Heat and mass transfer during fry-drying of sewage sludge

Deep-frying, which consists of immersing a wet material in a large volume of hot oil, presents a process easily adaptable to dry rather than cook materials. A suitable material for drying is sewage sludge, which may be dried using recycled cooking oils (RCO) as frying oil. One advantage is that this prepares both materials for convenient disposal by incineration. This study examines fry-drying of municipal sewage sludge using recycled cooking oil. The transport processes occurring during fry-drying were monitored through sample weight, temperature, and image analysis. Due to the thicker and wetter samples than the common fried foods, high residual moisture is observed in the sludge when the boiling front has reached the geometric center of the sample, suggesting that the operation is heat transfer controlled only during the first half of the process followed by the addition of other mechanisms that allow complete drying of the sample. A series of mechanisms comprising four stages (i.e., initial heating accompanied by a surface boiling onset, film vapor regime, transitional nucleate boiling, and bound water removal) is proposed. In order to study the effect of the operating conditions on the fry-drying kinetics, different oil temperatures (from 120 to 180 degrees C), diameter (D = 15 to 25 mm), and initial moisture content of the sample (4.8 and 5.6 kg water(.)kg(-1) total dry solids) were investigated.

Characteristics of the upper phase of bio-oil obtained from co-pyrolysis of sewage sludge with wood, rapeseed and straw

Sewage sludge was pyrolysed with 40% mixed wood, 40% rapeseed and 40% straw. The reason for the mixture of different biomass is to investigate the impact of co-pyrolysis on the upper phase of bio-oil in terms of changes to composition, elemental analysis, viscosity, water content, pH, higher heating value and acid number that could impact on their applications. The biomass was pyrolysed in a laboratory at 450 °C and bio-oil was collected from two cooling traps. The bio-oil obtained from co-pyrolysis of sewage sludge with wood, rapeseed and straw was analysed for composition using the gas chromatography mass spectrometry. The upper phase from the co-pyrolysis process was also characterised for ultimate analysis, higher heating values, water content, viscosity, pH and acid number. There was an increase in the amount of upper phase produced with co-pyrolysis of 40% rapeseed. It was also found that the upper phase from sewage sludge with mixed wood has the highest viscosity, acid number and lowest pH. The bio-oil containing 40% straw was found to have a pH of 6.5 with a very low acid number while the 40% rapeseed was found to have no acid number. Sewage sludge with 40% rapeseed was found to have the highest energy content of 34.8 MJ/kg, 40% straw has 32.5 MJ/kg while the 40% mixed wood pyrolysis oil has the lowest energy content of 31.3 MJ/kg. The 40% rapeseed fraction was found to have the highest water content of 8.2% compared to other fractions.

Increase of energy recovery from sewage sludge

The use of the pyrolysis process to obtain valuable products from biomass is amongst the technologies being investigated as a source for renewable energy. The pyrolysis process yields products such as biochar, bio-oil and non condensable gases. The main objective of this project is to increase energy recovery from sewage sludge by utilising the intermediate pyrolysis process. The intermediate pyrolysis has a residence time ranging from 5 to 10 minutes. The main product yields from sewage sludge pyrolysis are 50 wt% biochar, 40 wt% bio-oil and 10 wt% non condensable gases. The project was carried out on a pilot plant scale reactor with a load capacity of 20 kg/h. This enabled a high yield of biochar and bio-oil. The characterisation of the products indicated that the organic phase of the bio-oil had good fuel properties such as having high energy content of 39 MJ/kg, low acid number of 21.5, high flash point of 150 and viscosity of 35 cSt. An increase in pyrolysis experiments enabled large quantities of pyrolysis oil production. Co-pyrolysis of sewage sludge was carried out on laboratory scale with mixed wood, rapeseed and straw. It found that there was an increase in bio-oil quantity with rapeseed while co-pyrolysis with wood helped to mask the smell of the sludge pyrolysis oil. Engine test were successfully carried out in an old Lister engine with pyrolysis oil fractions of 30% and 50% blended with biodiesel. This indicates that these pyrolysis oil fractions can be used in similar engine types without any problems however long term effects in ordinary engines are unknown. An economic evaluation was carried out about the implementation of the intermediate pyrolysis process for electricity production in a CHP using the pyrolysis oil. The prices of electricity per kWh were found to be very high.

