bluuebunny/crossref_metadata_2025 huggingface dataset:
An innovative sludge management system based on separation of primary and secondary sludge treatment
Authors: Mininni G. , Braguglia C.M. , Ramadori R. , Tomei M.C.
Published: May 2018

An innovative sludge management system based on separation of treatment and disposal of primary and secondary sludge is discussed with reference to a sewage treatment plant of 500,000 equivalent person capacity. Secondary sludge, if treated separately from primary sludge, can be recovered in agriculture considering its relatively high content of nitrogen and phosphorus and negligible presence of pathogens and micropollutants. One typical outlet for primary sludge is still incineration which can be optimised by rendering the process auto thermal and significantly reducing the size of the incineration plant units (dryer, fluidised bed furnace, boiler and units for exhaust gas treatment) in comparison with those required for mixed sludge incineration. Biogas produced in anaerobic digestion is totally available for energy conversion when sludge treatment separation is performed, while in the other case a large proportion may be used as fuel in incineration, thus reducing the net electric energy conversion from 0.85-0.9 to 0.35-0.4 MW for the plant considered.
Direct generation of electricity from sludges and other liquid wastes
Authors: Dentel S.K. , Strogen B. , Chiu P.
Published: May 2018

Recently it has been shown that electrical energy can be harvested from marine sediments, simply by connection of an electrode (anode) in anaerobic marine sediments to an electrode in the aerobic zone above the sediments. We have now shown that similar applications are available in sludge treatment. Using a reactor with graphite foil electrodes in an aerated aerobic and anaerobic sludge zone, electrical current was generated, and enhanced when an additional organic substrate (acetate) was added. Electron microscopy, x-ray diffraction, and PCR examination of the anode surface showed no surface colonization and no increase in Geobacter relative to a control, indicating that microbial use of the anode as an electron acceptor was indirect through the use of redox mediators. Given the demonstration of electricity generation from sludge, the potential for similar applications, using other organic waste sources, is evaluated.
Thermal drying of wastewater sludge with crack formation
Authors: Chen J.B. , Peng X.F. , Tao T. , Lee D.J.
Published: May 2018

We examined in this work the drying characteristics of wastewater sludge. The drying flux of the constant-rate period for sludge cake could be up to 40% higher than that from a sand bed. Owing to the considerable volume shrinkage of cake, cracks would form and develop on the crack surface, which yielded three-dimensional but rather than the one-dimensional cake structure assumed in conventional drying theories. The crack length was fully developed in the first 30 min of drying, while the width of crack increased linearly with time. Using these data the drying flux from the cracks was estimated. Enhanced drying flux was noticeable which depended on the crack shape and the crossflow velocity.
Development of sludge based stable aqueous Bacillus thuringiensis formulations
Authors: Brar S.K. , Verma M. , Tyagi R.D. , Valéro J.R. , Surampalli R.Y. , Banerji S.K.
Published: May 2018

This study focuses on development of aqueous flowable (suspension) formulations for Bacillus thuringiensis (Bt) based biopesticides from wastewater sludge. Different inerts like sorbitol, sodium monophosphate, sodium metabisulphite, sorbic acid, propionic acid, Tween-80, Triton X-100 and glycerol were tested for formulations. Five different formulations for non-hydrolyzed (NH) secondary sludges were tried and the best combination selected on the basis of various physical parameters like viscosity, particle size, suspendibility, entomotoxicity, and microbiological purity tests. F5 formulations (for secondary sludge) comprising sorbitol, sodium monophosphate and sodium metabisulphite gave better physical and biological characteristics with a small effect on entomotoxicity and spore concentration after 120 days at pH 6, 6.5 and temperatures 40 and 50°C and viscosity change at 40 and 50°C. The formulations were more stable at pH 4.0 to 5.0 and temperatures 4 to 30°C whereas at pH 6.0 and 6.5 and temperatures 40 and 50°C, there was degeneration of the product. Lower proteolytic activity and physical factors like ionic strength and surface group changes at pH 6 and 6.5 were responsible for the instability of the formulation.
Removal of geosmin and 2-methylisoborneol by biological filtration
Authors: Elhadi S.L.N. , Huck P.M. , Slawson R.M.
Published: May 2018

The quality of drinking water is sometimes diminished by the presence of certain compounds that can impart particular tastes or odours. One of the most common and problematic types of taste and odour is the earthy/musty odour produced by geosmin (trans-1, 10-dimethyl-trans-9-decalol) and MIB (2-methylisoborneol). Taste and odour treatment processes including powdered activated carbon, and oxidation using chlorine, chloramines, potassium permanganate, and sometimes even ozone are largely ineffective for reducing these compounds to below their odour threshold concentration levels. Ozonation followed by biological filtration, however, has the potential to provide effective treatment. Ozone provides partial removal of geosmin and MIB but also creates other compounds more amenable to biodegradation and potentially undesirable biological instability. Subsequent biofiltration can remove residual geosmin and MIB in addition to removing these other biodegradable compounds. Bench scale experiments were conducted using two parallel filter columns containing fresh and exhausted granular activated carbon (GAC) media and sand. Source water consisted of dechlorinated tap water to which geosmin and MIB were added, as well as, a cocktail of easily biodegradable organic matter (i.e. typical ozonation by-products) in order to simulate water that had been subjected to ozonation prior to filtration. Using fresh GAC, total removals of geosmin ranged from 76 to 100% and total MIB removals ranged from 47% to 100%. The exhausted GAC initially removed less geosmin and MIB but removals increased over time. Overall the results of these experiments are encouraging for the use of biofiltration following ozonation as a means of geosmin and MIB removal. These results provide important information with respect to the role biofilters play during their startup phase in the reduction of these particular compounds. In addition, the results demonstrate the potential biofilters have in responding to transient geosmin and MIB episodes.
Geosmin occurrence in riverine cyanobacterial mats: is it causing a significant health hazard?
Authors: Bláha L. , Sabater S. , Babica P. , Vilalta E. , Maršáálek B.
Published: May 2018

