Sludge Accumulation Research Articles

Biological performance and trace organic contaminant removal by a side-stream ceramic nanofiltration membrane bioreactor

This study evaluated the performance of a side-stream ceramic nanofiltration membrane bioreactor (NF-MBR) system with respect to basic water quality parameters as well as trace organic contaminant (TrOC) removal efficiency. The results show a stable biological performance of the continuous NF-MBR system with high effluent quality (total organic carbon < 4 mg L−1 and NH4+–N below the detection limit). Significantly higher performance by this NF-MBR in comparison to the conventional microfiltration/ultrafiltration MBR regarding the removal of a large number of TrOCs was observed. TrOC removal efficiency depended on their hydrophobicity and molecular features. All hydrophobic compounds (LogDpH=6 > 3) were well removed (>85%), except diazinon (59 ± 7%). Hydrophilic compounds containing electron donating groups were also well removed (>90%). By contrast, hydrophilic compounds containing electron withdrawing groups were poorly removed (8–54%). Most of the 40 TrOCs investigated in this study did not accumulate in the sludge. Only three hydrophobic compounds, namely amitriptyline, triclosan and triclocarban showed considerable accumulation in sludge (>500 ng g−1). Mass balance indicated biodegradation/transformation as the most significant TrOC removal mechanism by this NF-MBR.

Enhancement of biodiesel production by cultivating Dipodascaceae moderated-filamentous granular sludge with sugar-containing wastewater

Utilizing excess sludge from a wastewater treatment plant to produce biodiesel has become an increasingly popular topic. However, the low lipid content in activated sludge has hindered the application of biodiesel production from excess sludge. This study was designed to enhance biodiesel production from granular sludge fed with synthetic sugar-containing wastewater. Granules cultivated at different initial sludge loading rates had different morphologies and microbial structure. Low seed biomass and high initial sludge loading resulted in the dominance of the white filamentous fungi Dipodascaceae in granular sludge, thereby enhancing the lipid accumulation of granular sludge and changing the biodiesel constituent produced from the sludge. However, overgrowth of filamentous fungi deteriorated the settling and compression ability of granular sludge. Thus, controlling the filamentous fungi at a moderate level through an effective operating strategy is of great importance to biodiesel production from a granular sludge system fed with sugar-containing wastewater.

Pathogens and fecal indicators in waste stabilization pond systems with direct reuse for irrigation: Fate and transport in water, soil and crops

Wastewater use for irrigation is expanding globally, and information about the fate and transport of pathogens in wastewater systems is needed to complete microbial risk assessments and develop policies to protect public health. The lack of maintenance for wastewater treatment facilities in low-income areas and developing countries results in sludge accumulation and compromised performance over time, creating uncertainty about the contamination of soil and crops. The fate and transport of pathogens and fecal indicators was evaluated in waste stabilization ponds with direct reuse for irrigation, using two systems in Bolivia as case studies. Results were compared with models from the literature that have been recommended for design. The removal of Escherichia coli in both systems was adequately predicted by a previously-published dispersed flow model, despite more than 10years of sludge accumulation. However, a design equation for helminth egg removal overestimated the observed removal, suggesting that this equation may not be appropriate for systems with accumulated sludge. To assess the contamination of soil and crops, ratios were calculated of the pathogen and fecal indicator concentrations in soil or on crops to their respective concentrations in irrigation water (termed soil-water and crop-water ratios). Ratios were similar within each group of microorganisms but differed between microorganism groups, and were generally below 0.1mLg−1 for coliphage, between 1 and 100mLg−1 for Giardia and Cryptosporidium, and between 100 and 1000mLg−1 for helminth eggs. This information can be used for microbial risk assessments to develop safe water reuse policies in support of the United Nations' 2030 Sustainable Development Agenda.

