bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of chlorination bulking control on water quality and phosphate release/uptake in an anaerobic-oxic activated sludge system
Authors: Chang W.C. , Jou S.J. , Chien C.C. , He J.A.
Published: May 2018

This study evaluates the effect of chlorination bulking control on water quality and phosphate release/uptake in an anaerobic-oxic activated sludge system. A series of batch experiments with different specific NaOCl mass dose were conducted to determine the sludge settling properties, supernatant water quality and phosphate metabolism behavior of filamentous bulking sludge. The harvested sludge was from a continuous-flow anaerobic-oxic (A/O) activated sludge pilot-plant, i.e., enhanced biological phosphorus removal (EBPR) system, operated with 15 days of sludge retention time. The filamentous bacteria in the A/O pilot plant were identified to be Thiothrix according to Eikelboom's classification techniques, which was in accordance with the high influent sulfate concentration of this study (50 mg/L sulfate). Increasing NaOCl concentration, as revealed by experimental results, obviously decreased the sludge settling properties (SVI values and zone settling velocities) and meanwhile significantly reduced supernatant water quality (COD, SS, TP) mainly due to higher suspended solids caused by floc disruption. Moreover, the nine-hour batch experiments indicated that high NaOCl dosage (40 mg/gMLSS) completely deteriorated phosphate metabolism of EBPR sludge. Such a high dosage of chlorination further confirmed overdosing through disappearance of intracellular PHB and death of protozoa by microscopic investigation. Still, phosphate release/uptake behavior of EBPR sludge properly functions at low NaOCl dosage (5 mg/g MLSS). Besides, phosphate metabolism worsens rapidly before the SVI value reaches its lowest level. These findings imply that determining NaOCl requirement with merely SVI values can readily result in chlorination overdosing. Proper NaOCl dosage requires a delicately balanced consideration between sludge settling improvement, water quality demand and phosphate metabolism. Batch test of phosphate release/uptake is apparently a prerequisite to conclude an appropriate NaOCl dosage for bulking control.
Compost odor control using high carbon wood ash
Authors: Rosenfeld P.E. , Grey M.A. , Suffet I.H.
Published: May 2018

A pilot study on the feasibility of using high carbon wood ash to control composting odor emissions was conducted at a green material composting facility. The study's treatments consisted of adding 0%, 12.5%, and 25% high carbon wood ash by volume to green material compost feedstock in three separate windrows. The wood ash has properties similar to activated carbon with an active surface area of 105 square metres per gram on a dry weight basis. The odorant emission data suggest that the higher percentage wood ash treatment results in the most effective control of most compost odors and that wood ash provides effective treatment of volatile fatty acids and some aldehydes and ketones. The 25% wood ash treatment resulted in more effective treatment of odors for a longer time period than the 12.5% treatment. Acetaldehyde had the highest concentration in the control (14,000 times its odor threshold concentration), was reduced by high carbon ash by over 97% but remained 386 times its reported odor threshold concentration after 14 days. Ethyl mecaptan and ammonia were produced in the process and were also over their reported human detection limits.
Inorganic polysulfides’ quantitation by methyl iodide derivatization: dimethylpolysulfide formation potential
Authors: Goifman A. , Ryzkov D. , Gun J. , Kamyshny A. , Modestov A.D. , Lev O.
Published: May 2018

Inorganic polysulfides are important intermediates in the formation of dimethylpolysulfides and possibly other volatile sulfur compounds of environmental significance. Currently, direct determination of these ions in the concentration range of natural systems is practically impossible, particularly under oxic conditions. Polysulfide quantification by derivatization with methyl iodide or d6-methyl iodide is emerging as a valuable alternative method for studies of polysulfide formation in natural systems. This manuscript presents detailed studies aimed at the evaluation of this method. We determined the conversion of the inorganic polysulfides to dimethylpolysulfides by methylation with methyl iodide. Close to 100 per cent of the molar concentration of polysulfide salts were converted to organic polysulfides for very low concentrations of dissolved polysulfide solutions, but only a small recovery was obtained for high concentrations of polysulfide precursors or when the solubility limit was exceeded. The recovery of polysulfides based on the calculated dissolved polysulfide concentration exceeds 1,000 per cent for very low dissolved concentrations of polysulfides. This unexpected dependence is attributed to continuous inorganic polysulfide formation from hydrogen sulfide and sulfur precipitate concurrent with, and in fact driven by, the methylation process.
Processing dewatered sewage sludge using electrokinetic technology
Authors: Wang J.Y. , Zhang D.S. , Stabnikova O. , Tay J.H.
Published: May 2018

