bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence and Significance of Toxic Cyanobacteria in Southern Africa
Authors: Scott W. E.
Published: May 2018

A comprehensive list is provided of more than forty cyanobacterial species and genera reported to have toxic properties. In South Africa the majority of animal poisonings since 1927 have been caused by a single species Microcystis aeruginosa. Although other toxic species also occur in southern Africa, to date they have been of little practical significance. The widespread distribution of M. aeruginosa throughout southern Africa indicates a tremendous potential for toxic blooms to develop with increasing eutrophication. Using HPLC techniques up to six different toxin variants have been quantified in natural blooms of M. aeruginosa collected in different parts of South Africa. The amounts and proportions of the different toxins in the different samples varied over a wide range. Several additional unidentified toxins were detected.
Epidemiological Study of Beach Water Pollution and Health-Related Bathing Water Standards in Hong Kong
Authors: Cheung W. H. S. , Hung R. P. S. , Chang K. C. K. , Kleevens J. W. L.
Published: May 2018

A prospective epidemiological study was undertaken in Hong Kong in 1987, in which 18,741 usable responses were obtained. It showed bathing in the coastal beaches of Hong Kong poses an increased risk of developing gastrointestinal, ear, eye, skin, respiratory and total illness. Swimmers immersed in the more polluted beach waters are exposed to a significantly higher risk of contracting swimming-associated gastrointestinal, skin, respiratory and total illness. E. coli was found to be the best indicator for swimming-associated gastroenteritis and skin symptoms amongst the bathers, and a linear relationship could be established. Staphylococci was a good indicator for ear, respiratory and total illness, and should be used in complementary to E. coli. Beach water quality objectives for both E. coli and staphylococci have been proposed. A 4-tier classification system (rather than a single acceptability criterion) based on swimming-associated health risks has been developed for the beaches of Hong Kong. Information on the bacterial water quality and health risk levels of individual beaches is reported to the public both annually and fortnightly, so that beach-goers can choose where to go for swimming based on health effects data.
Advancements in Toxicity Testing Applied to Design and Control of Biological Processes
Authors: Herricks E. E. , Rittmann B. E. , Grady C. P. L. , Pascoe D. , Somlyódy L. , Fleit E. , Olah J. , van der Gaag M. , van de Guchte C. , Verstraete W. , Dries D. , Schowanek D.
Published: May 2018

Toxicity testing is an essential tool for assessing the effects of, and fate of, many low-concentration toxicants in wastewater treatment systems. Toxicity testing can be divided into two parts: diagnostic toxicology evaluates the toxicity of a contaminant, effluent, or process, and toxicological engineering bases engineering design on the removal or production of toxicity. This paper presents six recent advancements in diagnostic toxicology and toxicological engineering identified by members of the Specialty Group on Hazard Assessment and Control of Environmental Contaminants. They are: (1) an ecological framework for applying toxicity testing, (2) biological early warning systems for on-line detection of toxic inputs, (3) inplant testing to detect and mitigate a toxic upset, (4) methods for rapid and cost-effective detection of genotoxins, (5) an approach for determining what discharged component must be controlled to eliminate an ecosystem disturbance, and (6) an application of process kinetics to design biological processes that are resistant to toxic upsets.
Peroxide Pre-Oxidation of Recalcitrant Toxic Waste to Enhance Biodegradation
Authors: Carberry J. B. , Benzing T. M.
Published: May 2018

Land disposal is required for industrial chemicals which are not readily biodegraded. Such compounds lead to adverse effects on the environment if they escape containment. Recalcitrant and persistent hydrocarbons and chlorinated chemicals are inherently resistant to any degree of biodegradation and cause a growing threat to underground aquifer quality. Hydrogen peroxide is a potentially economical method of pre-oxidation utilized to enhance the biodegradation of persistent and recalcitrant organics in contaminated soil systems. This pre-oxidation technology was examined in a laboratory respirometer using three model toxic organic chemicals: toluene, trichloroethylene and pentachlorophenol. Microbial cultures were selected from contaminated sites for the degradation of each model organic chemical. The rate at which the microbes degraded the organic chemicals in unoxidized aqueous systems was compared to the rate of degradation in peroxide pre-oxidized aqueous systems. Results indicated that pre-oxidation enhanced the biodegradation of trichloroethylene and pentachlorophenol. Toluene, in contrast, was not significantly oxidized by pretreatment with hydrogen peroxide, and its biodegradation rate was not enhanced by the oxidation pre-treatment process.
Removal of Chlorophenols from Water by Photocatalytic Oxidation
Authors: Tseng J. M. , Huang C. P.
Published: May 2018

Photocatalyst, TiO2, upon irradiation with uv light produces electrons and positive holes. The positive holes are strong oxidation agents that can oxidize organic compounds such as chlorophenol to mineral acids e.g. HC1 and CO2. Factors such as pH, chlorophenol concentration, concentration of TiO2 and inorganic electrolytes that may affect the oxidation of chlorophenol were investigated. The rate of the chlorophenol oxidation follows a first order reaction with respect to the chlorophenol concentration and independent of pH. The rate increases with concentration of TiO2, reaches a maximum level at 3 g/L then decreases to a constant value upon further increase in TiO2. Increasing the degree of chlorination appears to increase the extent and the rate of oxidation. For mono-chlorophenols the extent of oxidation follows: 4-chloro > 3-chloro > 2-chloro phenol. For dichlorophenols, the order is 2,6-dichloro ≈ 2,5-dichloro > 2,4-dichloro≈ 2,3-dichlorophenol. For symmetrical chlorophenols, the oxidation increases in the order: 4-chloro > 2,5-dichloro > 2,4,6-trichlorophenol. Pentachlorophenol is rapidly decomposed but the extent of oxidation is not complete.
Sorption of Polycyclic Aromatic Hydrocarbons onto Natural Solids: Determination by Fluorescence Quenching Method
Authors: Shimizu Y. , Liljestrand H. M.
Published: May 2018

