bluuebunny/crossref_metadata_2025_split huggingface dataset:
Treatment of Acidic Effluents with Limestone Instead of Lime
Authors: Maree J. P. , du Plessis P. , van der Walt C. J. 
Published: May 2018

Traditionally acid mine water is neutralised with lime (Ca(OH)2) Limestone (CaCO3) can be used as an alternative to lime as it is much cheaper. The aim of this study was to investigate the practicality of using cheaper limestone (CaCO3) as an alternative. Beaker and semi-continuous studies were carried out to determine the quality of the water after lime treatment to various pH-values, the influence of CaCO3 dosage, particle size and aeration time on neutralisation rate and the effect of gypsum, magnesium, iron(II) and iron (III).
The rate of neutralisation is fast when stoichiometric dosages of lime are applied. If sufficient crystallisation is allowed, partial removal of sulphate is achieved, as well as complete removal of heavy metals, depending on the pH of the treated water. With limestone the rate of CaCO3 neutralisation depends on the dosage of CaCO3 and particle size. Aeration marginally accelerated the rate of neutralisation as a result of CO2 stripping. Partial sulphate removal is achieved as a result of CaSO4 crystallisation while magnesium, if present, co-precipitates with the CaSO4. Iron(III) and aluminium(III) are effectively removed but the rate of neutralisation is dramatically retarded by dissolved iron(II). Iron(III) has no influence on the rate of acid water neutralisation. During semi-continuous fluidised bed studies, CaCO3 in the limestone was completely utilised when the particle size was greater than 0.150 mm. The capital costs for lime and limestone neutralisation in a f luidised-bed reactor are similar, but the chemical cost in case of limestone neutralisation amounts to only 29% of that of lime.
The Forecasting of Hydrogen Sulphide Gas Build-Up in Sewerage Collection Systems
Authors: Matos J. S. , de Sousa E. R. 
Published: May 2018

The presence of hydrogen sulphide gas in sewerage collection systems is a common source of odour nuisance, corrosion of sewers and toxic atmospheres. The hydrogen sulphide build-up in the sewer air may be related to sulphide concentrations in the flowing sewage and with other factors, such as turbulence, aerodynamic conditions of the ventilating air now and roughness of the unsubmerged surfaces.
In the present work, a mathematical model is presented for forecasting hydrogen sulphide gas build-up along gravity sewers, which is based on the analysis of a differential mass balance equation applied to a sewer reach. Good correlation was obtained, comparing the results of the model with experimental information collected in the Funchal main trunk sewer. Funchal city is the capital of Madeira, a Portuguese island in the middle of the Atlantic Ocean, and its main trunk sewer was put into operation at the beginning of 1980.
Nitrification, Denitrification and Biological Phosphate Removal in Sequencing Batch Reactors Treating Piggery Wastewater
Authors: Bortone G. , Gemelli S. , Rambaldi A. , Tilche A. 
Published: May 2018

In Italy, because of the high concentration of animals in many agricultural areas, not all piggery manure can be landspread. Considering their chemical characteristics - high concentration in organics and nutrients -processes providing the removal of COD, N & P have to be adopted. Other aspects have to be considered with regard to cost saving and simple management.
In order to study a simple andreliable treatment system, two 51 bench-scale SBRs were built. Each reactor treated 500 ml/d of clarified (after centrifugation) piggery wastewater.
A cycle with the following alternating phases of reaction was chosen: first denitrification and phosphorus release, first oxidation-nitrification, second denitrification and second oxidation-nitrification. The systems showed good flexibility and enhanced removal of COD, N and P was easily reached modifying the duration of each phase. The best efficiency in N removal has been noticed in the reactor in which the feeding distribution was done in the two denitrification phases, allowing a better use of the organic substrate for the denitrifying bacteria. This confirmed that the limiting factor, in the removal of N from piggery wastewater, is represented by the too high ratio TKN/COD. Anyway good removals of COD (~93%), N (88-93%) and P(~95%) were obtained in both reactors. A relevant concentration of unbiodegradable COD - at the adopted HRT, SRT and reaction temperature - was still present in the effluent of both reactors (~300 mg/l).
Track studies allowed the evaluation of the nitrification and denitrification kinetic constants. Their values were higher than the ones reported in the literature. No inhibition of the nitrifying activity due to high concentration of N-NH4 (&gt;80 mg N/l), was observed.
Specific studies on biological phosphate removal have been carried out. In spite of the high concentration of P in the biomass and the low concentration of P in the effluent, showing a surplus biological P removal, no P release was observed; this might have been masked by biologically induced chemical precipitation. In fact, piggery wastewaters are rich in metals and a high concentration of metal-bound P was analytically observed. However, a high concentration of polyphosphates has been analytically determined in the biomass. This should confirm the presence in the microbial community of bacteria performing the surplus P removal.
Treatment of Domestic Sewage in Macrohydrophyte Ponds
Authors: Xu H. , Wang B. , Yang Q. , Liu R. 
Published: May 2018

