Sludge Extraction Research Articles

Gain modulation of manual following response associated with galvanic vestibular stimulation

In this study, the impacts of sucrose addition and the application of beet pulp as carbon source on nitrogen loss during sewage sludge composting were evaluated in a lab-scale reactor. Response surface methodology (RSM) was used to optimize the method of sucrose addition. The relationship between biodegradability (5 day biochemical oxygen demand (BOD5) content) of sludge extraction solution and ammonia emission was investigated. With the nitrogen loss ratio as a dependent variable, the conditions (adding ratio of 0.02 (w (sucrose):w (sewage sludge)), adding time of 59.3 h and adding solid sucrose (without water) were chosen. The developed model was verified to have a high degree of accuracy. The BOD5 content of sludge extraction was obviously increased to 62.3 mg/g volatile solid (VS) and 213.9 mg/gVS by adding sucrose and beet pulp. Ammonia emission could be further reduced by 56.7% through adding beet pulp. The results suggested that the high biodegradability of carbon source might be the main reason that beet pulp could efficiently reduce the nitrogen loss during composting.

Membrane bioreactor performances: comparison between continuous and sequencing systems

Nowadays, membrane bioreactor performancesare well known in term of quality of pollutantremoval from wastewater including possibility oftreated water reuse. As regards the excess sludgeproduction, the strict levels of environmentaldirective and the limiting disposal options,imposed to develop strategies on the reductionof biomass production in wastewater treatment [1].A type of strategy consists in limiting the amountof substrate supplied to the biomass, i.e. the foodto microorganisms (F/M) ratio. In this substrate-limited condition the allocation of the substrateis preferentially turned to maintenance energyrequirements [2,3]. However, to ensure a capabil-ity of the system to treat acceptable organicvolumetric loadings, development of reactors withhigh biomass concentration is essential. On thisway, fixed cultures and specially membrane bio-reactors (MBR) appears as adequate solutions. Indeed, according to Pirt theory [3], it seemspossible, for a given F/M ratio, to reach asteady state biomass con centration in a continu-ous system without any sludge extraction andconsequently, a MBR system should be able toachieve a stable biomass concentration in thereactor avoiding any excess sludge production.As well Ref. [4] showed that the initial sub-strate/biomass ratio is a critical parameter inbatch experiments: when cell growth is limitedby carbon source, low initial substrate/biomassratios, the bacterial metabolism imposed stor-age compounds synthesis. This phenomenon —synthesis and consumption — leads to biomassconversion yields lower than a biomass replica-tion process which is favourable at highsubstrate/biomass ratios [5]. This result may bean important point when comparing continuousand sequencing bioreactor functioning at thesame organic loading. Indeed a continuousfeeding of the reactor corresponds to a continu-ous low F/M ratio (with adapted MLVSS in thereactor) then a sequencing system will receivemomentously higher F/M ratio during the feedperiod. The aim of this work is to study and comparethe biological and filtration performances of twoimmersed membranes bioreactors, one is operat-ing in a sequencing way (MSBR), the other onein a continuous way (MCBR). The operations

Factorial experimental design for recovering heavy metals from sludge with ion-exchange resin

Wastewaters containing heavy metals are usually treated by chemical precipitation method in Taiwan. This method can remove heavy metals form wastewaters efficiently, but the resultant heavy metal sludge is classified as hazardous solid waste and becomes another environmental problem. If we can remove heavy metals from sludge, it becomes non-hazardous waste and the treatment cost can be greatly reduced. This study aims at using ion-exchange resin to remove heavy metals such as copper, zinc, cadmium, and chromium from sludge generated by a PCB manufacturing plant. Factorial experimental design methodology was used to study the heavy metal removal efficiency. The total metal concentrations in the sludge, resin, and solution phases were measured respectively after 30 min reaction with varying leaching agents (citric acid and nitric acid); ion-exchange resins (Amberlite IRC-718 and IR-120), and temperatures (50 and 70 °C). The experimental results and statistical analysis show that a stronger leaching acid and a higher temperature both favor lower heavy metal residues in the sludge. Two-factors and even three-factor interaction effects on the heavy metal sorption in the resin phase are not negligible. The ion-exchange resin plays an important role in the sludge extraction or metal recovery. Empirical regression models were also obtained and used to predict the heavy metal profiles with satisfactory results.