A fluorescence quenching method was used to determine the sorption of polycyclic aromatic hydrocarbons (PAHs) onto natural solids in batch experiments. This method is based upon the observation that PAHs fluoresce in aqueous solution but not when associated with natural solids. It avoids problems of incomplete solid-liquid separation. As natural solids, eleven different USEPA soils and sediments were used. Anthracene and 2-aminoanthracene, which are respectively non-ionic and ionic PAHs, were chosen as sorbates. The fractional decrease in fluorescence intensity as a function of added natural solid concentration is referred to as Stem-Volmer plots. The plots were linear for all natural solids investigated. The conditional sorption coefficients (Ksc) at pH 6 through 8 and I=0.1 M were obtained as the slopes of the plots. While the Ksc values of anthracene were independent of pH, the values of 2-aminoanthracene decreased with increasing pH. The Ksc values of anthracene correlated well with the organic carbon content of natural solids. However, the values of 2-aminoanthracene did not depend on the content of organic carbon in natural solids. For 2-aminoanthracene, inorganic matrices of the natural solids may contribute to the sorption.
Process Internal Measures to Reduce Pulp Mill Pollution Load
Authors: Gullichsen Johan
Published: May 2018

There are several options to modify present pulping processes towards reduced environmental impact. The industry is readily adopting those that have reached the status of proven technology. New process variations are being developed.

Process internal measures alone will not be sufficient to reach acceptable, levels. External effluent treatment will always be required. Internal abatement measures should concentrate on reducing pollution potential at the very source but also on improving the conditions for efficient external treatment.

The overall production cost will increase when applying internal pollution abatement options. The marginal addition is however small.
The Effects of Chlorination Conditions on the AOX and Chlorinated Phenol Content of Kraft Bleach Plant Wastewaters
Authors: McFarlane Paul N. , Allison Robert W. , Clark Thomas A. , Mackie Keith L.
Published: May 2018

A central composite experimental design was used to develop models of the yields of Adsorbable Organic Halide (AOX) and chlorophenolic compounds in wastewaters produced by bleaching oxygen delignified kraft pulps. The following five variables were used to control the bleaching conditions: total available chlorine, chlorine dioxide substitution, incoming kappa number, chlorination time and temperature. The total available chlorine and the chlorine dioxide substitution were the most important parameters in all the models developed. The yields (g.tonne−1) of AOX and total chlorophenolic compounds increased linearly with increasing total chlorine application. Elevating the level of chlorine dioxide substitution caused the yield of AOX to decrease linearly while the yield of total chlorophenols diminished in a non-linear manner. Increasing the level of chlorine dioxide substitution at a given total chlorine application is an effective means of reducing the emissions of both AOX and chlorinated phenols.
Closing Paper Mill Whitewater Circuits by Inserting an Anaerobic Stage with Subsequent Treatment
Authors: Huster R. , Demel I. , Geller A.
Published: May 2018

In the past few years, the paper industry has been able significantly to reduce the specific amount of effluent it produces. It is considered that the standard now achieved is not susceptible of improvements without a loss of product quality. The problem substances imported with the raw materials will tend rather to increase the specific amount of effluent produced by paper mills that process waste paper, and it will only be possible to operate completely closed circuits in exceptional cases. Integrating a biological purification plant into the Whitewater circuit can help to solve this problem, which is specific to waste paper. Operating a purification plant in the half-stuff production sector makes it possible to achieve substantially lower quantities of specific effluent even in integrated paper mills if the water circuits for half-stuff production and for the papermachine are kept largely separate, and if the freshwater intake is effected via the papermachine's circuit. Possibilities of reducing the specific quantity of effluent produced in wood-free production processes are not discussed, since the use of biological plants in this sector appears problematic for a variety of reasons. The use of anaerobic technology - with appropriate subsequent treatment if necessary - appears suitable because of its favourable energy balance. The possibilities and limits of using anaerobic technology for treating highly concentrated effluents from paper mills are largely known. The use of this technology in the Whitewater circuits of paper mills is still in the planning stage. Simple model calculations can be used to estimate the effects of operating a purification plant on the equilibrium concentrations in the white-water circuit and to detect possible problems.
Thermophilic Anaerobic Treatment of Sulfate-Rich Pulp and Paper Integrate Process Water
Authors: Rintala J. , Sanz Martin J. L. , Lettinga G.
Published: May 2018

Anaerobic treatment of sulfate - rich (COD/SO4 ratio 1.4-2.1) clarified Whitewater from a thermomechanical pulping (TMP) process was studied in three laboratory-scale upflow anaerobic sludge blanket (UASB) reactors at 55°C and in batch digesters at 55° and 65°C. Different seed materials were used in the UASB reactors.

