Types Of Sewage Sludge Research Articles

Biological Composition of Sewage Sludge in the Aspect of Threats to the Natural Environment

One of the prerequisites for sustainable development is integrated waste management, including sewage sludge. Besides its good fertilization properties, sewage sludge, which is an inevitable by-product of sewage treatment, accumulates toxic chemical substances and dangerous pathogenic and toxicogenic organisms. Uncontrolled introduction of sewage sludge into soil might pose a serious threat to food chain and natural soil microfl ora. This in effect might disturb the ecological balance in a particular ecosystem. This study presents author's own investigations of the sanitary conditions of sewage sludge and the conditions after the processes of aerobic and anaerobic stabilization. The investigated sewage sludge originated from a municipal wastewater treatment plant. The sewage sludge samples were transferred onto proliferation and diagnostic media. The results of the analysis obtained in this study confi rmed that sewage sludge is a material which is rich in microorganisms, including pathogenic bacterial species such as: Escherichia coli and Salmonella typhimurium. Mycological tests demonstrated that sewage sludge is a material which is conducive to proliferation of yeast- -like and mould-like fungi, among which both pathogenic and toxinogenic species can be present. Quantitative analysis of the investigated sewage sludge demonstrated that the processes of stabilization reduce the content of microorganisms but they do not guarantee product safety in sanitary terms. A huge variability and variety of biological composition points to the need for further research in the fi eld of sanitary characteristics of sewage sludge and survival rate in microorganisms from different types of sewage sludge.

Ultrasonic sludge pretreatment under pressure

The objective of this work was to optimize the ultrasound (US) pretreatment of sludge. Three types of sewage sludge were examined: mixed, secondary and secondary after partial methanisation (“digested” sludge). Thereby, several main process parameters were varied separately or simultaneously: stirrer speed, total solid content of sludge (TS), thermal operating conditions (adiabatic vs. isothermal), ultrasonic power input (PUS), specific energy input (ES), and for the first time external pressure. This parametric study was mainly performed for the mixed sludge. Five different TS concentrations of sludge (12–36g/L) were tested for different values of ES (7000–75,000kJ/kgTS) and 28g/L was found as the optimum value according to the solubilized chemical oxygen demand in the liquid phase (SCOD). PUS of 75–150W was investigated under controlled temperature and the “high power input – short duration” procedure was the most effective at a given ES. The temperature increase in adiabatic US application significantly improved SCOD compared to isothermal conditions. With PUS of 150W, the effect of external pressure was investigated in the range of 1–16bar under isothermal and adiabatic conditions for two types of sludge: an optimum pressure of about 2bar was found regardless of temperature conditions and ES values. Under isothermal conditions, the resulting improvement of sludge disintegration efficacy as compared to atmospheric pressure was by 22–67% and 26–37% for mixed and secondary sludge, respectively. Besides, mean particle diameter (D[4,3]) of the three sludge types decreased respectively from 408, 117, and 110μm to about 94–97, 37–42, and 36–40μm regardless of sonication conditions, and the size reduction process was much faster than COD extraction.

A comparative study of aerobically digested and undigested sludge in preparation of magnetic chars and their application in 1-diazo-2-naphthol-4-sulfonic acid adsorption

In this work, two types of sewage-sludges, aerobically digested and undigested sewage sludge, were used as precursors in the preparation of chars with magnetic property. The two solids were characterized to establish their textural and chemical properties. Due to different elemental composition, chars from the digested sludge were found to contain zeolite-like minerals such as NaP1 zeolite, which enables its abilities of anion exchange, while chars from undigested sewage sludge exhibited a well-degreed graphite structure. 1-Diazo-2-naphthol-4-sulfonic acid (1,2,4-Acid) was used as a model pollutant to investigate its adsorption on prepared chars. The adsorption kinetics of 1,2,4-Acid onto both chars followed pseudo-second-order kinetics. The simulated Langmuir–Freundlich model illustrated that the equilibrium adsorption amount of 1,2,4-Acid was 102.8 and 105.3mg/g, respectively, at 303K. The adsorption amount declined on digested chars, whereas kept stable on the other in the presence of sodium chloride, suggesting the diversity in adsorption behavior.