Thermal stability of sewage sludge pyrolysis oil

The stability of the oil phase obtained from intermediate pyrolysis process was used for this investigation. The analysis was based on standard methods of determining kinematic viscosity, gas - chromatography / mass - spectrometry for compositional changes, FT-IR for functional group, Karl Fischer titration for water content and bomb calorimeter for higher heaating values. The methods were used to determine changes that occurred during ageing. The temperatures used for thermal testing were 60 °C and 80 °C for the periods of 72 and 168 h. Methanol and biodiesel were used as solvents for the analysis. The bio-oil samples contained 10 % methanol, 10 % Biodiesel, 20 % Biodiesel and unstabilised pyrolysis oil. The tests carried out at 80 °C showed drastic changes compared to those at 60 °C. The bio-oil samples containing 20 % biodiesel proved to be more stable than those with 10 % methanol. The unstabilised pyrolysis oil showed the greatest changes in viscosity, composition change and highest increase in water content. The measurement of kinematic viscosity and gas chromatograph mass spectrometry were found to be more reliable for predicting the ageing process.

Fractionation of Zn, Cd and Pb in a Tropical Soil After Nine-Year Sewage Sludge Applications

A long-term field experiment was carried out in the experiment farm of the Sao Paulo State University, Brazil, to evaluate the phytoavailability of Zn, Cd and Pb in a Typic Eutrorthox soil treated with sewage sludge for nine consecutive years, using the sequential extraction and organic matter fractionation methods. During 2005-2006, maize (Zea mays L.) was used as test plants and the experimental design was in randomized complete blocks with four treatments and five replicates. The treatments consisted of four sewage sludge rates (in a dry basis): 0.0 (control, with mineral fertilization), 45.0, 90.0 and 127.5 t ha(-1), annually for nine years. Before maize sowing, the sewage sludge was manually applied to the soil and incorporated at 10 cm depth. Soil samples (0-20 cm layer) for Zn, Cd and Pb analysis were collected 60 days after sowing. The successive applications of sewage sludge to the soil did not affect heavy metal (Cd and Pb) fractions in the soil, with exception of Zn fractions. The Zn, Cd and Pb distributions in the soil were strongly associated with humin and residual fractions, which are characterized by stable chemical bonds. Zinc, Cd and Pb in the soil showed low phytoavailability after nine-year successive applications of sewage sludge to the soil.

Barium uptake by maize plants as affected by sewage sludge in a long-term field study

Along-term experiment was carried out under field conditions in Jaboticabal, SP, Brazil, with the objective of evaluating the concentration of Ba in soil and in maize plants grown in a soil treated with sewage sludge for nine consecutive years. During 2005/2006, maize was used as test plants and the experimental design was in randomized complete blocks with four treatments and five replicates. Treatments consisted of: 0.0, 45.0, 90.0 and 127.5 t ha(-1) sewage sludge (dry basis). Sewage sludge application increased soil Ba concentration. Barium accumulated in the parts of maize plants were generally affected by the successive applications of sewage sludge to the soil. However, the concentration of Ba in maize grain did not exceed the critical levels of Ba for human consumption. Sewage sludge applied to soil for a long time did not affect dry matter and grain production, nevertheless had the similar effect of mineral fertilization. Published by Elsevier B.V.

CALCINED SLUDGE SINTERING EVALUATION BY HEATING MICROSCOPY THERMAL ANALYSIS

Aiming the use of the sewage sludge produced in one of the largest Brazilian wastewater treatment stations as a raw material for the ceramic industry, the sintering process of the ashes produced from its calcination was evaluated by heating microscopy thermal analysis (HMTA). From the microprocessed images, a method was developed to obtain HMTA dimensional change curves as a function of temperature, equivalent to those usually obtained from dilatometers or by thermomechanical analysis (TMA). The final product after sintering at 1050 degrees C, characterized by X-ray fluorescence spectrometry, scanning electron microscopy and X-ray dispersive energy, indicates the presence of a vitreous phase containing phosphorus, which explains the good sintering properties of the studied calcined sludge, as shown from its HMTA dimensional change curve.