The highest COD removal efficiency (effluent sulfide stripped) achieved was approximately 65 % in the UASB reactors. About 55 % COD removal efficiency was obtained at a loading rate of about 41 kgCODm−3d−1 in the UASB reactor seeded with thermophilic sludge cultivated with volatile fatty acids (VFAs). The total sulfide present in the liquid phase after anaerobic treatment accounted for approximately 65-78 % and 15-61 % of the removed COD in the batch digesters and the UASB reactors, respectively. Sulfate reduction was almost complete in the batch digesters, whereas about 24-64 % of sulfate was reduced in the UASB reactors. Acetate utilization for sulfate reduction was apparent in the batch digesters, whereas that could not be demonstrated in the UASB reactors. Sulfate reduction in the UASB reactors was obviously substrate limited.

In conclusion, thermophilic anaerobic treatment is an alternative for the treatment of warm sulfate rich TMP process water.
Decrease of Pollutant Level of Bleaching Effluents and Winning Valuable Products by Successive Flocculation and Microbial Growth
Authors: Milstein O. , Haars A. , Krause F. , Hüttermann A.
Published: May 2018

The bulk of organic matter from spent bleaching effluent (SBE), either from chlorination and extraction stages or a mixture of both, can be precipitated with polycationic polymers. The mixtures of polyethy-lenimine and modified (containing cationic side groups) starches, can precipitate from bleaching effluent about 75% of adsorbable organic chlorine (AOX), 59% of chemical oxygen demand (COD) and 80% of colour. These mixtures contained less polyimine in comparison to when polyimine was used aline thus saving material costs. After removal of chloroorganics of high molecular mass by precipitation growth of microorganisms in SBE was facilitated. The supernatant of the treated SBE supplemented with glucose and ammonium sulfate supported active growth of fungi from different genera, particularly from Aspergillus spp., Penicillium spp., Basidiomycetes, Aureobasidium. The fungi tested showed appreciable degradation activity regarding monochlorophenols,as well as additional reduction of AOX. During the growth in the treated SBE, Aureobasidiumpullulans decreased the content of AOX remaining after precipitation, and at the same time synthesized and excreted in a surrounding media exopolysaccharides. Pullulan, synthesized in appreciable level by Aureobasidium sp, could easily be isolated from the media. Isolated exopolysaccharides did not contain organochlorine. Fungal polysaccharides synthesized in SBE might be considered as an additional benefit that eventually will be able to reduce further the running costs of the SBE treatment.
Biological Dehalogenation of Kraft Mill Wastewaters
Authors: Bryant Curtis W. , Barkley William A.
Published: May 2018

A single-stage aerobic biological treatment system was developed specifically to convert organically bound chlorine to inorganic chloride. In initial laboratory tests, greater than 90% reduction of AOX was achieved in synthetic dichlorophenol, commercial pentachlorophenol, and combined kraft wastewaters, and less than a week was required for startup/acclimation. A six-month field test of the process on a pentachlorophenol wastewater was very successful under highly variable influent conditions. No chlorinated byproducts were detected, and measurements strongly indicated that dehalogenation had occurred.

Recent experiments found Cl/El wastewater to be most easily treatable by the aerobic process, followed by combined lagoon influent, El wastewater, and finally lagoon effluent. However, results have indicated that application of the treatment process to kraft AOX reduction can become feasible only if further process improvements can be defined.
Formation of Chlorophenols and Related Compounds in Natural and Technical Chlorination Processes
Authors: Hodin Fredrik , Borén Hans , Grimvall Anders , Karlsson Susanne
Published: May 2018

Surface water was halogenated by the addition of: (i) chloroperoxidase, hydrogen peroxide and chloride; (ii) hydrogen peroxide and chloride or bromide; (iii) hypochlorite. Analysis of adsorbable organic halogen (AOX), halogenated phenols and purgeable organic compounds showed that reactions (i) and (ii) produced almost the same halogenated compounds. It was also shown that active chlorine occurred as an intermedi-ate in reaction (i). Reaction (ii) implied a marked halogenation only after the addition of bromide, and this reaction was enhanced by a low pH. Existing evidence that 2,4,6-trichlorophenol may be naturally produced was strengthened. Some evidence was also obtained indicating that enzyme-mediated reactions may contribute to the natural formation of dibenzo-p-dioxins.
Activated Sludge Treatment of Kraft Mill Effluents from Conventional and Oxygen Bleaching
Authors: Nevalainen J. , Rantala P.-R. , Junna J. , Lammi R.
Published: May 2018

Conventional and oxygen bleaching effluents from hardwood kraft pulp mills were treated in laboratory-scale activated sludge processes. The main interest was the fate of organochlorine compounds in the activated sludge process.

In the treatment of conventional bleaching wastewaters the BOD7-reduction was 80-91 % and in oxygen bleaching wastewaters 86-93 %. The respective CODCr removals were about 40 % and about 50 %.

The AOX reductions were on average 22 % and 40 % in the treatment of conventional and oxygen bleaching effluents, respectively. The reductions of chlorinated phenols, guajacols and catecols were usually more than 50 % in both reactors. Very little accumulation of AOX into the sludge was observed. The stripping of AOX from aeration unit was insignificant.
Anaerobic Degradation of PCP and Phenol in Fixed-Film Reactors: The Influence of an Additional Substrate
Authors: Hendriksen H. V. , Larsen S. , Ahring B. K.
Published: May 2018

The anaerobic degradation of pentachlorophenol (PCP) and phenol was examined in two lab-scale fixed-film reactors. Anaerobic digested sewage sludge from a municipal treatment plant was used as inoculum. The reactors were fed a mineral medium containing PCP (1-2 mg/l) and phenol (4-6 mg/l). In addition one of the reactors received 1 g/l glucose as an easily degradable carbon source.

