Search

In this study, the degradation performance of nutrients in zeolite trickling filter (ZTF) with different influent C/N ratios and aeration conditions was investigated. Microaeration was beneficial for enhancing NH4+-N removal performance. Due to the sufficient carbon source supply under a C/N ratio of 8, a high removal efficiency of NH4+-N and TN was simultaneously observed in ZTF. In addition, TN removal mainly occurred at the bottom, which might be explained by the sufficient nutrients available for bacteria to multiply in this zone. The abundant genera were Acinetobacter, Gemmobacter, Flavobacterium, and Pseudomonas, all of which are heterotrophic nitrification-aerobic denitrification (HNAD) bacteria. In addition, biofilm only slowed down the adsorption rate but did not significantly reduce the adsorption capacity of zeolite. Bio-zeolite had NH4+-N well adsorption capacity and bio-desorption capacity. Biological nitrogen removal performance was superior to physicochemical absorption of zeolite. The results suggested that the physicochemical of zeolite and biochemical reactions of microorganism coupling actions may be the main nitrogen transformation pathway in ZTF. Our research provides a reference for further understanding the nitrogen removal mechanism of zeolite bioreactors.

The existence of risk factors of wastewaters to high organic materials, phenol compound, chlorinated compound and other complex providing a discharge of receptive waters could be serious hazards cr...

Due to their limited ability for nutrient removal, trickling filter systems (TFS) have almost fallen into oblivion today, even though they are robust and energy-efficient treatment systems. The advantage of this process technology, however, is the sessile biomass, which allows long periods of starvation without rinsing out the biomass. Therefore, this technology is promising for treating organic-polluted, intermittent stormwater-runoff. Several combinations with activated sludge systems (ASS) use the trickling filter as pre-treatment, requiring two separate treatment systems. This combines the advantages of both systems, but is paid with increased investment costs and space requirement. Due to these concerns, a trickling filter was developed that allows a nutrient removal without an additional ASS and exemplary tested for treating stormwater runoff of a silo facility. Beside aerobic conditions, anoxic and anaerobic steps have to be ensured during the process for nutrient removal. For this, the TFS is ponded with a mix of purified wastewater from the secondary clarification tank (containing nitrate) and untreated raw water (containing degradable COD). This allows both, an integration of upstream-denitrification and enhanced-biological-phosphorous-removal (EBPR). During the anoxic step, nitrate removal rates of 0.8 kg

Anaerobic sewage treatment is a proven technology in warm climate regions, and sponge-bed trickling filters (SBTFs) are an important post-treatment technology to remove residual organic carbon and nitrogen. Even though SBTFs can achieve a reasonably good effluent quality, further process optimization is hampered by a lack of mechanistic understanding of the factors influencing nitrogen removal, notably when it comes to mainstream anaerobically treated sewage. In this study, the factors that control the performance of SBTFs following anaerobic (i.e., UASB) reactors for sewage treatment were investigated. A demo-scale SBTF fed with anaerobically pre-treated sewage was monitored for 300 days, showing a median nitrification efficiency of 79% and a median total nitrogen removal efficiency of 26%. Heterotrophic denitrification was limited by the low organic carbon content of the anaerobic effluent. It was demonstrated that nitrification was impaired by a lack of inorganic carbon rather than by alkalinity limitation. To properly describe inorganic carbon limitation in models, bicarbonate was added as a state variable and sigmoidal kinetics were applied. The resulting model was able to capture the overall long-term experimental behaviour. There was no nitrite accumulation, which indicated that nitrite oxidizing bacteria were little or less affected by the inorganic carbon limitation. Overall, this study indicated the vital role of influent characteristics and operating conditions concerning nitrogen conversions in SBTFs treating anaerobic effluent, thus facilitating further process optimization.

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 BOD5 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.

Biofilm reactors retain microbial cells in the form of biofilm which is attached to free moving or fixed carrying materials, thus providing a high active biomass concentration and automatic liquid and solid separation. Nowadays, microbial biofilm reactors have been widely used in high-strength wastewater treatment where very high pollutant removal efficiency is required, which usually requires excessive space and aeration energy for conventional activated sludge-based treatment. This paper provides an overview of microbial biofilm reactors developed over the last half-century, including moving bed biofilm reactor (MBBR), trickling filter (TF) reactor, rotating biological contactor (RBC), membrane biofilm reactor (MBfR), passive aeration simultaneous nitrification and denitrification (PASND) biofilm reactor, for their applications in high-strength wastewater treatment of not only removing carbon, nitrogen, sulphur but also a variety of oxidized contaminants including perchlorate and bromate. Despite the advance of biofilm reactor that exhibits high resistance to excessive pollutants loading, its drawbacks both from engineering and microbiological point of view are reviewed. The future prospects of biofilm reactor are also discussed in this review paper.