Toxicity endpoints (nonspecific cytotoxicity, hepatotoxicity, neurotoxicity, immunotoxicity, and mutagenicity) were studied in cyanobacterial mats obtained from a shallow river. Some of the cyanobacterial mats tested were known to be non-geosmin producers, while others were geosmin-producers. No microcystin-like compounds were detected by HPLC in any of the biofilm samples. The mutagenicity and neurotoxicity of biofilm metabolites was negligible, and generally weak adverse effects of biofilm extracts detected in a battery of in-vitro assays indicated relatively low human health risks associated with biofilm toxicity. While the toxicity responses detected in the studied biofilms were weak, effects were not related to production of geosmin. It was therefore concluded that the production of this metabolite cannot be taken as an indication per se of the existence of a health hazard.
Public thresholds for chlorinous flavors in U.S. tap water
Authors: Mackey E.D. , Baribeau H. , Crozes G.F. , Suffet I.H. , Piriou P.
Published: May 2018

Considering this rapid growth in the purchasing of bottled water and home filtration devices, utilities are increasingly concerned about consumer dissatisfaction with tap water quality. This project aimed to characterize public perceptions of chlorinous flavors in drinking water, and how these impact customers' choices with respect to consumption of tap water alternatives. On-site taste tests at seven water utilities with 30 to 40 panelists at each site, were conducted using a forced-choice triangle test method (ASTM method E679-91) to measure public sensitivity to chlorine and chloramine in drinking water. The chlor(am)ine concentration increased from set to set. The best-estimate sensitivity limit for each panelist was the geometric mean of that concentration at which the last miss occurred and the next (adjacent) higher concentration. The measured sensitivity limit of average American populations to free chlorine (159 persons tested) and chloramine (93 persons tested) in tap water were 0.8 and 3.7 mg/L Cl2, respectively. These thresholds are much higher than those previously reported in the literature using trained FPA panels. No significant differences were observed between tap water users and users of tap water alternatives or between the various markets tested with respect to average sensitivity, though individual sensitivity varied widely.
Nitrogen removal of high strength wastewater via nitritation/denitritation using a sequencing batch reactor
Authors: Lai E. , Senkpiel S. , Solley D. , Keller J.
Published: May 2018

The sequencing batch reactor (SBR) process concept was applied to achieve efficient ammonium removal via nitrite under both laboratory and pilot-scale conditions. Both sets of experimental results show that without pH control or carbon addition the nitritation process consistently converted approximately 50% of the ammonium from biosolids dewatering liquids to nitrite with hydraulic retention times (HRT) as short as 10 h. The results from the pilot-scale study also indicate that the selective oxidation of ammonium to nitrite is a reliable process as the accumulation of nitrate was never an issue during a 330-day trial. The SBR process concept was extended to achieve complete nitrogen removal through nitritation and denitritation in the laboratory scale. The experimental results indicate that a total reduction of 96-98% of the ammonium nitrogen from biosolids dewatering liquids (influent concentration typically 1,200 g m-3 ) was achieved with a short HRT of 1.1 d and a removal rate of 1.05 kgNm-3d-1. This process concept was tested at pilot scale where the nitritation process could be started up without temperature control in a short period of time. Nitrogen removal rates up to 1.2 kgNm-3d-1 at an HRT of 0.88 d have been obtained. COD to nitrogen ratios required in the pilot plant were consistently in the range 1.6-1.9 kgCOD kg-1N removed.
Sludge minimization technologies - an overview
Authors: Øegaard H.
Published: May 2018

The management of wastewater sludge from wastewater treatment plants represents one of the major challenges in wastewater treatment today. The cost of the sludge treatment amounts to more than the cost of the liquid in many cases. Therefore the focus on and interest in sludge minimization is steadily increasing. In this paper an overview is given for sludge minimization (sludge mass reduction) options. It is demonstrated that sludge minimization may be a result of reduced production of sludge and/or disintegration processes that may take place both in the wastewater treatment stage and in the sludge stage. Various sludge disintegration technologies for sludge minimization are discussed, including mechanical methods (focusing on stirred ball-mill, high-pressure homogenizer, ultrasonic disintegrator), chemical methods (focusing on the use of ozone), physical methods (focusing on thermal and thermal/chemical hydrolysis) and biological methods (focusing on enzymatic processes).
Bacterial composition of activated sludge - importance for floc and sludge properties
Authors: Nielsen P.H. , Thomsen T.R. , Nielsen J.L.
Published: May 2018