Particulate and gaseous emissions during fluidized bed combustion of semi-dried sewage sludge: Effect of bed ash accumulation on NOx formation

Combustion of two semi-dried sewage sludges in a 110mm has been characterized in terms of particulate and gaseous emissions. Sludges differed in that they had been conditioned – at the flocculation stage of wastewater treatment – either with Ca-based inorganics or with polyelectrolytes. Combustion was efficient for both sewage sludges under all the operating conditions tested. Significant differences have instead been observed between the two types of sewage sludges as regards particulate and macro-pollutant gaseous emissions (SO2, NOx). NOx formation is significantly influenced by ash accumulation inside the bed only when sewage sludge conditioned with Ca-based inorganics is fired. The time-resolved profiles of NOx concentration and the mass flow rate of the elutriated fines have been worked out to evaluate the fuel nitrogen yield to NOx as a function of ash accumulated inside the bed divided by the air mass feed rate. Experimental results have been compared with data present in literature.

Power production from different types of sewage sludge using microbial fuel cells: A comparative study with energetic and microbiological perspectives

Fuel recovery from sewage sludge is a promising energy production method, which can simultaneously address energy issue and environmental concerns associated with waste treatment. This study evaluates power productions from different types of sewage sludge in microbial fuel cells (MFCs) with energetic and microbiological perspectives. Results show that the recovered organic matter (ROM), a kind of anaerobic sewage sludge, is a good candidate for bioelectricity generation compared to conventional waste activated sludge (WAS), giving a maximum power output of 38.1 W m−3. The lower internal resistance of the MFC fed with ROM is attributed to the higher concentration of soluble chemical oxygen demand (SCOD) in the anolyte. At a nominal solid retention time of 8 day, 60.2 ± 4.9% of the total COD in the ROM is removed. The initial chemical composition and microbial consortium in ROM demonstrates the highest exoelectrogenesis potential compared with other WAS samples. The syntrophic communities formed on the surface of anode electrodes enable the successful conversion of the substrates into bioelectricity. Although the recovered energy cannot outweigh the operation costs of the bioelectrochemical systems, the total expenditure for ROM treatment herein is reduced by 30–50% compared to those for WAS.

The influence of phosphorus on ash fusion temperature of sludge and coal

Sewage sludge gasification can result in significant environmental benefits. However, the influence of sewage sludge on the process is not recognized in an adequate degree. The purpose of the present study was to investigate the ash fusion temperature (AFT) of coal-sewage sludge (SS) and the influence of phosphorus on it. Ash fusion characteristics of six types of coals, one type of sewage sludge, and the corresponding coal-sewage sludge blends were measured. Chemical and mineralogical compositions of blended ashes at different temperatures were determined. Ash fusion temperatures of most coals are lowered by adding sewage sludge, because Ca and Na in sewage sludge ash can react with refractory minerals from coal to form low temperature eutectic. The influence of phosphorus on mixture AFT depends greatly on the Al2O3/(CaO+Na2O+K2O) (A/CNK) molar ratio of bulk ash. Phosphorus tends to react with calcium to form refractory minerals in subaluminous systems (A/CNK<1), but mainly exists in amorphous materials and beneficial for decreasing ash fusion temperature in peraluminous systems (A/CNK>1).

Removal of sulfonamide antibiotics upon conventional activated sludge and advanced membrane bioreactor treatment

This work reports the removal efficiencies of nine sulfonamides (SAs) and one of their acetylated metabolites during conventional activated sludge (CAS) and membrane bioreactor (MBR) treatments. Two different types of membranes were studied, hollow-fiber membranes and flat-sheet membranes, in two separate pilot plants operating in parallel to a full-scale CAS treatment. A total of 48 water samples and 16 sewage sludge samples were analyzed by liquid chromatography-tandem mass spectrometry. We obtained 100% elimination in the MBR effluents for three SAs (sulfadiazine, sulfadimethoxine, and sulfamethoxypyridazine) and the metabolite. For the rest of the SAs, the removal efficiencies during CAS and MBR treatments were similar and usually below 55%. Sulfamethizole was the most recalcitrant SA, exhibiting negative removal efficiencies in all the treatments investigated. The concentrations of SAs in the different sewage sludge types were also calculated and ranged from 0.01 to 11 ng g(-1). Furthermore, adsorption and biodegradation of SAs in activated sludge were investigated in two sets of batch reactors, which were spiked at high and low concentration (1,000 and 50 ng mL(-1), respectively). All SAs followed a similar trend and, with the exception of sulfathiazole, were not fully eliminated after 25 days of treatment.