Anaerobic ammonia oxidation to nitrogen gas using nitrite as the electron acceptor (anammox process) is considered a cost-effective solution for nitrogen removal after an anaerobic pre-treatment process. In this study, we conducted a laboratory-scale experiment to develop a single-stage partial nitritation–anammox process in a sponge-based trickling filter (STF) reactor, inoculated with anammox sludge, simulating the treatment of anaerobically pretreated concentrated domestic sewage without mechanical oxygen control. The influent ammonia concentration was 100 mg-N·L−1. The KLa of the STF reactor was higher than those observed for conventional activated sludge processes. The STF reactor performed at 89.8 ± 8.2% and 42.7 ± 16.9% ammonia and TN removal efficiency, respectively, with a nitrogen loading rate of 0.55 ± 0.20 kg-N·m−3·day−1 calculated based on sponge volume. Microbial community analysis of the STF-retained sludge indicated that both autotrophic and heterotrophic nitrogen removal occurred in the reactor.

To demonstrate the feasibility of Enhanced Pond and Wetland (EPW) system for the treatment of Biological Trickling Filter (BTF) effluent, pilot-scale EPW systems were installed and operated in New Zealand climate conditions. The system consisted of: two High Rate Algal Ponds (HRAPs) followed by gravity Algal Harvesters (AHs), two Surface Flow Constructed Wetlands (SFCWs), and a Woodchip Denitrification Filter (WDF). The wastewater treatment performance of each treatment component was monitored fortnightly over six months (late autumn to winter) in terms of TSS, total and soluble BOD5, nutrients (N and P) and E. coli removal. Algal biomass production, algal harvest efficiency, and algal dominance in the HRAPs were also determined. The pilot-scale system maintained low final effluent TSS and BOD5 concentrations below 5 and 8 mg L−1 respectively, and achieved high removal of nitrogen (NH4-N: ∼95%; NO3-N: 77%), phosphorus (DRP: ∼65%) and E. coli (at least 3-log E. coli removal) throughout the experimental period. Particularly in autumn, the HRAPs achieved almost complete removal of both NH4-N (5.0 to

An ultra-low energy consumption continuous flow (UECF) process was used for enhanced nitrogen removal from rural sewage. The ammonia in sewage was first oxidized to nitrite in a bio trickling filter (BTFPN) supplemented with natural oxygen. A stable nitrite accumulation ratio (NAR) of 93.2% was maintained by adding 5 mg/L NH2OH every seven days. BTFPN effluent was then combined with certain portion of rural sewage (1:1.2 to 1:1.5) and introduced to an upflow anaerobic sludge blanket reactor, where the nitrogen-containing pollutants were removed by Anammox process (UASBAMX). Effluent total nitrogen (TN) of 6.7 mg/L and a TN removal efficiency of 93.7% were obtained when influent chemical oxygen demand (COD), NH4+-N and TN were 321.9, 74.2 and 82.7 mg/L, respectively. Advanced nitrogen removal, based on the desirable cooperation between Anammox bacteria (Ca. Brocadia, 2.3%) and partial denitrification bacteria (Thauera, 4.2%), was achieved over 300 days of stable operation. Considering the nitrogen balance, 57.9% of nitrate generated in Anammox was reduced to nitrite by partial denitrification, and Anammox contributed 88.1% of nitrogen removal and 7.6% of denitrification. Compared with conventional nitrification and denitrification processes, UECF requires no mechanical aeration, no external carbon, produces 76.6% less external sludge, and reduces CO2 emissions by 92.3%.