Activated sludge flocs consist of numerous constituents which, together with other factors, are responsible for floc structure and floc properties. These properties largely determine the sludge properties such as flocculation, settling and dewaterability. In this paper we briefly review the present knowledge about the role of bacteria in relation to floc and sludge properties, and we present a new approach to investigate the identity and function of the bacteria in the activated sludge flocs. The approach includes identification of the important bacteria and a characterization of their physiological and functional properties. It is carried out by use of culture-independent molecular biological methods linked with other methods to study the physiology and function, maintaining a single cell resolution. Using this approach it was found that floc-forming properties differed among the various bacterial groups, e.g. that different microcolony-forming bacteria had very different sensitivities to shear and that some of them deflocculated under anaerobic conditions. In our opinion, the approach to combine identity with functional analysis of the dominant bacteria in activated sludge by in situ methods is a very promising way to investigate correlations between presence of specific bacteria, and floc and sludge properties that are of interest.
Performance evaluation of hybrid and conventional sequencing batch reactor and continuous processes
Authors: Tam H.L.S. , Tang D.T.W. , Leung W.Y. , Ho K.M. , Greenfield P.F.
Published: May 2018

Bench-scale systems, using conventional and compact hybrid activated sludge configurations, were set up to evaluate the systems' nitrification–denitrification performance, operating sludge age/MLSS concentration and sludge settleability at a Hong Kong municipal STW. Configurations tested were the continuous clarifier modified Ludzack Ettinger (MLE) and the sequencing batch reactor (SBR) with and without hybrid suspended biofilm carriers. Results demonstrated that the hybrid SBR and MLE systems consistently achieved close to complete nitrification (effluent NH4-N = 2.4 and 6.9 mg/L) and 75% and 67% removal of nitrogen (N) (effluent NO3-N < 10 mg/L) with an overall hydraulic retention time of only 7.5 hours, operating sludge age as short as 5.2 days, and mixed liquor suspended solids concentration of ∼1,300 mg/L with a sludge volume index of 109 and 229 mL/g, respectively. The most sensitive and slowest growing nitrifiers attached to the hybrid biofilm carriers. This allowed the hybrid processes to be operated at a sludge age shorter than the critical nitrifying sludge age while still retaining near complete nitrification. In contrast, to achieve complete nitrification, the conventional MLE system needed to be operated at 1.5 to 2.5 times the critical sludge age. These results indicate that the hybrid MLE configuration is a suitable process for use in upgrading existing conventional works for N removal and for increasing hydraulic capacity of existing N removal works, without major civil works modifications, in Hong Kong. For new works, consideration might be given to the use of the hybrid SBR, which shows a more stable N removal performance than the MLE process due to its inherent in-basin equalization capacity and better reaction conditions for nitrification in terms of higher initial NH4-N level. It was also observed that the conventional SBR produced better nitrification performance than the hybrid MLE process tested. Design parameters and operating conditions of the hybrid systems should be subjected to further full-scale trial for higher hydraulic capacity and N removal performance.
Biological denitrification in a sequencing batch reactor
Authors: Dangcong P. , Yi W. , Hao W. , Xiaochang W.
Published: May 2018

Biological denitrification was studied in an SBR to investigate the performance. The experimental results showed that granular sludge with high activity and good settling ability can be developed smoothly in the reactor. With the granular sludge, high nitrate loading rate (0.48 kg NO3-N dm−3 d−1) and removal efficiency (more than 99%) can be achieved. Scanning electronic microscope examination showed that only rod-shape bacteria existed on and within the granules, which confirmed indirectly that filamentous bacteria do not utilize nitrate and nitrite as electron acceptors. SBR is an alternative and effective technology for biological denitrification.
Investigation and assessment of sludge pre-treatment processes
Authors: Müller J.A. , Winter A. , Strünkmann G.
Published: May 2018

The pre-treatment of sludges by disintegration will result in a number of changes in sludge properties. Floc destruction as well as cell disintegration will occur. This leads to an increase of soluble substances and fine particles. Furthermore, biochemical reactions may appear during or immediately after disintegration. The influence of disintegration of excess sludge on anaerobic digestion was studied in full scale. A stirred ball mill, an ultrasound disintegrator, a lysate centrifuge and ozone treatment were used. The results of the degradation process were compared to a reference system without pre-treatment. An enhancement of the degree of degradation of 7.4% to 20% was observed. The pollution of sludge water as well as the dewatering properties of the digested sludge were investigated. COD and ammonia in the sludge water were increased and a higher polymer demand was observed while the solid content after dewatering stayed almost unchanged. Based on these results the cost effectiveness has been assessed taking into account different conditions (size of WWTP, cost for disposal, etc.). Capital and energy costs are the main factors while the decrease in disposal costs due to the reduced amount of sludge is the main profit factor.
Process performance and change in sludge characteristics during anaerobic digestion of sewage sludge with ozonation
Authors: Goel R. , Komatsu K. , Yasui H. , Harada H.
Published: May 2018