After 6 months of continuous operation, the removal of PCP in the reactor with no glucose added was approximately 60%, whereas the removal in the reactor with glucose reached 98%. Tetrachlorophenol (TeCP) and trichloro-phenol (TCP) were found as degradation products and the removal of these compounds was also significantly enhanced by the presence of glucose. Phenol degradation was approximately 70% with glucose added and 95% without glucose.
Phosphorus Fixation in the Sludge Treatment System of a Biological Phosphorus Removal Process
Authors: Fujimoto N. , Mizuochi T. , Togami Y.
Published: May 2018

One of the major problems connected with the biological phosphorus removal process is that the phosphorus absorbed by the activated sludge may be released if the sludge is handled incorrectly, and this makes it difficult to treated sewage efficiently. Therefore, phosphorus in the return water from the sludge treatment process must be carefully controlled and reduced. Lime and ferric chloride were added to fix phosphorus in the digestion tank. Phosphorus fixation improved with the addition of lime. The digestion ratio reached a maximum at about 0.8 mol/mol to total phosphorus (T-P) with lime addition and decreased thereafter. Lime or ferric chloride was added to the supernatant to fix phosphorus. Ferric chloride removed suspended solids (SS) and phosphorus more efficiently than lime. A combination of these chemicals gave the most favourable results: a phosphorus fixation ratio of 90% or more was attained at a dosage of about 1 mol/mol. Magnesium ammonium phosphate (MAP) was efficiently formed by adding magnesium to the supernatant, and by increasing the system pH to at least 8 by the addition of sodium hydroxide or by aeration. The phosphorus removal ratio in pilot plant experiments was 70%, and granulated MAP was produced.
High Biological Nutrient Removal from Domestic Wastewater in Combination with Phosphorus Recycling
Authors: Rensink J. H. , Eggers E. , Donker H. J. G. W.
Published: May 2018

Pilot plant studies on biological nutrient removal and using settled domestic waste water have been carried out in combination with phosphorus recycling on the basis of crystallisation of calcium phosphate on sand pellets in a fluidized bed-reactor. The bioreactor had been divided into four zones, respectively anaerobic, aerobic, anoxic and aerobic. To eliminate nitrate sludge recirculation for denitrification, a part of the influent was led to the anoxic zone. In the by-pass of the bioreactor a phostripper tank was incorporated followed by a fluidized bed-reactor. The experiments carried out at low F/M ratios and at a constant and variable influent flow resulted in nearly 100% P-removal. P-total effluent was lower than 0.1 mg P/l. The total nitrogen content in the effluent amounted to an average value of approximately 16 mg N/l.
Biological Denitrification of Waste Water from Wet Lime–Gypsum Flue Gas Desulphurization Plants
Authors: Holm Kristensen G. , Jepsen S. E.
Published: May 2018

Waste water from flue gas desulphurization by the wet lime-gypsum process is characterized by high contents of nitrate (150–300 mg/l N) and chloride (10–30 g/l Cl) and high temperature (40–50°C). Continuous and batch experiments with biological denitrification were performed with suspended cultures in lab-scale reactors fed with synthetic waste water with chloride concentrations up to 30 g/l Cl. Process temperatures in the range of 30–50°C were investigated. Acetate was added as carbon source. The results of the experiments show that biological denitrification was feasible at the extreme environmental conditions prevailing in wet lime–gypsum flue gas desulphurization waste water. Stable continuous denitrification was performed at chloride concentrations up to 30 g/l and at temperatures up to 45°C. A temperature optimum of 40°C was found for nitrate removal. At 50°C the denitrification had ceased in the reactors. In batch experiments an increased tendency to intermediate nitrite accumulation at increased temperatures and increased chloride levels was observed. This indicates that efforts should be made to equal out load variations in high chloride and high temperature biological denitrification in order to avoid periodical nitrite accumulation.
Population Dynamics of Bacteria for Phosphorus Removal in Sequencing Batch Reactor (SBR) Activated Sludge Processes
Authors: Okada M. , Murakami A. , Lin C. K. , Ueno Y. , Okubo T.
Published: May 2018

Laboratory-scale sequencing batch reactor (SBR) activated sludge processes were operated using synthetic wastewater to clarify the effects of sludge retention time(SRT) and organic substrates on the accumulation of bio-P-bacteria. The accumulation of bio-P-bacteria could be enhanced by wide variation in concentration of organic substrates by giving a short fill period and sufficient anaerobic conditions. However, the accumulation could not be enhanced in the reactor operated with SRT less than 25 d in spite of the higher, more than 0.1 d−1, specific growth rates observed in the isolated strains of bio-P-bacteria. The specific growth rates of bio-P-bacteria were estimated at 0.040 d−1, 0.030 d−1 and 0.035 d−1 in the SBR activated sludge processes fed with sodium acetate (A), glucose and polypeptone (GP) and polypeptone (P), respectively. Therefore, a large sludge retention time would be necessary for the accumulation of bio-P-bacteria. Volatile fatty acids (VFA), such as sodium acetate (A), seemed to be more effective than other organic substrates (GP and P) for the accumulation of bio-P-bacteria in activated sludge ecosystems.
Design Considerations for Nutrient Removal Activated Sludge Plants
Authors: Pitman A. R.
Published: May 2018

