Sewage Sludge as Inhibitor of the Formation of Persistent Organic Pollutants during Incineration

With the objective of suppressing dioxins and furans (PCDD/Fs) emission in municipal solid waste incineration plants (MSWI), different chemical inhibitors have been tested. Among these inhibitors, nitrogen and sulphur compounds can significantly suppress PCDD/Fs formation via de novo synthesis, which gives very interesting results with very little capital investment. In recent years, the possibility of using waste rich in nitrogen and/or sulphur as a source of inhibitor compounds has been considered, and thus has reduced the emissions of pollutants while the waste is treated. The effect of adding sludge from urban sewage treatment plants in three variants has been specially studied: directly mixing the waste, using the decomposition gas of the previously dried sludge, and using the decomposition gas of the sludge together with other inhibitors such as thiourea. Reduction of emissions in laboratory tests using model samples indicated the efficiency to be higher than 99%, using sewage sludge (SS) as an inhibitor whereas, in actual MSWI plants, the efficiency can be as high as 90%.

The technology of wastewater sludge vitrification in comparison with other processing methods

Специалистами компании ООО «НТЦ «Экопромтех» разработана инновационная технология остеклования илового осадка сточных вод, позволяющая значительно сократить объем отходов и получить на выходе безопасный остеклованный материал для использования в строительстве. Приводится сравнение технологии остеклования с другими способами переработки осадка: депонированием, сбраживанием осадка в метантенках, сушкой, пиролизом, каталитическим и классическим сжиганием. В России более 90% образующихся иловых осадков депонируются. При сохранении этой тенденции неизбежен рост плеча перевозки осадка. Использование необработанного илового осадка в качестве удобрения повышает риск загрязнения почвы. Финансовые модели проектов с внедрением метантенков за счет продажи биогаза или электроэнергии не окупаются. В случае применения метода сушки для получения топлива из осадка расходуется практически столько же тепловой энергии, сколько содержится в конечном продукте. Поэтому себестоимость высушенного илового осадка как топлива не будет меньше стоимости природного газа, а с учетом других операционных затрат, включая доставку до потребителя, превысит стоимость газа в 2–3 раза. Пиролиз с получением ликвидных продуктов находится на стадии разработки, что потребует проведения большого количества исследований. Технология каталитического сжигания осадка без предварительной сушки не решает основные проблемы любого сжигания и приводит к определенным трудностям: риск эмиссии суперэкотоксикантов сохраняется, золу необходимо утилизировать, затруднено поддержание автотермического режима, катализатор изнашивается и требует замены. Технология остеклования имеет ряд преимуществ, готова к масштабированию и промышленному внедрению. The experts of Ekopromtekh R & D Centre, LLC have developed an innovative technology for vitrification of wastewater sludge that provides for reducing significantly the volume of wastes and obtaining a safe vitrified material to be used in construction. A comparison of the vitrification technology with other methods of sludge processing is given: depositing, sludge digestion in digesters, drying, pyrolysis, catalytic and classical incineration. In Russia, more than 90% of the generated sludge is landfilled. If this trend persists, an increase in the sludge hauling distance is inevitable. Using unprocessed sludge as fertilizer increases the risk of soil contamination. Financial models of projects that envisage using digesters and selling biogas or electricity do not pay off. In case of using the drying method to obtain fuel from sludge, almost the same amount of thermal energy is consumed as the final product contains. Therefore, the cost of dried sludge as a fuel will not be less than the cost of natural gas, and taking into account other operating costs, including delivery to the consumer, will exceed the cost of gas by 2–3 times. Pyrolysis to obtain marketable products is under development and involves a lot of research. The technology of catalytic incineration of sludge without preliminary drying does not solve the main problems of any incineration process and causes certain difficulties: the risk of emission of superecotoxicants remains; the ash must be disposed of, the autothermal regime is difficult to maintain, the catalyst wears out and requires replacement. The vitrification technology has a number of advantages, it is ready for scaling and industrial implementation.

TG pyrolysis of a mixture of dried sludge from urban wastewater and wood pellets and identification of the composition of the resulting gases by infrared spectroscopy

The recent tendency of sewage sludge disposal is targeted towards the gasification for heat generation in small towns far from waste incineration plants. The scope of this article is to present the investigation into the mixture of dried sewage sludge and wood pellets during pyrolysis by thermogravimetry (TG) with evolved gas analysis by TG-coupled Fourier transformation infrared spectroscopy (FTIR) method. The maximum intensity of mass loss of sewage sludge material occurs at 300–310°C temperature and it differs from wood cellulose case of 360°C. The 50:50% mixture of these materials was investigated in more details. Pyrolysis reaction kinetics is described by a variation of three constituent parts from TG data. Prefactor A and activation energy E of the Arrhenius law were found, and reaction order n was determined by the Ozawa method employing Avrami phase change. The maximum of gas evolution is always related to the most intense mass loss, and gas composition correlates with the initial material.