An experimental study was carried out on the treatment of domestic sewage by macrohydrophyte ponds, including water hyacinth and water peanut (AlterantheraPheloxiroides) ponds. The study indicated that both the water hyacinth and water peanut ponds were more effective and efficient in removing BODs (90-98%), TP (75-85%), PO4(90-99%), SS (90-95%), total bacteria (99.9-99.99%), and E. Coli (99-99.9%) in their growth seasons compared with the algae/bacterial symbiotic ponds with the pollutant removal rate constant ratio (k value in WHP or WPP/k value in ABP ponds) being: COD, 4.0-5.0, BOD5, 1.5-2.0, TN, 1.5-2.0, NH4+−N,2.0-3. 01 TP, 3.5-4.0; and PO43−2.8-5.7. The study found that the intensification effect was mainly ascribed to the microbial community in the root system, which was found to consist of Bacillus, Pseudomonas, Alcaligens, Brevibacterium, Ammonia fier, Nitrosonionas, Nitrobacter, and Denitrifier.
A mathematical model to describe the water flow pattern and BOD5 removal rule across the WPP pond based on the diffusion flow pattern model was developed with very low D values, which means that the water flow in the WHP and WPP ponds is near plug flow pattern.
Treatment Standards and Wastewater Discharge Fee in Germany
Authors: Imhoff K. R. 
Published: May 2018

The Federal German Water Law of 1976 postulated for the first time that a license for the discharge of wastewater into public water courses might only be granted when the wastewater prior to the discharge is treated according to the actual standards. Also since 1976 it was decided that for the residual pollution of wastewater a pollution fee has to be paid.
Assuming certain loads per capita one can calculate that presently three pollution units have to be paid per capita and year for untreated domestic wastewater. One pollution unit is assessed with 50 DM per year in 1991 but the price will be increased to 90 DM per year in future.
Since the pollution units encompass COD, nitrogen, phosphorus, heavy metals and chlorinated carbon compounds the pollution unit is a very good tool to compare the effectiveness of treatment. For different drainage systems one can also calculate the residual pollution units per litre and second for low flow conditions.
Comparative Rates of Disinfection of Microbial Indicator Organisms in Chlorinated Sewage Effluents
Authors: Rippey S. R. , Watkins W. D. 
Published: May 2018

The densities of several microbial indicator organisms, including fecal coliforms, enterococci, Clostridiumperfrinaens, and a male-specific bacteriophage group, were determined in the pre- and post-chlorinated effluents of three wastewater treatment plants during a rainfall event when the plants were operating near maximum flow capacity. These studies were undertaken to determine the effects of elevated flow rates on the relative rates of inactivation of the microbial indicators due to chlorine disinfection.
Three distinctly different responses to chlorine treatment were observed. The vegetative bacterial organisms (fecal coliforms and enterococci) were most sensitive, the male-specific bacteriophage group was considerably more refractory, and c. perfringens, a bacterial spore-former, was highly resistant to inactivation by the disinfecting agent. These findings are significant for two reasons. First, the vegetative bacterial indicators did not reliably index the decay rates of the bacterial virus under the field conditions experienced. This has important public health ramifications to consumers of certain seafood products and to marine recreationists. Second, because of the highly refractory nature of the c. perfrinaens spore, this microbial indicator has practical use in assessing the magnitude of the impacts (source strengths) of sewage contaminated wastewaters on estuarine and marine environments.
Phosphate Precipitation with On-Site Alkali Generation
Authors: Kolbé F. F. , Terblanche J. S. 
Published: May 2018