Effects of sewage sludge amendment on the properties of two Brazilian oxisols and their humic acids

The effect of sewage sludge (SS) amendment on the general properties of the top layers of a sandy and a clayey oxisols and on the nature of their humic acid (HA) fractions was evaluated by chemical and physico-chemical techniques. The amended soils, especially the sandy soil, benefited of SS amendment by increasing their pH to above neutrality and enhancing the contents of C, N, P, and Ca and cation exchange capacity. The SS-HA-like sample showed larger H and N contents and a greater aliphatic character and humification degree than the HAs isolated from non-amerided soils. The composition and structure of amended soil HAs were affected by SS application as a function of soil type and layer. In particular, N-containing groups and aliphatic structures of SS-HA-like sample appears to be partially incorporated in the amended soil HAs, and these effects were more evident in the HAs from the sandy oxisol. (C) 2007 Elsevier Ltd. All rights reserved.

Native tree seedling growth when fertilized with different amounts of dry sewage sludge and mineral fertilizer

The increasing volume of urban sewage nowadays generates considerable amount of sludge to be disposed of. One environmentally adequate destination could be the application of treated and stabilized sludge (biosolids) to forest plantations as fertilizer and soil conditioner. The purpose of this study was to analyze the feasibility of applying sewage sludge, evaluating its effects on native tree seedlings. The species evaluated were aroeira-pimenteira (Schinus terebinthifolia Raddi), cabreuva-vermelha (Myroxy-Ion peruiferum L. f.), pau-de-viola (Cytarexyllum myrianthum Cham), unha-de-vaca (Bauhinia forficata Link), which are usually planted in forest restoration. Seedlings were cultivated in pots, containing a volume of 4 dm(3) of soil, within a greenhouse. The study was developed in the proximity of Campinas, SP, Brazil, and installed in November, 2003. The design was entirely randomized including seven treatments: control; mineral fertilization; and different doses of sewage sludge (biosolids) complemented with potassium, due to the low concentration of this element in the sludge produced by the wastewater treatment plant of Barueri (Metropolitan region of Sao Paulo city). The results showed that the application of different dosages of biosolids promoted different responses in stem height and biomass production. The treatment with 20 g/dm(3) of dry sewage sludge promoted both the highest growth and the highest seedling biomass production, compared to the control treatment. All native tree species treated with the highest dosage of sewage sludge showed a growth similar to that of mineral fertilization. The seedlings of aroeira-pimenteira, pau-de-viola, and unha-de-vaca, all typical species of the initial succession in natural forest ecosystems, grew and produced more biomass than cabreuva-vermelha, a typical species of the final forest succession.

Ammonia volatilization in soil treated with tannery sludge

The utilization of tannery sludge in agricultural areas can be an alternative for its disposal and recycling. Despite this procedure may cause the loss of nitrogen by ammonia volatilization, there is no information about this process in tropical soils. For two years a field experiment was carried out in Rolandia (Parana State, Brazil), to evaluate the amount of NH(3) volatilization due to tannery sludge application on agricultural soil. The doses of total N applied varied from zero to 1200 kg ha(-1), maintained at the surface for 89 days, as usual in this region. The alkalinity of the tannery sludge used was equivalent to between 262 and 361 g CaCO(3) per kg. Michaelis-Menten equation was adequate to estimate NH(3)-N volatilization kinetics. The relation between total nitrogen applied as tannery sludge and the potentially volatilized NH(3)-N, calculated by the chemical-kinetics equation resulted in an average determination coefficient of 0.87 (P > 0.01). In this period, the amount of volatilized NH(3) was more intense during the first 30 days; the time to reach half of the maximum NH(3) volatilization (K(m)) was 13 an 9 days for the first and second experiments, respectively. The total loss as ammonia in the whole period corresponded in average to 17.5% of the total N applied and to 35% of the NH(4)(+)-N present in the sludge. If tannery sludge is to be surface applied to supply N for crops, the amounts lost as NH(3) must be taken into consideration. (C) 2010 Elsevier Ltd. All rights reserved.