Biotrickling filter (BF) is an effective ammonia-contain odour purification device for organic waste composting. However, proper disposal of nitrogen-rich trickling liquid (TL) discharged from the BF is consider ‘the last-mile problem’ for the application of this coupled system. Although our previous study demonstrated that reusing a TL as moisture conditioning agent for a composting system could promote compost maturity and nitrogen content, the exploration of the intrinsic promotion mechanism was obscured by the complexity (i.e., multiple forms of nitrogen contained) of the TL. Thus, a simulated TL (STL, pH =7.18) containing exclusively nitrate nitrogen was reused to condition the moisture of composting in this study. Effects of STL addition phase [adding STL in mesophilic (days 0–9),​ thermophilic (days 4–13), and cooling period (days 13–22)] on the performance of composting were explored. Results revealed that the organic degradation was partly promoted by adding STL in thermophilic or cooling period, but mightily inhibited in mesophilic period. Furthermore, adding STL in thermophilic period stimulates the denitrification of nitrate-N into dinitrogen at high temperature, whereas most of added nitrate-N was retained in compost product when adding STL in cooling period. Eventually, STL addition effectively increased total nitrogen (TN) by 2%–9%, especially the nitrate nitrogen by 10–11 times. Notably, adding STL rarely affected nitrous oxide and greenhouse gas emission. Therefore, STL can be reused to condition the moisture of compost in a proper composting phase (i.e., thermophilic period) as defined in term of the enhancement of TN and nitrate content of compost product.

Summarization: Energy requirement for wastewater treatment is of major concern, lately. This is not only due to the increasing cost of electrical energy, but also due to the effects to the carbon footprint of the treatment process. Conventional activated sludge process for municipal wastewater treatment may consume up to 60% of the total plant power requirements for the aeration of the biological tank. One way to deal with high energy demand is by eliminating aeration needs, as possible. The proposed process is based on enhanced primary solids removal, based on advanced microsieving and filtration processes, by using a proprietary rotating fabric belt MicroScreen (pore size: 100–300 μm) followed by a proprietary Continuous Backwash Upflow Media Filter or cloth media filter. About 80–90% reduction in TSS and 60–70% reduction in BOD5 has been achieved by treating raw municipal wastewater with the above process. Then the partially treated wastewater is fed to a combination low height trickling filters, combined with encapsulated denitrification, for the removal of the remaining BOD and nitrogen. The biosolids produced by the microsieve and the filtration backwash concentrate are fed to an auger press and are dewatered to about 55% solids. The biosolids are then partially thermally dried (to about 80% solids) and conveyed to a gasifier, for the co-production of thermal (which is partly used for biosolids drying) and electrical energy, through syngas combustion in a co-generation engine. Alternatively, biosolids may undergo anaerobic digestion for the production of biogas and then electric energy. The energy requirements for complete wastewater treatment, per volume of inlet raw wastewater, have been calculated to 0.057 kWh/m3, (or 0.087 kWh/m3, if UV disinfection has been selected), which is about 85% below the electric energy needs of conventional activated sludge process. The potential for net electric energy production through gasification/co-generation, per volume of inlet raw wastewater, has been calculated to 0.172 kWh/m3. It is thus obvious, that the proposed process can operate on an electric energy autonomous basis. Παρουσιάστηκε στο: Journal of Environmental Management

The potential of three different kind of reactors and active biomass to be used as inoculum for nitrogen removal was verified. Sludge samples were collected from a Membrane Bioreactor (MBR), a previous tank of a Moving Bed Biofilm Reactor (MBBR) and a Trickling Filter (TF). Samples were compared according to bacterial activity in batch tests and their microbiology (16 s rRNA sequences). The microorganisms examined were: AOB, NOB, anammox bacteria and OHO. Results showed that the richest sample was from MBR (Chao value equals 581). However, the bacterial activity was greater in MBBR sample (qAOO,NH4 equals 0.002 mgN·mgVSS−1·h−1; qNOO,NO2_NO3 equals 0.001 mgN·mgVSS−1·h−1 and qNOX_N2,SB equals 10.0 mgN·mgVSS−1·h−1). Therefore, MBBR WWTP was shown to have the best inoculum and operating conditions for nitrogen conversion and removal. Besides, if aeration is provided as low as necessary for AOB to start the activity in denitrification tank, simultaneous partial nitrification, and denitrification (SPND) can occur.