A new process configuration combining anaerobic digestion with ozonation, and operated at long SRT, was studied with the objective of on-site reduction in sludge quantity and improving biogas recovery. The process performance with respect to solid reduction efficiency and other important process parameters like accumulation of inorganic solids, changes in sludge viscosity and dewatering characteristics were evaluated from the data of long term pilot scale continuous experiments conducted using a mixture of primary and secondary municipal sewage sludge. Due to sludge ozonation and long SRT, high VSS degradation efficiency of approximately 80% was achieved at a reactor solid concentration of 6.5%. A high fraction of inorganic solid (>50%) consisting mainly of acid insoluble and iron compounds was found to accumulate in the reactor. The high inorganic content accumulated in the digested sludge did not, however, contribute to the observed increase in sludge viscosity at high solid concentration. The sludge viscosity was largely found to depend on the organic solid concentration rather than the total solid content. Moreover, higher inorganic content in the digested sludge resulted in better sludge dewaterability. For a quick assessment of the economic feasibility of the new process, an economic index based on the unit cost of digested sludge disposal to unit electric cost is proposed.
Monitoring pH and electric conductivity in an EBPR sequencing batch reactor
Authors: Serralta J. , Borrás L. , Blanco C. , Barat R. , Seco A.
Published: May 2018

This paper presents laboratory-scale experimentation carried out to study enhanced biological phosphorus removal. Two anaerobic aerobic (A/O) sequencing batch reactors (SBR) have been operated during more than one year to investigate the information provided by monitoring pH and electric conductivity under stationary and transient conditions. Continuous measurements of these parameters allow detecting the end of anaerobic phosphorus release, of aerobic phosphorus uptake and of initial denitrification, as well as incomplete acetic acid uptake. These results suggest the possibility of using pH and electric conductivity as control parameters to determine the length of both anaerobic and aerobic phases in an A/O SBR. More valuable information provided by monitoring pH and electric conductivity is the relation between the amount of phosphorus released and the conductivity increase observed during the anaerobic stages and which group of bacteria (heterotrophic or polyphosphate accumulating) is carrying out the denitrification process.
Biotechnology of intensive aerobic conversion of sewage sludge and food waste into fertilizer
Authors: Wang J.-Y. , Stabnikova O. , Tay S.T.-L. , Ivanov V. , Tay J.-H.
Published: May 2018

Biotechnology for intensive aerobic bioconversion of sewage sludge and food waste into fertilizer was developed. The wastes were treated in a closed reactor under controlled aeration, stirring, pH, and temperature at 60¡C, after addition of starter bacterial culture Bacillus thermoamylovorans. The biodegradation of sewage sludge was studied by decrease of volatile solids (VS), content of organic carbon and autofluorescence of coenzyme F420. The degradation of anaerobic biomass was faster than biodegradation of total organic matter. The best fertilizer was obtained when sewage sludge was thermally pre-treated, mixed with food waste, chalk, and artificial bulking agent. The content of volatile solid and the content of organic carbon decreased at 24.8% and 13.5% of total solids, respectively, during ten days of bioconversion. The fertilizer was a powder with moisture content of 5%. It was stable, and not toxic for the germination of plant seeds. Addition of 1.0 to 1.5% of this fertilizer to the subsoil increased the growth of different plants tested by 113 to 164%. The biotechnology can be applied in larger scale for the recycling of sewage sludge and food wastes in Singapore.
Characterization and evaluation of potential reuse options for wastewater sludge and combined sewer system sediments in Mexico
Authors: Jiménez B. , Méndez J.M. , Barrios J.A. , Salgado G. , Sheinbaum C.
Published: May 2018

Combined sewer systems generate sediments that have characteristics similar to those of primary sludge. Mexico City has such a system composed of a network of pipes, regulation structures (dams, basins) and open channels. The annual generation of sediments is estimated at 2.8 Mm3, which includes 0.41 Mm3 of sludge. As a result, the total capacity for transporting water is reduced considerably, making it necessary to extract yearly an approximate 0.85 Mm3 of those materials and to send them to a final disposal site with a capacity that is being exhausted. As part of the local Governmental effort, this project evaluates the quality of sediments from 6 dams, 4 regulation basins, 2 open channels, and 3 transfer stations. Also, sludge from 20 wastewater treatment plants was sampled. The results showed an important presence of lead and hydrocarbons in some sediments, and some sludge samples contained arsenic and nickel above the limits. Moreover, microbial levels exceeded the limits in all the sediments and sludge samples. Erosion was linked to the generation of an important amount of sediments based on lead concentration. A classification was established to determine the degree of contamination of the sediments as well as the required treatment to allow their potential reuse.
Polyhydroxyalkanoates production by activated sludge in a SBR using acetate and propionate as carbon sources
Authors: Lemos P.C. , Serafim L.S. , Reis M.A.M.
Published: May 2018