Factors Leading to the Formation of a Resistive Thin Film at the Bottom of Aluminum Electrolysis Cells

Studies on sludge formation in aluminum electrolysis cells are rare and typically do not distinguish the deposits at the center of the cell from those composing the ledge toe because low voltage lost is expected at the center of the cell. However, high amount of sludge in the center leads to the formation of a thin film in an intermediate zone between the ledge toe and this center thick sludge accumulation. Looking at sludge deposits through composition mapping and microstructure analysis coming from four aluminum cells of two different aluminum reduction technologies, major factors leading to a thin resistive film were identified. This includes the formation of a suspension on the top of the thick deposit at the center of the cell, its displacement through magnetohydrodynamic induced movement by the metal pad, and the growth and thickening of a carbide sublayer making the thin film even more resistive. Correlation between thickening of the thin film and cathode voltage drop increase was observed. The postmortem analysis performed on six laboratory experiments was found useful to support different observations made on the industrial cells at lower cost.

Effect of Sludge Behavior on Performance of Centrifugal Contactor

The effects of sludge behavior on the performance of a centrifugal contactor were investigated. Sludge accumulation during the operation of the centrifugal contactor was observed only in the rotor. Based on the sludge accumulation behavior, the effects of rotor sludge accumulation on the performance of phase separation and extraction were investigated using several types of rotors, which simulated different sludge accumulation levels in the separation area. It was confirmed that rotor sludge accumulation would affect the phase separation performance but not the extraction performance. This can be explained by the structure of the centrifugal contactor, wherein the extraction reaction and phase separation mainly proceed in the housing and rotor, respectively.

Gallbladder sludge associated with ceftriaxone therapy for typhoid fever in Nigerian children: A case series

Ceftriaxone is a third-generation cephalosporin with a wide spectrum of activity against both gram-negative and gram-positive organisms. Ceftriaxone has proven efficacy against severe and difficult-to-treat community-acquired infections including typhoid fever and other sepsis syndromes caused by multi-drug resistant organisms. Several studies including prospective studies exist in the literature that described the accumulation of sonographically demonstrable sludge (or precipitates) in the gallbladder and sometimes in the urinary tract. The accumulation of sludge occurs during therapy for severe infections in some children identified with certain predisposing factors. The condition is often asymptomatic but might be associated with clinical features that could mimic disease progression in patients with intra-abdominal manifestations of infection such as typhoid fever. Five Nigerian children aged between 4 and 11 years developed demonstrable gallbladder sludge (precipitate) while on treatment for typhoid fever with ceftriaxone. Three of the children manifested clinical features suggestive of gallbladder precipitate accumulation following commencement of the antibiotic, while the other two did not. Ceftriaxone therapy was continued to completion in all the cases along with conservative management. Four of the children recovered and had resolution of the sludge, while the fifth died of multi-organ failure after surgery for intestinal perforation. Although several studies exist in the literature regarding this condition, our search using Medline and Google Scholar did not identify such reports from children in Nigeria or sub-Saharan Africa. The cases are presented to create awareness on the possibility of occurrence of a drug-induced biliary precipitate formation in children.

Effect of abalone farming on sediment geochemistry in the Shallow Sea near Wando, South Korea

Wando County has grown up to 93% of the total abalone produced in South Korea since the late 1990s; however, this production has been decreasing in recent years. The objectives of this study were to understand the potential contamination risks of abalone farming and to examine the influence of intensive abalone farming on sediment quality by analyzing grain-size composition, organic matter (total organic carbon (TOC), total nitrogen (TN), total sulfur (TS)) and heavy metal content, pH, and 210Pb geochronology. The results of organic matter analysis from surface and core sediment (length: 64 cm) showed that the area around the abalone farm had oxic marine-to-brackish conditions, but that the area directly below an abalone cage (location 7) had reductive conditions, with a C/S ratio of ~2. The average TN levels in the surface and core sediments were 0.25% and 0.29%, respectively, and this was predominantly due to the use of seaweed for feed. The low sediment pH (surface, 7.23; core, 7.04), indicates that acidification of the bottom sediment has gradually increased since the initiation of abalone farming and is likely due to the continuous accumulation of uneaten feed and feces. Heavy metal pollution was not apparent based on the examination of EF and Igeo, although the excess metal flux of Ni, Pb, Cu, Co, As, and Cd increased toward surface of the sediment core. These sediment changes may be caused by the rapid accumulation (sedimentation rate: 1.45 cm/year) of sludge discharged from the abalone farm and may be controlled by tidal currents, physiography, water depth, and tidal ranges.