Commercially available membrane electrolysis equipment can be used to produce substantial quantities of caustic soda from salt (NaCl) with chlorine gas being produced as a by-product. This caustic soda may be employed to raise the pH of the final effluent in order to achieve high levels of phosphate precipitation or removal in the form of crystallization. The pH may then be lowered, prior to final discharge, by re-carbonation utilising combusted biogas, which is produced on-site.
At the Kempton Park wastewater treatment works, which achieves biological phosphate removal by means of the Phostrip process, laboratory scale tests proved the commercial viability of this process. It was found that a dosage of 150 mg/l of caustic soda was needed to reach a redox potential of −250 mV, at which point the phosphate content of the stripper overflow was reduced from 30 mg/l to under 1 mg/l. The savings effected in the cost of chlorinating the final effluent, entirely offsets the cost involved.
A number of other possible process configurations are proposed, with treatment costs varying from 0,8 to 5,3c/kl, which compares favourably with biological or other methods of chemical treatment, which typically range from 3 to 6 c/kl (costs given in SA cents = 0,35 US cents).
Concepts for Minimizing Emissions at Activated Sludge Plants
Authors: Pincince A. B. 
Published: May 2018

In the next few years, the need to decrease emissions of odors and volatile organic compounds will become increasingly important in the design and operation of wastewater treatment plants.
The primary methods for decreasing emissions are adding precipitating chemicals to raw wastewater, using velocity-controlled or vortex-type gritchambers, eliminating or decreasing free falls, covering tanks andchannels, decreasing stripping in aeration tanks, minimizing chlorine use, operating treatment plants properly, and collecting and treating vented air.
The methods cannot all be used simultaneously at a single treatment plant, and some of them might prove to be too costly, except in special circumstances. Nevertheless, they are worth considering.
A New Operation of Carbohydrate-Containing Wastewater Treatment in an Anaerobic Fluidized Bed System
Authors: Matsumoto A. , Sakamoto M. , Noike T. 
Published: May 2018

The effects of pH on the characteristics of conversion of starch to methane in anaerobic digestion were investigated by using a laboratory-scale anaerobic fluidized bed reactor over the pH range of 5.8-7.0. Furthermore, a new operation method was proposed to treat wastewater containing starch effectively.
At pH 6.2, starch was decomposed well and methane was also formed well. The phenomenon showed methanogenesis in an attached growth system developed more tolerance for lower pH than in suspended growth type systems. After all, pH 6.2 was the optimum pH value for conversion of starch tomethane in our experiment.
From these results, it is proposed that the more effective anaerobic digestion is made possible by the operation at low pH (for example 6.2) which accelerates acidogenesis and doesn't inhibit methanogenesis in attached growth systems.
Phosphorus Removal in Constructed Wetlands Using Gravel and Industrial Waste Substrata
Authors: Mann R. A. , Bavor H. J. 
Published: May 2018