Process performance of dry, batch anaerobic digestion of sewage sludge: methanogenic seed mixtures

A dry, batch anaerobic digestion (DBAD) process was tested on two sewage sludge types with different methanogenic seed fractions under laboratory conditions. The aim was to indicate optimal sludge:seed mixing ratios and analyse process performance based on degradation rate and reactor-specific methane production. The attained results were compared with the performance of a liquid-state, laboratory-scale stirred reactor (SR). A mixing ratio of at least 1:1.25 (sludge:seed) yielded processes free from significant inhibitions. Further seeding increments resulted in slightly better performances, but much lower sludge fractions treated in the reactors. Compared with the SR process, the DBAD reactors produced comparable degradation rates albeit in a significantly longer process and with somewhat lower reactor-specific methane production rates. These findings indicate that the DBAD method may provide a viable alternative to liquid-state processes if sludge drying is already applied and reactor volume requirements are of importance.

Influence of activated carbon and biochar on phytotoxicity of air-dried sewage sludges to Lepidium sativum

The goal of the research was to determine the phytotoxicity (using Lepidium sativum) of two activated carbon/biochar-amended sewage sludges. Apart from the impact of the AC/biochar dose, the influence of biochar particle diameter (<300, 300–500 and >500μm) and the influence of the contact time (7, 60, 90 days) between AC/biochar and sewage sludges on their phytotoxicity was also assessed. No negative impact of sewage sludges on seed germination was observed (P>0.05). The application of AC or biochar to the sludges positively affected root growth by reducing the harmful effect by 7.8 to 42% depending on the material used. Furthermore, the reduction range clearly depended on the type of sewage sludge. No differences were observed in the inhibition of the toxic effect between both biochar types used and the biochar particle size. The extension of the contact time between AC/biochar and sewage sludges had a negative impact on root growth.

바이오디젤 생산을 위한 원료로서 국내 도시 하수슬러지의 활용성 평가( I ) - 지방산메틸에스테르(FAMEs)의 수율 및 조성 비교 -

This study was performed to assess the possibility of application of sewage sludge which is the side-product from domestic sewage treatment plant to the materials for biodiesels by investigating the yields and composition of the lipids and fatty acid methyl esters(FAMEs) from soxhlet extraction and in-situ transesterification. As the results, yields of in-situ transesterification were higher than soxhlet extraction. In comparison by sewage sludge type, yields of sewage sludge mixed nightsoil or livestock were higher than a single sewage sludge. And maximum yield showed up to 14 wt%. Fatty acid composition of extracted lipids and synthesized FAMEs consists of palmitic acid(C16:0), palmitoleic acid(C16:1), stearic acid(C18:0), oleic acid(C18:1), and linoleic acid(C18:2).

Drug-Resistant Microorganisms in Soils Fertilized with Sewage Sludge

One of the methods of sewage sludge disposal, which is based on its fertilizing properties, is its use in nature, e.g. in farming (if all the permissible standards are met). However, the sludge used for soil fertilization might also contain heavy metals, pathogenic microorganisms, thus causing contamination in soil foundation and deterioration of the conditions for development of indigenous organisms. Particular threat is posed by the exi st ence of drug-resistant microorganisms in sewage sludge. This problem has not been researched in detail yet. The authors of the present study aimed to determine qualitative changes in drug-resistant microorganisms in sandy soil fertilized with selected sewage sludge. Sewage sludge after different types of drying process (natural and solar) was added to the degraded sandy soil. The effect of the methods of sewage sludge drying on concentration of drug-resistant microorganisms in soil fertilized with the sludge was analysed. The study demonstrated that sewage sludge dried naturally in drying beds pose threat to soil environment and, potentially, to people and animals which have contact with fertilized soils. In sandy soils fertilized with these types of sewage sludge, pathogenic forms which exhibit resistance to first-line antibiotics can be found.

Characterization and environmental implications of nano- and larger TiO2 particles in sewage sludge, and soils amended with sewage sludge

Titanium dioxide (TiO(2)) is the most extensively used engineered nanoparticle to date, yet its fate in the soil environment has been investigated only rarely and is poorly understood. In the present study, we conducted two field-scale investigations to better describe TiO(2) nano- and larger particles in their most likely route of entry into the environment, i.e., the application of biosolids to soils. We particularly concentrated on the particles in the nano-size regime due to their novel and commercially useful properties. First, we analyzed three sewage sludge products from the US EPA TNSSS sampling inventory for the occurrence, qualitative abundance, and nature of TiO(2) nano- and larger particles by using analytical scanning electron microscopy and analytical (scanning) transmission electron microscopy. Nano- and larger particles of TiO(2) were repeatedly identified across the sewage sludge types tested, providing strong evidence of their likely concentration in sewage sludge products. The TiO(2) particles identified were as small as 40 nm, and as large as 300 nm, having faceted shapes with the rutile crystal structure, and they typically formed small, loosely packed aggregates. Second, we examined surface soils in mesocosms that had been amended with Ag nanoparticle-spiked biosolids for the occurrence of TiO(2) particles. An aggregate of TiO(2) nanoparticles with the rutile structure was again identified, but this time TiO(2) nanoparticles were found to contain Ag on their surfaces. This suggests that TiO(2) nanoparticles from biosolids can interact with toxic trace metals that would then enter the environment as a soil amendment. Therefore, the long-term behavior of TiO(2) nano- and larger particles in sewage sludge materials as well as their impacts in the soil environment need to be carefully considered.

