Press Dewatering of Sludge with Applications of an Electric Field

In the paper industry today, there is a rising concern over the question of what to do with the paper mill sludge. Although in the past most of the sludge was sent to a landfill, this disposal method is becoming less and less acceptable due to increasing environmental concerns, decreasing landfill space and increasing costs. Since sludge contains a large fraction of water, one of the alternatives is to increase the dewaterability of the sludge through the use of electrokinetic forces. Increased dewatering of the sludge would allow for more economical alternatives to sludge disposal, such as incineration, as well as decrease the sludge handling, transportation, and disposal costs by reducing both volume and weight. The main objective of this thesis was to determine if the application of an electric current through a sludge press would increase the amount of dewatering in the sludge. A simulated press that allowed for the sludge to be pressed in-between two charged screens and water to be collected from both the top and bottom of the press was designed and constructed. During experimentation, drainage amounts and final sludge consistency was collected under varying voltage applications and compared to a control run with no voltage. From the results, it could be concluded that the application of an electric field did indeed help increase the dewaterability of the sludge. The results also show that ion migration does take place in the sludge with positively charged particles carrying water molecules towards the negatively charged screen. Further studies in applying this concept at higher pressing consistencies as well as other applications is recommended

Modeling Temporal Pattern and Event Detection using Hidden Markov Model with Application to a Sludge Bulking Data

This paper discusses a method of modeling temporal pattern and event detection based on Hidden Markov Model (HMM) for a continuous time series data. We also provide methods for checking model adequacy and predicting future events. These methods are applied to a real example of sludge bulking data for detecting sludge bulking for a water plant in Chicago

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

The effectiveness of anaerobic digestion in removing estrogens and nonylphenol ethoxylates

This is the post-print version of the final paper published in Journal of Hazardous Materials. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.The fate and behaviour of two groups of endocrine disrupting chemicals, steroid estrogens and nonylphenol ethoxylates, have been evaluated during the anaerobic digestion of primary and mixed sewage sludge under mesophilic and thermophilic conditions. Digestion occurred over six retention times, in laboratory scale reactors, treating sludges collected from a sewage treatment works in the United Kingdom. It has been established that sludge concentrations of both groups of compounds demonstrated temporal variations and that concentrations in mixed sludge were influenced by the presence of waste activated sludge as a result of transformations during aerobic treatment. The biodegradation of total steroid estrogens was >50% during primary sludge digestion with lower removals observed for mixed sludge, which reflected bulk organic solids removal efficiencies. The removal of nonylphenol ethoxylates was greater in mixed sludge digestion (>58%) compared with primary sludge digestion and did not reflect bulk organic removal efficiencies. It is apparent that anaerobic digestion reduces the concentrations of these compounds, and would therefore be expected to confer a degree of protection against exposure and transfer of both groups of compounds to the receiving/re-use environment.Thames Water, Yorkshire Water, and EPSRC

Reducing Decomposition Time in Landfills by an Aerobic Process

This experiment was performed to determine if sludge produced by the paper industry could be composted faster by promoting the aerobic degradation process. To perform this experiment, I chose a sludge produced by a virgin pulp mill. Once I collected sludge, it was dewatered to a moisture content of sixty-five percent or less. As soon as the sludge was dewatered, I set up four separate composting systems, three of which were run under aerobic conditions and one that was run under anaerobic conditions. The anaerobic conditions only had sludge and plastic for its bulking agent. In the aerobic systems there were three different types of bulking agents used; pine bark, plastic and compost. In the aerobic systems air was introduced into the system. To determine how fast each of the processes was composting, I collected the gases that were produced by each of the systems. The gases that are produced by an anaerobic process was carbon dioxide and methane, whereas an aerobic process produces carbon dioxide and water. Therefore, by analyzing the gases produced by each of the systems periodically and determining the amount of carbon dioxide produced by each of the systems, one can determine the rate of decomposition of the sludge for each of the separate systems. Also the chemical oxygen demand (COD) was determined for each of the system, before and after the degradation occurred. COD was used to measure that content of organic matter in the sludge. This also helped in determining the degradation that has occurred in each of the systems

Standardization of activated sludge for biodegradation tests

Activated sludges are an inoculum source commonly used in biodegradation studies, as wastewater treatment facilities constitute an entry point to the environment for many chemicals. In this paper, the main issues relating to the use of activated sludge in biodegradability tests are presented. Special attention is also devoted to discussing the factors affecting both the activity of the microbial communities and the test results. After a short survey of the state of the art of microbiology of activated sludge, the paper focuses on the methods used to reduce the variations in the diversity, quality and quantity of these communities. Finally, use of surrogates as reference materials in biodegradability tests is discussed

Laboratory measurements of radiance and reflectance spectra of dilute secondary-treated sewage sludge

The National Aeronautics and Space Administration (NASA), in cooperation with the Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA), conducted a research program to evaluate the feasibility of remotely monitoring ocean dumping of waste products such as acid and sewage sludge. One aspect of the research program involved the measurements of upwelled spectral signatures for sewage-sludge mixtures of different concentrations in an 11600-liter tank. This paper describes the laboratory arrangement and presents radiance and reflectance spectra in the visible and near-infrared ranges for concentrations ranging from 9.7 to 180 ppm of secondary-treated sewage sludge mixed with two types of base water. Results indicate that upwelled radiance varies in a near-linear manner with concentration and that the sludge has a practically flat signal response between 420 and 970 nm. Reflectance spectra were obtained for the sewage-sludge mixtures at all wavelengths and concentrations

Mesophilic anaerobic co-digestion of sewage sludge with glycerine: Effect of solids retention time

The main objective of this paper is to examine the effect of the increase in organic loading rates (OLRs), by reducing the solids retention time (SRT) from 20 d to 5 d, in single-phase mesophilic anaerobic co-digestion of sewage sludge with glycerine (1% v/v). It was experimentally confirmed that anaerobic co-digestion of these biowastes under steady-state conditions can achieve an 85 ± 5% reduction in volatile fatty acids (VFA) at SRTs of between 20 and 9 d, with a methane production yield of around 0.8 l CH4/l/d. Decreases in the SRT not only allow the sludge stability and biogas production to be maintained, but also lead to an increase in the waste that could be treated and lower operating costs. Therefore, mesophilic anaerobic co-digestion of sewage sludge and glycerin at a SRT lower than 20 d is possible and preferable due to being more economical and environmentally friendl

Composting and vermicomposting waste paper sludge

Increasing legislative and economic pressure to find more sustainable methods of organic waste management has fuelled innovation in biological treatment technology. By-products of paper manufacturing industries provide a large source of organic waste, which is known to have a high environmental impact. This waste paper sludge has been shown to be amenable to biological treatment. Recent research has confirmed that windrow-composting and vermicomposting techniques have potential to treat these wastes and share many economic and environmental benefits. Many authors have suggested that sludge specific composting methods need to be developed and this research aims to provide fundamental data in this respect. The treatment of specific waste paper sludges was investigated through small and larges calee xperimentsw ith the aim of optimising thesep rocessesw ith minimal intervention. Identical samples of a selected waste paper sludge feedstock were used in large scale investigations into the application of each composting technique, and the performance of each process and resulting products was evaluated. Windrow composting and vermicomposting were found to stabilise and enhance waste paper sludge in very different ways, producing unique products. In terms of processing, windrow composting resulted in more rapid rates of stabilisation and although the performance of the vermicomposting process was less effective in these respects, it afforded additional benefits as a treatment of waste paper sludge. Both processes were found to stabilise and enhance waste paper sludge but the selection of one system or the other will depend largely on the objectives of the project and the criteria required of the finished product