host-specific Bacteroidales and mtDNA markers. BacHum and gyrB markers (human-specific), BacR and Bovine mtDNA markers (cattle-specific), and Pig2Bac and Swine mtDNA markers (pig-specific) were judged the best-performing markers. Then, these selected markers were applied to MST to identify the sources of fecal contamination in 59 river water samples collected at 21 sites. Of them, 20 (95%), 21 (100%), and 16 (76%) sites were positive for at least one human, cattle, and pig marker, respectively, indicating the need for immediate action and monitoring to control fecal pollution.

Nutrient Removal from Industrial Wastewater Systems Using Controlled Activated Sludge Treatment

Biological treatment with activated sludge as an alternative treatment was studied, and nitrogen and phosphorus were monitored. This scheme involves modifying the treatment tank by dividing it into anoxic and aerobic sections. According to this scheme, the process simulation was performed using Hydromantis' GPS-X 7.0 computer software. Wastewater discharges are usually generated by various industrial activities such as the milk (dairy) processing industry, petroleum processing refineries and slaughterhouses, which were studied in detail. The economic evaluation (cost estimation) of removing nutrients has been done using the CapdetWorks 4.0 computer simulation software. A cost sensitivity analysis has also been performed for the variable influent flows, altering the alpha factor for oxygen transfer during the aeration process and serving as a typical variable. The simulation procedure and economic evaluation have been carried out for a complete wastewater treatment plant, including both treatment lines (the water line and the sludge line simultaneously), and the derived results have been represented through illustrated graphs, tables, and meaningful diagrams.

Perencanaan dan penghitungan pengolahan limbah tahu di Pabrik Tahu Banggle, Jombang

Background: The soybean processing industry into tofu has environmental impacts. This industry generates waste in the form of wastewater, which if discharged without prior management will cause damage and pollution to the environment. One of them is the Banggle tofu factory in Jombang. This study aims to create a plan and calculation of wastewater treatment installations at the factory. Methods: The research method is laboratory testing to determine the quantity of wastewater and direct observation to determine field conditions so that appropriate plans can be made according to the field conditions. Finding: This study found that the largest wastewater discharge is 18,000 L/day or 18 m3/day. Therefore, pipes are buried underground to avoid leakage. This research also produces the sizes that must be met by the wastewater treatment tank as a result of calculations. Conclusion: These sizes need to be considered in the installation of wastewater treatment facilities.

Fungal contamination of the water distribution system of a tertiary hospital water supply system in a resource-limited setting.

Fungal contamination of hospital water distribution systems has been implicated in outbreaks of healthcare-associated infections. To evaluate the prevalence of fungi in the water distribution system of a tertiary hospital in Nigeria. This was a descriptive cross-sectional study. Swabs and water samples were collected from taps and faucets in the hospital categorized into low (Accidents and Emergency Unit, Children Emergency Unit, Acute Stroke Unit and the 24 in-patient hospital wards) and high-risk (Renal Dialysis Unit, Central Sterile Services Department, Theatres and Intensive Care Units (ICUs)) units based on the vulnerability of patients being managed there. The membrane filtration method for water analysis was used. Where possible, isolates cultured were identified to species level. In total, 105 water and 49 swab samples were collected for analysis. All analysed water samples grew fungi. A total of 289 (high-risk; n = 178; low-risk; n = 111) and 76 fungi isolates were recorded from water and swab samples, respectively, with 31 different species identified. Aspergillus was the most predominant genus with five different species: Aspergillus niger (9.9%), terreus (4.4%), flavus (3.3%), fumigatus (8.8%) and versicolor (2.20%) isolated. Twenty-five and 18 species of fungi were identified in the low and high-risk units, respectively. The labour ward (n = 46; 25.8%) and modular theatre (n = 47; 42.3%) were the most contaminated units. Cladosporium spp. and Paecilomyces spp. were the most frequently isolated fungi in the low and high-risk units, respectively. The dialysis centre (n = 9; 8.1%) and renal transplant theatre (n = 7; 6.31%) had the lowest contamination rates in the high-risk units. Aspergillus niger, Cephalosporium curtipes, Penicillium chrysogenum and Penicillium glabrum were each identified in 4/6 units from which swabs were taken. The facility had no documented protocol for its water safety and quality. Our data reveal a high rate of contamination of hospital water sources by fungi, some of which are known to cause life-threatening infections. For better water treatment and water tank cleaning and disinfection, a standard protocol is advised. Ensuring that the water distribution systems in hospital settings are free of fungal contaminants is important to prevent the possibility of waterborne mycosis outbreaks.

