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Gilthead sea bream (Sparus aurata) was raised in six individual recirculating aquaculture systems (RAS) whose biofilters' performance was analyzed. Fish were fed with three different diets (a control diet, a fishmeal-based diet (FM), and a plant meal-based diet (VM)) and with three different feeding strategies (manual feeding to apparent satiation, automatic feeding with restricted ration, and auto-demand feeding). For every combination of diet and feeding strategy, the mean oxygen consumption, ammonia excretion, and ammonia removal rate were determined. Fish fed with the VM diet consumed the most oxygen (20.06 ± 1.80 gO2 consumed kg−1 day−1). There were significant differences in ammonia excretion depending on the protein content and protein efficiency of the diet, as well as depending on feeding strategy, which in turn affected ammonia removal rates. Fish fed by auto-demand feeders led to the highest mean ammonia removal rate (0.10 gN-TAN removed m−2 biofiltration area day−1), while not leading to peaks of high ammonia concentration in water, which preserve fish welfare and growth. [ABSTRACT FROM AUTHOR]

Despite the global water crisis, the significant potential of trickling filter systems as a crucial auxiliary option for sustainable water supply has received insufficient attention. Therefore, this study presents the first-ever evaluation of the environmental impacts of trickling filter application in wastewater treatment, focusing on eco-environmental burdens. Additionally, the study explores greenhouse gas emissions, energy, and exergy footprints, providing novel insights into the environmental implications of using trickling filters for wastewater treatment. The study's findings indicate that the consumption of heat and electricity in trickling filters has significant environmental impacts, particularly on land use (93.24%), freshwater/marine eutrophication (∼81.98%), and human health (45.36%). The majority of the energy required for trickling filter operation is supplied by fossil fuels (96.02%), resulting in increased greenhouse gas emissions (65.58%). The exergy of trickling filters is highly efficient, accounting for over 95% of the system's energy. Mathematical modeling reveals that anaerobic digestion and secondary clarifier have the highest energy consumption, with contributions of 94.65% and 2.63%, respectively. Construction expenses account for almost 88% of the total cost, with anaerobic digestion (42.15%) and trickling filters (35.39%) being the most costly components. The cost of treating 1 m3 of wastewater is estimated at 0.52 $/m3. Sensitivity analysis demonstrates that electricity (14.66%) and heat (18.65%) significantly impact terrestrial ecotoxicity and land use, respectively. This study presents a framework for future investigations in this field. • The most TF environmental burdens related to heat (54.24%) and electricity (10.26%). • More than 80% of the total costs were consumed for the construction phase. • The cost of 1 m3 wastewater treatment using TF was 0.52 $/m3. • The exergy analysis indicated a significant contribution of natural gas (60.88%). • The anaerobic digester was the main contributor to the energy footprint (94.65%). [ABSTRACT FROM AUTHOR]

The main objective of wastewater treatment is to remove carbon and other nutrients from municipal and industrial effluents in order to protect the environment and human health. Typical wastewater treatment is usually achieved by a combination of physical, chemical and biological methods. In this work, municipal wastewater was depurated using chemically enhanced primary treatment (CEPT) in combination with a pilot-scale trickling filter. Lab scale experiments (Jar-tests) were carried out in order to determine the optimum dosage of chemicals. Selection criteria were the organic load removal efficiency and the low operational cost. Coagulation-flocculation process was conducted through polyaluminium chloride (PAC) and the cationic polyelectrolyte (Zetag 8180) addition. By combining CEPT and trickling filter, tCOD (total Chemical Oxygen Demand), sCOD (soluble Chemical Oxygen Demand), BOD5 (5-day Biochemical Oxygen Demand), NH4+-N, TSS (Total Suspended Solids), VSS (Volatile Suspended Solids) and PO43−-P removal efficiencies were estimated to be 89, 82, 93, 60, 96, 96 and 78%, respectively. It is concluded that biological filtration contributed significantly in nutrients removal processes. Moreover, the obtained effluent was low in carbon and rich in nitrogen, which can be applied for restricted irrigation after disinfection, complying with the discharge limits set in the Greek Joint Ministerial Decree 145116/2011. [ABSTRACT FROM AUTHOR]

The presence of active pharmaceutical ingredients (APIs) in the environment is of growing concern and effluents from wastewater treatment works (WwTWs) are one of the major sources. This research combines the outputs of a multimillion pound UK program of work to evaluate the fate of APIs in the wastewater treatment process. A combination of analysis of measured data and modelling has been applied to 18 APIs, representing a wide range of medicinal application and physico-chemical characteristics. Some isomers (for atorvastatin) and metabolites (for sertraline, carbamazepine and erythromycin) were also included. High variability was observed between removal rates for individual APIs between WwTW, which after statistical analysis could not be explained by the nominal WwTW process (e.g. activated sludge or trickling filter). Nor was there a clear relationship between API removal and physico-chemical parameters such as pKa, charge or log Kow. A publically available sewage process model, SimpleTreat 4.0 which has been rigorously validated and is now being used for exposure assessment with REACH legislation for organic chemicals and within the Biocidal Products Regulation by the European Medicines Agency for APIs, was used to estimate removal rates with which to compare with measured data. SimpleTreat provided estimates of removal rates within ±30% of observed values for the majority of the APIs measured, with the use of readily available WwTW specific parameters such as flow, total suspended solids and BOD data. The data and correlations provided in this study provide support for any future considerations regarding the management of API discharge to the aquatic environment. Unlabelled Image • Removal efficiency data for 19 pharmaceuticals and 4 metabolites in 45 UK sewage works • Activated sludge vs trickling filter works performance not significantly different • Removal not simply explained by phys-chem characteristics of pharmaceutical • Removal poorly correlated to sewage works sanitary determinands • SimpleTreat model capable of predicting removal to within 30% of measured values [ABSTRACT FROM AUTHOR]

Abstract Aerated Constructed Wetlands are a state-of-the-art design that provides a different physical and chemical environment (compared to traditional passive wetland designs) for the wastewater treatment processes and, thus, may have different pathogen removal characteristics. In order to establish the fate of bacterial and viral indicators, a field study was carried out at a Sewage Treatment Works (STW) in the UK (serving 20,000 pe). The STW consists of primary and secondary sedimentation tanks and trickling filters (TF) as the biological stage. A large (1,160 m2) pilot aerated Vertical Flow Constructed Wetland (AVFCW) was constructed at the STW as tertiary stage receiving ¼ of the total flow rate, i.e., 1250 m3/day. Effluent quality of the AVFCW complied with national and international standards for environmental discharge and reuse. For the first time, two sets of bacterial (Faecal coliforms, E.coli and intestinal enterococci) and viral indicators (Somatic coliphages, F -RNA specific bacteriophages and human-specific B. fragilis GB124 phages) were simultaneously investigated in an AVFCW and TF. High elimination rates were detected (up to 3.7 and 2.2 log reduction for bacteria indicators and phages, respectively) and strong correlations between the two sets were found. The superior efficiency of the aerated Constructed Wetlands in microbiological contamination removal compared to passive wetland systems was established for the first time, which may have implications for process selection for wastewater reuse. This field study therefore provides new evidence on the fate of bacteriophages and a first indication of their potential use for performance evaluation in TF and aerated Constructed Wetlands. It also demonstrates that the combination of TF with aerated constructed wetlands could be a novel and effective treatment scheme for new STW or for the upgrade of existing STW. Graphical abstract Unlabelled Image Highlights • Trickling filters and an experimental aerated Constructed Wetland were investigated. • Effluent quality below discharge legal limits even without a final disinfection step • 2–3.5log removal efficiency of three bacterial and three bacteriophages indicators • Strong correlations imply phages use as performance indicators in aerated wetlands. • Aerated Wetlands outperform passive systems in microbiological contamination removal. [ABSTRACT FROM AUTHOR]