High content of heavy metals and presence of pathogens in the dewatered sewage sludge have been the main obstacles for land application of sewage sludge-made fertilizer. The aim of this study was to xamine the effects of the innovative electrokinetic (EK) technology on removal of heavy metals from sewage sludge, on the reduction of pathogens, and on sludge chemical characteristics. The results showed that the removal efficiencies for Zn, Cu, Ni, Cr, As and Pb were 94.9%, 95.4%, 89.7%, 67.8%, 31.2% and 18.7%, respectively. Acidification pretreatment of the dewatered sludge for 29 h decreased the content of heterotrophic bacteria from 1.5 × 108 c.f.u./g of wet sludge to 1.1 × 104 c.f.u./g of wet sludge. Although the initial content of total coliforms and fecal coliforms in sewage sludge were 5.8 × 105 c.f.u./g of wet sludge and 4.0 × 105 c.f.u./g of wet sludge, respectively, no viable cells were detected. Minor losses of K and N were detected, but the loss of P was found to be significant in EK treated sewage sludge. The treated sludge has technically considered as very stable based on the carbon dioxide evolution rate.
NOM and MIB, who wins in the competition for activated carbon adsorption sites?
Authors: Hepplewhite C. , Newcombe G. , Knappe D.R.U.
Published: May 2018

The adsorption of an odour compound common in drinking water, 2-methylisoborneol (MIB), was studied on two activated carbons in the presence of 13 well-characterised natural organic matter (NOM) solutions. It was found that, although the carbons and the NOM solutions had a wide range of characteristics, the major competitive mechanism was the same in all cases. The low molecular weight NOM compounds were the most competitive, participating in a direct competition with the MIB molecule for adsorption sites. Equivalent background concentration (EBC) calculations indicated a relatively low concentration of directly competing compounds in the NOM. Some evidence of pore restriction was also seen, with microporous carbons most affected by low molecular weight NOM, and mesoporous carbons impacted by the higher molecular weight compounds.
Response of an EBPR population developed in an SBR with propionate to different carbon sources
Authors: Pijuan M. , Baeza J.A. , Casas C. , Lafuente J.
Published: May 2018

The effect of different carbon sources (propionate, acetate, butyrate and glucose) on an enhanced biological phosphorus removal biomass developed with propionate as the sole carbon source was studied. Firstly, a group of different cycle studies was carried out using each substrate independently and then, another cycle study was performed with a mixture of substrates. Propionate was found to be the substrate with the highest substrate uptake rate in both sets of experiments. It was also the volatile fatty acid (VFA) which required less reducing power and less P-release to be uptaken. Four different polyhydroxyalkanoate (PHA) monomers produced during the anaerobic phase were detected, and PHB, PHV and PH2MV were quantified. Significant differences in PHA composition were obtained depending on the carbon source. The carbon recovery ratio for the anaerobic phase was also evaluated. The lowest value observed among the different cycle studies was obtained for butyrate, while the highest value was obtained for acetate.
Direct energy recovery from primary and secondary sludges by supercritical water oxidation
Authors: Svanström M. , Modell M. , Tester J.
Published: May 2018

Supercritical water oxidation (SCWO) oxidizes organic and biological materials virtually completely to benign products without the need for stack gas scrubbing. Heavy metals are recovered as stabilized solid, along with the sand and clay that is present in the feed. The technology has been under development for twenty years. The major obstacle to commercialization has been developing reactors that are not clogged by inorganic solid deposits. That problem has been solved by using tubular reactors with fluid velocities that are high enough to keep solids in suspension. Recently, system designs have been created that reduce the cost of processing sewage sludges below that of incineration. At 10 wt-% dry solids, sludge can be oxidized with virtually complete recovery of the sludge heating value as hot water or high-pressure steam. Liquid carbon dioxide of high purity can be recovered from the gaseous effluent and excess oxygen can be recovered for recycle. The net effect is to reduce the stack to a harmless vent with minimal flow rate of a clean gas. Complete simulations have been developed using physical property models that accurately simulate the thermodynamic properties of sub- and supercritical water in mixtures with O2, N2, CO2, and organics. Capital and operating cost estimates are given for sewage sludge treatment, which are less costly than incineration. The scenario of direct recovery of energy from sludges has inherent benefits compared to other gasification or liquefaction options.
The performance of a nitrogen-fixing SBR
Authors: Dennis M.A. , Cotter M.L. , Slade A.H. , Gapes D.J.
Published: May 2018

A laboratory study has successfully demonstrated that a nitrogen deficient thermomechanical pulping wastewater can be effectively treated in a sequencing batch reactor (SBR) operated under conditions of biological nitrogen fixation (the N-ViroTech® process). In comparison to continuous stirred tank reactor activated sludge (CSTR-AS) configurations operated under either nitrogen fixing or nitrogen supplemented conditions, slightly lower removals of dissolved organic material were observed in the SBR. However, this was largely offset by significantly better suspended solids removal in the SBR, which contributes to the overall COD discharge. The settleability and dewaterability of sludge produced by the SBR was significantly better than that obtained from the nitrogen fixing CSTR-AS reactors, and comparable to that of a nitrogen supplemented system. Consistently low total and dissolved nitrogen discharges from the N-ViroTech® systems demonstrated the advantage of this system over ones requiring nitrogen supplementation. The feast–famine regime of an SBR-type configuration has significant potential for the application of this technology in the treatment of nitrogen deficient waste streams, particularly those in which conventional single-stage systems may be susceptible to sludge bulking problems.
Deflocculation effects due to chemical perturbations in sequencing batch reactors
Authors: Henriques I.D.S. , Kelly R.T. , Love N.G.
Published: May 2018

