Laboratory Testing Methods for Centrifugal Sludge Dewatering Processes

Sludge dewatering is an important part of the municipal and industrial wastewater treatment. The purpose of sludge dewatering is to reduce organic ingredients, as well as the volume and weight of the sludge. Sludge treatment removes odour, improves hygiene by removing pathogenic organisms and prepares sludge for further utilisation or disposal. Although different instrumentation and process steps vary from one wastewater treatment plant to another, the sludge dewatering part of the process remains one of the most costly parts of the process, and the most challenging in terms of the chemistry involved. It is also the most highly regulated area of the industry. During the last decade, centrifugal sludge dewatering has largely replaced a great number of other instrumentation set-ups such as belt filter presses or drying beds in the municipal wastewater treatment plants. Due to the high shear force environment, demanding performance requirements are created for the dewateringaid chemicals used in centrifugal sludge dewatering. The heart of the dewatering process lies in the detailed chemical composition of the sludge dewatering chemicals. The sludge dewatering chemicals are typically different compositions of charged acrylamide-co-polymers, with different structural elements such as charge, molecular weight and structuring. The application research and product development are highly dependent on accurate laboratory methods, finetuned to describe the process environment with the real application

Science and technology of the mechanical thermal dewatering

In the work at hand basic experimental results are presented for the mechanical/thermal dewatering (MTE, German abbreviation for ‘Mechanisch/Thermische Entwässerung’, also used for ‘mechanical/thermal expression’ in English), during which lignites or other moisture containing materials are dewatered by the combined application of heat and mechanical forces. Models are developed for the description of the kinetics during the dewatering of the different materials based on soil-mechanical fundamentals, rheology and rate-process-theory. Using mercury intrusion porosimetry (MIP), helium pycnometry, CO2 adsorption and other techniques, it is investigated, how MTE process conditions, such as temperature and pressure, affect the physical properties pore size distribution and pore diameters, specific surface area, skeletal and ‘true’ density, hardening, compressibility and shrinkage behaviour of low rank coals from Australia, Greece and Germany. The results provide a detailed insight in process kinetics and mechanism, in coal structure and structural changes during the dewatering process. Additionally re-hydration and combustibility of MTE products as well as the removal of minerals from lignites during the MTE process is investigated. Results from the mechanical/thermal dewatering and water leaching tests are compared, which prove, that the MTE process is a powerful technique for the removal of both water and alkali components from lignite and younger biomass fuels like straw. Reductions of the concentration of sodium in lignite and potassium in straw between 70 and 85% are obtained. The results thus demonstrate, that the MTE process is also suitable for the upgrading of lignites and biomass fuels to prevent corrosion and slagging in power plants. The development of the plant and process engineering for the dewatering of lignite and for the combined leaching and dewatering of biomass fuels is presented and technological modifications required for the dewatering of waste materials and suspensions like galvanising sludge are described. The technical implementation is demonstrated based on the laboratory and technical scale dewatering units at the University of Dortmund and the pilot and demonstration plants located in Frechen and at the power plant Niederaußem. Efficiencies for different dry lignite fired power plant concepts with integrated mechanical/ thermal lignite dewatering are calculated and compared to the results obtained for other drying and dewatering processes. Depending on the origin and water content of the lignite, power plant efficiencies can be increased by up to 20 percent and specific CO2 emissions can be reduced by the same amount by the implementation of the MTE process in technical scale power plants. The results prove, that the MTE process is a remarkable advance compared to the existing methods

Sludge Production and Disposal for Small Cold Climate Bio-Treatment Plants

Ultimate disposal of wastewater sludge has long been a problem which to a large degree has been ignored. Haney (1971) stated that: "Until process sludge can be handled with minimum environmental impact, we cannot claim to have a viable wastewater treatment process". The relationship of sludge disposal to total treatment processes is emphasized by the fact that sludge handling and disposal represents up to 50 percent of the total treatment capital and operating costs (Burd, 1968). Processing of wastewater sludge will, no doubt, receive increased attention in the future because of environmental concerns for our air, land and water. The present technology for processing wastewater treatment plant sludge is well established and includes conditioning, dewatering, and disposal. Many of these processes are highly sophisticated and relatively expensive. Most of the more advanced processes are unsuitable for small wastewater treatment facilities in Alaska.The work upon which this report is based was supported in part by funds (Proj. A-033-ALAS) provided by the United States Department of the Interior, Office of Water Resources Research, as authorized under the Water Resources Act of 1964, as amended