The treatment of high-strength anaerobic digester effluent in laboratory-scale trickling filters for nitrification and then anaerobic filters for denitrification is reported. Five media types were investigated in the trickling filters: biochar, granular activated carbon (GAC), zeolite, Pall rings, and gravel. Three media were tested in five denitrifying filters: sand (S), bamboo wood chips (B), eucalyptus wood chips (E), bamboo with sand (B+S), and eucalyptus with sand (E+S). The different wood chips served as a supplemental electron donor for denitrification. From six months of operation, biochar, GAC, zeolite, Pall rings, and gravel media had turbidity (NTU) removal efficiencies of 90, 91, 77, 74, and 74%, respectively, and ammonia removal efficiencies of 83, 87, 85, 30, and 80%, respectively, which was primarily by nitrification to nitrate. For the anaerobic filters, S, B, B+S, E, and E+S had nitrate removal efficiencies of 30, 66, 53, 35, and 35%, and turbidity removal efficiencies of 88, 89, 84, 89, and 88%, respectively. Biochar and bamboo were selected as the best combination of media for trickling filter and anaerobic filter sequential treatment. Based on an average initial influent of 600 mg NH 3 -N L −1 , 50 mg NO 3 -N L −1 , and 980 NTU, the biochar filter's effluent would be 97 mg NH 3 -N L −1 , 475 mg NO 3 -N L −1 , and 120 NTU. The bamboo filter's final effluent would be 82 mg NH 3 -N L −1 , 157 mg NO 3 -N L −1 , and 13 NTU, which corresponds to 63% removal of total N and 99% removal of turbidity. These filter media thus present a simple option for sustainable post-treatment for nitrogen management and effluent polishing in low-resources settings. [ABSTRACT FROM AUTHOR]

The effects of floc structural characteristics, i.e. shape and dense biomass distribution, were evaluated on ultraviolet (UV) disinfection resistance, represented by the tailing level of the UV dose response curve (DRC). Ellipsoid-shaped flocs of similar volume and different projected circularities were constructed in-silico and a mathematical model was developed to compare their UV DRC tailing levels (indicative of UV-resistance). It was found that floc shape can significantly influence tailing level, and rounder flocs (i.e. flocs with higher circularity) were more UV-resistant. This result was confirmed experimentally by obtaining UV DRCs of two 75–90 μm floc populations with different percentages (20% vs. 30%) of flocs with circularities higher than 0.5. The population enriched in less circular flocs (i.e. 20% flocs with circularities >0.5) had a lower tailing level (at least by 1-log) compared to the other population. The second model was developed to describe variations in UV disinfection kinetics observed in flocs with transverse vs. radial biomass non-homogeneity, indicative of biofilm-originated vs. suspended flocs. The varied-density hemispheres model and shell-core model were developed to simulate transverse and radial non-homogeneity, respectively. The UV DRCs were mathematically constructed and biofilm-originated flocs showed higher UV resistance compared to suspended flocs. The calculated UV DRCs agreed well with the experimental data collected from activated sludge and trickling filter flocs (no fitting parameters were used). These findings provide useful information in terms of designing/modifying upstream processes for reducing UV disinfection energy demand. [ABSTRACT FROM AUTHOR]

The abundance of ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) was investigated in full-scale two-stage trickling filters (TF) and moving bed bioreactor (MBBR) treating municipal wastewater. Biofilm samples were collected for 17 months from nitrifying TF (NTF), biochemical oxygen demand TF (BTF), and MBBR media. The abundance of AOA and AOB was determined using a quantitative PCR approach targeting the ammonia monooxygenase subunit A gene of archaea and bacteria. AOA were dominant in the NTF and MBBR, while AOB dominated in the BTF. AOA and AOB were more abundant during warmer months, and AOA were detected in the BTF only during warmer months. In laboratory nitrification activity experiments, ammonia oxidation to nitrite decreased when AOA populations from the NTF and MBBR were inhibited, demonstrating that AOA contributed to nitrification. This study has shown that AOA outnumber AOB and contribute to ammonia oxidation in full-scale nitrifying biofilm processes. [ABSTRACT FROM AUTHOR]

The need of wastewater (WW) treatment is increasing along with the production of WW and its disposal without treatment. With a smaller footprint, ease of operation, and relatively less cost, trickling filter (TF) wastewater treatment systems have been considered to be more adoptable for domestic and industrial WW treatment in underdeveloped and/or developing countries - particularly for Asia and Africa. A relatively lowcost and operationally effective TF wastewater treatment system was developed using farm waste cotton sticks as biofilm support media. During the operation of the TF system, flow rates vary from 1.7 to 4.6 m3/hr. The attained removal efficiency for BOD (biological oxygen demand) was 69-78% and for chemical oxygen demand (COD) was 65-80%. The solids removal in TF system was 38-56% for total suspended solids (TSS) and 20-36% for total dissolved solids (TDS). Other aggregates such as turbidity and color removal were 32-54% and 25-42%, respectively. Four to five months of trouble-free operation of the developed TF system indicated the robustness and reliability of the system. Cotton sticks appeared to be a degradation-resistant alternative filter media for the TF system. Moreover, it is useful for reducing potential impacts of WW re-use at the farm level. Treated effluents through the TF system can be re-used as an irrigation water supplement in under-developed and/or developing countries. [ABSTRACT FROM AUTHOR]

Ozonation and three (biological) filtration techniques (trickling filtration (TF), slow sand filtration (SSF) and biological activated carbon (BAC) filtration) have been evaluated in different combinations as tertiary treatment for municipal wastewater effluent. The removal of 18 multi-class pharmaceuticals, as model trace organic contaminants (TrOCs), has been studied. (Biological) activated carbon filtration could reduce the amount of TrOCs significantly (>99%) but is cost-intensive for full-scale applications. Filtration techniques mainly depending on biodegradation mechanisms (TF and SSF) are found to be inefficient for TrOCs removal as a stand alone technique. Ozonation resulted in 90% removal of the total amount of quantified TrOCs, but a post-ozonation step is needed to cope with an increased unselective toxicity. SSF following ozonation showed to be the only technique able to reduce the unselective toxicity to the same level as before ozonation. In view of process control, innovative correlation models developed for the monitoring and control of TrOC removal during ozonation, are verified for their applicability during ozonation in combination with TF, SSF or BAC. Particularly for the poorly ozone reactive TrOCs, statistically significant models were obtained that correlate TrOC removal and reduction in UVA254 as an online measured surrogate parameter. [ABSTRACT FROM AUTHOR]

A full-scale study has been conducted to assess the bioaugmentation efficiency of trickling filter process to treat petrochemical wastewater from a lubricant industry recycling waste oils. During 45 weeks, the organic loading rate (OLR) in the trickling filter was increased stepwise from 0.9 to 4 kg of chemical oxygen demand (COD)/(m³-day) at the end of the upgrading period as the flow rate (FR) reached the value of 30 m³/day. The removal, obtained in terms of percentage, for COD ranged from 60 to 84.5 and greater than 98 for total n-alkane (TNA), while those of total kjeldahl nitrogen (TKN) and total phosphor (TP) were about 32 and 55, respectively. The analytical profile index (API) of trickling biofilm has confirmed that 5 strains are closely related to Acinobacter junii, Stenotrophomonas maltophilia, Vibrio vulnificus, Vibrio metschnikovi, Pseudomona slulzeri and Trichosporon spp2. [ABSTRACT FROM AUTHOR]