Toxic shock-induced deflocculation was examined for activated sludge exposed to six different classes of industrially relevant chemical toxins: an electrophilic solvent (1-chloro-2,4-dinitrobenzene, CDNB), a heavy metal (cadmium), a hydrophobic chemical (1-octanol), an uncoupling agent (2,4-initrophenol, DNP), alkaline pH, and weakly complexed cyanide. The concentrations required to inhibit respiration by 50% were used to shock sequencing batch reactors (SBRs) containing a nitrifying (10-day solids retention time (SRT)) and a non-nitrifying (2-day SRT) biomass. Effluent total suspended solids (TSS) and soluble potassium were monitored to examine deflocculation caused by a bacterial stress response mechanism called glutathione-gated potassium efflux (GGKE). Reactors were monitored for recovery over a period of 3 SRTs or less. At the concentrations tested, CDNB, cadmium and pH 11 were found to cause significant increases in effluent TSS concentrations and showed elevated levels of potassium. In contrast, octanol, DNP and cyanide did not induce severe deflocculation and showed moderate increases in effluent potassium levels. Recovery of effluent TSS and potassium concentrations to control levels generally did not correlate, supporting the hypothesis that reflocculation requires regrowth of biomass. These results suggest that different chemicals induce deflocculation in SBRs, but deflocculation is not necessarily caused by the GGKE mechanism in all cases.
Quantification of pollution loads from CSOs into surface water bodies by means of online techniques
Authors: Gruber G. , Winkler S. , Pressl A.
Published: May 2018

Based on novel technologies, a modular online monitoring station suitable for continuous application in sewer networks, wastewater treatment plants and receiving water bodies has been designed. The monitoring station serves as the backbone of a water quality pilot network. As one part of this network a sewer monitoring station has been installed at a combined sewer overflow in Graz to quantify pollution concentrations and loads in the combined sewer and into the receiving water and is operated since October 2002. The design and equipment of the measurement station and first operating experiences and results are given in this paper.
Turbidity-based monitoring of particle concentrations and flocculant requirement in wastewater pre-treatment
Authors: Mels A.R. , Spanjers H. , Klapwijk A.
Published: May 2018

The removal of particulate organic material in the first step of wastewater treatment may result in significant savings of reactor volume and energy at wastewater treatment plants, because the organic loading to pursuing unit operations can be reduced. This article describes experiments into the possibility of using turbidity measurements as a tool to quantify the concentration of particles in raw wastewater and, based on the result, assess the organic polymer requirement. A feed forward polymer dosing strategy based on a fixed polymer to influent-turbidity ratio was developed and tested. The experimental work confirms that turbidity measurements can be used to quantify particulate COD. For the investigated wastewater (both untreated and flocculated samples) a linear relationship was found in a wide range of particulate COD (100–900 mg O2.l−1) and turbidity (50–450 NTU). On-line turbidity measurements showed that the particle concentrations in the tested municipal wastewater varied significantly. During dry weather conditions the turbidity fluctuated from 100 to 400 NTU, while in rainy periods fluctuations of 100 to >1,000 NTU were measured. The tested turbidity-related polymer dosing method could be used to create different, constant levels of particle removal, despite large particle concentration variations in the influent. Moreover, it resulted in higher removal efficiencies and a more stable operation compared to the dosing of fixed polymer dose per unit of volume.
Detection of aquatic colloids in drinking water during its distribution via a water pipeline network
Authors: Wagner T. , Bundschuh T. , Schick R. , Köster R.
Published: May 2018

Laser-induced Breakdown Detection (LIBD) is a highly sensitive method for the direct detection of nano-particles (colloids). During the detection process plasmas are generated on single particles by a focused laser beam, the resulting plasma light emissions are detected optically. The method is based on the difference in breakdown thresholds of liquid and solid matter, it is lower for solid material. The laser pulse energy is adjusted precisely so that in the pure liquid no breakdown events occur, and only in the presence of colloids is the breakdown threshold in the focal volume exceeded. The spatial distribution of several thousand recorded plasma flashes within the focal volume reveals the mean particle diameter. The evaluation of the number of breakdown events per number of laser pulses results in a breakdown probability, together with the particle size the concentration is calculated using specially-designed computer software. Compared to conventional laser light scattering methods the LIBD is approximately 6 orders of magnitude more sensitive for particles smaller than ca. 0.05 μm. Together with laser light obscuration the LIBD technique has been used successfully for the quantification of aquatic nano-particles during drinking water processing and its distribution via a pipeline network of nearly 1,700 km total length. In addition, the particulate content of several brands of mineral water has been investigated.
Investigation on effects of aggregate structure in water and wastewater treatment
Authors: Chau K.W.
Published: May 2018