Electrokinetic Treatment of Sludge

Disposal of sludge has become a major issue in the pulp and paper industry because of the decreased space in landfills and the possibility of pollution from the sludge. By increasing the amount of solids in the sludge (dewatering), the sludge could be disposed of using less land or by incineration, composting, or other method. The dewatered sludge is easier to handle also because of its decreased volume. The method of dewatering which was used for the experiment was by electrokinetics. Electrokinetics is the technology of separating solids and liquids from suspensions of finely divided solids or colloidal particles using an electrical potential. Using four different power levels, a final solids level of 5.9% was reached and a decreased volume of almost 50%. This data showed that electrokinetics does have the potential to greatly reduce the volume of material which needs to be disposed of. It may also be able to increase the solids level to a higher level with further modification

Electro-kinetic technology as a low-cost method for dewatering food by-product

Increasing volumes of food waste, intense environmental awareness, and stringent legislation have imposed increased demands upon conventional food waste management. Food byproducts that were once considered to be without value are now being utilized as reusable materials, fuels, and energy in order to reduce waste. One major barrier to the valorization of food by-products is their high moisture content. This has brought about the necessity of dewatering food waste for any potential re-use for certain disposal options. A laboratory system for experimentally characterizing electro-kinetic dewatering of food by-products was evaluated. The bench scale system, which is an augmented filter press, was used to investigate the dewatering at constant voltage. Five food by-products (brewer’s spent grain, cauliflower trimmings, mango peel, orange peel, and melon peel) were studied. The results indicated that electro-kinetic dewatering combined with mechanical dewatering can reduce the percentage of moisture from 78% to 71% for brewer’s spent grain, from 77% to 68% for orange peel, from 80% to 73% for mango peel, from 91% to 74% for melon peel, and from 92% to 80% for cauliflower trimmings. The total moisture reduction showed a correlation with electrical conductivity (R2¼0.89). The energy consumption of every sample was evaluated and was found to be up to 60 times more economical compared to thermal processing

Procedure to research characteristics of finely dispersed coal bearing sludge

Розглянута методика досліджень властивостей тонко дисперсних осадів, що впливає на процес фільтрування. Приведені дослідження процесів, які відбуваються в порах осадів на мікрорівні. За результатами досліджень визначено максимальний час,необхідний для зневоднення вугільних осадів шламової крупності. Одержані залежності необхідного часу зневод-нення від проникності осадів,перепаду тиску та товщини осадів.Рассмотрена методика исследования свойств тонкодисперсних осадков, которые влияют на процесс фильтрования. Приведены исследования процессов, которые происходят в порах на микроуровне. По результатам исследований определено максимальное время, необходимое для обезвоживания угольных осадков шламовой крупности. Получены зависимости необходимого времени обезвоживания от проницаемости осадков, перепада давления и толщины осадков.The lacks of existent methods of quality of finely dispersed sediments, which influence on filtration process. There are investigations which took place in pores on micro level. By results of re-searchers the maximum time which is necessary of dewatering of slim-sediment with various permeability is defined. The time of dewatering, which depends on permeability of sediments, pressure dif-ference and thickness of sediments, is defined

Review of geomechanical problems of accumulation and reduction of mining industry wastes, and ways of their solution