Effect of supersaturated dissolved oxygen on growth-, survival-, and immune-related gene expression of Pacific white shrimp (Litopenaeus vannamei).

Oxygen concentration is an essential water quality parameter for aquaculture systems. Recently, supersaturated dissolved oxygen (DO) has been widely used in aquaculture systems to prevent oxygen depletion; however, the long-term effects of supersaturated DO exposure on aquatic animals have not been studied. In this study, we examined the effects of supersaturated DO on the growth, survival, and gene expression of Pacific white shrimp (Litopenaeus vannamei). Specific pathogen-free shrimp with a body weight of 8.22 ± 0.03 g were randomly assigned to two groups with four replicates at a density of 15 shrimps per tank. Shrimp were cultivated in recirculating tanks containing 50 L of 15 ppt seawater in each replicate. Oxygen was supplied at 5 mg/L to the control tanks using an air microbubble generator and at 15 mg/L to the treatment tanks using a pure oxygen microbubble generator. Shrimp were fed commercial feed pellets containing 39% protein at 4% of their body weight per day for 30 days. Average daily growth (ADG) and feed conversion ratio (FCR) were determined on days 15 and 30. Shrimp molting was measured every day. Individual hemolymph samples were obtained and analyzed for total hemocyte count, differential hemocyte count, and expression of growth- and immune-related genes at the end of the experiment. Long-term exposure to supersaturated DO significantly affected shrimp growth. After 30 days of supersaturated DO treatment, the final weight and ADG were 14.73 ± 0.16 g and 0.22 ± 0.04, respectively. Shrimp treated with normal aeration showed significantly lower weight (12.13 ± 0.13 g) and ADG (0.13 ± 0.00) compared with the control group. FCR was 1.55 ± 0.04 in the treatment group and 2.51 ± 0.09 in the control group. Notably, the shrimp molting count was 1.55-fold higher in the supersaturated DO treatment than in the supersaturated DO treatment. The expression of growth-related genes, such as alpha-amylase, cathepsin L, and chitotriosidase, was 1.40-, 1.48-, and 1.35-fold higher, respectively, after supersaturated DO treatment. Moreover, the treatment increased the expression of anti-lipopolysaccharide factor, crustin, penaeidin3, and heat shock protein 70 genes by 1.23-, 2.07-, 4.20-, and 679.04-fold, respectively, compared to the controls. Supersaturated DO increased growth and ADG production and decreased FCR. Furthermore, enhanced immune-related gene expression by supersaturated DO may improve shrimp health and reduce disease risk during cultivation.

Adaptation of African and Striped Catfish in Peat Water of Low pH

The adaptation of African (Clarias gariepinus) and striped catfish (Pangasianodon hypophthalmus) on peat water with low pH­ was successfully done. The treated fish were reared on a mixture gradient of peat water and borehole water in the fiber tanks as an adaptation process, with a control treatment of 100% borehole water. After adapting to 100% peat water, catfish were then transferred into the enclosure nets (hapa) and placed on a man-made peat water pond. The mortality, length, weight of catfish, and water quality parameters were recorded and measured. Results showed that subject catfish can be adapted and adapt with peat water of low pH from the fingerling size to adult with small mortality. Fish were acclimatized and gradually adapted after 58 days in the fiber tanks with nearly 100% peat water, and let for the next 38 days. The growth rate of both catfish between the treatment and control tank did not significantly differ. Fish was then moved to the enclosure nets on the ponds after 96 days. This indicates that by adaptation mechanism, catfish can survive and grow in peat water of low pH and possibly be reared in dynamic peat waters (rivers, lakes, and ponds).