The fractal structure and particle size of flocs are generally recognized as the two most crucial physical properties having impact on the efficiency of operation of several unit processes in water and wastewater treatment. In this study, an experimental investigation is undertaken on the effect of aggregate structure in water and wastewater treatment in Hong Kong. The fractal dimension of the resulting aggregate is employed as a measure of the aggregate structure. Small angle light scattering technique is used here. Different amounts of polymers are mixed to bacterial suspensions and the resulting structures are examined. The addition of polymer may foster aggregate formation by neutralization of the bacterial surface charge and enhance inter-particle bridging. The aggregation behavior may affect the efficiency of certain water and wastewater treatment processes such as dewatering and coagulation. The impacts of aggregate structure on two representative processes, namely, ultra-filtration membrane fouling and pressure filter dewatering efficiency, are studied. It is found that the looser flocs yield a more porous cake and less tendency to foul whilst more porous filter cakes yield more ready biosolids dewatering.
Nano silica removal from IC wastewater by pre-coagulation and microfiltration
Authors: Huang C. , Jiang W. , Chen C.
Published: May 2018

Microfiltration (MF) coupled with pretreatment by coagulation was adopted in the treatment of chemical mechanical polishing (CMP) wastewater from IC manufacturing plants, containing high concentrations of silica. Poly-aluminium chloride (PACl) was the coagulant, while the cationic polyacrylamide (PAA) was the flocculant aid. Preliminary tests were performed with the raw CMP wastewater in order to determine the optimal coagulation condition for subsequent microfiltration. Analysis of the particle size distribution shows that nearly all silica particles were enlarged from nano scale to at least 4 μm in diameter after the pre-treatment. The pre-treated wastewater was then filtered through a polytetrafluoroethylene (PTFE) membrane with a pore size 0.5 μm at a constant vacuum pressure. Trace amounts of PAA in addition to the PACl coagulation can effectively increases the permeate flux.
Turbidity current in a circular settling tank
Authors: Fujisaki K. , Nagata N.
Published: May 2018

This paper deals with turbidity currents in a circular settling tank. A mathematical model with a k-ɛ turbulence model has been developed. Using this mathematical model, the following unique properties of turbidity currents in a circular settling tank are demonstrated: turbulence induced by the turbidity currents remains after most sediment particles have settled down. This residual turbulent diffusivity has a serious effect on the settling of finer particles. This phenomenon is a very important result in this study. Especially, in the case of a smaller densimetric Froude number, which is a stronger density effect, this residual turbulence effect increases, and also decreases the removal ratio in the downstream with low concentration. Generally, the bottom density current enhances the sediment transport near the tank bottom, while the bottom shear gives reversal influence. When the settling velocity is high, the settling ends under the developing stage both of the turbidity current and of the bottom boundary layer. On the contrary, if the settling velocity is low, the sediment travels a long distance, where the boundary layer is built up, resulting in the reduction of sediment transport near the tank bottom. The overall properties of the density-affected settling tank are also investigated in terms of the removal ratio.
A case study of dissolved air flotation for seasonal high turbidity water in Korea
Authors: Kwon S.B. , Ahn H.W. , Ahn C.J. , Wang C.K.
Published: May 2018

A DAF (Dissolved-Air-Flotation) process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when freshwater algae blooms occur or raw water turbidity becomes high. Pre-sedimentation is operated in case when the raw water turbidity is very high due to rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of the raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than the conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while the removal of them by sedimentation is more difficult. One of the main concerns for DAF operation is a high raw water turbidity. DAF is not adequate for raw water, which is more turbid than 100 NTU. In order to avoid this problem, pre-sedimentation basins are installed in the DAF plant to decrease the turbidity of the DAF inflow. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, it is suggested that pre-sedimentation with optimum coagulation prior to DAF is the appropriate treatment scheme.
The environmental, economic and societal consequences of inadequate nitrogen pollution controls
Authors: Randall C.W.
Published: May 2018

Because adequate nutrient controls were not established in the USA and other countries when there were past opportunities to do so, nutrient pollution of estuaries and coastal waters has resulted in the impairment of ecosystems and major reductions or collapse of fisheries at numerous sites around the world, resulting in major economic and societal impacts. The root problem is that political policies and processes have permitted municipalities, developers, industries and farmers to expand and operate without paying the full cost of their activities. Their expanded activities have occurred at the expense and displacement of those who rely on the productivity and recreational value of our estuarine and coastal waters. Some governments have developed remedial nutrient control programs, but most of them have been poorly conceived, under funded and inadequately enforced, resulting in small increments of progress that tend to be lost because of inadequate land use and immigration controls. It is proposed that establishment of comprehensive nutrient controls is needed throughout the world to preserve and protect estuarine and coastal waters, and to protect or re-establish fisheries, for both economic and societal stability. Nitrogen is the key nutrient for the establishment of control strategies. It is recommended that nutrient recovery from wastewaters and controlled reuse of both water and nutrients be widely implemented as a part of nutrient control strategies.
Some thoughts about future perspectives of water and wastewater management
Authors: Wilderer P.A.
Published: May 2018