Complete solids retention activated sludge process.

In a slaughterhouse's full-scale extended aeration activated sludge wastewater treatment plant (WWTP), operating under complete solids retention time, the evolution of mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) concentration, food to micro-organisms ratio (F/M) and substrate utilization rate (SUR) were studied for over a year. Biomass growth phases in correlation to sludge biological and morphological characteristics were studied. Three distinguished growth phases were observed during the 425 days of monitoring. The imposed operational conditions led the process to extended biomass starvation conditions, minimum F/M, minimum SUR and predator species growth. MLSS and MLVSS reached a stabilization phase (plateau phase) where almost zero sludge accumulation was observed. The concept of degradation of the considered non-biodegradable particulate compounds in influent and in biomass (cell debris) was also studied. Comparison of evolution of observed sludge yields (Yobs) in the WWTP with Yobs predictions by activated sludge models verified the degradation concept for the considered non-biodegradable compounds. Control of the sedimentation process was achieved, by predicting the solids loading rate critical point using state point analysis and stirred/unstirred settling velocity tests and by applying a high return activated sludge rate. The nitrogen gas related sedimentation problems were taken into consideration.

When it can be useful look to gallbladder: 2 clinical cases

D.A.N. 6 years old, comes to our attention for vomiting and fever. The laboratory investigations show neutrophilic leukocytosis and increased inflammatory markers. She starts intravenous rehydration and antibiotic (Ceftriaxone) therapy with resolution of symptoms after 2 days when diarrhea appears. The third day ultrasound abdomen shows gallbladder contracted with content characterized by biliary sludge collected in a shadow back. She starts UDCA therapy. The new control after about a month of therapy shows complete resolution. Diagnosis: pharmacological pseudogallstones (Ceftriaxone therapy). D.S.F. 5 years old, comes to our observation for uncontrollable vomiting, fever and diarrhea. The laboratory investigations show neutrophilic leukocytosis, elevated lever-associated enzymes and inflammatory markers. Ultrasound abdomen shows cholecystitis with accumulation of biliary sludge in the sloping with acute adenomesenteritis. Diagnosis: acute cholecystitis in adenomesenteritis. Antibiotic and UDCA therapy led to complete remission of symptoms. Gallstones in children is rare (incidence between 0.15% and 0.22%), and often begins with acute cholecystitis. The biliary sludge does not necessarily comes before a calcoluos disease. The treatment with UDCA, however, is useful in resolution of symptoms and it can prevent the formation of calculous. The pseudogallstones has an incidence of 25–40% of patients with antibiotic therapy. It has a spontaneous resolution after discontinuation of therapy, which usually it can be seen from two weeks to five months from interruption.

Autosomal recessive polycystic kidney disease: Hepatic manifestations in relation to kidney failure

D.A.N. 6 years old, comes to our attention for vomiting and fever. The laboratory investigations show neutrophilic leukocytosis and increased inflammatory markers. She starts intravenous rehydration and antibiotic (Ceftriaxone) therapy with resolution of symptoms after 2 days when diarrhea appears. The third day ultrasound abdomen shows gallbladder contracted with content characterized by biliary sludge collected in a shadow back. She starts UDCA therapy. The new control after about a month of therapy shows complete resolution. Diagnosis: pharmacological pseudogallstones (Ceftriaxone therapy). D.S.F. 5 years old, comes to our observation for uncontrollable vomiting, fever and diarrhea. The laboratory investigations showneutrophilic leukocytosis, elevated lever-associated enzymes and inflammatory markers. Ultrasound abdomen shows cholecystitis with accumulation of biliary sludge in the slopingwith acute adenomesenteritis. Diagnosis: acute cholecystitis in adenomesenteritis. Antibiotic andUDCA therapy led to complete remission of symptoms. Gallstones in children is rare (incidence between 0.15% and 0.22%), and often begins with acute cholecystitis. The biliary sludge does not necessarily comes before a calcoluos disease. The treatment with UDCA, however, is useful in resolution of symptoms and it can prevent the formation of calculous. The pseudogallstones has an incidence of 25–40% of patients with antibiotic therapy. It has a spontaneous resolution after discontinuation of therapy, which usually it can be seen from two weeks to five months from interruption.