In order to better achieve efficiently simultaneous desulfurization and denitrification/S0 recovery of wastewater, the intervention of sulfur oxidizing bacteria (SOB) and denitrifying bacteria (DNB) was employed to avoid the collapse critical points (the dramatically decrease of S/N removal efficiency) under the fluctuated load. With the assistance of DNB and SOB, collapse critical point of trickling filter (TF) was delayed from the P8 (105–114 d) to P10 stage (129–138 d). The treatment efficiency of nitrogen and sulfur was the highest with the S/N ratio of 3:1. The bioaugmentation of DNB and SOB at collapse critical point could effectively regulated collapse situation, which further increased the maximum system utilization/elimination capacity to 4.50 kg S m−3·h−1 and 0.90 kg N m−3·h−1 (increased by 56.89% and 65.56% in comparison to control). High-throughput sequencing analysis indicated that Proteobacteria (average 78.59%) and Bacteroidetes (average 9.30%) were dominant bacteria in the reactor at all stages. As the reaction proceeds, the microbial community was gradually dominated by some functional genera such as Chryseobacterium (average 2.97%), Halothiobacillus (average 22.71%), Rhodanobacter (average 14.02%), Thiobacillus (average 9.01%), Thiomonas (average 16.70%) and Metallibacterium (average 21.63%), which could remove nitrate or sulfide. Both of Principal Component Analysis (PCA) and Canonical Correlation Analysis (CCA) demonstrated the important role of DNB/SOB during the long-term run in the trickling filters (TFs).

To cut down aeration power for nitrification, we constructed a biological nitrification–denitrification process with a trickling filter for nitrification and an anaerobic biological filter for denitrification. The influences of temperature and chemical oxygen demand (COD) loading on the nitrification and denitrification performance of the process are discussed in this paper through experimental and empirical modeling approaches. The model constants were determined by the experimental data of the process using municipal wastewater in Ryukoku University. Then, the influences of temperature and COD loading were estimated by the model. The COD levels required for NO3–N removal depended on both, the temperature and influent COD/NO3–N ratio. A lower temperature and higher influent COD/NO3–N ratio increased the COD requirement, because of the different responses between denitrifying bacteria and heterotrophic bacteria against temperature, COD, and NO3–N concentrations. In addition, our experimental system could satisfy the Japanese effluent standard at temperatures higher than 12 °C. The dissolved nitrogen (DN) concentration in the final effluent was more strongly affected by the NH4–N discharged from the trickling filter than it was by the residual NO3–N in the effluent from the denitrification tank. Therefore, the enhancement of the nitrification efficiency in the trickling filter was inferred to enhance the nitrogen removal efficiency. To prevent a low nitrogen removal efficiency at temperatures lower than 15 °C, it was necessary to set the low hydraulic loading.

This article presents the feasibility evaluation and preliminary design of a wastewater treatment plant upgrade supported by simulation. The existing facility was based on trickling filters, and the objective of the upgrade was to achieve nutrients removal. The proposed solution modifies the existing primary clarifier to host an anaerobic-anoxic suspended growth reactor, which is an alternative that, to our knowledge, has not been proposed or explored so far. The trickling filters would remain as aerobic reactors. In this study, the novel treatment scheme has been assessed for the first time, through model simulations. The modified treatment train was simulated, showing that the anoxic zone is able to denitrify satisfactorily achieving the required effluent nitrogen concentration. However, to promote biological phosphorus removal, an additional aerobic zone combined with a bypass of activated sludge from the anoxic zone to the first trickling filter is needed, in order to provide aerobic conditions to the phosphate accumulating organisms. Several combinations of additional aerobic volume and sludge bypass flowrate were found to successfully achieve both nitrogen and phosphorus removal, using the existing facilities without the need for new reactors neither implementing modifications that could put the trickling filters' physical integrity at risk. The novel treatment scheme could be applied in other cases with similar flowsheet in the same context.

NO and NO2 (NOx) in the atmosphere are major pollutants which cause serious environmental problems such as acid deposition, photochemical smog, and ozone hole. Fossil fuel combustion is the main source of NOx. Biological technology is an alternative for NOx removal from flue gas due to its low cost, high efficiency, and easy operation (Barnes et al. 1995). Biofilter and biotrickling filter are the two most commonly used structures, in both of which the denitrifying bacteria are immobilized onto the packing material in the reactor and reduce the NOx to N2 (Jin et al. 2005). However, the flue gas usually contains 2–10% oxygen, which would inhibit the denitrification process and result in poor NO removal efficiency (Lee and Apel 1998; Niu et al. 2014). Herein, the unique advantages of aerobic denitrification provide a new way to solve this problem (Jiang et al. 2009).