Optimisation of a large WWTP thanks to mathematical modelling

Better controlling and optimising the plant's processes has become a priority for WWTP (Wastewater Treatment Plant) managers. The main objective of this project is to develop a simplified mathematical tool able to reproduce and anticipate the behaviour of the Tougas WWTP (Nantes, France). This tool is aimed to be used directly by the managers of the site. The mathematical WWTP model was created using the software WEST. This paper describes the studied site and the modelling results obtained during the stage of the model calibration and validation. The good simulation results have allowed to show that despite a first very simple description of the WWTP, the model was able to correctly predict the nitrogen composition (ammonia and nitrate) of the effluent and the daily sludge extraction. Then, a second more detailed configuration of the WWTP was implemented. It has allowed to independently study the behaviour of each of four biological trains. Once this first stage will be completely achieved, the remainder of the study will focus on the operational use of a simplified simulator with the purpose of optimising the Tougas WWTP operation.

Endoscopic Management of Biliary Obstruction Caused by Cavernous Transformation of the Portal Vein

Background Symptomatic biliary obstruction caused by cavernous transformation of the portal vein isan extremely rare disorder for which there is no consensus as to optimal treatment. The results of endoscopic treatments in a small group of patients is reviewed. Methods A total of 10 patients (5 men, 5 women; mean age 36.1 years, range 17–48 years) with severe biliary strictures were treated between 1995 and 2001. Biliary sphincterotomy was performed in all patients. Four patients also underwent balloon dilation, nasobiliary drainage, and stone or sludge extraction by using a balloon. All patients had stent insertion. Observations The mean duration of therapy was 3.3 years (range 1–7 years). There was no complication directly related to the endoscopic procedures except for hemobilia that occurred in one patient during stent removal. Cholangitis developed in 5 patients during the therapy period and was treated endoscopically. In 4 patients, significant improvement in the biliary stricture was observed and stents were removed in 3. These patients were followed without stent insertion for one year. Conclusions Endoscopic management of biliary stricture caused by cavernous transformation of the portal vein appears to be effective and safe.

Chlorophenols in digested U.K. sewage sludges

This paper describes a method developed for the analysis of chlorophenols in liquid sewage sludges. After a comparison of different extraction procedures, wet sludge extraction with a solvent mixture of hexane and isopropyl alcohol was selected. Twelve sewage sludges from rural, urban and industrial sewage treatment works in north-west England were analysed by capillary GC-ECD, using a derivatization procedure. The total chlorophenol content ranged between 9.8 and 60.5 mg/kg (38.7–99.2 μg/l), with a mean of 34.6 mg/kg (70.4 μg/l). The most abundant chlorophenol was 2,4-dichlorophenol, which had a mean concentration of 26 ± 15.7 mg/kg (51.6 ± 19.6 μg/l); pentachlorophenol concentrations ranged between 0.1 and 2.04 mg/kg (0.21–3.76 μg/l). Chlorophenols with known sources and/or those which are known degradation products were found in the greatest abundance. The data are discussed in relation to literature reported figures and the inputs of chlorophenols to sludge amended agricultural soils is assessed.

Closed Loop Computer Control of a Wastewater Treatment Process

The application of digital computer control to municipal wastewater treatment processes is steadily gaining popularity. Within the next few years this mode of control is expected to become a standard feature of larger wastewater treatment plants. The purpose of this paper is threefold: first, to acquaint those outside the wastewater industries of the general concepts of wastewater treatment so they may appreciate some of the requirements imposed on the control computer; second, to present the overall control laws that regulate the feedback control of a pure oxygen activated sludge and anaerobic digestion processes; and third, to describe the control system architecture and present the general philosophy of on-line closed loop control of Metro Denver’s new pure oxygen activated sludge process. Operating experience in the use of a remote multiplexing scheme with distributed digital processing to provide feedback control will be discussed. System capabilities to be outlined not only include such standard features as control of influent flow splitting between two treatment facilities, representative sample withdrawal, pump scheduling and chemical dosage control, but also such state-of-the-art highlights as on-line predictive control of activated sludge returning to match diurnal flow patterns, primary sludge extraction, aeration reactor trim level and waste solids extraction.