The present study develops membrane hybrid system for drinking water that combines a trickling filter (TF) and a thin-layer biosand filter (TBSF) prior to membrane. Two different types of trickling filter (submerged and protruding) were placed before the biosand filter (BSF) with two different sand depths (40 and 3 cm). The effectiveness of the TBSF was measured in terms of the reduction in levels of total organic carbon, turbidity, Escherichia coli, and bacteriophage MS2. The hybrid systems with a TF + BSF + MF membrane showed higher TOC removal and turbidity reduction than hybrid systems only with BSF + MF membrane. The TOC removal and turbidity reduction by the hybrid systems with a TF were much more stable than those of hybrid systems without a TF throughout the operating period despite the changing level of the TOC. The removal of E. coli by hybrid systems with a TF was greater (usually >99.99%) and more stable than that by the hybrid systems without a TF. However, the removal of bacteriophage MS2 by the hybrid systems with a TF was only moderate (~99%) and not greatly different from that by the hybrid systems without a TF. [ABSTRACT FROM AUTHOR]

In developing countries, good-quality water is contaminated due to the disposal of untreated municipal and industrial wastewater (WW) into natural water reservoirs. Most of the wastewater is not treated properly according to international standards, and usually is disposed of and/or utilized for irrigation without appropriate treatment. The main hurdles in providing wastewater treatment (WWT) in developing countries include high costs, and the poor design, installation, and operation of conventional WWT systems. Therefore, the present study explores the maize cobs trickling filter-based (MCTF) low-cost WWT option for developing countries like Pakistan, India, and Bangladesh. In this regard, indigenous media trickling filter was designed and developed using maize cobs as packing material for biofilm growth. The MCTFWWT system was continually operated and monitored for six months at constant hydraulic wastewater loading of about 113±2 m3 per m2 per day. The experimental data covers winter and summer seasons with temperature variations from 23°C to 43°C. System performance was evaluated by means of various WWT parameters, including biological and chemical oxygen demands (BOD5 and COD), total suspended and dissolved solids (TSS and TDS), turbidity, and color - before and after WWT. Experimental results showed that the MCTF-WWT system successfully removed about 79% BOD and 75% COD on average. The key reason for effective BOD and COD removal was rapid development of microbial film (within the first two weeks). Furthermore, the MCTF-WWT system removed 42-46% TSS, 28-30% TDS, 43-46% turbidity, and 33-37% color. The study concludes that the MCTF-WWT system is an effective and economical WWT option for irrigation/agricultural applications in developing countries. [ABSTRACT FROM AUTHOR]

Wastewater treatments are considered important means to control the environmental transmission of human norovirus (NoV). Information about NoV concentrations in untreated and treated effluents, their seasonality and typical removal rates achieved by different treatment processes is required to assess the effectiveness of sewage treatment processes in reducing human exposure to NoV. This paper reports on a characterisation of concentrations of NoV (genogroups I and II) in untreated sewage (screened influent) and treated effluents from five full scale wastewater treatment works (WwTW) in England. Results are shown for effluent samples characteristic of primary- (primary settlement, storm tank overflows), secondary- (activated sludge, trickling filters, humus tanks) and tertiary (UV disinfection) treatments. NoV occurrence in untreated sewage varied between years. This variation was consistent with the annual variation of the virus in the community as indicated by outbreak laboratory reports. Significant differences were found between mean NoV concentrations in effluents subject to different levels of treatment. Primary settlement achieved approximately 1 log 10 removal for both genogroups. Concentrations of NoV and Escherichia coli in untreated sewage were of the same order of magnitude of those in storm tank overflows. Of the secondary treatments studied, activated sludge was the most effective in removing NoV with mean log 10 removals of 3.11 and 2.34 for GI and GII, respectively. The results of this study provide evidence that monitoring of NoV in raw sewage or treated effluents could provide early warning of an elevated risk for NoV and potentially help prevent outbreaks through environmental exposure. They also provide evidence that elimination of stormwater discharges and improvement of the efficiency of activated sludge for NoV removal would be effective for reducing the risk of environmental transmission. [ABSTRACT FROM AUTHOR]

Biological oxidation has been researched as a viable alternative for treating waters with high manganese (Mn) concentrations, typically found in mine drainage or in some geological formations. In this study, laboratory-scale trickling filters were constructed to compare the Mn removal efficiency between filters inoculated with the Mn oxidizing bacteria,Pseudomonas putida, and filters without inoculation. Manganese oxidation and removal was found to be significantly greater in trickling filters withPseudomonas putidaafter startup times of only 48 h. Mn oxidation inPseudomonas putidainoculated trickling filters was up to 75% greater than non-inoculated filters. One-dimensional advective-dispersive models were formulated to describe the transport of Mn in trickling filter porous media. Based on the experimental transport parameters obtained, the model predicted that a filter depth of only 16 cm is needed to reduce influent concentration of 10 mg L−1to 0.05 mg L−1. [ABSTRACT FROM PUBLISHER]

This paper conducts a comparative assessment of the environmental impacts of three methods of treating primary clarifier effluent in wastewater treatment plants (WWTPs) through life cycle assessment methodology. The three technologies, activated sludge (AS), high rate anaerobic-aerobic digestion (HRAAD), and trickling filter (TF), were assessed for treatment of wastewater possessing average values of biochemical oxygen demand and total suspended solids of 90 mg L-1 and 70mg L-1, respectively. The operational requirements to process the municipal wastewater to effluent that meets USEPA regulations have been calculated. The data for the AS system were collected from the East Honolulu WWTP (Hawaii, USA) while data for the HRAAD system were collected from a demonstrationscale system at the same plant. The data for the TF system were estimated from published literature. Two different assessment methods have been used in this study: IMPACT 2002þ and TRACI 2. The results show that TF had the smallest environmental impacts and that AS had the largest, while HRAAD was in between the two but with much reduced impacts compared with AS. Additionally, the study shows that lower sludge production is the greatest advantage of HRAAD for reducing environmental impacts compared with AS. [ABSTRACT FROM AUTHOR]