Purpose. The identification of geomechanical problems of mining industry wastes accumulation and substantiation of the ways for their solution with the possibility of processing the watery technogenic feedstock by fine classification with dewatering. Methods. To achieve this purpose, an integrated approach is used in this work, which includes the scientific and technical analysis of research according to wastes accumulation, state statistics data, analytical studies of the strata compaction ratio of aqueous rocks, affecting the subsidence of the earth surface. This also includes the bench experimental studies to establish the dependence of changes in moisture content and the extraction of fine classes in screened products depending on the screening time at shock-vibrating screening by a new method for separating the enrichment wastes before to stockpile them into a pond. Findings. The developed mathematical apparatus has been proposed for determining the parameters of geomechanical processes in technogenic massifs. It has been shown that in order to reduce the technogenic load and manifestation of negative geomechanical processes, it is necessary to reduce the area of land under the waste ponds and the accumulated volumes themselves of mining and enrichment wastes. The dependences have been established of the preliminary enrichment complex on the qualitative parameters of the feedstock and the technological parameters of the equipment. It has been revealed that the mineral stock, formed from wide grain-size classes with a high content of particles less than 0.2 mm, is dewatered up to 18 – 22% by traditional methods and is practically not classified. Originality. A mathematical model has been proposed of screening and dewatering kinetics, which takes into account comprehensively the initial distribution of particles and liquid throughout the height of the screened material layer, segregation, mixing, sifting, vibrational transportation features (rate, multiplicity and number of falls over the period of vibrational transportation) and change in the height of the layer. This model is different due to the account of the mutual influence of classification by coarseness and dewatering. Practical implications. The represented dependences can be used to predict the development of negative geomechanical processes. The obtained results make it possible by means of a calculation to determine rational parameters of the screen and screening process with dewatering at processing of various feedstock with the use of initial data. The use of technology, which includes a fine classification in wastes processing, will allow: increase the economic efficiency of enterprises; to expand the feedstock base for construction, coke and chemical industries and power industry; to solve the problems of creating additional containers for storing the wastes; to improve significantly the environmental situation in the mining and processing regions.Мета. Виділення геомеханічних проблем накопичення відходів гірничодобувної промисловості та обґрунтування шляхів їх вирішення з можливістю переробки обводненої техногенної сировини шляхом тонкої класифікації зі зневодненням. Методика. Для досягнення поставленої мети в роботі використано комплексний підхід, що включає науково-технічний аналіз досліджень щодо накопичення відходів, даних державної статистики, аналітичні дослідження величини ущільнення пластів водомістких порід, що впливає на просідання поверхні, а також стендові експериментальні дослідження зі встановлення залежності зміни вологості й вилучення тонких класів у продуктах грохочення залежно від його тривалості при віброударному грохоченні новим способом для розділення відходів збагачення перед їх складуванням у накопичувач. Результати. Запропоновано розроблений математичний апарат щодо визначення параметрів геомеханічних процесів у техногенних масивах. Показано, що для зменшення техногенного навантаження та проявів негативних геомеханічних процесів необхідно скоротити площу земель під накопичувачами відходів та обсяги самих накопичуваних відходів видобутку і збагачення. Встановлено залежності комплексу попереднього збагачення від якісних параметрів вихідної сировини та технологічних параметрів обладнання. Виявлено, що мінеральна сировина, сформована з широких класів крупності з великим вмістом частинок менше 0.2 мм, традиційними способами зневоднюється до 18 – 22% і практично не класифікується. Наукова новизна. Запропоновано математичну модель кінетики грохочення і зневоднення, що комплексно враховує початковий розподіл часток і рідини за висотою шару матеріалу, що грохочеться, сегрегацію, перемішування, просіювання, особливості вібротранспортування (швидкість, кратність і кількість падінь за період вібротранспортування) та зміну висоти шару, що відрізняється урахуванням взаємного впливу класифікації за крупністю й зневоднення. Практична значимість. Наведені залежності можуть бути використані для прогнозування розвитку негативних геомеханічних процесів. Застосування технології, що включає тонку класифікацію, при переробці відходів дозволить підвищити економічну ефективність підприємств; розширити сировинну базу для будівельних, коксохімічних виробництв і енергетики; вирішити проблеми створення додаткових ємностей для складування відходів; значно поліпшити екологічний стан у видобувних і переробних регіонах.Цель. Выделение геомеханических проблем накопления отходов горнодобывающей промышленности и обоснование путей их решения с возможностью переработки обводненного техногенного сырья путем тонкой классификации с обезвоживанием. Методика. Для достижения поставленной цели в работе использован комплексный подход, включающий научно-технический анализ исследований по накоплению отходов, данных государственной статистики, аналитические исследования величины уплотнения пластов водосодержащих пород, влияющей на проседание поверхности, а также стендовые экспериментальные исследования по установлению зависимости изменения влажности и извлечения тонких классов в продуктах грохочения в зависимости от его продолжительности при виброударном грохочении новым способом для разделения отходов обогащения перед их складированием в накопитель. Результаты. Предложен разработанный математический аппарат по определению параметров геомеханических процессов в техногенных массивах. Показано, что для уменьшения техногенной нагрузки и проявления негативных геомеханических процессов необходимо сократить площадь земель под накопителями отходов и объемы самих накапливаемых отходов добычи и обогащения. Установлены зависимости комплекса предобогащения от качественных параметров исходного сырья и технологических параметров оборудования. Выявлено, что минеральное сырье, сформированное из широких классов крупности с большим содержанием частиц менее 0.2 мм, традиционными способами обезвоживается до 18 – 22% и практически не классифицируется. Научная новизна. Предложена математическая модель кинетики грохочения и обезвоживания комплексно учитывающая начальные распределения частиц и жидкости по высоте слоя грохотимого материала, сегрегацию, перемешивание, просеивание, особенности вибротранспортирования (скорость, кратность и количество падений за период вибротранспортирования) и изменение высоты слоя, отличающаяся учетом взаимного влияния классификации по крупности и обезвоживания. Практическая значимость. Приведенные зависимости могут быть использованы для прогнозирования развития негативных геомеханических процессов. Применение технологии, включающей тонкую классификацию, при переработке отходов позволит повысить экономическую эффективность предприятий; расширить сырьевую базу для строительных, коксохимических производств и энергетики; решить проблемы создания дополнительных емкостей для складирования отходов; значительно улучшить экологическую обстановку в добывающих и перерабатывающих регионах.The authors express particular gratitude to the management and employees of PJSC “United Mining Chemical Company”, Vilnohirsk Mining Metallurgic Integrated Plant, branch of TSOF Pavlohradska, DTEK Pavlohradvuhilia PJSC for providing the factual materials (enrichment wastes) to conduct research under laboratory conditions