Based on more than 10 years' experience with biological nutrient removal in Johannesburg, this paper highlights aspects which should be borne in mind in the design of such processes. Feed sewage quality and the question of treating raw or settled sewage are considered. More importantly, methods of rendering the feed more suitable for biological phosphorus removal are detailed. As nitrate feedback to the anaerobic zone can often mitigate against good phosphorus removal, methods of obviating this are covered. In this respect the need for, and placement of a second anoxic zone are discussed. Process type and configuration are covered as well as zone retention periods and the split of process volume into unaerated and aerated fractions. Aeration systems and the tailoring of aeration to process needs are also discussed. Two problems that have been experienced in many full-scale plants are bulking sludges and prolific growths of nuisance scums. Methods of minimising these problems are discussed. Finally, mixed liquor and return sludge recycles; aspects to be borne in mind in the design of final clarifiers and the provision of standby chemical addition are discussed.
The Effect of Contact Tank Operation on Bulking Sludge and Biosorption Processes
Authors: Rensink J. H. , Donker H. J. G. W.
Published: May 2018

Pilot plant studies with settled domestic waste water were carried out to study the influence of a contact tank on bulking sludge control. It has been clearly proved that the configuration of the contact tank plays a decisive role in preventing or curing bulking sludge. A rectangular contact tank with a substrate gradient ensured well-settling sludge, while a circular contact tank - completely mixed - was not able to control bulking sludge. Stirring or aerating of the rectangular contact tank did not make a difference in the sludge quality during continuous process operation. Great differences in biosorption and COD-removal were measured between well-settling and poor-settling sludge. A detention time of 30 minutes of the sludge-water mixture in the rectangular tank guaranteed - on the basis of biosorption and COD-removal - a more stable and reliable process for controlling bulking sludge than 10 minutes.
Self-Immobilization of Aerobic Activated Sludge–A Pilot Study of the Aerobic Upflow Sludge Blanket Process in Municipal Sewage Treatment
Authors: Mishima K. , Nakamura M.
Published: May 2018

The Aerobic Upflow Sludge Blanket (AUSB) Process is a new biological wastewater treatment process applying the concept of the self-immobilization to aerobic activated sludge. This report discussed the experimental results for municipal sewage treatment using the pilot AUSB apparatus. The sludge produced in the AUSB process formed granules (diameter: 2 - 8 mm), showing excellent settleability. Under the condition of 1.57 kg/m3 day of BOD volumetric loading in winter, the following quality was obtained for the treated water : 20 mg/ℓ of BOD and 9.6 mg/ℓ of SS. The MLSS in the AUSB reactor was maintained at 8200 mg/ℓ.
Soluble Microbial Product Formation in Biological Systems
Authors: Boero V. J. , Eckenfelder W. W. , Bowers A. R.
Published: May 2018

The formation of soluble microbial products was evaluated in batch reactors using radiolabeled 14C-phenol and 14C-glucose. Soluble microbial products, SMP, resulted from intermediates or end products of substrate degradation and endogenous cell decomposition. On an organic carbon basis, the SMP produced after A8 hours averaged 1A.7 (±3.7) percent of the initial phenol and 3.1 (±0.4) percent of the initial glucose. The SMP were categorized as substrate utilization products, having a biodegradable and non-biodegradable fraction, and biomass associated products, which were only non-biodegradable. A model was developed based on kinetic relationships between several macroscopic compartments, which consisted of the initial substrate, cell mass, and the three SMP categories. Based on the experimental data, zero and first order kinetics were sufficient to describe the disappearance of the initial substrates and the net SMP, i.e., total SMP produced less SMP biodegraded to yield CO2 and/or new biomass. Both phenol and glucose adhered to the same kinetic model, but the rate constants were considerably different.
Development of High-Performance Thermophilic Two-Phase Digestion Process
Authors: Aoki Nobuhiro , Kawase Mitsuo
Published: May 2018

Anaerobic digestion of anaerobic sewage sludge leads to the generation of methane gas and reduction of the sludge volume. Because conventional digestion requires a long time, the digestion facilities must be large. We studied decomposing volatile suspended solids (VSS) in sewage sludge, capacitating high acid generation rates and a high-speed methane evolution reactor to reduce retention time for anaerobic digestion. We also studied how to increase VSS reduction ratio by using bio-technology. The high-performance thermophilic two-phase digestion (HPTTD) process is proposed as a innovative digestion system which has high-rate reducing and high-ratio reduction of volatile suspended solids in sewage sludge. This thermophilic digestion process consists of sludge conditioning, acidification and methanation steps. In the sludge conditioning step, sewage sludge is conditioned with thermal treatment and dosed with a protolytic enzyme. In the next step, acidification, acid fermentation is carried out at 70°C; this temperature is higher than that of conventional fermentation (conventional thermophilic digestion process: 55°C). In the methanation step an anaerobic fixed-bed reactor is used. In the digestion experiments using excess sludge, we obtained a 30% higher VSS reduction ratio (78% at HPTTD process) than that of conventional mesophilic digestion,
Calcium Carbonate Precipitation in Anaerobic Waste Water Treatment
Authors: Svardal K.
Published: May 2018