There is a great need for simple methods for digestate management for potential household sanitation systems based on anaerobic digestion of minimally diluted fecal waste in countries that lack safe sanitation. Herein, a full-scale three-stage filter for nitrogen and phosphorus removal from anaerobic digester effluent was implemented in Madagascar. It included a trickling filter with crushed charcoal (for aerobic nitrification), a submerged anaerobic filter with bamboo chips (for denitrification), and a submerged filter with scrap iron (for phosphorus removal). All filter materials were sourced locally. Three parallel replicate systems were operated in two sequential 8-week phases for a total of 16 continuous weeks. Though the influent feed was not as expected, with much of nitrogen in the feed coming in as organic N and not as NH3–N, the filters still removed 38–49% of total incoming nitrogen. The filters achieved high rates of nitrogen transformation along with removing solids (73–82% turbidity removal), chemical oxygen demand (67–75% removal), and phosphorus (31–50% removal). Overall, the reaction rates from this full-scale study were in line with previous lab-scale investigations with scaled-down systems, supporting their application in real-world scenarios. Based on this study, simple effluent filters can support nutrient removal for small-scale and onsite fecal sludge treatment systems., Graphical abstract Image 1, Highlights • High-strength anaerobic digester effluent was treated in three-stage filters. • Full-scale filters were constructed in Madagascar using all local materials. • Crushed charcoal trickling filters achieved nitrification rates up to 0.13 kgN m−3 d−1. • Bamboo woodchip filters achieved denitrification rates up to 0.03 kgN m−3 d−1. • Scrap iron filter removed 126 gP m−3 d−1 with 23.2 gP kg−1Fe capacity.

Most conventional hydrogenotrophic denitrification reactors based on packed- or fluidized-bed present a similar H2 delivery scheme of continuous gas purging to the atmosphere in order to improve H2 transfer rates and enable discharge of N2 gas produced during denitrification. This operation results in a significant release of H2 gas to atmosphere with its related economic and safety concerns. The current research proposes a novel pressurized high-rate hydrogenotrophic reactor for denitrification without gas purging. The investigation performed refutes a prevalent notion that N2 gas accumulates in the headspace of a closed reactor during denitrification. Instead, this research shows that during continuous operation a gas–liquid equilibrium is established in the reactor according to Henry’s law and excess N2 gas is carried out by the effluent in dissolved form. Therefore, no gas purging is required and H2 loss is limited only to the dissolved H2 in the effluent. As a consequence, a simple low-cost and high-rate reactor with closed headspace can be designed for denitrification. The proposed reactor is operated as a trickling filter where water is recirculated over biofilm carriers with high surface area. The feasibility of the proposed reactor was shown for two effluent concentrations of 10 and 1 mg NO3−-N/L. Average denitrification rates of 2.1 ± 0.2 and 1.06 ± 0.06 g NO3−-N/(Lreactor d) with H2 utilization efficiencies of 92.8% and 96.9% were measured for the two effluent concentrations, respectively. Higher denitrification rates of up to 5 g NO3−-N/(Lreactor d) were observed at higher recirculation flow rates and higher partial pressures of H2.

Wastewaters generated from several industrial sources containing organic substrates present a vital basis for harnessing bioenergy. Aerobic wastewater treatment methods, for instance, activated sludge process and trickling filter are unsustainable due to constant energy requirements for aeration, and sludge management. Currently, Microbial Fuel Cell (MFC) technology presents an appropriate alternative for energy positive wastewater treatment and permits synchronized wastewater treatment, bioelectricity production, and resource recovery via bioelectrochemical remediation mediated by electroactive microbes. The added advantage of using MFC technology for effluent treatment is that several bio-based processes including removal of biochemical and chemical oxygen demand, nitrification, denitrification, sulfate removal and removal of heavy metals can be carried out in the same bioreactor. Thus, MFCs can both substitute and complement the conventional energy-intensive technologies for efficient removal as well as the recovery of sulfate, nitrogen, and phosphate without any tertiary treatment. Thus, the present review covers the recent advances in the utilization of microbial fuel cell technology for the removal of organic as well as recalcitrant pollutants from a wide range of industrial and domestic effluents with the simultaneous production of low-cost energy. Further this review discusses the hybrid systems developed in integration with conventional treatment systems to make the process energy neutral and thus pave a way to scale-up the MFCs for sustainable wastewater treatment. Moreover, some critical challenges related to the field applications of microbial fuel cell technology dealing with a wide range of effluents, have also been analyzed and presented.