In many developing countries, inadequate access to safe drinking water is a major cause of morbidity and mortality. Furthermore, approximately 100 million people worldwide are exposed to arsenic (As) in drinking water. The World Health Organization is thus now encouraging the development and supply of a low-cost technology that can treat domestic water. The present study combined the use of a trickling filter (TF) with a biosand filter (BSF). Additionally, to remove As (V) from water, the use of the absorbents Fe–Mn–Si (FM-α) and zero-valent iron was experimentally investigated. Different compositions of influent were supplied in five stages. Efficiency was analyzed in terms of the total organic carbon, turbidity, UV 254 , As (V) content, flux, power consumption, total solids, and volatile solids of samples taken from four treatment systems (M-1: membrane, M-2: BSF + membrane, M-3: TF + membrane, and M-4: TF + BSF + membrane). Results show that the removal of organic matter and decline in flux over 45 d reduced in the order M-4 > M-2 > M-3 > M-1. The combination of TF, BSF, and M-4 was shown to have the most stable operation even under shock loading. The biofilm of the BSF and sieving effect played an important role in reducing the content of organic matter. The recovered flux of M-1 decreased and the M-1 membrane was backwashed four times. In comparison, M-3 required backwashing four times, M-2 required backwashing once, and M-4 did not require backwashing during operation. The M-4 system removed 95% of organic matter without any cleaning of the top soil throughout the experiment and reduced turbidity by 99%. Between systems M-1 to M-4, the most effective system was M-4 because of its stable operation without backwashing of the membrane throughout the experimental period. The M-2 system with FM-α embedded in the layers of sand removed 77% of As (V), while the M-4 system, using zero-valent iron adsorbents, removed 97% of As (V). [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the effects on treatment efficiency of oxidation–reduction (redox) conditions that are caused by different water saturation levels within vertical-flow constructed wetlands (VFCW), with specific attention to phosphorus (P) retention. The study was conducted by monitoring over 18 weeks a pilot-scale system consisting of a biological aerobic trickling filter as a biological pre-treatment step, followed by ferric chloride (FeCl 3 ) addition for phosphate removal and a stage of VFCW. By adjusting the water saturation level, the VFCW was operated successively under fully unsaturated, partly saturated, completely saturated (flooded), and then again unsaturated conditions. Redox potentials (Eh) were measured at three different levels within the VFCW. Results revealed that Eh was logically affected by the water-saturation level and the feeding–resting periods. Treatment efficiency was very good under fully unsaturated and partly saturated conditions. Under flooded conditions, the performance of the filter declined when the flood was maintained for around one week. However, VFCW regained its previous efficiency after the effluent was drained out and aerobic conditions were restored, indicating that the system was resistant and robust enough that periodical flooding did not affect its performance afterwards. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the efficiency of an intensified process of vertical flow constructed wetland having the following particularities: (i) biological pretreatment by trickling filter, (ii) FeCl3 injection for dissolved phosphorus removal and (iii) succession of different levels of redox conditions along the process line. A pilot-scale set-up designed to simulate a real-scale plant was constructed and operated using real wastewater. The influences of FeCl3 injection and water saturation level within the vertical flow constructed wetland stage on treatment performances were studied. Three different water saturation levels were compared by monitoring: suspended solids (SS), total phosphorus (TP), dissolved chemical oxygen demand (COD), ammonium, nitrate, phosphate, iron, and manganese. The results confirmed the good overall efficiency of the process and the contribution of the trickling filter pretreatment to COD removal and nitrification. The effects of water saturation level and FeCl3 injection on phosphorus removal were evaluated by analysis of the correlations between the variables. Under unsaturated conditions, good nitrification and no denitrification were observed. Under partly saturated conditions, both nitrification and denitrification were obtained, along with a good retention of SSs. Finally, under saturated conditions, the performance was decreased for almost all parameters. [ABSTRACT FROM AUTHOR]

This study investigated down-flow hanging sponge (DHS) technology as a promising trickling filter (TF) using sponge media as a biomass carrier with an emphasis on protection of the biomass against macrofauna overgrazing. A pilot-scale DHS reactor fed with low-strength municipal sewage was operated under ambient temperature conditions for 1 year at a sewage treatment plant in Bangkok, Thailand. The results showed that snails (macrofauna) were present on the surface of the sponge media, but could not enter into it, because the sponge media with smaller pores physically protected the biomass from the snails. As a result, the sponge media maintained a dense biomass, with an average value of 22.3 gVSS/L sponge (58.1 gTSS/L sponge) on day 370. The snails could graze biomass on the surface of the sponge media. The DHS reactor process performance was also successful. The DHS reactor requires neither chemical treatments nor specific operations such as flooding for snail control. Overall, the results of this study indicate that the DHS reactor is able to protect biomass from snail overgrazing. [ABSTRACT FROM AUTHOR]

A study was conducted of treatment performance and nitrogen transformation processes in a trickling filter (TF) used to treat micro-polluted source water under variable hydraulic loading rates (HLRs), ranging from 1.0 to 3.0 m 3 /m 2 d. The TF achieved high and stable COD (97.7–99.3%) and NH 4 + -N (67.3–92.7%) removal efficiencies. Nitrification and anaerobic ammonium oxidation were the dominant nitrogen removal processes in the TF. Path analysis indicated that amoA /anammox and amoA /( narG + napA ) were the two key functional gene groups driving the major processes for NH 4 + -N and NO 2 − -N, respectively. The analysis also revealed that anammox/ amoA and nxrA /( nirK + nirS ) were the two key functional gene groups affecting processes associated with the NO 3 − -N transformation rate. The direct and indirect effect of functional gene groups further confirmed that nitrogen transformation processes are coupled at the molecular level, resulting in a mutual contribution to nitrogen removal in the TF. [ABSTRACT FROM AUTHOR]

The wastewater industry is under pressure to optimize performance of sewage treatment works (STW), while simultaneously reducing energy consumption. Using a process configuration selection matrix, this paper explores the practicability of placing a hypothetical cross flow structured plastic media (CFSP) trickling filter (TF) immediately ahead of an existing conventional trickling filter process (CTFP), without intermediate clarification. The viability of this configuration is subsequently demonstrated using an empirical multispecies TF model. This predicts the enhanced nitrification performance of the CTFP by simulating prior removals of biochemical oxygen demand (BOD). The model predictions propose that prior 50-80% BOD removals can allow for further reductions in effluent ammoniacal nitrogen (NH4-N) concentrations of 40-70%, respectively. This illustrates that adopting low energy TF technologies can eliminate the requirement for more energy intensive alternatives, such as submerged aerated filters (SAF). Moreover, this configuration maximizes the potential of existing assets, while simultaneously improving nitrification robustness when compared with tertiary nitrification processes. [ABSTRACT FROM AUTHOR]

To better understand pharmaceutical fate during wastewater treatment, analysis in both aqueous and particulate phases is needed. Reported herein is a multi-residue method for the determination of ten pharmaceutical drugs and the personal care product triclosan in wastewater matrices. Method quantitation limits ranged from 7.6 to 76.6 ng l − 1 for aqueous phases and from 7.0 to 96.7 ng g − 1 for particulate phases. The analytical method was applied to attain a complete process mass balance of a pilot-scale activated sludge plant (ASP) operated under controlled conditions. The mass balance (inclusive of aqueous and particulate concentrations at all sample points) was used to diagnose removal, revealing pharmaceuticals to be separable into three fate pathways: (a) biological degradation, (b) sorption onto activated sludge and (c) resistant to removal from the aqueous phase. These differences in fate behaviour explained a broad range of secondary removal observed (− 8 to 99%). The ASP was also simultaneously compared to a full-scale trickling filter (TF) works whilst receiving the same influent wastewater. Performance of the ASP and TF was similar, achieving total pharmaceutical removals of 253 and 249 μg g − 1 biochemical oxygen demand (BOD) removed, respectively. This corresponded with reductions in total pharmaceutical load of 91 and 90% (ANOVA, p - value > 0.05). Interestingly, despite low suspended solid concentrations final effluents of both the ASP and TF contained significant concentrations of some chemicals in the particulate phase. Individually, triclosan and the antibiotics ofloxacin and ciprofloxacin were within the particulate phase of effluents at concentrations ranging from 26 to 296 ng l − 1 . [ABSTRACT FROM AUTHOR]