Dietary administration of yeast (Saccharomyces cerevisiae) hydrolysate from sugar byproducts promotes the growth, survival, immunity, microbial community and disease resistance to VP (AHPND) in Pacific white shrimp (Litopenaeus vannamei)

This study investigated the effects of yeast hydrolysate (YH) from sugar byproducts on various parameters in Pacific white shrimp (Litopenaeus vannamei). The study found no significant differences in water quality parameters across all treatment tanks, ensuring that the observed effects were not due to environmental variations. There were no significant differences in growth parameters between the control group and groups receiving YH at different dosages. However, the group given YH at 10.0 g/kg feed exhibited a notably higher survival rate and higher expression of growth-related genes (IGF-2 and RAP-2A) in various shrimp tissues. YH was associated with enhanced immune responses, including lysozyme activity, NBT dye reduction, bactericidal activity, and phagocytic activity. Notably, the 10.0 g/kg feed group displayed the highest phagocytic index, indicating a dose-dependent immune response. Expression of immune-related genes (ALF, LYZ, ProPO, and SOD) was upregulated in various shrimp tissues. This upregulation was particularly significant in the gills, hepatopancreas, intestine, and hemocytes. While total Vibrio counts remained consistent, a reduction in green Vibrio colonies was observed in the intestine of shrimp treated with YH. YH, especially at 5.0 and 10.0 g/kg feed dosages, significantly increased survival rates and RPS values in response to AHPND infection. The findings of this study suggest that incorporating additives derived from yeast byproducts with possible prebiotic properties obtained from sugar byproducts can lead to positive results in terms of enhancing growth performance, immunity, histological improvements, and resistance to V. parahaemolyticus, the causative agent of acute hepatopancreatic necrosis disease (AHPND).

Wastewater Treatment using The Photosynthetic Bacteria at Parksarp Village, Xaythany District, Vientiane Capital

Untreated waste water from the piggery farm will damage the environment and society, if, it is discharged to environment, in particular, direct impact on surrounding communities. The propose of the research is to investigate the characteristics and efficiency of the photosynthetic bacteria in employing on wastewater treatment systems. The experiment is designed and simulated the stabilization tank system that includes: an aerobic tank, sedimentation (excess sludge) tank, clear water tank and all tanks are used the same size of 50 liters, wastewater from a piggery farm was introduced into the treatment tank with a dry matter ratio 5% of the total water mass. Therefore, BOD5, COD, TSS, TKN, and pH were made prior to entering the treatment tank, photosynthetic bacteria is added 200 ml per week, detention time 7 days and after 25 days of treatment. The experiment found that, BOD5, COD, TSS, TKN concentrations reduce continuously from 366 mg/l - 192 mg/l (47.54%), 90,000 mg/l - 4,000 mg/l (95.56 %), 30 mg/l - 7 mg/l (76.67%) and 3.92 mg/l - 0.08 mg/l (97.96%), respectively.

Carbon Footprint and Energy Recovery Potential of Primary Wastewater Treatment in Decentralized Areas: A Critical Review on Septic and Imhoff Tanks

The present work is a critical review on the carbon footprint and energy recovery potential of septic and Imhoff tanks for primary wastewater treatment. From an online search of research papers, a lack of up-to-date research about gas emissions from Imhoff tanks emerged. Additionally, available literature data should be extended to incorporate the effect of seasonal variations, which may be relevant due to the fact that both systems work under environmental conditions. The literature generally agrees on the positive effect of temperature increase on biogas and methane production from both septic and Imhoff tanks. Additionally, sludge withdrawal is an important operational feature for gas production in these reactors. More recently, the application of electrochemical technologies and the installation of photovoltaic modules have been studied to enhance the sustainability of these decentralized solutions; in addition, sludge pretreatment has been investigated to raise the obtainable methane yields due to limited sludge biodegradability. Further research is needed to assess the effective sustainability of biogas collection and valorization from existing septic and Imhoff tanks, considering the limited biogas generation and the implementation of these systems in decentralized wastewater treatment scenarios (rural or mountain areas). Contrary to the intensive research on greenhouse gas mitigation strategies applied to centralized systems, solutions specifically designed for gas emission mitigations from septic and Imhoff tanks have not attracted the same scientific interest up to now. More generally, given the widespread application of these two options and their potential significant contribution to the overall carbon footprint of wastewater treatment technologies, much more research must be performed in the future both on the quantification of gas production and on the applicable strategies to reduce their carbon footprint.

Growth Performance of &lt;i&gt;Salmostoma bacaila&lt;/i&gt; in Biofloc System

The present research work was study on the growth performance of Salmophasia bacaila in the biofloc culture system for the period of 28 days from the second week of September to second week of October 2022.The initial weight of fingerlings of the Salmophasia bacaila were 0.667 gm and cultured for 28 days in the experimental tanks at30 fish/tank. The experiment was designed in two tanks, one tank was used as control, while the other tank was used as biofloc treatment tank. The mean value of water temperature, pH, dissolved oxygen, water hardness, alkalinity in biofloc treatment system were 24.6℃, 7.9, 4.88mg/l, 128.14mg/l and 124.42mg/l respectively. The control set registered the mean value of water temperature 23.5℃, pH 8.6, dissolved oxygen 5.1mg/l, hardness 123.50mg/l&amp; alkalinity 118.66mg/l. The SGR was 1.97observed in biofloc treatment while in control tank the same was1.73. 77% survival rate of fishes were registered in the under biofloc treatment and 73% in the control tank.

