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This study aimed to characterize raw municipal and dairy wastewaters. The quality of the collected wastewaters was determined by measuring 30 quality parameters, such as phenols, oxidation-reduction potential, oil and grease, total organic carbon (TOC), manganese, total viable count of bacteria (TVC), salinity, and biodegradability. Results were compared with wastewater disposal standards. This study also aimed to describe the potential application and performance of biological trickling filters (BTFs) in municipal and dairy wastewater treatment. Detailed reviews of trickling filter models were explained. Results revealed that two wastewater samples exceeded standard limits. The raw municipal and dairy wastewaters need treatment prior to disposal to the natural environment. Additionally, BTFs are efficient municipal and dairy wastewater treatments. [ABSTRACT FROM PUBLISHER]

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]

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 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]

Two pilot-scale trickling filters were used in order to estimate Cr(VI) reduction through biological mechanisms in biofilm reactors operated in SBR mode with recirculation using different filter media types, i.e. plastic media and calcitic gravel. The feed concentrations of Cr(VI) examined were about 5, 10, 20, 30, 50 and 100mg/l, while the concentration of the organic carbon was constant at 400mg/l, in order to avoid carbon limitations in the bulk liquid. Maximum reduction rates of 4.8 and 4.7gCr(VI)/d were observed for feed Cr(VI) concentration of about 5mgCr(VI)/l, for the filters with the plastic support material and the gravel media, respectively. The reduction rates were significantly affected by the feed Cr(VI) concentration in both bioreactors. A dual-enzyme kinetic model was used in order to describe Cr(VI) reduction by aerobically grown mixed cultures. Model predictions were found to correspond very closely to experimental quantitative observations of Cr(VI) reduction at both pilot-scale trickling filters used. [Copyright &y& Elsevier]

The performance in the removal of estrogenicity from wastewater was studied in three wastewater treatment plants (WWTPs). Different treatment processes were evaluated: stabilization ponds and trickling filter. Sampling was performed from the input to the output of the treatment systems. The total estrogenic activity was determined with MCF-7-derived cell lines which express the endogenous estrogen receptor α. The two wastewater stabilization ponds with long retention time had high removal of estrogenicity (90% to 95%). Trickling filters despite being effective at removing organic load were less effective in removing estrogenicity (42%), and post tertiary ponds enhanced estrogenicity removal. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work was to assess the effectiveness of a biological trickling filter for the treatment of wastewaters produced by a company manufacturing organic dyes and varnishes. The combined wastewater effluent was fed to a pilot-scale trickling filter in two feeding modes, continuously and as a sequencing batch reactor (SBR). The biodegradability of the diluted wastewaters that were subjected to physicochemical treatment, using Ca(OH)2 and FeSO4, was initially studied using a continuously operated trickling filter. The system efficiency ranged up to 60–70% for a hydraulic loading of 1.1m3/m2 day and up to 80–85% for a hydraulic loading 0.6m3/m2 day. A stable chemical oxygen demand (COD) removal efficiency of 60–70% was achieved even in the case of undiluted wastewater at a hydraulic loading of 1.1m3/m2 day. The effectiveness of biological treatment of a mixture of the company''s main wastewater streams was also examined. The microorganisms developed in the trickling filter were able to efficiently remove COD levels up to 36,000mg/L, under aerobic conditions at pH values between 5.5 and 8.0. Depending on the operating conditions of the system, about 30–60% of the total COD removal was attributed to air stripping caused by the air supply at the bottom of the filter, whereas the rest of the COD was clearly removed through biological action. The proposed biological treatment process based on a trickling filter, which was operated either continuously or even better in an SBR mode, appears as a promising pretreatment step for coping with dye manufacturing wastewaters in terms of removing a significant portion of the organic content. [Copyright &y& Elsevier]

Abstract: This review deals with the main mechanisms and parameters affecting design and performance of trickling filters in aquaculture. Relationships between nitrification rates and easily accessible process parameters, like bulk phase concentration of TAN, O2, organic matter (COD), nitrite, temperature, HCO3 −, pH and the hydraulic loading of the trickling filter, are discussed in relation to the design and operation of such filters. Trickling filter design procedures are presented and one of them, a model describing the nitrification performance of trickling filters by plug-flow characteristics, is discussed in greater detail. Finally, practical aspects in relation to filter design and operation are presented. [Copyright &y& Elsevier]