The use of vertical flow constructed wetlands (VFCW) is growing rapidly in Europe for domestic wastewater treatment in small communities. In order to improve denitrification and dephosphatation as compared to classical VFCW, the Azoé-NP ® process has been developed. The process line consists of: a biological aerobic trickling filter as a primary treatment stage, ferric chloride (FeCl 3 ) addition for phosphorus (P) treatment and two stages of partially saturated VFCW. A municipal wastewater treatment plant using Azoé-NP ® process has been monitored during eight years through 44 campaigns of 24 h time-proportional inlet–outlet sampling followed by analyses of TSS, BOD 5 , COD, TKN, NO 3 –N and TP concentrations. The results revealed good performances of the overall treatment. To better characterize the performance of each treatment step, five additional 24 h monitoring campaigns were performed with samples taken from four different points along the treatment line. Results showed a good performance in dissolved carbon removal and nitrification by the trickling filter. The main part of the treatment was found to be done by filtration throughout the first filtration stage. Nitrate removal was achieved principally at the second filtration stage. Phosphorus migration through the first stage and its slight retention at the second stage was observed. [ABSTRACT FROM AUTHOR]

The process performance of a down-flow hanging sponge (DHS) reactor for treating low strength sewage (biochemical oxygen demand (BOD) 20-50 mg/L) was investigated in Bangkok, Thailand. The hydraulic retention time (HRT) was set at 4 h during the start-up period and was reduced to 1.5 h in a stepwise manner. Throughout the 300-day operational period, the DHS reactor shows high performance with respect to the removal of total suspended solid (>90% total suspended solid removal efficiency). No clogging of sponge media was observed in response to the self-digestion phenomena of the biofilm. At a HRT of 1.5 h, the BOD removal efficiency was sufficiently high (about 85%). The pathogen Escherichia coli and other coliform bacteria were removed almost completely as well (removal was 99.4% and 98.1%, respectively). Regarding the retained sludge activity measurement, the nitrite oxidation rate was higher than the ammonium oxidation rate (0.031 and 0.022 gram of nitrogen per gram of volatile suspended solids per day, respectively). In the 300 days of operation, the amount of excess sludge production was negligible. Thus, no sludge treatment system is required. Introduction of the DHS system in developing countries is recommended because this system requires a relatively small area, and has low electricity consumption and operation costs. [ABSTRACT FROM AUTHOR]

Vertical Flow Treatment Wetland (VF-TW) systems achieve high efficiencies in terms of carbon related parameters removals from domestic wastewaters. Nitrogen removal is also efficient but optimisations are still needed. This article reports and discusses experimental data collected from 24-h monitoring campaigns of 29 full-scale VF-TWs, having different configurations and operation time up to 13 years. All monitored systems gathered 1 or 2 stage(s) of unsaturated or partially saturated VF-TW. Additionally, some of those included an aerobic biological Tricking Filter (TF) prior to TW stage(s). Results firstly showed that the implementation of a TF improved TSS, COD and BOD 5 removal rates in the monitored systems. Regarding nitrogen removal, the association of TF with one stage of partially saturated vertical TW was found to achieve around 79% of nitrification in average and up to 92% in some cases. In the configurations where TF was associated to 2 successive stages of TW, almost all total nitrogen removal by nitrification/denitrification was achieved at the outlet of the first-stage TW. The contribution of the second-stage TW in denitrification was found very low due to limited availability of organic carbon to support heterotrophic denitrification. Specific solutions to enhance the contribution of the second stage in the denitrification process are discussed. [Display omitted] • Field monitoring data from different 29 treatment wetland are discussed. • Implementation of trickling filter improved all treatment efficiencies. • Carbon depletion was identified in 2nd-treatment wetland stage. • Operating conditions should be optimized to enhance denitrification in 2nd-stage. [ABSTRACT FROM AUTHOR]

Wastewater treatment plants use a variety of bioreactor types and configurations to remove organic matter and nutrients. Little is known regarding the effects of different configurations and within-plant immigration on microbial community dynamics. Previously, we found that the structure of ammonia-oxidizing bacterial (AOB) communities in a full-scale dispersed growth activated sludge bioreactor correlated strongly with levels of NO entering the reactor from an upstream trickling filter. Here, to further examine this puzzling association, we profile within-plant microbial biogeography (spatial variation) and test the hypothesis that substantial microbial immigration occurs along a transect (raw influent, trickling filter biofilm, trickling filter effluent, and activated sludge) at the same full-scale wastewater treatment plant. AOB amoA gene abundance increased >30-fold between influent and trickling filter effluent concomitant with NO production, indicating unexpected growth and activity of AOB within the trickling filter. Nitrosomonas europaea was the dominant AOB phylotype in trickling filter biofilm and effluent, while a distinct ' Nitrosomonas-like' lineage dominated in activated sludge. Prior time series indicated that this ' Nitrosomonas-like' lineage was dominant when NO levels in the trickling filter effluent (i.e., activated sludge influent) were low, while N. europaea became dominant in the activated sludge when NO levels were high. This is consistent with the hypothesis that NO production may cooccur with biofilm sloughing, releasing N. europaea from the trickling filter into the activated sludge bioreactor. Phylogenetic microarray (PhyloChip) analyses revealed significant spatial variation in taxonomic diversity, including a large excess of methanogens in the trickling filter relative to activated sludge and attenuation of Enterobacteriaceae across the transect, and demonstrated transport of a highly diverse microbial community via the trickling filter effluent to the activated sludge bioreactor. Our results provide compelling evidence that substantial immigration between coupled process units occurs and may exert significant influence over microbial community dynamics within staged bioreactors. [ABSTRACT FROM AUTHOR]

In this research, an experimental laboratory plant was constructed in order to evaluate the effect of recirculation ratio, organic loading and suspended solids loading on the removal efficiency of trickling filter with plastic media. The plant consisted of four biological trickling filter which were similar in shape, each with a volume equal to (35 liters). Synthetic wastewater was used to operate the plant. To study the impact of recirculation ratio on the system, three of these plants (first, second and third) were operated on recirculation ratio of (100%, 200% and 300%) respectively, whereas the fourth operated without recirculation. To study the effect of increase organic loading, the study program was divided into nine stages, in the three continuation following stages the organic loading rate was steady then increasing in the three suffix continuation following stages thus until ultimate ninth stage, beginning with (1.5 kg COD/m3·day) then (2.1 kg COD/m3·day) and up to (2.7 kg COD/m3·day). The results of the study revealed that; the removal efficiency of the biological trickling filter increase when the recirculation operation was exist, and the efficiency increased when increase recirculation ratio, so the average efficiency of first stage removal of organic loading was in the trickling filters (first, second, third and fourth ) (84.5%, 86.3%, 87.5%, 80%) respectively. The results also showed that; increasing organic and suspended solid loading decreases removal efficiency of organic matter, ammonia and phosphate. [ABSTRACT FROM AUTHOR]

Highlights: [•] Thin iron scraps layer paved in the trickling filter enhanced the TP removal. [•] Zeolite trickling filter under intermittent water feeding benefits nitrification. [•] Coarse media in the first stage inhibits clogging of the latter infiltration stage. [•] Better influent dispersion for MSL was achieved owing to the two-stage design. [•] Two-stage filter system appeals to decentralized treatment of sewage well. [ABSTRACT FROM AUTHOR]