Precipitation of calcium in anaerobic treatment can be a severe problem, especially for fixed bed reactors. In order to assess calcium precipitation quantitatively, an equilibrium model has been developed. It is based on concentrations in the influent (COD, TOC, TIC, alkalinity, Ca2+,TKN) conditions in the reactor (pH, temperature) and equilibrium constants. The model has been verified for different waste waters in pilot scale and full scale investigations.
Competition and Inhibition of Sulfate Reducers and Methane Producers in Anaerobic Treatment
Authors: Choi Euiso , Rim Jay M.
Published: May 2018

Competition for substrate between sulfate reducing and methane producing bacteria, and the inhibitory effects of sulfide produced from microbial sulfate reduction were investigated in this study for the selection of a proper anaerobic treatment process using laboratory anaerobic contact units. Substrates used were both synthetic waste with various COD/SO42− ratios, and industrial wastes. Sulfate reducers and methane producers were very competitive at COD/SO42− ratio of 1.7 to 2.7. As the ratio increased/methane producers predominated, and sulfate reducers were predominating as the ratio decreased. Inhibitory concentrations were 2000 mg/l sulfate (160 to 200 mg/l sulfide) for sulfate reducers and 1200 mg/l sulfate (120 to 140 mg/l sulfide) for methane producers with synthetic substrate. But sulfide inhibitory concentrations were varied with hydraulic or organic loading rates and substrate used. As loading rates increased/the inhibitory effect was greater. A sulfide concentration of 240mg/l did not inhibit methane producers for sea-food waste treatment.
Anaerobic Filter Treatment of Sulfate-Containing Wastewaters
Authors: Parkin G. F. , Sneve M. A. , Loos H.
Published: May 2018

The use of anaerobic biological processes for the treatment of industrial wastewaters has significant merit. When high levels of sulfate are present, the sulfate is biologically reduced to sulfide, the result being potential toxicity to the consortia of organisms responsible for producing methane. An upflow anaerobic filter-fed propionate as a substrate was used to study the interaction between sulfate-reducing bacteria and methane-producing bacteria. Hydraulic retention times of one and two days were used, organic loading rates were varied from 3 to 5 g COD/L-day, and feed COD/S ratios were varied from 20/1 to 8/1. Unionized hydrogen sulfide and dissolved sulfide levels associated with decreased process performance were approximately 110 mg S/L and 350 mg S/L, respectively. These levels are significantly higher than those levels causing inhibition in completely mixed-reactors. Most of the sulfate reduction and propionate removal took place in the first 300 mm of the 1050-mm-long reactor, indicating that sulfate reduction and methane production were occurring in the sane location in the filter.
Pilot Plant Studies on Biological Sulphate Removal from Industrial Effluent
Authors: Maree J. P. , Hulse G. , Dods D. , Schutte C. E.
Published: May 2018

Sulphate-rich industrial effluents present a serious environmental pollution problem. A biological sulphate removal process has been developed for the treatment of such effluents. In this process, sulphate is converted to hydrogen sulphide in the anaerobic stage when an energy source, such as molasses, sugar or producer gas is added. The hydrogen sulphide is stripped off in a stripping stage, with a carrier gas such as nitrogen. The gas is recycled through a ferric solution where it is oxidized to elemental sulphur. In a subsequent aerobic stage, degradation of organic carbon residuals and calcium carbonate crystallization are achieved simultaneously. In this study the anaerobic stage of the process was evaluated on pilot scale. After the inoculation period, sulphate was removed continuously for a period of 100 days from 2200 mg/l to below 200 mg/l. For the first part of the study acetic acid served as energy source as the sugar content of molasses was allowed to ferment. Thereafter fresh molasses was supplied as energy source and the bacterial culture had to adapt to utilize sugar in molasses as energy source. A volatile suspended solids (VSS) concentration of 27 g/l was present in the packing material of the anaerobic reactor. With this VSS-value, a hydraulic retention time of 12 hours was needed for sulphate removal.
Phosphate Removal in a Biofilm Reactor
Authors: González-Martinez Simón , Wilderer Peter A.
Published: May 2018

Biological phosphate removal was achieved in a laboratory scale fixed bed biofilm reactor. To create the conditions required to enrich for phosphate accumulating bacteria, the reactor was periodically filled and drained, and the aerator periodically turned on and off (Sequencing Batch Reactor strategy). The reactor performed very effectively, but it took several weeks to reach steady-state. The highest phosphate uptake rates were observed when sequestration of the organic substrates was accomplished at an early stage of the anaerobic process phase, and release of phosphate at the expense of sequestered or stored substrates (endogenous phosphate release) was encouraged. In the range between 15°C to 25°C, the temperature had only minor effects. The biofilm dry weight contained about 5 per cent phosphate.
Effect of Short-Term and Long-Term Changes in Hydraulic Conditions on Nitrifying Biofilm
Authors: Kugaprasatham Sivapragasam , Nagaoka Hiroshi , Ohgaki Shinichiro
Published: May 2018