The ideals of sustainability have a longer history than is sometimes realised, as they can be traced back to the insights of Von Carlowitz in 1713. However in the intervening centuries early successes in sanitation based on the “flushing sewer” led engineers to focus too much on sewerage-based solutions that are increasingly uneconomic and unequal to the challenges arising from population growth and urbanisation. The future strategy for globally sustainable sanitation will surely involve source separation and recycling and reuse: these are the technologies that environmental scientists and engineers should now be addressing.
Ammonium nitrogen removal from slurry-type swine wastewater by pretreatment using struvite crystallization for nitrogen control of anaerobic digestion
Authors: Kim B.U. , Lee W.H. , Lee H.J. , Rim J.M.
Published: May 2018

Precipitation of ammonium together with phosphate and magnesium is a possible alternative for lowering the nitrogen content of wastewater. In this study we examine the removal of ammonium nitrogen and phosphorus from slurry-type swine wastewater containing high concentrations of nutrients by the addition of phosphoric acid along with either calcium oxide or magnesium oxide, which leads to the crystallization of insoluble salts such as hydroxyapatite and struvite. The struvite crystallization method showed a high capacity for the removal of nitrogen when magnesium oxide and phosphoric acid were used as the magnesium and phosphate sources, respectively. When it was applied to swine wastewater containing a high concentration of nitrogen, the injection molar ratio of Mg2+:NH4+:PO43- that gave maximum ammonium nitrogen removal was 3.0:1.0:1.5.
Automatic control of external carbon source addition for nitrogen removal in sewage with low C/N ratios
Authors: Nam H.U. , Kim Y.O. , Lee J.H. , Hur S.H. , Park T.J.
Published: May 2018

For cost-effective nitrogen removal from sewage with low C/N ratios, an automatic control system for the addition of external carbon based on oxidation-reduction potential (ORP) data in an anoxic reactor has been developed. In this study, it was carried out with a pilot-scale modified Bardenpho process. This consisted of anoxic1, aerobic1, anoxic2 and aerobic2 stages with an external recycle ratio of 150% (Q/Qinf), and a media packing ratio of 2.4%-2.9% (v/v) in the aerobic reactor. As a result of applying the automatic control system for the minimization of the external carbon source dosage, the dosage was decreased by about 20%. This estimate was based on ORP compared with a stable dosage of 75mg/L based on the C/NOx-N ratio of the anoxic influent. It was necessary that the ORP set-value be regulated from -120 mV to Ð80 mV because influent NH4+-N concentration varied from 12 to 15 mg/L due to rainfall. Correspondingly, the demanded dosages were decreased. Drift of the the real-time value in control system was more stable after changing the ORP set-value from -120 mV to -80 mV.
Comparison of sequentially combined carbon with sole carbon in denitrification and biological phosphorus removal
Authors: Cho E.S. , Ahn K.-H. , Molof A.H.
Published: May 2018

The sequentially combined carbon (SCC) of methanol and acetic acid was used for the biological nutrient removal (BNR). Its BNR performance was compared with methanol or acetic acid as a sole carbon substrate. Compared to the sole carbon substrate, the use of SCC demonstrated the highest overall TIN removal of 98.3% at a COD ratio of 30 mg COD/l of methanol/50 mg CDO/l of acetic acid. Furthermore, denitrification was more enhanced when methanol was used as one of the SCC, rather than as a sole carbon source. Complete phosphorus removal was accomplished with a non-detectable o-P concentration when SCC was added. This research also showed that aerobic denitrifiers appear to prefer acetic acid to methanol, and the amount of poly-§-hydroxybutyrate (PHB) stored by P accumulating organisms (PAOs) using acetic acid in the anoxic zone could be another important factor in improving the aerobic denitrification. The SCC was a very favorable carbon source for the aerobic denitrification since acetic acid was utilized more efficiently for P-release in accordance with increase of PHB stored in the cell of PAOs by removing nitrogen first using methanol.
Treatment of swine wastewater using MLE process and membrane bio-reactor
Authors: Chung Y.-J. , Choi H.-Na , Cho J.-B. , Park S.-K.
Published: May 2018

The aim of this study was to develop the optimum integrated treatment system for slurry type swine wastewater through field testing. Although composting and liquid composting are the most desirable processes to treat swine wastewater, inadequate composting has been blamed as critical non-point source pollutants. In the area with limited crop land and grass land, the most feasible method to handle slurry type swine wastewater would be that the solids portion from the solids/liquid separation process is treated by composting and then the liquid portion is treated by a series of wastewater treatment processes, including physicochemical treatment system and biological nutrient removal systems such as the modified Ludzack Ettinger (MLE) process and MLE process coupled with a membrane, to satisfy the different effluent criteria. When using the appropriate solids/liquid separation system, the removal efficiency of SS, CODCr, and TKN was 92.4%, 73.6%, and 46.0%, respectively and the amount of bulking agent required for composting and organic loading rate for the following wastewater treatment system can be reduced by 94.8% and 84.7%, respectively. When treating the effluent from solids/liquid separation process by MLE process, the optimal volume fraction for denitrification was 20% of total reactor volume and the optimum ratio of F/M and FN/M were increased with increase of C/N ratio. Since the effluent quality of MLE process is not enough to discharge, the DAF process was operated with addition of FeCl3 and cationic polyelectrolyte. The effluent from the DAF process was treated in the MLE process coupled with a crossflow ultrafiltration membrane to satisfy more stringent effluent criteria. When external carbon source is added to keep 6.0 of C/N ratio, the efficiency of denitrification is best. The optimum linear velocity and transmembrane pressure for MBR process was 1.8m/sec and 2.1atm, respectively. By addition of external carbon source, nitrogen compounds, especially NOx-N, were considerably removed. And by addition of powdered activated carbon, the removal efficiency of CODCr and CODMn and the membrane flux were increased dramatically.
Selection of slow growing organisms as a means for improving aerobic granular sludge stability
Authors: de Kreuk M.K. , van Loosdrecht M.C.M.
Published: May 2018