In this work, sludge was submitted to aerobic dynamic substrate feeding. Two sequencing batch reactors were operated, with acetate or propionate as carbon substrates. When acetate was used the system only produced a homopolymer of polyhydroxybutyrate (PHB). In order to maximize the PHB production, tests with different concentrations of acetate and ammonia were preformed. The best results (67.2% of PHB by cell dry weight) were obtained for 0.7 Nmmol/l of ammonia and 180 Cmmol/l of acetate. The PHB cell content was further improved by pupulse addition of substrate, three times 60 Cmmol/l of acetate, reaching a value of 78.5%. Propionate can be used as a precursor for hydroxyvalerate. In conjunction with other substrates, it allows for the formation of copolymers, which present better processing properties on commercial applications. Tests with different concentrations of propionate and ammonia were performed. Under the operating conditions used, the maximum PHA accumulated inside cells was 34.8%, with 30 Cmmol/l of propionate and no ammonia.
The influence of settling time on the formation of aerobic granules
Authors: McSwain B.S. , Irvine R.L. , Wilderer P.A.
Published: May 2018

Aerobic granular sludge, without the addition of carrier material, has only been reported in one suspended growth system, the Sequencing Batch Reactor (SBR) operated with short fill and settling periods. Recent studies have demonstrated that extracellular polysaccharides increased with the formation of aerobic granules, and that the shear force may stimulate production of these polysaccharides. In the study described herein, two SBRs were operated with the same shear force (air flow rate 275 L h−1) and two different settling times (2 and 10 min). Only the reactor with 2 min settling formed completely granular sludge, although granules were present in both reactors. Community analysis using 16S rRNA PCR products and DGGE showed that the communities diverged quickly after reactor start-up. For samples taken at steady-state, the granular population was more stable and less diverse than the flocculent reactor. EPS extraction of samples using cation exchange resin yielded similar values for aerobic granular sludge and previously reported anaerobic granules. While differences in the protein and TOC content between the flocculent and granular reactors increased appreciably as the sludge became more granular, the protein to polysaccharide ratio was relatively constant. The experiment confirmed previous theories that short settling times in SBRs select for granular sludge. The settling time results in granular sludge having a higher EPS protein content and a less diverse but more stable population.
Utilization of sludge in building material
Authors: Okuno N. , Ishikawa Y. , Shimizu A. , Yoshida M.
Published: May 2018

Several thermal solidification processes have been developed mainly in Japan. They are lightweight aggregates, brick, interlocking tile, char, and slag. A full-scale plant of them has been successfully operated for more than 10 years. The quality of the end products is better than the traditional ones. They are all substitutive to existing ones. The Japanese experience proves that all the processes are technically feasible, but not economically. Their manufacturing cost is always higher than market price. In addition, they consume large amounts of energy. However, if they are identified for a process of sludge disposal, all of them are worth considering for a big city where there is no place for the sludge to go. The end products can be reused inside the city. A new alternative is “Portland cement”. A Portland cement manufacturer accepts sewage sludge, if being paid some amount of money. An average payment is US$100 each 1,000 kg of ash or sludge cake. The Portland cement manufacturer accepts either cake or ash at the same price. It is about 50 to 30% of the energy cost of thermal solidification. The question is which is the better, dewatered cake or incinerated ash, for the Portland cement application. The answer is “it depends on the distance between the sewage plant and the Portland cement plant.”
Sustainable sludge management in developing countries
Authors: Jimenez B. , Barrios J.A. , Mendez J.M. , Diaz J.
Published: May 2018

Worldwide, unsanitary conditions are responsible for more than three million deaths annually. One of the reasons is the low level of sanitation in developing countries. Particularly, sludge from these regions has a high parasite concentration and low heavy metal content even though the available information is limited. Different issues needed to achieve a sustainable sludge management in developing nations are analysed. Based on this analysis some conclusions arise: sludge management plays an important role in sanitation programs by helping reduce health problems and associated risks; investments in sanitation should consider sludge management within the overall projects; the main restriction for reusing sludge is the high microbial concentration, which requires a science-based decision on the treatment process, while heavy metals are generally low; adequate sludge management needs the commitment of those sectors involved in the development and enforcement of the regulations as well as those that are directly related to its generation, treatment, reuse or disposal; current regulations have followed different approaches, based mainly on local conditions, but they favour sludge reuse to fight problems like soil degradation, reduced crop production, and the increased use of inorganic fertilizers. This paper summarises an overview of these issues.
Anaerobic rumen SBR for degradation of cellulosic material
Authors: Barnes S.P. , Keller J.
Published: May 2018

Hydrolysis of organic particulates under anaerobic conditions is generally regarded as the rate limiting step in solid digestion processes. Rumen-based ecosystems appear to achieve very high hydrolysis rates for cellulosic organic material. This study aimed at the development and demonstration of an anaerobic sequencing batch reactor (SBR) process operating with a rumen-based microbial inoculum. Fibrous alpha cellulose was used as sole carbon substrate and the use of an SBR operating cycle allowed the utilisation of a high liquid flow rate (hydraulic retention time of 0.67 d) while maintaining a much longer solids retention time of 7 d. Complete mass balances for carbon and nitrogen, as well as COD balancing allowed the full haracterisation of the process stoichiometry and kinetics. Elemental analysis of the biomass revealed a composition of C5H4.8O2.4N0.7, which is quite different from other generic biomass compositions used in the literature. The anaerobic rumen SBR was compared with another rumen-based reactor system in the literature which used a continuous filtration process for solid/liquid separation. This comparison showed that the volatile fatty acid production rate from cellulose in the anaerobic SBR was comparable with the performance achieved in the continuous system, although loading, substrate type and media composition were quite different between these two studies. Further evaluation of the anaerobic rumen SBR is required to determine its practical application for other substrates and to demonstrate the scale-up potential of this concept.
Fault detection in a real-time monitoring network for water quality in the lagoon of Venice (Italy)
Authors: Ciavatta S. , Pastres R. , Lin Z. , Beck M.B. , Badetti C. , Ferrari G.
Published: May 2018