Skin effect in the heat and mass transfer model for sewage sludge drying

The thermal drying of sewage sludge was studied in the 30–65 °C temperature range with two types of sewage sludge, showing different behaviour in the formation of a skin during the drying process. Twenty-one runs were carried out at different temperatures and air flows in an apparatus that provided a continuous flow of air. Small sewage sludge spheres and cylindrical tablets were produced to study the kinetics. During each run, the variation of moisture content vs. operation time was monitored, and during some tests, the temperature inside the sample as well. A kinetic model was developed to correlate the experimental data, both moisture content and temperature, vs. time. The resulting kinetic parameters (mass transfer coefficient, heat transfer coefficient, skin effect parameter, diffusion coefficient and activation energy) are discussed with reference to correlations and kinetic parameters presented in the literature. In general, the model seemed to suitably reproduce the experimental moisture and temperature data. For some runs there were significant deviations between the experimental and calculated temperatures, which could be explained by an evaporation effect taking place at the surface of the thermocouple wire placed inside the sludge spheres. The kinetic parameters have been used for simulation of continuous dryers. Finally, an analysis of the influence of the different parameters on the drying process has been carried out in order to obtain a general model valid for different types of sewage sludges.

Effects of Different Types of Sludge on Soil Microbial Properties: A Field Experiment on Degraded Mediterranean Soils

The recycling of suitable organic wastes can enhance soil fertility via effects on soil physical, chemical and biological properties. To compare the effects of digested (DS), thermally dried (TDS) and composted dewatered (CDS) sewage sludge on soil microbiological properties, an experiment was conducted at field sites for more than one year (401 d) when applied to two Mediterranean degraded soils (loam and loamy sand soils). All three types of sewage sludge had a significant effect on measured parameters. In a short time, the plots of both loamy sand and loam soils amended with TDS showed the highest microbial basal respiration (loam soil: P < 0.01; loamy sand soil: P < 0.001) and carbon mineralization coefficient (loam soil: P < 0.01; loamy sand soil: P < 0.001). Furthermore, on loamy sand soil, the plots amended with TDS showed the highest microbial metabolic quotient ( qCO 2) ( P < 0.05). This study revealed that the addition of sludge caused transient non-equilibrium effects on almost all soil microbial properties. However, there were no differences one year later because the remaining organic carbon was stable and quite similar in all treatments. These results may have practical implications for the rehabilitation of degraded soils.

Multi‐residue method for the analysis of pharmaceutical compounds in sewage sludge, compost and sediments by sonication‐assisted extraction and LC determination

A method for the simultaneous determination of 16 pharmaceutical compounds in three types of sewage sludge (primary, secondary and anaerobically digested dehydrated sludge), compost and sediment samples is described. Pharmaceutical compounds evaluated were nonsteroidal anti-inflammatory drugs (acetaminophen, diclofenac, ibuprofen, ketoprofen, naproxen and salicylic acid), antibiotics (sulfamethoxazole and trimethoprim), an anti-epileptic drug (carbamazepine), a beta-blocker (propranolol), a nervous stimulant (caffeine), estrogens (17alpha-ethinylestradiol, 17beta-estradiol, estriol and estrone) and lipid regulators (clofibric acid, metabolite of clofibrate and gemfibrozil). The method is based on the ultrasonic-assisted extraction, clean-up by SPE and analytical determination by HPLC with diode array and fluorescence detectors. The best extraction recoveries were achieved in a three-step extraction procedure with methanol and acetone as extraction solvents. Extraction recoveries of several pharmaceutical compounds as caffeine were highly dependent on the type of sample evaluated. The applicability of the method was tested by analyzing primary, secondary and anaerobically digested dehydrated sludge, compost and sediment samples from Seville (Southern Spain). Ten of the sixteen pharmaceutical compounds were detected in sludge samples and five in compost and sediment samples. The highest concentration levels were recorded for ibuprofen in sewage samples, whereas salicylic acid and 17alpha-ethinylestradiol were detected in all of the samples analyzed.