Recently, several groups have showed the occurrence of aerobic granular sludge. The excellent settling characteristics of aerobic granular sludge allow the design of very compact wastewater treatment plants. In laboratory experiments, high oxygen concentrations were needed to obtain stable granulation. However, in order to obtain energy efficient aeration and good denitrification low oxygen concentrations would be required. From earlier research on biofilm morphology, it was learned that slow growing organisms influence the density and stability of biofilms positively. To decrease the growth rate of the organisms in the aerobic granules, easily degradable substrate (e.g. acetate) has to be converted to slowly degradable COD like microbial storage polymers (e.g. PHA). Phosphate or glycogen accumulating bacteria perform this conversion step most efficiently. In this paper it is shown that the selection of such bacteria in aerobic granules indeed led to stable granular sludge, even at low oxygen concentrations.
Scientific basis for the design of small activated sludge systems
Authors: Orhon D. , Karahan-Gül Ö , Sözen S.l , Artan N.
Published: May 2018

The study presents an evaluation of the oxygen requirement and sludge production, modeled in terms of fundamental processes reflecting different biochemical transformations in activated sludge systems. Modern modeling concepts define substrate utilization and endogenous decay as major processes requiring final electron acceptors. Substrate and sludge components may be defined in terms of different parameters. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) are the traditional substrate parameters. COD also serves to define biomass along with volatile suspended solids (VSS) parameter. Estimation of oxygen requirement and sludge production for aerobic activated sludge systems covering basic biochemical processes are defined for different substrate and sludge parameters, considering that each calculation is associated with a different stoichiometry on the basis of a selected parameter set. The German regulations are examined and the biochemical bases of the coefficients in the regulatory expressions are set in terms of fundamental model constants.
Trickling filters for upgrading low technology wastewater plants for nitrogen removal
Authors: Pearce P.
Published: May 2018

Previous work through the 1990s in the Thames Water region in the UK has demonstrated the ability of the trickling filter process to produce fully nitrified effluents, reliably throughout the year. The original data used for the nitrification model derivations have been reanalysed, to investigate the degree of nitrogen removal across the process. Removals of total nitrogen ranging from 0% to over 50% were observed across the trickling filter process and calculated total nitrogen removals of 26-63% were obtained when primary treatment was included. The degree of nitrogen removal and biological denitrification (excluding cellular assimilation) was found to be strongly influenced by BOD load, irrigation velocity and media size. Regression models were produced which gave good predictive relationships for the data ranges used.

The models produced worked for filters used with and without a recirculation of effluent nitrate which suggests that a significant degree of nitrification occurred in areas of high heterotroph activity (BOD removal). The simplicity and energy efficiency of the trickling filter process, combined with its capacity for full nitrification and partial denitrification, make the process attractive as a combined process used with pond systems in developing countries where nitrogen removal may be required. Some of these synergies have already been developed with the PETRO® process in South Africa.
Introduction to the IWA Task Group on Biofilm Modeling
Authors: Noguera D.R. , Morgenroth E.
Published: May 2018

An International Water Association (IWA) Task Group on Biofilm Modeling was created with the purpose of comparatively evaluating different biofilm modeling approaches. The task group developed three benchmark problems for this comparison, and used a diversity of modeling techniques that included analytical, pseudo-analytical, and numerical solutions to the biofilm problems. Models in one, two, and three dimensional domains were also compared. The first benchmark problem (BM1) described a monospecies biofilm growing in a completely mixed reactor environment and had the purpose of comparing the ability of the models to predict substrate fluxes and concentrations for a biofilm system of fixed total biomass and fixed biomass density. The second problem (BM2) represented a situation in which substrate mass transport by convection was influenced by the hydrodynamic conditions of the liquid in contact with the biofilm. The third problem (BM3) was designed to compare the ability of the models to simulate multispecies and multisubstrate biofilms. These three benchmark problems allowed identification of the specific advantages and disadvantages of each modeling approach. A detailed presentation of the comparative analyses for each problem is provided elsewhere in these proceedings.
Intermittent sand filtration for wastewater treatment in rural areas of the Middle East - a pilot study
Authors: Sabbah I. , Ghattas B. , Hayeek A. , Omari J. , Haj Y. , Admon S. , Green M.
Published: May 2018