In the context of monitoring water quality in natural ecosystems in real time, on-line data quality control is a very important issue for effective system surveillance and for optimizing maintenance of the monitoring network. This paper presents some applications of recursive state-parameter estimation algorithms to real-time detection of signal drift in high-frequency observations. Two continuous-discrete recursive estimation schemes, namely the Extended Kalman Filter and the Recursive Prediction Error algorithm, were applied to assuring the quality of the dissolved oxygen (DO) time series, as obtained from the Lagoon of Venice (Italy) during August 2002, through the real-time monitoring network of the Magistrato alle Acque (the Venice Water Authority). Results demonstrate the effectiveness of the methodology in early detection of a probable drift in the DO signal. Comparison of these results with those obtained from the application of a related recursive scheme (a Dynamic Linear Regression procedure) suggests the strong benefits of approaching the problem of on-line data quality control with several (not merely a single) independent such estimation methods.
TSS concentration in sewers estimated from turbidity measurements by means of linear regression accounting for uncertainties in both variables
Authors: Bertrand-Krajewski J.-L.
Published: May 2018

In order to replace traditional sampling and analysis techniques, turbidimeters can be used to estimate TSS concentration in sewers, by means of sensor and site specific empirical equations established by linear regression of on-site turbidity T values with TSS concentrations C measured in corresponding samples. As the ordinary least-squares method is not able to account for measurement uncertainties in both T and C variables, an appropriate regression method is used to solve this difficulty and to evaluate correctly the uncertainty in TSS concentrations estimated from measured turbidity. The regression method is described, including detailed calculations of variances and covariance in the regression parameters. An example of application is given for a calibrated turbidimeter used in a combined sewer system, with data collected during three dry weather days. In order to show how the established regression could be used, an independent 24 hours long dry weather turbidity data series recorded at 2 min time interval is used, transformed into estimated TSS concentrations, and compared to TSS concentrations measured in samples. The comparison appears as satisfactory and suggests that turbidity measurements could replace traditional samples. Further developments, including wet weather periods and other types of sensors, are suggested.
Control of an anaerobic reactor towards maximum biogas production
Authors: Liu J. , Olsson G. , Mattiasson B.
Published: May 2018

A new control strategy is introduced for operating anaerobic digestion processes efficiently at high load. The control system includes a cascade controller embedded into a rule-based supervisory system based on extremum-seeking control. The control system measures pH and biogas production rate and varies the organic load by manipulating the influent flow. Good control performances were achieved during the start-up and steady-state running operations and during rejection of disturbances. The control system can run the process under a high load condition and efficiently reject disturbances without explicit measurement of the influent characteristics.
Flocs through the looking glass
Authors: Jefferson B. , Jarvis P. , Sharp E. , Wilson S. , Parsons S.A.
Published: May 2018

The paper describes the investigation of how the make up of raw water influences the physical properties of flocculated suspensions. The work focuses on the properties of four characteristic organic fractions separated as a function of their hydrophobicity. Mesoscale data indicates that the hydrophobic fractions dominate the make up of the water and are the most easily removed. Microscale and nanoscale data reveals that the fulvic acid fraction (FAF) generates statistically smaller and more compact flocs than those formed by the other fractions and the hydrophilic fractions form the most internally open and dendritic structures. The FAF fraction was also seen to dominate the zeta potential response of the raw water.
The duplicity of floc strength
Authors: Jarvis P. , Jefferson B. , Parsons S.
Published: May 2018

The breakage of flocs is dependent upon the strength of the bonds holding the aggregate together. The present work describes the breakage and re-growth behaviour of three different types of floc, these were: 1) coagulant precipitate flocs, 2) turbidity flocs and 3) organic matter flocs. Floc aggregates were exposed to increased levels of shear on a conventional jar tester and the sizes of the flocs were observed dynamically using a laser diffraction instrument. The organic flocs showed most resistance to breakage across the whole range of shears under investigation. The dynamic procedure provided detailed information on particle size distributions (PSD). Large and small scale degradation events could be identified from analysis of the PSD data. All of the flocs under investigation showed little re-growth potential after breakage. The precipitate and organic flocs showed slightly better re-aggregation of the small floc sizes.
Environmental nano-pollutants (ENP) and micro-interfacial processes
Authors: Tang H. , Wang D. , Ge X.
Published: May 2018