International audience; Most of the tropical areas have sanitation problems to contend with. The French system of vertical flow treatment wetlands (FS-VFTW) fed with raw wastewater could be a good water and sludge management solution. The purpose-adapted tropical design can reduce area requirement to below 1 m²/population equivalents (p.e.). The Taupinière FS-VFTW on Martinique Island was built according to this design, with one stage but with a saturated layer at the bottom of the filter and a simplified trickling filter (TF) added for further treatment to meet the high performances targeted. Unsaturated/saturated vertical-flow filters (US/S FS-VFTW) have shown improved performances on total nitrogen, carbon and suspended solids removal in temperate climates, but the performances in tropical conditions remain unknown. Here, we report on real-world-operation in the French Overseas Territories (FOT), the reliability and performances of this VFCW tropical-design. The system experienced loading conditions ranging from 30% to 165% of nominal carbonaceous biological oxygen demand (BOD5), as well as tropical rainstorms that brought over 7 times the nominal hydraulic load. Over a period of 3 years, 29 campaigns collected 24-hr flow-proportional samples at each treatment stage (raw wastewater, FS-VFTW outlet, TF outlet). When applied loads were close to nominal values, the US/S FS-VFTW itself guarantees 85/90/60/50% removal and 125/25/40/50 mg/L at the outlet for chemical oxygen demand (COD)/total suspended solids (TSS)/total Kjeldahl nitrogen (TKN)/total nitrogen (TN), respectively. By comparison with US/S systems in mainland France, it appears that the warmer tropical-climate temperatures facilitate both nitrification and denitrification kinetics. Performances in overload conditions confirm that the US/S FS-VFTW remains robust and reliable although COD and TKN removal are impacted, especially after strong tropical rain events. By adding a simple compact trickling filter to a US/S FS-VFTW, the treatment system delivers high-level performances (>95% removal for BOD5, COD, TSS and TKN) at less than 1m²/p.e.

To improve denitrification and phosphorus removal in VFCWs, the French company SCIRPE has developed a patented process called Azoe® which comprises biological pre-treatment on a trickling filter followed by two stages of partially saturated vertical flow filters planted with reeds. Phosphorus removal is carried out by addition of FeCl3 at the outlet of the biological trickling filter. Phosphorus thus precipitated accumulates mainly on the surface of the first filter in the form of a sludge layer. After several years of operation, this surface layer represents a stock of phosphorus potentially mobilizable as a function of the biophysicochemical conditions of the environment. However the fate of organic and mineral micropollutants, (pharmaceutical residues, pesticides, metals, etc.) in the system is poorly known. In the present study, the performance of these systems was studied by monitoring an Azoe® plant in operation. The results confirmed the very good efficiency in carbon and nitrogen treatment, the good stability of phosphorus retention, and a high rate of removal or retention of most micropollutants analyzed.

We investigated the removal of nitrogen and phosphate from the effluent of a sewage treatment plant over a long-term operation in bioreactors packed with different combinations of wood and iron, with a trickling filter packed with foam ceramics for nitrification. The average nitrification rate in the trickling filter was 0.17 kg N/m3∙day and remained at 0.11 kg N/m3∙day even when the water temperature was below 15 °C. The denitrification and phosphate removal rates in the bioreactor packed with aspen wood and iron were higher than those in the bioreactor packed with cedar chips and iron. The bioreactor packed with aspen wood and iron continued to remove nitrate and phosphate for >1200 days of operation. The nitrate removal activity of a biofilm attached to the aspen wood from the bioreactor after 784 days of operation was 0.42 g NO3-N/kg dry weight wood∙ day. There was no increase in the amount of dissolved organic matter in the outflow from the bioreactors.

With the objective of developing a post-treatment process for anaerobically digested livestock wastewater, an innovative natural treatment system composed of two units is proposed. The first trickling filter unit further reduced biochemical oxygen demand and achieved a certain degree of nitrification. The second soil-plant unit was targeted at the removal and recovery of nutrients N, P and K. For the feasibility study, a bench-scale soil column test was carried out, in which red ball earth and alfalfa were utilized for treating synthetic nutrient-enriched wastewater. Through long-term operation, the nitrification function was well established in the top layers, especially the top 20 cm, although a supplementary denitrification process was still required before discharge. P and K were retained by the soil through different mechanisms, and their plant-available forms that remained in the soil were considered suitable for indirect nutrient reuse. As for alfalfa, with wastewater application it fixed more N from the atmosphere, and directly recovered 6% of P and 4% of K input from wastewater. More importantly, alfalfa was verified to have an indispensable role in stimulating the soil nitrifying microorganisms by sustaining their abundance during substrate (NH3) and oxygen scarcity, and enhancing cell-specific nitrification potential during substrate (NH3) and oxygen sufficiency. The proposed system is expected to be further improved, and adopted as a sound countermeasure for livestock wastewater pollution.