This paper concentrates on Intermittent Sand Filtration (ISF) as a polishing stage for effluent from a facultative pond. During the three-year research program, the system operated with an influent flow-rate of 500-1,000 L/day and an average BOD concentration of 200-400 mg BOD/L, with the corresponding hydraulic and BOD loadings of 110-200 L/m2/day and 20-40 gBOD/m2/day, respectively. Flow to the ISF was applied intermittently with a different number of doses in each run. In addition, the effects of the frequency and the duration of rest periods (no feeding) were studied. Removal of 90-95% of BOD and 75-90% of COD and TSS was achieved consistently throughout the study period. Elevated levels of nitrification were observed with 95-100% removal of NH3. The ISF performed best when fed with 5-10 doses/day. Reducing the daily number of doses to 3/day at the same hydraulic loading rate resulted in a 20-30% reduction in removal efficiency. The 2-4 week rest period had no effect on the biological activity in the subsequent run. However, rest periods of more than 30 days were found to negatively affect removal efficiency.
Methanotrophic biodegradation of cis-1,2-dichloroethylene in a continuously fed fixed-film bioreactor
Authors: Arcangeli J.P. , Arvin E.
Published: May 2018

Co-metabolic biodegradation of cis-dichloroethylene (cis-DCE) was investigated in a bench-scale fixed-film bioreactor inoculated with a mixed culture of methane oxidising bacteria. The aim of this work was to identify factors that affect the cis-DCE biodegradation. It was observed that the presence of methane was necessary to enhance the biodegradation of cis-DCE, but an excess of methane inhibited the cis-DCE removal. cis-DCE did not inhibit the methane biodegradation at concentrations up to 300 μg/L. Maximum cis-DCE removal was observed with a methane bulk concentration ranging from 0.2 to 0.7 mg/L. It was found that the activity of the biofilm was located in the upper 100 μm of the biofilm. On the basis of this study it is concluded that careful control of the oxygen and methane concentrations as well as of the biofilm thickness is necessary in order to optimise the biodegradation of cis-DCE in fixed film bioreactors.
A software nitrate sensor based on ammonium and redox signals
Authors: Cecil D.
Published: May 2018

We have computed the nitrate concentration in the activated sludge in real-time using a model, which is a subset of ASM1. The model is in operation at two WWTPs where oxygen, ammonium and redox are measured online in the aeration tanks. The model uses these measurements to continuously adjust its values for the influent ammonium concentration, the nitrification rate, the denitrification rate and the net hydrolysis. Then it computes the nitrate concentration. This value is updated every 10 s. The model results have been compared with the output from a Dr Lange in-situ nitrate sensor at one of these WWTPs. The systematic difference between these two measurements is less than 0.2 mgN l-1 and 90% of the differences are between -1.1 and 1.1 mgN l-1.
The fate of legionellae within distribution pipe biofilms: measurement of their persistence, inactivation and detachment
Authors: Storey M.V. , Långmark J. , Ashbolt N.J. , Stenström T.A.
Published: May 2018

Distribution pipe biofilms present a currently unquantified public health risk to consumers receiving water for domestic potable and non-potable use. The aim of this study was to quantify the numbers of legionellae, used here as model bacterial pathogens, that may accumulate, persist within and detach from distribution pipe biofilms. L. pneumophila recovered by standard culture from an 8 week-old biofilm formed within a novel pilot-scale water distribution system represented 1% of those present in the adjacent bulk water. A combined chlorine concentration exceeding 0.2 mg.L-1 eliminated culturable sessile legionellae altogether, though the reduction in FISH-positive cells represented just 75 ± 25% of the original amount, compared to a 5-log reduction in culturable cells during the same period. Where there was < 0.1 mg.L-1 combined chlorine, an exponential decay/loss of sessile L. pneumophila was observed (k = 0.37 - 0.41) over the course of a 38-day experimental period. The inoculation of the system with 1 μm fluorescent microspheres and legionellae demonstrated that removal of the latter was dominated by chemical disinfection, with erosion and biological grazing playing lesser roles. Under turbulent (Re ∼5000) conditions, larger clusters of biofilm become detached from substrata, with more than 90% of sessile legionellae mobilised into the bulk water phase. Interaction with both biofilms and a thermophilic Acanthamoeba isolate reduced the susceptibility of legionellae to thermal inactivation by between one and two orders of magnitude, though it increased their sensitivity to chemical (free and combined chlorine) disinfection.
Full scale fluidized bed anaerobic reactor for domestic wastewater treatment: performance, sludge production and biofilm
Authors: Mendonça N.M. , Niciura C.L. , Gianotti E.P. , Campos J.R.
Published: May 2018