The concepts of nano-science and technology are penetrating into the aspects of environmental science and technology. Environmental nano-pollutants (ENP) is suggested. as a specific category of pollutants that presents many common critical characters impacting the natural and social ecosystems. The outstanding properties are the various reactions in the macro-interfacial processes. Several examples as the adsorption of rare-earth metals on Chinese loess, the adsorption of PAHs on aquatic sediments with humic substances and the speciation of nano-flocculants in the water and wastewater treatment are discussed in the paper.
Influence of the size of membrane foulants on the filterability of WWTP-effluent
Authors: te Poele S. , Roorda J.H. , van der Graaf J.H.J.M.
Published: May 2018

The application of membrane filtration for the polishing of wastewater treatment plant (wwtp) effluent is more and more widely used. However, fouling problems are still not well understood. In order to investigate the role of particles in dead-end ultrafiltration of wwtp-effluent, Roorda studied the influence of pre-filtrated wwtp-effluent on the filterability. In addition this research investigates the relation between the filterability of the different fractions in the wwtp-effluent and the amount of organic foulants in these fractions. The results show a relation between the filterability and supra-dissolved particles in the fractions <0.45 and <0.2 μm. The amount of COD, colour, proteins and polysaccharides in these fractions are found of minor importance. A significant increase in filterability is found between the fractions <0.2 and <0.1 μm as well as a significant decrease in amount of polysaccharides. It is suggested that an essential feature in understanding membrane fouling during ultrafiltration of wwtp-effluent is to investigate the influence of supra-dissolved particles on the filterability as well as the influence of the amount of organic foulants (total organic carbon, proteins, polysaccharides, colour and humic substances) on the reversibility.
Irreversible and reversible adhesion between virus particles and hydrolyzing-precipitating aluminium: a function of coagulation
Authors: Matsushita T. , Matsui Y. , Inoue T.
Published: May 2018

The infectivity of viruses (Qβ, MS2, T4, and P1) after dosing virus-contaminated water with 4 types of aluminium coagulant was investigated. The concentrations of infectious viruses were determined after dissolving aluminium hydroxide flocs in alkaline solution. The concentration of infectious viruses did not recover to the initial value after a short floc-dissolution time (5 s). Although the infectious virus concentration increased as the floc-dissolution time was extended to 5 h, it did not recover fully. Irreversible adhesion between virus particles and aluminium coagulant is responsible for the insufficient recovery. We interpret this phenomenon as a virucidal activity of the aluminium coagulant. All tested aluminium coagulants (PACl, alum, and reagent grade aluminium chloride and aluminium sulfate) inactivated all types of viruses tested. PACl had the highest virucidal activity. The virucidal activity of aluminium coagulants was lower in river water, presumably owing to the presence of natural organic matter.
Effect of residual ozone on membrane fouling reduction in ozone resisting microfiltration (MF) membrane system
Authors: Lee S. , Jang N. , Watanabe Y.
Published: May 2018

The effect of residual ozone on reducing the membrane fouling was investigated using ozone resisting microfiltration membrane. It was found out that the fouling was reduced effectively by maintaining residual ozone in the membrane module. To clarify the reason why the residual ozone reduces the membrane fouling, research was focused on the molecular degradation reaction and particle destabilization reaction induced by residual ozone. The major reason of membrane fouling reduction was attributed to the reduction of reversible resistance induced by the cake layer. The reversible resistance was reduced due to degradation of organic substances in the cake layer. In addition to degradation reaction, the increase of fouling particle size due to residual ozone in the cake layer is another important process for fouling reduction. This effect has been referred to as ozone-induced destabilization reaction. The calcium present in the raw water influenced this reaction. The increase of fouling particles size improves the filterability through the cake layer and backwashing efficiency.
Behavior of micro-particles in monolith ceramic membrane filtration with pre-coagulation
Authors: Yonekawa H. , Tomita Y. , Watanabe Y.
Published: May 2018

This paper is intended to clarify the characteristics unique to monolith ceramic membranes with pre-coagulation by referring to the behavior of micro-particles. Flow analysis and experiments have proved that monolith ceramic membranes show a unique flow pattern in the channels within the element, causing extremely rapid flocculation in the channel during dead-end filtration. It was assumed that charge-neutralized micro-particles concentrated near the membrane surface grow in size due to flocculation, and as a result, coarse micro-particles were taken up by the shearing force to flow out. As the dead end points of flow in all the channels are located near the end of the channels with higher filterability, most of the flocculated coarse particles are formed to a columnar cake intensively at the dead end point. Therefore cake layer forming on the membrane other than around the dead end point is alleviated. This behavior of particle flocculation and cake formation at the dead end point within the channels are unique characteristics of monolith ceramic membranes. This is why all monolith ceramic membrane water purification systems operating in Japan do not have pretreatment equipment for flocculation and sedimentation.
Study of a three-stage fluidized bed process treating acrylic synthetic-fiber manufacturing wastewater containing high-strength nitrogenous compounds
Authors: Cheng S.-S. , Chen Y.-N. , Wu K.-L. , Chuang H.-P. , Chen S.-D.
Published: May 2018