Comparative Study of Hot Air Drying and Microwave Drying for Dewatered Sludge

Large amounts of sludge are generated from wastewater treatment in seafood processing industries. Most of the dewatered sludge in Thailand is not utilized and disposed by landfilling. The dried sludge utilization as refuse-derived fuel (RDF) is an alternative solution due to the gross calorific value (GCV), which is greater than 21.9 MJ/kg. However, the key obstacle is its high moisture content of 87.4% (wet basis). Therefore, drying methods using hot air and microwave techniques were investigated for preparing dried sludge. The effects of hot air temperatures (100-150 °C) and microwave power levels (100-800 W) were compared on drying kinetics, specific energy consumption (SEC), and characteristics of the dried products. The results showed that drying times were decreased by increasing the hot air temperatures. In the same way, the increase in microwave power levels decreased the drying time. The application of microwaves contributed to reducing the drying time by more than 46% compared to the hot air. The reduction of drying times resulted in the saving SEC. The GCV of the dried sludge decreased with the decrease in the volatile matter (VM) due to the high component of VM as 79.5-80.3% (dry ash-free basis). The sludge dried by the microwaves showed a lower GCV than the hot air products. However, dried sludges still had high GCV (≥ 20.8 MJ/kg). Furthermore, the minimal variation of the product characteristics demonstrated that the microwave technique could be applied as an alternative drying method with a rapid process compared to the conventional hot air technique.

Characterization and recycling of textile sludge for energy-efficient brick production in Ethiopia

In recent years, an enormous amount of sludge is generated every day from zero liquid discharge treatment plant due to rapid expansion of industrial parks in Ethiopia. About 30,000 tons of partially dried sludge discharged to the environmental without proper waste management from all industrial parks. Thus, posing serious environmental problems. One of the most plausible means to recycle the excess sludge resource is converting it into energy-efficient brick by combining with clay. Bricks were prepared by incorporating textile sludge at different proportions (10–40%) and temperature (600, 900 and 1200 °C). Clay and sludge samples were collected from the Addis Ababa brick factory PLC and Hawassa Industrial Park. Results revealed that 10 and 20% sludge bricks satisfied criteria of class “A” bricks as per Ethiopia standards, with the compressive strength of 30.43 and 29.10 Mpa, respectively, at 1200 °C. About 26 and 50% of energy were saved during firing of 10 and 20% sludge-containing bricks, respectively, compared with pristine clay bricks. Moreover, too low concentrations of selected heavy metals found in the brick leachate, showing the sludge, were effectively stabilized in the burnt clay bricks. Thus, based on the results, we suggest the rapid utilization of huge amount of partially dried sludge resources for low-cost and efficient large-scale brick production. This will mutually benefit both the industrial parks and brick production industries. In addition, this will create thousands of jobs to the local people. Above all, the solid waste will be managed properly at textile industrial parks.

Compaction as a sustainable alternative to dried sludge from poultry slaughterhouse wastewater for energy generation

ABSTRACT: The generation of wastes in poultry abattoirs has increased considerably in recent years due to the growing demand for chicken meat. This fact, combined with the current need for developing new forms of renewable energy from biomass, and the lack of disposal facilities, motivated this study. We determined the technical feasibility of the barbecue charcoal production using briquettes produced with different blends containing sludge from a poultry abattoir and Pinus spp. shavings. To that end, we have mixed both residues by gradually adding 10 to 90 % of sludge in the blends, which resulted in 9 treatments containing sludge, and 1 containing only shavings. After that, we produced four briquettes of each treatment and charred them by using a heating ramp. After charring, we submitted the charcoal to the analyzes of Moisture Content (MC), Bulk Density (BD), Compressive Resistance (CR), Gross Calorific Value (GCV), and Proximate Analysis (PA). We calculated the Gravimetric Yield (GY) and the Energy Density (ED) by using the results from the other analyzes. Results showed that the CR, the GCV, the Volatile Matter (VM), and the Fixed Carbon Content (FC) of the charcoals decreased by increasing the proportion of sludge in the blends. However, the charcoals’ bulk density (BD) increased, which also increased its energy density (ED) and ash content (AC). The best blend to produce charcoal for household use was the one containing 90 % of sludge and 10 % of Pinus spp. shavings.

Drying Bed Volume Design Analysis for Reducing Environmental Impact of WTP Residuals

Sand Drying Bed (SDB) is designed for reducing the potential environmental impact caused by Water Treatment Plants – WTP residuals. Currently, the technical document of SNI (Indonesian National Standard) is still difficult to be applied by the engineer in determining required SDB’s volume based on WTP’s capacity and raw water conditions. The purpose of this research is to analyze WTP’s sludge production for designing SDB’s volume. The research was taken place at Pajangan WTP (50 l/s capacity) and Bantar System of Kartamantul WTP (400 l/s capacity) in Yogyakarta Special Province, which use Progo River as raw water source. The data used in the analysis is raw water turbidity compilation data, TSS (Total Suspended Solid) fluctuations rate of raw water, coagulant dosage used, specific gravity range of dried sludge and imhoff settling ratio based on laboratory tests. The results obtained show that one-year production of dry sludge on Pajangan WTP Unit is estimated to reach 244.55 m3/year from the total number of WTP residual (water and sludge) produced of around 43,158.52 m3/year. Meanwhile, the dry sludge produced on Kartamantul WTP Unit is estimated to reach 1,550.49 m3/year from the total number of WTP residual produced of around 273,635.22 m3/year. Then, each of Pajangan and Kartamantul WTP unit produced about 2.365 m3/day and 1.874 m3/day sludge for every 1 liter/second of raw water. This large amount of sludge leads the SDB has to be better designed.