Field study comparing the effect of hydraulic mixing on septic tank performance and sludge accumulation

ABSTRACTThis study investigates the effect of hydraulic mixing on anaerobic digestion and sludge accumulation in a septic tank. The performance of a septic tank equipped with a hydraulic mixer was compared with that of a similar standard septic tank over a period of 10 months. The study was conducted in two phases: Phase-I – from May to November 2013 (6 months); Phase-II – from January to May 2014 (4 months). Hydraulic mixing effectively reduced the effluent biological oxygen demand (BOD) and total suspended solids, and reduced the sludge accumulation rate in the septic tank. The BOD removal efficiencies during Phase-II were 65% and 75% in the standard septic tank and a septic tank equipped with hydraulic mixer (Smart Digester™), respectively. The effect of hydraulic mixing reduced the rate of sludge accumulation from 0.64 cm/day to 0.27 cm/day, and increased the pump-out interval by a factor of 3.

DESIGN OF DOMESTIC SCALE BIO-DIGESTER ASSEMBLY, EXPERIMENTATION FOR BIOGAS PRODUCTION AND COMPARISON OF RESULTS WITH CONVENTIONAL DIGESTER

The work explored various digesters that are currently under implementation, explored their pros and cons and designed a digestion gas collection mechanism suitable for small scale applications. Internal mixing being uneconomical in the domestic and individual scale, it is not being practiced which has to be compensated with large hydraulic retention time to prevent sludge accumulation and scum formation. This in turn reduces the plant capacity for gas production. Our design configuration incorporates automatic and controlled pressure swing mechanisms incorporated by the gas production which acts as the driving force for slurry circulation in the digester and promotes gas recovery as well as improve digestion efficiency. The configuration was run in 20 l and 50 L scales and observed for the physical constraints encountered during operation, recorded for change in digestion parameters with changes in substrate and organic loading rates and also recorded the gas production which was compared with the results in the literature as well as conventionally operated domestic scale digesters.

Control of mixing for optimal formation of dynamic membrane in MBRs

Dynamic membranes (DMs) formed upon cost-effective mesh filters are considered as convenient alternatives to conventional membranes in membrane bioreactors (MBRs). This novel study investigates how hydrodynamics resulting from aeration rates of 2.5, 5, 10, and 15 L/min and agitation speeds of 100, 200, 300, and 400 rpm affect the sludge particle size, soluble microbial product (SMP), accumulation of sludge upon filter media, fouling propensity, effluent turbidity, and separation properties of DMs. The results conveyed that mixing flow and mixing intensity affect sludge properties considerably as well as DMs formed in the MBR. Despite fouling propensity, sludge mean particle size and dry weight of DMs decreased by increasing aeration rate and agitation speed. Optimum performance in terms of turbidity removal and blue pigment separation was obtained at the aeration rate of 5 L/min and the agitation speed of 300 rpm. In addition, more uniform DMs were formed by the flow pattern created by agitation which improved the performance. The DM formed by the agitation speed of 300 rpm could remove approximately 82% of blue pigments with a mean particle size of 0.9μm which performs similar to microfiltration.

Mathematical model for predicting sludge accumulation in septic tanks based on operational parameters: effect of hydraulic mixing

AbstractReporting sludge accumulation in septic tanks as a constant rate is no longer accepted, and there is a need for a model that predicts sludge accumulation in septic tanks taking into consideration the continuous consumption of sewage solids by microorganisms. This study presents the development of mathematical model that predicts sludge accumulation in septic tanks and to investigate the effect of mixing on solids digestion. The mathematical model takes into consideration the effect of different operational parameters (influent and effluent) as well as the bacterial kinetics in predicting the sludge accumulation in septic tanks. The model predicts with R2 &gt; 0.88 the sludge accumulation rate in standard septic tank calculated by empirical models developed by Weibel in 1955, and by Bounds in 1995. The model was also used to estimate the typical pump‐out interval for different tank volumes and the sludge accumulation inside septic tanks at different operational parameters.