The paper presents research of a prototype moving bed biofilm reactor (MBBR). The device was used for the post-denitrification process and was installed at the end of a technological system consisting of a septic tank and two trickling filters. The concentrations of suspended biomass and biomass attached on the EvU Perl moving bed surface were determined. The impact of the external organic carbon concentration on the denitrification rate and efficiency of total nitrogen removal was also examined. The study showed that the greater part of the biomass was in the suspended form and only 6% of the total biomass was attached to the surface of the moving bed. Abrasion forces between carriers of the moving bed caused the fast stripping of attached microorganisms and formation of flocs. Thanks to immobilization of a small amount of biomass, the MBBR was less prone to leaching of the biomass and the occurrence of scum and swelling sludge. It was revealed that the maximum rate of denitrification was an average of 0.73 gN-NO3/gDM·d (DM: dry matter), and was achieved when the reactor was maintained in external organic carbon concentration exceeding 300 mgO2/dm3 chemical oxygen demand. The reactor proved to be an effective device enabling the increase of total nitrogen removal from 53.5% to 86.0%.

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.

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 TFs 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 NH(4)(+)-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.

An anaerobic denitrification module with improved stability for closed aquaculture systems is described. The module was fitted to a recirculating fish mariculture system. The 18 m3 system consisted of a fish basin, a nitrification trickling filter and the module reported here, which was composed of a stirred slurry basin and two subsequent sedimentation tanks. Commercial fish feed (pellets) introduction into the slurry basin simulated nutrient input equivalent to 450 kg of fish biomass. About 50 kg of the sea bream, Sparus aurata, were introduced to bioassay water quality. Conditions remained stable as long as the mixing remained regular (16 wk). Feeding and sampling continued for an additional 6 wk of irregular mixing, during which time water quality gradually deteriorated causing 19% mortality of the stocked fish population. The system removed a majority of the total dissolved nitrogen (N) by denitrification and total phosphorus (P) by immobilization in the sludge. The rate of denitrification approached 9 mmol N/L/d. Hydrogen sulfide concentration in the fish basin remained low. The results constitute a proof-of-concept for the utility and resilience of slurry basins in the control of anaerobic processes and the maintenance of good water quality in recirculating fish culture.

A trickling filter (TF) is one of the oldest biological wastewater technologies that has been used for over 100 years. With years of evolution, modern trickling filters can be built up to 12 m (40 ft) tall with the use of high-performance plastic media. Modern flow distribution and ventilation systems can also be incorporated to improve TF performance. The treatment capacity of modern filters has been significantly increased in comparison with that of old rock filters. The application of trickling filter technologies has also been greatly expanded from early BOD roughing to incorporate complete carbon oxidizing and nitrification. In many cases, trickling filters are designed in “stages” to achieve different treatment levels.

Removal of six active pharmaceutical ingredients in wastewater was investigated using chlorine dioxide (ClO2) or peracetic acid (PAA) as chemical oxidants. Four non-steroidal anti-inflammatory drugs (ibuprofen, naproxen, diclofenac and mefenamic acid) and two lipid-regulating agents (gemfibrozil and clofibric acid, a metabolite of clofibrate) were used as target substances at 40 microg/L initial concentration. Three different wastewaters types originating from two wastewater treatment plants (WWTPs) were used. One wastewater was collected after extended nitrogen removal in activated sludge, one after treatment with high-loaded activated sludge without nitrification, and one from the final effluent from the same plant where nitrogen removal was made in trickling filters for nitrification and moving-bed biofilm reactors for denitrification following the high-loaded plant. Of the six investigated compounds, only clofibric acid and ibuprofen were not removed when treated with ClO2 up to 20 mg/L. With increasing PAA dose up to 50 mg/L, significant removal of most of the pharmaceuticals was observed except for the wastewater with the highest chemical oxygen demand (COD). This indicates that chemical oxidation with ClO2 could be used for tertiary treatment at WWTPs for active pharmaceutical ingredients, whereas PAA was not sufficiently efficient.