The phosphorus removal efficiency of three gravel based constructed wetland systems (CWSs) has been investigated in a two year study in which secondary sewage effluent was treated. The constructed wetlands systems, 100m × 4m × 0.5m with an impervious liner, comprised an unplanted gravel “control” trench and gravel trenches planted with monoculture stands of either Typhaorientalis or Schoenoplectusvalidus. Inlet and outlet phosphorus concentrations and vertical and linear profiles of phosphorus were determined to characterise immobilisation/translocation through the systems. Laboratory phosphorus adsorption experiments were conducted with regional gravels and alternative adsorptive media including industrial slag and ash by-products.
Phosphorus adsorption in the large scale gravel systems was variable and ranged from −40% to 40%. Laboratory adsorption capacity studies conducted with the gravel substratum indicated that field adsorption potential could be successfully simulated and modelled.
Ion exchange experiments have been used to evaluate gravel and industrial conglomerates, with a view to improving phosphorus immobilisation through substratum selection and effluent flow management. Langmuir and Freundlich isotherms characterised phosphorus adsorption and the maximum adsorption capacity of regional gravels ranged from 25.8 to 47.5 μg P/g compared to blast furnace slag 160 to 420 μg P/g and fly ash 260 μg P/g. These results indicate that further investigations into the inclusion of industrial waste substrata in a CWS are warranted.
Influence of Particle Size Distribution on the Dewatering of Organic Sludges
Authors: Olböter L. , Vogelpohl A. 
Published: May 2018

The particle size distribution of different sludges from sewage treatment plants was compared. Since the dewaterability of a sludge depends on its particle size distribution, this property can be used to characterize dewaterability. Thus, as shown by an example, the change in the dewaterability by conditioning a sludge with a polymer reflects the change of the particle size distribution. The measurement of the particle size distribution at a defined position in a settling tube during the settling process may also be used to study the settling behaviour of a sludge.
The floc structure of sludges from different treatments varies in a wide range. It is not possible, therefore, to give a full characterization by the particle size distribution only. Furthermore, structural elements of the sludge flocs cannot be neglected. Taking this into consideration, new dewatering parameters have to be defined in order to characterize dewaterability as a function of the particle size distribution.
Household Membrane Bioreactor in Domestic Wastewater Treatment
Authors: Chiemchaisri C. , Yamamoto K. , Vigneswaran S. 
Published: May 2018

The activated sludge process coupled with hollow fiber membrane for solid-liquid separation was applied to treat low strength domestic wastewater.
Pilot-scale experimental unit used in this study consisted of 2 modules of 0.03 μm pore size with 9 m2 surface area each, immersed in the reactor which has a maximum working volume of 1.5 m3. Even when sewage was fed at varying rates following its diurnal flow variation to the bioreactor, good stability of the process was achieved which was shown by the consistency in treated water quality. The effluent turbidity and COD were well within the limits (less than 0.5 NTU and 3-5 mg/L). The transmembrane pressure drop was less than 20 cm Hg even after 2 months of operation. Application of jet aeration could be used to prolong the operational life of the membrane in the bioreactor. This system is an ideal one to be used as household wastewater treatment system.
A New Process to Treat Strong Biological Waste
Authors: Henry D. P. , Thomson R. H. 
Published: May 2018

Strong brewery waste was trickled through a vertical curtain consisting of two 3mm layers of reticulated Polyurethane foam bonded to a reinforcing nylon cloth core. A filamentous fungus, Geotrichum fragrans adhered to the curtain and provided a matrix for other yeasts and aerobic bacteria which include Kloeckera lindneri and a Candida sp., a Bacillus sp. and a Corynebacterium sp. The organisms grew as a lawn. To avoid anaerobiosis the lawn was harvested periodically by passing the curtain through rollers leaving a viable representative residue of the population. Passage through 6m of curtain reduced a TOD of 55,000 mgL−1 to 3,300 mgL−1 (94%). Probably the length of the curtain could be reduced to 4m with a residence time of 9.6h. One m2 of curtain with a 4m fall can treat 15Ld−1.
A further waste from pigs (2% solids) was acidogenically fermented to produce organic acids. The acids during clarification were used to kill the bacterial pathogens in the waste. The liquor was run through a curtain inoculated with suitable organisms. These removed the unpleasant odour and 88% of the TOD in a 4m passage through the curtain. Treatment time: fermentation 5d, clarification and removal of pathogens 2d, treatment in curtain 0.3d, total 7.3d.
Behavior of a Biological Fixed-Film System Treating Toxic and Nontoxic Organic Wastes
Authors: Hamoda M. F. 
Published: May 2018