The century-old trickling filters at the Daspoort Wastewater Treatment Works in Pretoria (Gauteng, South Africa) are known for their remarkable removal of nitrogen from municipal wastewater. Our study was conducted to identify the microbiological processes responsible for this phenomenon and to establish whether anammox bacteria may be involved. An aerobic and anaerobic bench top reactor, both inoculated with biofilm-covered stones from one of the filters, were spiked with ammonia-nitrogen (NH4+-N) and nitrite-nitrogen (NO2--N). These reactors were subsequently monitored by conducting stoichiometric analyses of chemical oxygen demand (COD), NH4+-N, NO2--N, and nitrate-nitrogen (NO3--N). In the aerobic reactor, the COD concentration decreased over the 56 h batch reaction period and nitrification was revealed by a decrease in NH4+-N and NO2--N concentrations. However, the NO3--N concentration showed no notable decrease. In contrast, in the anaerobic reactor the concentrations of COD, NH4+-N, NO2--N, NO3--N, as well as total nitrogen decreased during the batch reaction period. The decrease of both the NH4+-N and NO2--N concentrations, the latter to zero under anaerobic conditions, suggested that, in addition to heterotrophic denitrification, anaerobic ammonium oxidation (anammox) may also occur in the trickling filter biofilm. This was highlighted by the observation that ammonium removal in the anaerobic reactor stopped as soon as the nitrite concentration became zero. The ratio of nitrite:ammonium removal was 1.33 on average, which conforms to anammox behaviour. Gene sequence analysis was used to test for the possible presence of anammox bacteria in the trickling filter biofilm. Genomic DNA was extracted from trickling filter humus sludge and the polymerase chain reaction (PCR) was used to amplify taxonomically informative 16S rRNA gene sequences, using primers specific for selected anammox species. Subsequent sequence analysis, including using the online Basic Local Alignment Search Tool (BLAST), and constructing a phylogenic tree using a heuristic search strategy for Maximum Parsimony analysis, confirmed the presence of an anammox bacterium closely related to Candidatus 'Brocadia anammoxidans' and Candidatus 'Brocadia fulgida' on the biofilm-covered stones of the Daspoort trickling filters. [ABSTRACT FROM AUTHOR]

An ultra-performance liquid chromatography method using a triple quadrupole mass spectrometer was developed and validated for the determination of steroid oestrogens in wastewater matrices. To date, analytical methods established in the literature for 17α-ethinylestradiol have been unable to achieve the proposed predicted no effect concentration of 0.1 ng l−1. The extensive sample pretreatment and analytical methodology proposed herein enable 17α-ethinylestradiol to be determined at very low background concentrations with a theoretical method detection limit of 0.06 ng l−1which has been applied in real environmental matrices. During the validation process, a trickling filter wastewater treatment works was monitored to demonstrate the method's application. Oestrogen removal across the filters demonstrated good removals of natural free oestrogens (≥62.0%) with lower removals of the synthetic oestrogen 17α-ethinylestradiol (29.2%) from wastewaters at 10°C. The method's application illustrates its capability of detecting oestrogen concentrations in real wastewater samples comprising complex organics of comparatively high concentration. Furthermore, a complete process mass balance for 17α-ethinylestradiol is now attainable which has previously posed a challenge owing to the low environmental concentrations typically exhibited, but more significantly as a result of the lower sensitivity inherent in previously reported analytical methods. [ABSTRACT FROM PUBLISHER]

The Beaudesert Sewage Treatment Plant (STP), originally built in 1966 and augmented in 1977, is a typical biological trickling filter (TF) STP comprising primary sedimentation tanks (PSTs), TFs and humus tanks. The plant, despite not originally being designed for nitrogen removal, has been consistently achieving over 60% total nitrogen reduction and low effluent ammonium concentration of less than 5 mg NH3-N/L. Through the return of a NO3--rich stream from the humus tanks to the PSTs and maintaining an adequate sludge age within the PSTs, the current plant is achieving a substantial degree of denitrification. Further enhanced denitrification has been achieved by raising the recycle flows and maintaining an adequate solids retention time (SRT) within the PSTs. This paper describes the approach to operating a TF plant to achieve a high degree of nitrification and denitrification. The effectiveness of this approach is demonstrated through the pilot plant trial. The results from the pilot trial demonstrate a significant improvement in nitrogen removal performance whilst maximising the asset life of the existing infrastructure. This shows great potential as a retrofit option for small and rural communities with pre-existing TFs that require improvements in terms of nitrogen removal. [ABSTRACT FROM AUTHOR]

The paper compares the performance of two trickling filters (TFs) filled with plastic- or sponge-based packing media treating the effluent from an upflow anaerobic sludge blanket (UASB) reactor. The UASB reactor was operated with an organic loading rate (OLR) of 1.2 kgCOD m-3 d-1, and the OLR applied to the TF5 was 0.30-0.65 kgCOD m-3 d-1 (COD: chemical oxygen demand). The sponge-based packing medium (Rotosponge) gave substantially better performance for ammonia, total-N, and organic matter removal. The superior TF-Rotosponge performance for NH4+-N removal (80-95%) can be attributed to its longer biomass and hydraulic retention times (SRT and HRT), as well as enhancements in oxygen mass transfer by dispersion and advection inside the sponges. Nitrogen removals were significant (15 mgN L-1) in TF-Rotosponge when the OLRs were close to 0.75 kgCOD m-3 d-1, due to denitrification that was related to solids hydrolysis in the sponge interstices. For biochemical oxygen demand removal, higher HRT and SRT were especially important because the UASB removed most of the readily biodegradable organic matter. The new configuration of the sponge-based packing medium called Rotosponge can enhance the feasibility of scaling-up the UASB/TF treatment, including when retrofitting is necessary. [ABSTRACT FROM AUTHOR]

Abstract: Four trickling biofilter designs were assessed as low-energy alternatives to aerobic activated sludge (AS) for the treatment of personal care product industry wastes. The designs included partially submerged packed-media and sponge reactors with and without active aeration. Partial submergence was used to reduce active aeration needs. Simulated colourant wastes (up to COD=12,480mg/L, TN=128mg/L) were treated for 201days, including wastes with elevated oxidant levels. COD and TN removal efficiencies were always >79% and >30% (even without aeration). However, aerated sponge reactors consistently had the highest removal efficiencies, especially for TN (∼60%), and were most tolerant of elevated oxidants. This study shows sponge biofilters have great potential for treating colourant wastes because they achieve high treatment efficiencies and reduce energy use by >40% relative to AS systems. [Copyright &y& Elsevier]

Abstract: This work reports the degradation of nitrogen compounds in a commercial marine Recirculating Aquaculture System (RAS) aimed at the culture of sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). The annual production of fingerlings is around 18 million and the process includes a drum filter and a biological treatment in order to enhance the water quality. Ammonia measurements at the inlet of the biological system showed that the concentration of this compound followed a diurnal pattern closely related to the feeding of the fingerlings; thus every day after feeding around 8am, the concentration of ammonia started increasing, it reached a maximum about 8h after feeding and then continued decreasing until the following morning. With regard to nitrite concentration, no significant differences were observed between the values measured at the inlet and the outlet of the biological system during the day, with an average concentration of this compound ranging between 0.08 and 3.66mg NO2 −Nl−1. A drawback of ammonia removal by means of nitrification is the subsequent increase of nitrate as the final product of ammonia oxidation in the culture system. The nitrate concentration in the biofilters inlet was found to fluctuate between 22.33 and 55.44mg NO3 −Nl−1 during the characterization period. Partial water exchange was needed during the day in order to minimize the water losses during fish handling and to keep the concentration of nitrate below the maximum allowable level of 46mg NO3 −Nl−1 due to production requirements in the hatchery under study. The ammonia degradation within the biological system, obtained by the ammonia measurements and comparison of the values at the inlet and outlet of the trickling filters has been fitted satisfactorily to ½-order/0-order kinetic expressions in good agreement with the results found in literature for laboratory and pilot plant studies. Rate constants k (1/2-order) =0.49g1/2 m−1/2 day−1 and k (0-order) =0.64gm−2 day−1, have been obtained in this study for commercial trickling biofilters. Thus, this work reports for the first time the kinetics of ammonia oxidation in trickling biofilters installed in a commercial recirculating aquaculture marine water system. These results will provide useful information for the design of an appropriately sized biofilter in order to optimize the water quality and reduce the need to exchange water in this activity. [Copyright &y& Elsevier]