This paper describes the performance, sludge production and biofilm characteristics of a full scale fluidized bed anaerobic reactor (32 m3) for domestic wastewater treatment. The reactor was operated with 10.5 m.h-1 upflow velocity, 3.2 h hydraulic retention time, and recirculation ratio of 0.85 and it presented removal efficiencies of 71 ± 8% of COD and 77 ± 14% of TSS. During the apparent steady-state period, specific sludge production and sludge age in the reactor were (0.116 ± 0.033) kgVSS. kgCOD-1 and (12 ± 5)d, respectively. Biofilm formed in the reactor presented two different patterns: one of them at the beginning of the colonization and the other of mature biofilm. These different colonization patterns are due to bed stratification in the reactor, caused by the difference in local-energy dissipation rates along the reactor's height, and density, shape, etc. of the bioparticles. The biofilm population is formed mainly of syntrophic consortia among sulfate reducing bacteria, methanogenic archaea such as Methanobacterium and Methanosaeta-like cells.
Integrated control of nitrate recirculation and external carbon addition in a predenitrification system
Authors: Yuan Z. , Keller J.
Published: May 2018

The integrated control of nitrate recirculation and external carbon addition in a predenitrification biological wastewater treatment system is studied. The proposed control structure consists of four feedback control loops, which manipulate the nitrate recirculation and the carbon dosage flows in a highly coordinated manner such that the consumption of external carbon is minimised while the nitrate discharge limits (based on both grab and composite samples) are met. The control system requires the measurement of the nitrate concentrations at the end of both the anoxic and the aerobic zones. Distinct from ordinary control systems, which typically minimise the variation in the controlled variables, the proposed control system essentially maximises the diurnal variation of the effluent nitrate concentration and through this maximises the use of influent COD for denitrification, thus minimising the requirement for external carbon source. Simulation studies using a commonly accepted simulation benchmark show that the controlled system consistently achieves the designated effluent quality with minimum costs.
Carbonate addition - an effective remedy against poor activated sludge settling properties and alkalinity conditions in small wastewater treatment plants
Authors: Wett B. , Eladawy A. , Becker W.
Published: May 2018

The impact of marble powder on the performance of small seasonal treatment plants dealing with high ammonia concentrated wastewater has been investigated. The carbonate has been added to one of two parallel lab-scale SBR-systems as an alkalinity depot and a bio-carrier. The focus of the monitoring program was put on the measurement of carbon fractions in the liquid and the solid phase and on the alkalinity conditions. Monitoring results show a significant correlation between carbonate dosage (and corresponding inorganic carbon concentration and pH-value) and sludge volume index and nitrification rate.
Enhancing biological nitrogen removal in a small wastewater treatment plant by regulating the air supply
Authors: Fiter M. , Colprim J. , Poch M. , Rodríguez-Roda I.
Published: May 2018

Most of the small wastewater treatment plants in Catalonia were not designed to remove nutrients. However, the large safety margins built into their original engineering design has meant that, in many cases, it has been possible to remove part of the nitrogen without being controlled. This paper focuses on the practical experience carried out in one of these facilities, the Bisbal wastewater treatment plant, aimed at enhancing the biological nitrogen removal using simple, low-cost, easy-to-operate measurement and control. The control strategy, which is based on air supply regulation, was previously designed using simulation studies. A dissolved oxygen monitoring system was installed into the facility, while nitrogen concentrations were analysed every day. Optimal dissolved oxygen profiles in the oxidation ditch were identified, while the air supply strategy was modified according to the variations in the influent.
A critical process analysis of wine production to improve cost, quality and environmental performance
Authors: Sheridan C.M. , Bauer F.F. , Burton S. , Lorenzen L.
Published: May 2018

Wine production in South Africa is delocalised, with numerous small-to-medium sized producers within several regions within the Western Cape. Whilst adapting to new technological changes, producers have to respond to pressure from consumers and governments regarding the environmental consequences of winemaking, especially water usage and pollution. To date, no systematic analysis integrating the various aspects of winemaking in South Africa has been done. This study assessed both physical inputs and outputs. A detailed questionnaire was developed to broadly assess these parameters and was submitted to all cellars in South Africa. Case studies were performed at three cellars during the 2002 harvest season to validate the questionnaires and collect missing information. Based on this, and a cocurrent project, the following parameters were correlated to the tons of grapes presses per annum: effluent parameters which include chemical oxygen demand, suspended solids, total dissolved solids, sodium adsorption ratio, quantity of effluent; wine produced, water consumed, and electricity consumed. These parameters were used to develop an input/output model. This model may be used by wineries to predict their water and electrical consumption, wine produced and effluent characteristics provided they know the tonnage of grapes pressed per year.
Assessment of biofilm destabilisation and consequent facilitated zinc transport
Authors: Muris M. , Delolme C. , Gaudet J.-P. , Spadini L.
Published: May 2018

In infiltration basins, such as in any kind of porous media, bacteria may form biofilms. When conditions induce destabilization of this biofilm, resulting colloids are transported by the hydraulic flow. Some studies have focused on the role played by these bacterial colloids in pollutants transport in soil. This study deals with the ability of Pseudomonas putida to retain zinc and investigates the facilitated transport of this metal. Batch and columns experiments have been carried out. Bacteria display a great affinity for zinc in batch experiments and facilitated transport have been highlighted in a small extent, for the moment. A scenario of stabilization/destabilization of the biofilm has been designed and may be employed for further investigations.