Research on proposing solutions to reduce noise for the operation of air compressors in wastewater treatment system

Currently, aerobic biological methods are widely used for wastewater treatment. During the wastewater treatment process, air is forced by an air compressor into the biological treatment tank with high capacity, so, noise pollution often occurs during the system operation. This is affecting the health environment for workers, staff, and the surrounding population. Therefore, it is necessary to investigate and design a cover to reduce noise for the air compressor but not affect the operating efficiency of the device. The results in this study showed that after 30 minutes of continuous operation, the temperature around the air compressor increased by 2.5oC (from 29.5 to 32.0oC). The noise reduction is 4.0 dBA in case a polyurethane foam layer of 5 cm is used, and the noise reduction is 14.0 dBA if it is replaced with a mineral wool layer of 5 cm. The noise reduction is 17.0 dBA when combining the outer with a 5 cm polyurethane foam layer and the inner with a 5 cm mineral wool layer. Further, the noise reduction is reduced up to 24.0 dBA in case two layers of mineral wool (5 cm thick each) are used to form a homogeneous mass. Thus, using porous materials combined with mineral wool allows to reduce the noise level in accordance with the requirements of the QCVN 26:2010/BTNMT regulation (70 dBA).

Assessment of Phosphorus Mobilizing Capacity of Bacillus spp. Isolated from Mangrove Rhizospheric Sediment and its Potential Application in Aquaculture

Background: Phosphatase producing bacteria (PPB) plays a major role in mineralising organic P into inorganic form. Though application of bacterial biofertilizers are practiced in agriculture, their application is very limited in aquaculture. Method: The PPB isolates were screened and isolated from rhizospheric sediment of mangrove, Avicennia marina of Ennore creek, Tamil Nadu. Their P transformation potential and the possibilities of their application in aquaculture to mineralise organic P to inorganic P were studied. Result: Twenty PPB isolates were screened in the study site and their Alkaline Phosphatase (ALP) activity was in the range of 13.6-20.4 µmol.ml-1.hr-1. Out of this, five Bacillus sp isolates were selected to assess their P transformation potential at various salinity. The P mobilizing potential of these isolates were compared with the commercial PPB following a microcosm study for a period of 14 days. During the study period, there is a significant increase in phosphorus in water as well as ALP activity and available phosphorus concentrations in sediments were observed between control and treatment tanks. Among the treatment groups, B. subtilis treatment tanks showed maximum P in water ie. 1.60mg.L-1, followed by B. altitudinis –1.49mg.L-1; B. pumilus –1.47mg.L-1; the soil ALP activity was in the order of commercial P products greater than B. pumilus greater than B. subtilis greater than B. paramycoides greater than B. altitudinis greater than B. aryabhattai. In terms of available phosphorus content in sediments on 14th day, there is no significant difference observed between B. pumilus and commercial product with respect to available P content of sediment.

Saving Energy in Biological Wastewater Treatment by Using Extremely Low-Frequency Electric Field—Pilot-Scale Study

The results of a pilot-scale study on the influence of electric field use for stimulating the active sludge in the biological purification tank of a small capacity wastewater treatment plant (up to 600 m3/day) are presented. Through specific comparative chemical tests (DO, COD, N-NH4, and Pt) it was found that, by applying a sinusoidal electric field of 5 Vrms/m at 49.9 Hz on the active sludge suspension, the overall pollutant denitrification process speed is doubled compared with the reference case when no stimulation is used. Also, under identical operating conditions, the residual pollutant content of the biological treatment tank outlet water is reduced approximately three times for COD and approximately two times for N-NH4 and Pt compared to the reference tank. These findings lead to the conclusion that, by stimulating the active sludge microbial activity of the wastewater treatment plants by a sinusoidal electric field of 5 Vrms/m at 49.9 Hz, the time of the biological purification treatment can be reduced by approx. 50%. This leads to a corresponding decrease in energy consumption, which usually represents more than 30% of a wastewater treatment plant’s specific electricity consumption.