Hydraulic conditions affect the biofilms used in the treatment of very low concentration of pollutants. Effect of hydraulic conditions on nitrifying biofilm grown under a NH4-N concentration of about 1 mg/l (substrate-limiting condition) was investigated in a cylindrical reactor (ø40 cm × 46 cm (working height)). Velocity and turbulence at 4 mm from the wall of the reactor mixed by paddles were measured by a hotfilm anemometer. Nitrifying biofilm was grown on the wall of the reactor at a base hydraulic condition with average turbulent intensity of 6.6 cm/s. Turbulent intensity was reduced for a period of three to four times the hydraulic retention time and the resulting flux was measured at the end of this period (short-term). This short-term effect of turbulent intensity on specific flux (NH4-N flux/NH4-N concentration in bulk water) varied with turbulent intensity according to a power law of turbulent intensity in agreement with the theoretical expression derived for filamentous biofilms under turbulent conditions. When turbulent intensity was changed and kept at the changed value for several days (long-term), filamentous type biofilm with higher substrate flux was observed at high turbulent intensities but colony-type biofilms under low turbulent intensities showed reduced mass transfer.
The Performance of Stabilization Reservoirs as a Function of Design and Operation Parameters
Authors: Juanico Marcelo , Shelef Gedaliah
Published: May 2018

Stabilization Reservoirs were developed in Israel for the treatment and storage of wastewater for agricultural irrigation. These reservoirs were initially conceived just for seasonal storage of wastewater but soon the additional stabilization that they provide to effluents became evident. This paper formulates the first available equations for BOD and COD removal in Stabilization Reservoirs. Removal of BOD and COD is high (50 to 85 %) in terms of annual means, but sharply changes during the year. Three models to predict BOD and COD removals as a function of design and operation parameters are developed based on a large amount of data from four different reservoirs. The percentage of fresh effluents within the reservoir has a negative effect on BOD and COD removals. High water levels, and their concomitant low area/volume relationships, have also a negative effect on removal efficiency due to poor oxygenation of the water column. The percentage of fresh effluents within the system is a hydraulic parameter better than Residence Time, to analyze the performance of non-steady state wastewater treatment systems. The quality of the effluents released for irrigation from Stabilization Reservoirs deteriorates during the second half of the irrigation season. This deterioration is due to both the increase in the percentage of fresh effluents within the reservoir, and the occurrence of dead areas and short-circuiting phenomena at low water levels. These problems must be resolved by proper design and operation of the reservoirs in order to obtain a more homogeneous effluent quality along the irrigation season.
Bacterial (Total Coliform) Die-Off in Maturation Ponds
Authors: Qin D. , Bliss P. J. , Barnes D. , FitzGerald P. A.
Published: May 2018

A mathematical model of bacterial (total coliform) die-off in maturation ponds was developed based on first order kinetics. Laboratory single factor and dynamic model pond tests were carried out, using effluent from a municipal trickling filter wastewater treatment plant. Correlations were found between two groups of factors which were found to have a significant effect on the first order rate coefficient: the environmental factors, temperature, pH and organic loading; and the illumination-related factors, sunlight intensity, depth, algal concentration and turbidity. These correlations were used in the model along with the physical configuration factors, dimensions (depth, width and length), detention time and dispersion number and a calibrated dispersion model. Predictions of the bacterial die-off using the model agreed well with experimental results obtained from the dynamic model pond tests.
Nutrient Removal by High Rate Pond System in a Mediterranean Climate (France)
Authors: Picot B. , El Halouani H. , Casellas C. , Moersidik S. , Bontoux J.
Published: May 2018

The objective of the present study vas to ascertain the mechanisms involved in nitrogen and phosphorus removal from wastewater and to determine the most effective treatment conditions for removing these nutrients by high rate ponding in a Mediterranean climate. Tests carried out in Mèze (France) showed that variations of climatic factors (light and temperature), can be compensated by changes in detention times. The following strategy was adopted: the pond was operated with long detention times (8 days) in winter, which is characterized by low light intensity and low temperatures, and with short detention times (4 days) in summer, when the climatic conditions are more favorable. The results obtained show that the rates of HH4-N and PO4-P removal were high and stable (94 and 71%, respectively) during the study period February to September, 1988. The phenomena responsible for nutrient elimination in the high rate pond are the following: photosynthetic assimilation, volatilization of ammonia and precipitation of calcium phosphate due to the high pH obtained by intense algal photosynthetic activity. Wastewater treatment by high rate ponding appears to be an attractive technique for preventing eutrophication in receiving water.
Performance of an Integrated Ponding System Operated in Arid Zones
Authors: Puskas K. , Esen I. I. , Banat I. , Al-Daher R.
Published: May 2018

This research project was aimed at developing a ponding system for municipal wastewater treatment adapted to arid regions. High-rate algal ponds preceded by facultative ponds create a combined biological system that can provide treated effluent suitable for landscape irrigation or, after being upgraded, for agricultural irrigation; the system can also provide algae for soil conditioning or animal feed. A pilot plant was designed and constructed to study the operation and performance of the system, an intensive experimental program was introduced with in-situ measurements of the daily pond conditions and laboratory analysis of the pond effluents to evaluate the system and determine the design parameters.