The Effectiveness of Potassium Permanganate in Oxidizing Hydrogen Sulfide and in Aiding Mechanical Dewatering of Pulp and Paper Industry Sludges

Introduction Odorous compounds have long been a significant problem faced by mills treating their own wastewater. This problem can be compounded when mechanical dewatering equipment is used to process primary and secondary sludges. Plainwell Paper Company, a competitive producer of fine printing and technical specialty papers, is no exception to this rule. Along with the start-up of their new waste water treatment facility, which includes an Arus-Andritz sludge dewatering machine, came an irritating and potentially harmful odor problem. It was determined that the major cause of the odor was hydrogen sulfide

Contribution to the study of flocculation of digestate

The paper deals with the intensification of separating the solid phase of digestate using flocculants only. The separated solid phase should subsequently be used in agriculture for fertilising. Flocculants (polyacrylamides) are difficult to biodegrade. In this respect, they should not deteriorate the properties of the solid phase and the flocculant dose must be as low as possible. The research aimed to identify the optimal cationic flocculant and its application procedure which would enable a dosage that would be both economically and ecologically acceptable. We tested 21 cationic flocculants of different charge density and molecular weight and 1 mixture of two selected flocculants (Sokoflok 53 and Sokoflok 54) with the aim to discover the lowest possible dose of flocculating agent to achieve the effective aggregation of digestate particles. The lowest flocculant doses were obtained using the mixture of flocculants labelled Sokoflok 53 and Sokoflok 54 in 4:1 proportion, both of a low charge density and medium molecular weight, namely 14.54 g/kg of total solids for a digestate from the biogas plant Stonava and namely 11.80 g/kg of total solids for a digestate from the biogas plant Vrahovice. The findings also reveal that flocculation is most effective during two-stage flocculant dosing at different mixing time and intensity

Low Cost Dewatering of Waste Slurries

The U.S. Bureau of Mines has developed a technique for dewatering mineral waste slurries which utilizes polymer and a static screen. A variety of waste slurries from placer gold mines and crushed stone operations have been successfully treated using the system. Depending on the waste, a number of polymers have been used successfully with polymer costs ranging from $0.05 to$0.15 per 1,000 gal treated. The dewatering is accomplished using screens made from either ordinary window screen or wedge wire. The screens used are 8 ft wide and 8 ft long. The capacity of the screens varies from 3 to 7 gpm/sq. ft. The water produced is acceptable for recycling to the plant or for discharge to the environment. For example, a fine grain dolomite waste slurry produced from a crushed stone operation was dewatered from a nominal 2.5 pct solids to greater than 50 pct solids using $0.10 to$0.15 worth of polymer per 1,000 gal of slurry. The resulting waste water had a turbidity of less than 50 NTU and could be discharged or recycled. The paper describes field tests conducted using the polymer-screen dewatering system