Evaluation on the dewatering process of cyanobacteria-containing AlCl3 and PACl drinking water sludge

Most researches focused on the high efficiency removal of cyanobacteria from water phase during drinking water treatment, but did not address the potential danger of cyanobacterial cells being transferred into the sludge, especially during the dewatering process. In this study, the characteristics of cell lysis and microcystin (MC) release in the filtration of cyanobacteria-containing sludge were investigated. By evaluating filtration rates, filtrate microcystins (MCs) and turbidity levels, and SEM micrographs of the sludge in different operating conditions, the influences of mechanical actions and physical/chemical effects on the integrity of cyanobacterial cells were explicated, and the corresponding operation conditions were also optimized. The results showed that the sludge accumulation on unit filter area had significant influence on sludge dewatering characteristics, and with increase in the volume of sludge filtrated, more and more sludge accumulated on the surface of the filter media, resulting in reduced filtration rates and potential cyanobacteria lysis. More hydrophilic filter media with lower porosity should be chosen to enhance filtration efficiency. Compared with positive pressure filtration, vacuum filtration with low-destructibility should be a better choice considering the MC release. Under increased vacuum pressure, cyanobacteria-containing sludge had increasing filtration rate without causing damage of cyanobacterial cells. While the storage time of cyanobacteria-containing sludge should be severely restricted in actual water supply factories (4d for AlCl3 sludge and 2d for PACl sludge) to avoid the adverse influences of cyanobacteria lysis on sludge dewaterability and filtrate quality. This study produced deeper knowledge on the fate of cyanobacterial cells and intracellular MCs in the sludge dewatering process, and the results provided valuable scientific references for volume reduction of cyanobacteria-containing sludge in the actual treatment operations.

Changes in water quality of treated sewage effluents by their receiving environments in Tablas de Daimiel National Park, Spain.

The Tablas de Daimiel National Park (TDNP), a floodplain wetland located in the Upper Guadiana Basin (central Spain), receives pollution from wastewater treatment plants (WWTPs) discharging their treated sewage effluents (TSEs) to tributary channels to the wetland. The TSEs suffer transformations on their way to the TDNP, but the water quality is controlled only at the point of discharge. In this work, we analyse the change in water quality of the TSE from four urban WWTPs in the surroundings of the TDNP (Alcázar de San Juan, Daimiel, Manzanares and Villarrubia de los Ojos towns). The water samples were taken at the outlet of the plants and in the receiving environments, to analyse the water quality transformation of the TSE. The different discharge configurations of each WWTP have been related with the water quality transformation of their TSE, to interpret the influence of the hydro-geomorphology in the improvement or deterioration of the water quality of TSE. We found that the discharge of TSE into slow flow channels with macrophyte vegetation facilitates water self-purification but, with time, the accumulation of sludge in the beds of the effluents tends to be the cause of the deterioration of the water quality.

Evolution of defects in the production of capillary copper tubes

Features of capillary copper tubes include small internal diameter, increased wall thickness and a specified throughput capacity. This research aimed to reveal the reasons of throughput capacity fluctuations. Manufacturing processes include piercing, hot extrusion and drawing. Defects such as inclusions and pores can occur during all the stages of manufacturing. Inclusions were studied employing scanning electron microscopy. The emergence of porous structures surrounding the inclusions was revealed. It was shown that during drawing such pores turn into channels, which can be later destroyed due to pressure. This process was calculated and analyzed using the ABAQUS finite element analysis software. It was further demonstrated that the inner surface of capillary copper tubes could be destructed along with accumulation of sludge, which would be the cause of throughput capacity fluctuations.