More and more research effort has been put into the development of affordable and high-efficiency wastewater reclamation technology for small communities. In this study, an integrated chemically enhanced primary treatment (CEPT), trickling filter (TF) and ultrafiltration (UF) process was developed with success. Coagulant produced from fly ash was used to enhance primary treatment, while trickling filter packed with coal cinder through four-layer structure without aeration was employed for further removal of COD and ammonium-nitrogen from the CEPT effluent. 95 and 88% removal of COD and ammonium were achieved, while total phosphorus (TP) and suspended solid (SS) were found to be removed completely at a coagulant dosage of 2.5 mL/L in the CEPT-TF-UF system. The product water can meet the standard of Reuse of Recycling Water for Urban Water Quality Standard for Urban Miscellaneous Water Consumption (GB/T 18920-2002, China). [ABSTRACT FROM AUTHOR]

The paper analyses the concept and performance of different configurations of compact UASB/TF systems, without the final clarification stage, in relation to the removal of organic matter. The experiments were carried out in two sets of UASB/TF systems operating without secondary clarifiers, as follows: (i) four shallow (2.50 m height) TFs, each one filled with a different packing material; and (ii) two deep (4.20 m height) TFs, one filled with polyethylene corrugated sheets and the other with mixed polyethylene and sponge sheets. For the conditions tested (different packing material in shallow and deep TF), the UASB/TF systems had consistently complied (90 to 100% of the results) with the Brazilian discharge standards regarding to BOD, COD, and TSS parameters. The average BOD, COD and TSS effluent concentrations stayed below 40 mg BOD L-1, 100 mg COD L-1 and 50 mg TSS L-1, respectively. UASB/TF systems can constitute an attractive alternative for domestic wastewater treatment in small communities in developing countries, especially considering its operational simplicity and very low running costs. [ABSTRACT FROM AUTHOR]

Abstract: This study examined the composition and structure of nitrifying biofilms sampled from a high-rate nitrifying trickling filter which was designed to pre-treat raw surface water for potable supply. The filter was operated under a range of feed water ammonia and organic carbon concentrations that mimicked the raw water quality of poorly protected catchments. The biofilm structure was examined using a combination of fluorescence in situ hybridisation and scanning electron microscopy. Biopolymers (carbohydrate and protein) were also measured. When the filter was operated under low organic loads, nitrifiers were abundant, representing the majority of microorganisms present. Uniquely, the study identified not only Nitrospira but also the less common Nitrobacter. Small increases in organic carbon promoted the rapid growth of filamentous heterotrophs, as well as the production of large amounts of polysaccharide. Stratification of nitrifiers and heterotrophs, and high polysaccharide were observed at all filter bed depths, which coincided with the impediment of nitrification throughout most of the filter bed. Observations presented here specifically linked biofilm structure with filter functionality, physically validating previous empirical modelling hypotheses regarding competitive interactions between autotrophic and heterotrophic bacteria in biofilms. [Copyright &y& Elsevier]

The modern trickling filter typically includes the following major components: (1) rotary distributors with speed control; (2) modular plastic media (typically cross-flow media unless the bioreactor is treating high-strength wastewater, which warrants the use of vertical-flow media); (3) a mechanical aeration system (that consists of air distribution piping and low-pressure fans); (4) influent/recirculation pump station; and (5) covers that aid in the uniform distribution of air and foul air containment (for odor control). Covers may be equipped with sprinklers that can spray in-plant washwater to cool the media during emergency shut down periods. Trickling filter mechanics are poorly understood. Consequently, there is a general lack of mechanistic mathematical models and design approaches, and the design and operation of trickling filter and trickling filter/suspended growth (TF/SG) processes is empirical. Some empirical trickling filter design criteria are described in this paper. Benefits inherent to the trickling filter process (when compared with activated sludge processes) include operational simplicity, resistance to toxic and shock loads, and low energy requirements. However, trickling filters are susceptible to nuisance conditions that are primarily caused by macro fauna. Process mechanical components dedicated to minimizing the accumulation of macro fauna such as filter flies, worms, and snail (shells) are now standard. Unfortunately, information on the selection and design of these process components is fragmented and has been poorly documented. The trickling filter/solids contact process is the most common TF/SG process. This paper summarizes state-of-the art design and operational practice for the modern trickling filter. Water Environ. [ABSTRACT FROM AUTHOR]

Abstract: This article analyses the relation between wastewater quality parameters and particle size distribution (PSD) in three real wastewater treatment plants with different biofilm technologies: submerged biofilter system, trickling filter system, and rotating biological contactor system. The main quality parameters, (suspended solids, turbidity and COD), and PSD in the influent and effluent water of each different biofilm treatment were analyzed during 1year. The PSD was fitted using the power law (n(d p)=∂N(d p)/∂d p = A·d p − b ·Log(d p )) obtaining the coefficients A and b to define the particle distribution. Mathematical correlations between this coefficients and the rest of parameters studied were found (SS=0.0713·A 0.585, turbidity=4.549×10−4·A 1.096, COD=0.0201·A 0.774). The relation with the average particle size by mass was also found, (d pma =60.3137·b −2.242). Moreover a relation between PSD and the particle elimination efficiency of the secondary treatment was study, (η =2.844–2.498·b relative +0.0863·A relative). These expressions are very useful to understand the behavior of the biofilm treatment system using PSD analyses. [Copyright &y& Elsevier]

Abstract: The nonwoven nanofibre membranes in this study are made by the electrospinning technique. With a diameter ranging from 80nm to several hundred nanometers, the nanofibres have a large surface area to volume ratio and a very high porosity. The aim of the study was to evaluate the use of nanofibre microfiltration membranes in three different membrane bioreactor (MBR) set-ups. More specific, in an active sludge MBR (AS-MBR), an AS-MBR with flux performing enhancer MPE50 and in a trickling filter MBR (TF-MBR). The results showed that the nanofibre membrane performed best with the TF-MBR. This was due to the removal of turbidity by the trickling filter, and also because of a new membrane module configuration. The flux was higher than the other configurations, and more important, the flux was stable for 85days after which the experiment was stopped. Also different cleaning techniques with 0.5% NaOCl and 0.2% HCl were tested and compared in this study. The nanofibre membrane structure and strengths were not affected after the procedures for cleaning. Scanning electron micrograph (SEM) pictures show the nanofibre membrane being clean after 12h of the alkali and acid treatment. [Copyright &y& Elsevier]

Household on-site septic systems with secondary wastewater treatment in Anchorage. Alaska, were sampled and analyzed for performance parameters during the winter to spring months. System types included intermittent dosing sand filters (ISF), three types of recirculating trickling filters (RTF), and suspended-growth aeration tanks. Total nitrogen from the trickling filter and aeration tank effluent was fairly uniform, at approximately 30 mg/L. Total suspended solids (TSS) means were mostly less than 15 mg/L. The 5-day biochemical oxygen demand (BOD5) showed considerable variability, with means ranging from 9.2 mg/L for ISFs up to 39.5 mg/L for one type of RTF, even though this type has shown excellent results in several test programs. The data suggested that effluent temperature within the sample range had almost no effect on effluent concentrations of BOD5 or TSS and only a small effect on the removal of total nitrogen. Non-climatic factors were probably of equal importance to treatment results. [ABSTRACT FROM AUTHOR]