The treatment of industrial wastes containing both toxic and nontoxic organic compounds is often accomplished by biological processes. Despite its success in many instances, the complex nature of the effects of toxic substances on process performance and kinetics is not well understood. This study was conducted to examine the behavior of an aerated submerged fixed-film (ASFF) biological system receiving a mixture of toxic (phenol) and nontoxic (sucrose) bisubstrate and evaluate its kinetic parameters. Laboratory experiments were carried out using a 50-litre ASFF reactor composed of four equal compartments.
Heterogeneous biomass acclimated to a bisubstrate (phenol/sucrose) system demonstrated the preference of microorganisms to utilize sucrose with a slower concomitant utilization of phenol. However, the removal in a bisubstrate system is slightly higher than that in a single substrate system which may be attributed to the extra biomass accumulated from the utilization of the other substrate. A steady-state approach to process kinetics indicates that substrate removal in the first compartment follows the Monod model for both sucrose and phenol where no mhibition (Haldane rate expression) appears over the studied range of phenol concentrations up to 800 mg/l. Meanwhile, substrate removal in the second through fourth compartments is better described by a variable order model which is likely to be a function of the hydraulic loading.
The Acidogenic Digestion of the Organic Fraction of Municipal Solid Waste for the Production of Liquid Fuels
Authors: D'Addario E. , Pappa R. , Pietrangeli B. , Valdiserri M. 
Published: May 2018

Several reactors were tested for the anaerobic conversion of the organic fraction of municipal solid waste into volatile fatty acids. The reactors examined included Batch, Semi-Continuous Stirred Tank Reactor and Multistage-Counter Flow Reactor.
After reasonable retention times (12 days), Batch systems operating at 15% w/v of dry matter and under pH controlled at 6.5, gave better performances both in terms of total Volatile Fatty Acids (VFA) concentration (23-24 g/l) and conversion yield (215 g VFA/kg volatile solids). However, these conditions of reaction caused a high level of liquefaction of the feedstock which resulted in a difficult down-stream processing. On the contrary, the acidogenesis under uncontrolled pH, allowed the production of leachates directly processable for acids recovery. Based on this reason, the Multistage-Counter Flow Reactor, operating under uncontrolled pH, appeared to be the most promising system.
The leachate obtained from such a system was processed to obtain mixtures of C2-C7 methyl esters, potentially usable as octane enhancers. The digested solid was intended to be dried and refined to obtain soil amendment. A process for the treatment of municipal solid waste based on the previous steps and including conventional sorting facilities and units for the incineration of all residual solids, was evaluated to be economically comparable with landfilling. The revenues from the sales of esters and fertilizers were highly sensitive to the yield of the acidogenic step and to the value and the amount of the derived fertilizer. Further research is still in progress to improve the economics of the process. The activities are addressed to study proper procedures for the improvement of the down-stream processing of the mixtures originating from acidogenesis under almost neutral pH.
Prediction Rules for Biogas Valorisation in Municipal Solid Waste Landfills
Authors: Marticorena B. , Attal A. , Camacho P. , Manem J. , Hesnault D. , Salmon P. 
Published: May 2018

The objective of this study was to develop a tool to predict the quantity of biogas produced by a municipal solid waste (MSW) landfill site to allow the energy it represents to be exploited.
The model proposed is based on a first-order kinetic equation which describes the production of methane during in-situ decomposition of MSW. This equation was applied to a landfill site considering the MSW mass as a series of layers of waste of differing ages. The equation includes three parameters: MPo, the methane potential of fresh waste which is specific to MSW, d, the in-situ life duration of the waste which depends on the landfilling conditions and Ti, the filling rate, i.e. the rate at which waste is placed in the landfill site. This simple model, usable for all types of landfill and, by virtue of the parameters it uses, closely represents the site operating conditions. The approach was applied to the Villeparisis site and predicted a methane production rate of between 270 and 410 m3h−1, quite close to the measured value of 300 m3.h−1. In addition, the possibility of simulating variable landfill rates and waste life durations can be used to guide site management techniques to optimize the valorisation of the biogas and provide a global approach to the problem by incorporating leachate collection into the biogas exploitation calculations.