About 30 full-scale partial nitritation/anammox plants are established, treating mostly sewage sludge reject water, landfill leachate or food processing digestate. Although two-stage and one-stage processes each have their advantages, the one-stage configuration is mostly applied, termed here as oxygen-limited autotrophic nitrification/denitrification (OLAND), and is the focus of this review. The OLAND application domain is gradually expanding, with technical-scale plants on source-separated domestic wastewater, pre-treated manure and sewage, and liquors from organic waste bioenergy plants. A 'microbial resource management' (MRM) OLAND framework was elaborated, showing how the OLAND engineer/operator (1: input) can design/steer the microbial community (2: biocatalyst) to obtain optimal functionality (3: output). In the physicochemical toolbox (1), design guidelines are provided, as well as advantages of different reactor technologies. Particularly the desirable aeration regime, feeding regime and shear forces are not clear yet. The development of OLAND trickling filters, membrane bioreactors and systems with immobilized biomass is awaited. The biocatalyst box (2) considers 'Who': biodiversity and its dynamic patterns, 'What': physiology, and 'Where': architecture creating substrate gradients. Particularly community dynamics and extracellular polymeric substances (EPS) still require insights. Performant OLAND (3) comprises fast start-up (storage possibility; fast growth of anammox bacteria), process stability (endured biomass retention; stress resilience), reasonable overall costs, high nitrogen removal efficiency and a low environmental footprint. Three important OLAND challenges are elaborated in detailed frameworks, demonstrating how to maximize nitrogen removal efficiency, minimize NO and N(2)O emissions and obtain through OLAND a plant-wide net energy gain from sewage treatment.

Two columns were experimented to compare trickling filter with integrated A/O trickling filter (IA/OTT) in this study. Denitrification and phosphorus removal were limited in traditional trickling filter. By designing anoxic section, adding carbon source and recycling outflow, denitrification was enhanced in IA/OTT. Meanwhile, chemical-biological methods were used to improve the phosphorus removal. It was shown that removal efficiency of CODcr, NH3-N, TN and TP were ideal. Compared with the traditional trickling filter, especially, the removal efficiency of TN and TP were respectively about 35% and 50% higher.

Trickling filter has been extensively studied for the domestic wastewater treatment especially for the small scale plants in rural area. The performance of the trickling filter depends on the microbial community and their activity in the biofilms on the media. Nitrification. denitrification, and phosphorus removal of the trickling filter from the wastewater depend on the activity and the amount of the specific microorganisms responsible for the metabolism. For the estimation of the performance of a trickling filter, batch nitrification experiment and fluorescence in situ hybridization (FISH) were carried out to measure the microbial activity and its distribution on the media of the trickling filter. Batch nitrification activity measurement showed that the top part of the 1st stage trickling filter had the highest nitrification activity and the maximum activity was 0.002 g -N/g MLVSSh. It is thought that higher substrate (ammonia) concentration yields more nitrifying bacteria in the biofilms. The dominant ammonia oxidizer and nitrite oxidizer in the biofilm were Nitrosomonas species and genus Nitrospira, respectively, by FISH analysis. Less denitrifiers were found than nitrifiers in the biofilm by the probe Rrp1088 which specifically binds to Rhodobacter, Rhodovulum, Roseobacter, and Paracoccus. Phosphorus accumulating bacteria were mostly found at the surface of the biofilm by probe Rc988 and PAO651 which specifically binds to Rhodocyclus group and their biomass was less than that of nitrifiers.

The in situ activity and distribution of heterotrophic and nitrifying bacteria and their potential interactions were investigated in a full-scale, two-section, trickling filter designed for biological degradation of volatile organics and NH 3 in ventilation air from pig farms. The filter biofilm was investigated by microsensor analysis, fluorescence in situ hybridization, quantitative PCR, and batch incubation activity measurements. In situ aerobic activity showed a significant decrease through the filter, while the distribution of ammonia-oxidizing bacteria (AOB) was highly skewed toward the filter outlet. Nitrite oxidation was not detected during most of the experimental period, and the AOB activity therefore resulted in NO 2 − , accumulation, with concentrations often exceeding 100 mM at the filter inlet. The restriction of AOB to the outlet section of the filter was explained by both competition with heterotrophic bacteria for O 2 and inhibition by the protonated form of NO 2 − , HNO 2 . Product inhibition of AOB growth could explain why this type of filter tends to emit air with a rather constant NH 3 concentration irrespective of variations in inlet concentration and airflow.