The algal-bacterial ponding system performed satisfactorily providing treated effluent with less than 20 mg/l BOD, 130 mg/l COD, 40 mg/l total nitrogen and 25 mg/l NH3N. The average production of algal biomass was 250 kg/ha.d. Proper disinfection was achieved, indicated by average bacterial count of 5 N/ml total coliforms and 1000 N/ml total bacteria. The area's seasonal weather variations, dense wastewater and fluctuating organic and hydraulic load, did not adversely effect the system. The pilot operation proved the advantages and efficiency of the algal-bacterial pond system in arid regions.
The Effect of Operational Factors on Solid/Liquid Separation by Ultra-Membrane Filtration in a Biological Denitrification System for Collected Human Excreta Treatment Plants
Authors: Magara Y. , Itoh M.
Published: May 2018

One third of the total population of Japan is served by collected human excreta treatment systems for the sanitary treatment of human wastes. In order to cope with the stringent effluent quality regulations set for human excreta treatment plants, the high-load biological denitrification process with ultra-membrane filtration for solid/liquid separation has been recently developed. This system has big advantages not only with respect to the solid/liquid separation stage of biological treatment processes, but also as regards the cost and operational effectiveness of advanced treatment processes such as ozonation and activated carbon adsorption. However, problems can be experienced with the ultra-membrane filtration process because the attainable hydraulic load is completely governed by the permeation flux. Therefore, in order to utilized the ultra-membrane filtration process in a biological wastewater treatment system, the effects of the operational factors on the permeation flux have to be clarified. In this paper, the effects of factors such as water temperature, suspended solids concentration, driving pressure, and water velocity in the unit are described. It has become clear that in order to attain a stable permeation flux, the water temperature and suspended solids concentration should be kept as stable as possible. The results of the investigation of the development of cake or gel layer resistance showed that high pressure and high velocity give a high and stable permeation flux. However, it has also been shown that the optimum operational conditions are high pressure and low velocity, due to the energy costs for operation of the system.
Recovery of Direct Dye and Acid Dye by Adsorption on Chitosan Fiber – Equilibria
Authors: Yoshida H. , Fukuda S. , Okamoto A. , Kataoka T.
Published: May 2018

The recovery of direct dye and acid dye from dilute aqueous solution by adsorption on chitosan fiber, which is cheaper than an activated carbon fiber, appeared technically and economically feasible. The amounts of adsorption of Brilliant Yellow (direct dye) and Acid Orange II (acid dye) on the chitosan fiber were much larger than that for the activated carbon fiber, though these dyes were adsorbed well on the activated carbon fiber too. The experimental equilibrium isotherms were correlated by B.E.T. equation for a finite number of layers. The equilibrium isotherm was affected by the initial concentration of the dye and temperature considerably, but was little affected by coexisting salt NaCl. These dyes were desorbed by dilute aqueous solution of caustic soda, e.g. at 20mol/m3, irreversibly.
Removal of Trihalomethane Precursors from River and Lake Water by Activated Carbon Adsorption
Authors: Takeuchi Y. , Suzuki Y. , Koizumi A. , Soeda N.
Published: May 2018

A comprehensive study was undertaken to clarify the method of reducing trihalomethane and its precursors from river and lake water in view of drinking water purification. Sources of water were chosen among lakes and rivers in Eastern Japan and biological treatment and coagulative precipitation of the water samples were carried out prior to activated carbon adsorption. A strong relation was shown between TOC and THMFP of raw and treated samples, and the relation changed due to the extent of biological treatment. Though the chemical structure of substances which may cause trihalomethane formation is not clear, the content of ammoniacal nitrogen is responsible for the reduction of trihalomethane formation produced by the addition of chlorine. However, this does not mean that the reduction of chlorine dose can be achieved simply by the process of biological treatment.
Magnesium Induced Algal Flocculation in a Fluidized Bed
Authors: Elmaleh S. , Coma J. , Grasmick A. , Bourgade L.
Published: May 2018

The effectiveness of the use of seawater and of magnesium in the removal of microalgae from oxidation pond effluents was investigated using the jar test procedure. The results indicated that the major flocculating reaction is the magnesium hydroxide precipitation at pH 11.5. The next step was to intensify the liquid-solids separation by use of a fluidized bed flocculator packed with 800 µm inert resin particles provided with an inclined multitubular settler. The total suspended solids abatement could reach 95 % with a superficial upflow velocity of 30 m/h corresponding to a residence time through the whole unit of 5 minutes only. The energy requirement quantified by the pressure drop through the bed is very low. Besides, the waste sludge extracted from the settler is easily thickened.
Characteristics of Metal-Polysilicate Coagulants
Authors: Hasegawa T. , Hashimoto K. , Onitsuka T. , Goto K. , Tambo N.
Published: May 2018

The authors propose metal-polysilicate complexes as new inorganic polymer coagulants for the removal of colloidal suspensions. In the first part of this paper, procedures of silicic acid polymerization to attain very higher molecular weight polysilicates in a much more stable state than conventional methods are discussed. Then, a procedure for introducing metal ions such as aluminum and iron into the polymerized silicic acid is presented to give coagulation capability, i.e. charge-neutralizing capacity, to the polysilicic acid. Several new inorganic polymers are thus prepared as cationic coagulants. In the final part, the effectiveness of the proposed aluminum- or ferric-polysilicate coagulants for coagulation and flocculation is evaluated by means of conventional jar tests and pilot plant experiments. These studies show that both the resulting water quality and the rate of removal after sedimentation are greatly improved in comparison with conventional inorganic coagulants. Unlike conventional organic coagulants, these inorganic polymer coagulants are considered to be safe for human health because the safety of silicates and metal coagulants has been demonstrated by many years of utilization.