English

The listing of the Monongahela River as an impaired waterway prompted the Pennsylvania Department of Environmental Protection (PADEP) to adjust aqueous discharge limits to the river to no more than 250 mg/L of sulfate. In response to this, an analysis of water treatment options for a coal mining company was conducted at several non-operating mines in western Pennsylvania that discharge directly or indirectly to the Monongahela River. Given the extremely high capital and operations costs for typical sulfate reduction methods such as reverse osmosis and ion exchange, novel passive and semi-passive treatment options were explored. An ethanol-fed bioreactor system was selected, designed, and constructed in 2014 to test whether sulfate reducing bacteria could be utilized to remove sulfate in alkaline mine water to meet discharge limits. The unique design elements consist of metals removal circuit, ethanol feed circuit, and twin bioreactors bedded with large cobbles and seeded with sulfate reducing bacteria, but containing no additional carbon source. Biochemical performance has shown that sulfate reduction approaches 1500 mmol SO4 m -3/ day during warmer weather, one of the highest rates recorded in the literature. Effluent sulfate ranged from 58 to 400 mg/L at 16oC and about 1400 mg/L at 2oC compared to influent sulfate concentrations that averaged 2800 mg/L. In addition, the bioreactor produced 500-1500 mg/L of total alkalinity due to microbial metabolism supported by the ethanol, typically corresponding with sulfate decreases. Effluent metal concentrations were decreased to 1 mg/L Fe and 0.2 mg/L Mn. The recirculation loop was found to remove 90% of iron in the original settling pond prior to entering the reactors to minimize sludge accumulation. Additional

Development of comprehensive oil sludge recycling method

Current efficiency of using fuel and energy resources in Ukraine and CIS countries can be defined as one that does not meet modern requirements. This issue is particularly acute in the oil processing industry. One reason is excessive loss of hydrocarbons, including through the accumulation of oil sludge in open barns. The paper describes one of the solutions to the urgent problem, namely comprehensive recycling of oil sludge formed during oil processing in refineries. The composition and properties of oil sludge formed in the Turkmenbashi Refinery (Turkmenistan) and PJSC NPK-Halychyna (Ukraine) were investigated. Fundamental possibility of recycling organic oil sludge by shallow thermal degradation at temperatures of 420‑460 °C was defined. It was shown that thermal degradation residual can be used as an additive to raw materials for the bitumen production in an amount of up to 10 % by weight. Based on the results, the current oil sludge utilization scheme was proposed.

Identification of the function of extracellular polymeric substances (EPS) in denitrifying phosphorus removal sludge in the presence of copper ion

Industrial wastewater containing heavy metals that enters municipal wastewater treatment plants inevitably has a toxic impact on biological treatment processes. In this study, the impact of Cu(II) (0, 1.5, 2, 2.5, 3 mg/L) on the performance of denitrifying phosphorus removal (DPR) and microbial community structures was investigated. Particularly, the dynamic change in the amount and composition of extracellular polymeric substances (EPS), and the role of EPS in P removal, were assessed using three-dimensional excitation–emission matrix fluorescence spectroscopy combined with parallel factor (PARAFAC) analysis. The results showed that, after long-term adjustment, the P removal efficiency was maintained at 95 ± 2.7% at Cu(II) addition up to 2.5 mg/L, but deteriorated when the Cu(II) addition was 3 mg/L. The EPS content, including proteins and humic substances, increased with increasing Cu(II) additions at concentrations ≤2.5 mg/L. This property of EPS was beneficial for protecting phosphate-accumulating organisms (PAOs) against heavy metals, as both proteins and humic substances are strong ligands for Cu(II). Therefore, the PAOs abundance was still relatively high (67 ± 3%) when Cu(II) accumulation in sludge was up to 10 mg/g SS. PARAFAC confirmed that aromatic proteins could be transformed into soluble microbial byproduct-like material when microorganisms were subjected to Cu(II) stress, owing to their strong metal ion complexing capacity. The increase in the percentage of humic-like substances enhanced the detoxification function of the sludge EPS. EPS accounted for approximately 26–47% of P removed by adsorption when Cu(II) additions were between 0 and 2.5 mg/L. The EPS function, including binding toxic heavy metals and P storage, enhanced the operating stability of DPR systems. This study provides us with a better understanding of (1) the tolerance of DPR sludge to copper toxicity and (2) the function of sludge EPS in the presence of heavy metals in biological P removal systems.