Biogas production and valorization by means of a two-step biological process

The scope of this research work was to investigate biogas production and purification by a two-step bench-scale biological system, consisting of fed-batch pulse-feeding anaerobic digestion of mixed sludge, followed by methane enrichment of biogas by the use of the cyanobacterium Arthrospira platensis. The composition of biogas was nearly constant, and methane and carbon dioxide percentages ranged between 70.5-76.0% and 13.2-19.5%, respectively. Biogas yield reached a maximum value (about 0.4 m(biogas)(3)/kgCOD(i)) at 50 days-retention time and then gradually decreased with a decrease in the retention time. Biogas CO(2) was then used as a carbon source for A. platensis cultivation either under batch or fed-batch conditions. The mean cell productivity of fed-batch cultivation was about 15% higher than that observed during the last batch phase (0.035 +/- 0.006 g(DM)/L/d), likely due to the occurrence of some shading effect under batch growth conditions. The data of carbon dioxide removal from biogas revealed the existence of a linear relationship between the rates of A. platensis growth and carbon dioxide removal from biogas and allowed calculating carbon utilization efficiency for biomass production of almost 95%. (C) 2009 Elsevier Ltd. All rights reserved.

A simple closed-loop membrane process for the purification of active pharmaceutical ingredients

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Purification of complex biopharmaceuticals with new processes, advanced analytics and computer-aided process design tools

Dissertação para obtenção do Grau de Mestre em Biotecnologia

A review of the development of regional sludge treatment centres and a baseline characterisation of Irish sewage sludges

This Study assessed the development of sludge treatment and reuse policy since the original 1993 National Sludge Strategy Report (Weston-FTA, 1993). A review of the 48 sludge treatment centres, current wastewater treatment systems and current or planned sludge treatment and reuse systems was carried out Sludges from all Regional Sludge Treatment Centres (areas) were characterised through analysis of selected parameters. There have been many changes to the original policy, as a result of boundary reviews, delays in developing sludge management plans, development in technology and changes in tendering policy, most notably a move to design-build-operate (DBO) projects. As a result, there are now 35 designated Hub Centres. Only 5 of the Hub Centres are producing Class A Biosolids. These are Ringsend, Killamey, Carlow, Navan and Osberstown. Ringsend is the only Hub Centre that is fully operational, treating sludge from surrounding regions by Thermal Drying. Killamey is producing Class A Biosolids using Autothermal Thermophilic Aerobic Digestion (ATAD) but is not, as yet, treating imported sludge. The remaining three plants are producing Class A Biosolids using Alkaline Stabilisation. Anaerobic Digestion with post pasteurisation is the most common form of sludge treatment, with 11 Hub Centres proposing to use it. One plant is using ATAD, two intend to use Alkaline Stabilisation, seven have selected Thermal Drying and three have selected Composting. While the remaining plants have not decided which sludge treatment to select, this is because of incomplete Sludge Management Plans and on DBO contracts. Analysis of sludges from the Hub Centres showed that all Irish sewage sludge is safe for agricultural reuse as defined by the Waste Management Regulations {Use of Sewage Sludge in Agriculture) (S.I. 267/2001), providing that a nutrient management plan is taken into consideration and that the soil limits of the 1998 (S.I. 148/1998) Waste Management Regulations are not exceeded.

CO2, CH4 and N2O fluxes in an Ultisol treated with sewage sludge and cultivated with castor bean

Organic residue application into soil alter the emission of gases to atmosphere and CO2, CH4, N2O may contribute to increase the greenhouse effect. This experiment was carried out in a restoration area on a dystrophic Ultisol (PVAd) to quantify greenhouse gas (GHG) emissions from soil under castor bean cultivation, treated with sewage sludge (SS) or mineral fertilizer. The following treatments were tested: control without N; FertMin = mineral fertilizer; SS5 = 5 t ha-1 SS (37.5 kg ha-1 N); SS10 = 10 t ha-1 SS (75 kg ha-1 N); and SS20 = 20 t ha-1 SS (150 kg ha-1 N). The amount of sludge was based on the recommended rate of N for castor bean (75 kg ha-1), the N level of SS and the mineralization fraction of N from SS. Soil gas emission was measured for 21 days. Sewage sludge and mineral fertilizers altered the CO2, CH4 and N2O fluxes. Soil moisture had no effect on GHG emissions and the gas fluxes was statistically equivalent after the application of FertMin and of 5 t ha-1 SS. The application of the entire crop N requirement in the form of SS practically doubled the Global Warming Potential (GWP) and the C equivalent emissions in comparison with FertMin treatments.