The effects of fertilization with anaerobic, composted and pelletized sewage sludge on soil, tree growth, pasture production and biodiversity in a silvopastoral system under ash (Fraxinus excelsior L.)

AbstractIn silvopastoral systems, tree growth and the composition and productivity of pasture can be modified by management practices such as initial fertilization when tree seedlings are more sensitive to understorey competition. The aim of this study was to compare the effects of fertilization with different types of sewage sludge (anaerobic sludge, composted sludge and pelletized sludge), using different rates of incorporation and mineralization with traditional treatments (with and without mineral fertilizers) on the growth of newly established ash (Fraxinus excelsior L.) and on pasture development, to obtain sustainable management practices that enhance the growth of both components. Soil characteristics, tree growth, sward composition and pasture development were modified differently according to the type of sewage sludge used, and for similar total nitrogen inputs. Anaerobic sludge had a higher initial effect on both tree and pasture productivity. Pelletized sludge sustained better tree and pasture production. Composted sludge was found to be the most appropriate treatment for improving soil characteristics over the long term on sandy soils. It was concluded that pelletized sludge should be promoted because it enhances productivity, allows for better nutrient recovery and is less costly to store and apply compared with anaerobic sludge and composted sludge. No toxic concentrations of Zn or Cu were found in plants or in the soil despite higher concentrations being present in the applied sludge than in soil.

Substrate‐Induced Respiration of a Sandy Soil Treated with Different Types of Organic Waste

A sandy soil was amended with different types of sewage sludge (digested, dried, and composted) and pig slurry. The composted sludges displayed higher organic‐matter stability (39–45%) than only digested sludge (26–39%) or digested + dried sludge (23–32%). The microbial biomass of the dried sludge was undetectable. Digested and composted sludges and pig slurry displayed microbial biomasses (12492–13887 µg g−1, 1221–2050 µg g−1, and 5511 µg g−1, respectively) greater than the soil (108 µg g−1). The wastes were applied at seven doses, ranging from 10 to 900 g kg−1. Soils were incubated for 28 days. Substrate‐induced respiration (SIR) was measured for 12 consecutive hours on day 1 and on day 28. The results showed that SIR increased with the dose of organic amendment. However, SIR decreased when moderate doses of pig slurry or high doses of digested + dried sludge were tested. The possibility of using this inhibition as an ecotoxicological indicator is discussed.

Significance of Plant-induced Solubilization of Soil Nitrogen: A Case of Komatsuna Plants Grown in Fertilized Soils

Plant-induced solubilization of soil nitrogen (N) is a key process for plants to utilize the recalcitrant form of N. Toevaluate its contribution to plant uptake, the factors affecting the contribution and the forms of N solubilized by plants, we analyzed the results of a pot experiment in which komatsuna (Brassica rapa L. var. peruviridis) was grown in 3 different soils applied with 5 types of sewage sludge as a source of N for plants. The amount of N solubilized by plants, which was defined experimentally as the difference in the amount of solubilized N between the planted and unplanted treatments, varied with the soil types more than the types of sewage sludge. This accounted for 30% (Arenosol), 15% (Fluvisol) and 1.6% (Andosol) of the amount of N uptake on average. These percentages were high when the level of soil soluble N after the experiment was below approximately 30 mg kg-1. Sequential analyses of insoluble N in soil after the experiment indicated the occurrence of plant-induced solubilization of both bio-soluble and acid-soluble N in many of the Arenosol and Fluvisol treatments and that of acid-soluble N in the Andosol treatments. The plant-induced solubilization in the Andosol resulted in the accumulation of more labile bio-soluble N rather than enhanced plant uptake. For komatsuna grown in fertilized soil, the depletion of soluble N in the root zone seems to be important for the increase in the contribution of the plant-induced solubilization to uptake but not for the occurrence of the solubilization.

Agronomic characterisation of different types of sewage sludge: Policy implications

Agronomic characterisation of different types of sewage sludge: Policy implications

Agronomic characterisation of different types of sewage sludge: Policy implications

Spain is one of the main municipal sewage sludge producers of Europe. This paper aims to agronomically characterise different types of sewage sludge stabilised by different methods (anaerobically digested, composted, and pelletised) and deliver policy recommendations from the results of this characterisation. Anaerobic sewage sludge quality is found to be better in plants with a lower volume of water processing. Composted sludge shows the best quality from a heavy metal point of view, but its low available nitrogen content increases the input of heavy metals when spread, as compared to digested or pelletised sludge. Pelletised sludge has higher heavy metal content than anaerobically digested sludge. Despite the good quality of the sludges, future regulations, especially with regard to Cd levels, will limit the use of this waste in agriculture.