The application of nitrifying trickling filters (NTFs) to potable water treatment is less well understood than their application to wastewater treatment, particularly regarding the effect of low ammonia substrate concentrations and organic carbon loading on filter performance. A large pilot-scale NTF was operated under conditions that simulated the raw water quality of poorly protected catchments typically found in SE Asia, with the objective of reducing the ammonia driven chlorine demand during disinfection. The efficacy of a high rate NTF to remove low concentrations of ammonia (0.5-5.0 mg NH4-N L-1) in the presence of high organic carbon (1-12 mg soluble biochemical oxygen demand (sBOD5) L-1) was investigated. Results demonstrated that 90 to 100% of nitrification was maintained only when the carbon load was less than 0.7 g sBOD5 m-2 d-1 (<4 mg sBOD5 L-1). Once the organic load was increased beyond 0.75 to 2.1 g sBOD5 m-2 d-1 (4.5-12.1 mg sBOD5 L-1), a linear decline in nitrification from 70 to 15% was observed within a timeframe of 8 to 10 d. The impact of high organic loads on the distribution of nitrification down the NTF was also investigated. Results confirmed that carbon loads greater than 0.95 g sBOD5 m-2 d-1 (>5.5 mg sBOD5 L-1), severely suppressed nitrification throughout the entire filter bed. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the impact of microwave radiation on the efficiency of nitrification and on the percentage of ammonia-oxidizing bacteria in biofilm and to study the possibility of the occurrence of nonthermal effects caused by the interaction of microwaves and biofilm. Eight trickling filters with a biofilm were used in the experiment: four were exposed to microwave radiation, and four were heated with warm air as a control group. Microwave radiation at a frequency of 2.45 GHz was applied at an intensity of 18 W (0.01 W·cm-3 of the reactor packing), which increased the biofilm temperature by 6 °C compared with the ambient temperature. The hydraulic loading averaged 0.30 m3·m-2·h-1, and the organic loading equalled 1.93 g chemical oxygen demand (COD)·m-2·d-1. Microwave radiation had an effect on the concentration of nitrogen compounds in the biofilm, and microwave heating triggered alterations within the biofilm that increased the efficiency of both nitrification and denitrification and the percentage of ammonia-oxidizing bacteria. Cette étude détermine l’impact du rayonnement micro-onde sur l’efficacité de la nitrification et sur le pourcentage de bactéries oxydant l’ammoniac contenues dans le biofilm; elle examine également la possibilité d’effets non thermiques causés par l’interaction entre les micro-ondes et le biofilm. Huit lits bactériens à biofilm ont été utilisés dans l’expérience : quatre ont été exposés au rayonnement micro-onde et quatre ont été chauffés à l’air chaud et servaient de groupe témoin. Le rayonnement micro-onde de 2,45 GHz fourni était de 18 W (0,01 W·cm-3 de garniture de réacteur); il a augmenté la température du biofilm de 6 °C par rapport à la température ambiante. La charge hydraulique était en moyenne de 0,30 m3·m-2·h-1, la charge organique était de 1,93 g DCO·m-2·j-1. Le rayonnement micro-onde a changé les composés azoteux. Le réchauffement aux micro-ondes a modifié le biofilm, ce qui a augmenté l’efficacité de la nitrification et de la dénitrification et a accru le pourcentage de bactéries oxydant l’ammoniac. [ABSTRACT FROM AUTHOR]

Trickling filters were used to treat wash water from a wood gasifier. This wash water contained toxic substances such as ammonium, cyanide, phenols, and PAH. The goal was to develop a system that degraded toxic substances, and achieved full nitrification of ammonia. A 1 kW model wood gasifier plant delivered wash water for the experiments, which was standardised to a conductivity of 3mS/cm by dilution. Toxicity was assessed by bacterial luminescence detection, germination test with cress (Lepidium sativum), and pot plants cultivated in a hydroponic setup irrigated continuously with the wastewater. Treatment experiments were done in both planted and unplanted trickling filters. Plant yield was similar to conventional hydroponic production systems. The trickling filters achieved complete detoxification of phenol, PAH and cyanide as well as full nitrification. The specific elimination rates were 100 g m-3 Leca d-1 for phenols and 90 g m-3 Leca d-1 for ammonium in planted systems. In unplanted trickling filters circulated for 63 h, phenol concentration decreased from 83.5 mg/L to 2.5 mg/L and cyanide concentration from 0.32 mg/L to 0.02 mg/L. PAH concentrations were reduced from 3,050μg/L to 0.89μg/L within 68 days. The assays demonstrated the feasibility of using the technique to construct a treatment system in a partially closed circulation for gasifier wash water. The principal advantage is to convert toxic effluents from biomass gasifiers into a non-toxic, nitrogen-rich fertiliser water, enabling subsequent use in plant production and thus income generation. However, the questions of long-term performance and possible accumulation of phenols and heavy metals in the produce still have to be studied. [ABSTRACT FROM AUTHOR]

This paper gives an overview of the most important bioreactor configurations used in waste gas treatment, i.e., conventional and trickling biofilters, the bioscrubber, suspended-growth bioreactors, as well as two-liquid phase systems (stirred tank bioreactor and biotrickling filter). The historical evolution, main characteristics, and recent developments are described in each case. [ABSTRACT FROM AUTHOR]

Abstract: This chapter describes the possibility to combine wastewater treatment in recirculating aquaculture systems (RAS) with the production of crop plants biomass. In an aquaponic RAS established in Waedenswil, Zurich, the potential of three crop plants was assessed to recycle nutrients from fish wastewater. A special design of trickling filters was used to provide nitrification of fish wastewater: Light-expanded clay aggregate (LECA) was filled in a layer of 30 cm in vegetable boxes, providing both surface for biofilm growth and cultivation area for crop plants. Aubergine, tomato and cucumber cultures were established in the LECA filter and nutrient removal rates calculated during 42–105 days. The highest nutrient removal rates by fruit harvest were achieved during tomato culture: over a period of >3 months, fruit production removed 0.52, 0.11 and 0.8 gm−2d−1 for N, P and K in hydroponic and 0.43, 0.07 and 0.4 gm−2d−1 for N, P and K in aquaponic. In aquaponic, 69% of nitrogen removal by the overall system could thus be converted into edible fruits. Plant yield in aquaponic was similar to conventional hydroponic production systems. The experiments showed that nutrient recycling is not a luxury reserved for rural areas with litlle space limitation; instead, the additionally occupied surface generates income by producing marketable goods. By converting nutrients into biomass, treating wastewater could become a profitable business. [Copyright &y& Elsevier]

The paper analyses the concept and performance of compact UASB/TF systems in relation to configuration, use of innovative packing media and operational conditions. For the conditions tested, the UASB/TF systems had consistently complied with the Brazilian discharge standard regarding to COD, BOD and TSS parameters. However, some enhancements are still necessary in order to increase nitrification in the process. The conditions to promote nitrification in shallow TF (packed bed up to 2.50m height) seem to be compatible with the proposed simplification in the flowsheet, which is to operate the system without secondary clarifiers. [ABSTRACT FROM AUTHOR]