Polyacrylonitrile (PAN) is one of the major synthetic fibers commonly used in the mass production of clothing. The chemical synthesis of PAN is carried out by polymerization of the acrylonitrile (AN) monomers with co-monomers such as vinyl acetate, methyl acrylate and cyclohexyl acrylate. Using water quality analysis of the PAN wastewater, high concentration of organic nitrogen was found and the TKN/COD ratios achieved were 0.15Ð0.26, indicating the complicated biodegradation characteristics for the PAN wastewater. In order to enhance biodegradation of nitrogenous compounds in PAN wastewater, a combined three-stage process of thermophilic anaerobic/anoxic denitrification/aerobic nitrification fluidized bed reactors was employed. The results indicated that the concentration of effluent in the three-stage process of COD and organic nitrogen was 175 mg/L and 13 mg/L, respectively. Furthermore, molecular biotechnology was applied to study the microbial population in the thermophilic anaerobic fluidized bed reactor. From the results of denaturing gradient gel electrophoresis, the diversity of PAN-degrading bacteria would change in different volumetric loading. Furthermore, the bacteria communities in the thermophilic anaerobic fluidized bed reactor were also studied by fluorescence in situ hybridization and confocal laser scanning microscopy. Alpha and delta-Proteobacteria were dominant in the bacteria population, and some high G+C content bacteria and Clostridium could be characterized in this system.
Conceptual comparison of pink water treatment technologies: granular activated carbon, anaerobic fluidized bed, and zero-valent iron-Fenton process
Authors: Oh S.-Y. , Cha D.K. , Chiu P.C. , Kim B.J.
Published: May 2018

Pink water, explosive-laden wastewater produced in army ammunition plants is often treated using expensive and non-destructive granular activated carbon (GAC) adsorption. This paper compares GAC adsorption and two alternative treatment technologies, anaerobic GAC fluidized bed reactor and zero-valent iron-Fenton process. The bench-scale demonstration of the zero-valent iron-Fenton process with real pink water is reported. The features of three technologies are compared and their advantages and drawbacks are discussed.
Granulation of Anammox microorganisms in up-flow reactors
Authors: Imajo U. , Tokutomi T. , Furukawa K.
Published: May 2018

Experimental studies were performed to evaluate the feasibility of granulation of Anammox microorganisms for biomass retention in up-flow reactors. Two experimental studies, one using a 6.4-L lab-scale reactor with synthetic medium and the other using a 200-L pilot-scale reactor with half-nitrified reject water from a sludge digester were conducted. To enhance the granulation process, seed granules from a UASB reactor were added to both experimental reactors. Granulation of Anammox microorganisms was observed using both the synthetic medium and the reject water. The core of a large proportion of Anammox granules retained part of the original seed biomass. The Anammox granules had a slightly lower density than the seed granules from the UASB process, but the size and other physical properties were comparable. The successful granulation of the Anammox microorganisms led to a stable nitrogen removal performance. The maximum nitrogen removal rate of the lab-scale reactor was observed to be 2.9 kg/(m3·d) after 173 days of operation and that of the pilot-scale reactor was 6.4 kg/(m3·d) after 12 months of operation.
Anaerobic digestion elutriated phased treatment of piggery waste
Authors: Ahn Y.-H. , Bae J.-Y. , Park S.-M. , Min K.-S.
Published: May 2018

The performance of a novel high-rate anaerobic process, the anaerobic digestion elutriated phased treatment (ADEPT) process, for treating a slurry-type piggery waste (55 g COD/L and 37 g TS/L) was investigated. The ADEPT process consists of an acid elutriation slurry reactor for hydrolysis and acidification, followed by an upflow anaerobic sludge bed reactor for methanification. This process provides stable and high system performance with short HRT (7.4 d) and better effluent quality (2 g SCOD/L and 0.68 g VSS/L) due to the alkaline pH condition for hydrolysis/acidification phase, high refractory solids removal and ammonia toxicity reduction. The optimum pH and HRT for hydrolysis/acidogenesis of the piggery waste were 9 and 5 days at both 35°C and 55°C conditions. The hydrolysis and acidification rate in the mesophilic reactor were 0.05 d-1 and 0.11 d-1 , meaning that hydrolysis was a limiting step. SCOD production by the hydrolysis was about 0.26 g SCOD/g VSfed (3.6 g SCOD/g VS reduction). Methane production and content in the system were 0.3 L CH4/g VSfed (0.67 L CH4/g VS destroyed) and 80%, respectively, corresponding to 0.23 L CH4/g COD removal (@STP).
A study of NH3-N and P refixation by struvite formation in hybrid anaerobic reactor
Authors: Lee J.J. , Choi C.U. , Lee M.J. , Chung I.H. , Kim D.S.
Published: May 2018

This research is concerned with the removal of ammonia nitrogen and phosphorus in foodwaste by crystallization. Reductions have been achieved by struvite formation after the addition of magnesium ions (Mg2+). Magnesium ions used in this study were from magnesium salts of MgCl2. The results of our analysis using scanning electron microscopy and energy dispersive X-ray analysis showed that the amount of struvite in precipitated sludge grew enough to be seen with the naked eye (600-700μm). EDX analysis also showed that the main components of the struvite were magnesium and phosphorus. NH3-N removal efficiency using MgCl2 was 67% while PO4-P removal efficiency was 73%. It was confirmed that nitrogen and phosphorus could be stabilized and removal simultaneously through anaerobic digestion by Mg, NH3 and PO4-P, which were necessary for struvite formation.