This work aimed at evaluating the influence of the excess sludge produced in a trickling filter (TF) on the performance of a UASB reactor used for the combined treatment of domestic sewage and aerobic sludge. During phase 1 of the research, the UASB reactor/TF system was fed with domestic sewage pumped directly from the sewer collector of Arrudas stream, in Belo Horizonte -- Brazil. During phase 2, besides feeding the reactor with domestic sewage, the UASB reactor was also fed with the aerobic sludge from the trickling filter. The UASB reactor, with a volume of 420 litres, was operated at a mean hydraulic detention time of 5.6 hours in both operational phases. After 133 days of continuous monitoring, no detrimental effect was noticed on the performance of the UASB reactor regarding the return of the aerobic sludge produced in the TF. On the contrary, the COD results indicated a higher percentage of compliance with the discharge standards set forth by the Brazilian environmental legislation. During phase 2 of the research, when the UASB reactor was used for combined treatment of domestic sewage and excess aerobic sludge from the TF, the anaerobic effluent presented mean concentrations of 108 mgCOD.L-1, 57 mgBOD.L-1 and 18 mgTSS.L-1. [ABSTRACT FROM AUTHOR]

Fluorescent in situ hybridization (FISH) was used to quantify the ammonia-oxidizing populations within intact biofilm samples collected from a full-scale nitrifying trickling filter (NTF). Ammonia, nitrite, and nitrate concentrations were measured for aqueous samples taken in conjunction with biofilm samples at multiple filter depths. The ammonia removal capability of collected biofilms was evaluated by transferring the biofilms to laboratory batch reactors. Nitrate plus nitrite generation rates were calculated for the full-scale NTF and for the bench-scale reactors. Correlation coefficients for individual sampling events, calculated by simple linear regression of FISH signal area and nitrate plus nitrite generation rates for the full-scale NTF, ranged from -0.882 to 0.984. Correlation coefficients obtained for FISH signal area and nitrate plus nitrite generation rates for the bench-scale reactors ranged from 0.853 to 0.994 when using probe Nso19O and from 0.919 to 0.986 when using probe Neu23a. Occasional differences between the number of ammonia-oxidizing bacteria quantified by the probe Nso19O versus the NEU23a probe with depth suggest that genera other than Nitrosomonas are present in the NTF. Water Environ. Res., 75, 205 (2003). [ABSTRACT FROM AUTHOR]

National and international regulations require a minimum nitrogen removed efficiency of 70% in most public sewage treatment plaints. Unlike ill activated sludge plants, selective denitrification in trickling filters was not possible until now. Therefore the aim was to employ trickling filter plants for selective denitrification, using innovative technology that involved minimum capital expenditure. For selective denitrification, it is necessary to prevent as much as possible the transfer of oxygen into the trickling filter while feeding the nitrate to be removed, a process similar to upstream denitrification in the activated sludge process. In a test operation conducted in several sewage treatment plants for over a year, the new process with selective denitrification in a covered trickling filter has given successful results. The denitrification efficiency of this system is comparable to that of upstream denitrification in the activated sludge process. Thus, selective denitrification in the trickling filter is a practical alternative to other nitrogen removal processes, while maintaining the established advantages offered by the trickling filter process. [ABSTRACT FROM AUTHOR]

We analyse the interactions between the biofilm growth and the liquid flow distribution in a trickling filter. Experiments are carried out on 0.5 m³ pilot scale reactor. We determine both the liquid flowrate distribution by local measurements and the filter performance by measuring the conversion. The liquid superficial flowrate ranges between 0 and 0.9 m/h. The synthetic effluent consists of a water solution of beet molasses and potassium dihydrogenophosphate. The hydrodynamic modelling allows us to relate the characteristics of the liquid flow distribution and the reactor performance to a single set of packing parameters. The packing irrigation rate plays a key role. Our results confirm the definite effect that the biofilm activity may have on the quality of the liquid flow distribution. [ABSTRACT FROM AUTHOR]

A two year pilot plant study has been performed in order to evaluate a nitrifying trickling filter (NTF) process within an upgrading project for increased nutrient removal. The operation of the filters was very stable without upsets due to predators. The filter microfauna was dominated by worms and the presence of filter fly larvae was limited. Suggested predator control methods like flooding or varying the flushing intensity did not affect the identified microfauna. By operating the filters in a two stage alternating series filtration mode, higher nitrification rates and lower effluent ammonia concentrations could be reached simultaneously in comparison to operating the filters in a single stage filtration mode. [ABSTRACT FROM AUTHOR]

The variables affecting nitrification in biofilms are identified on a theoretical basis. The influence of various design and operational parameters which affect the resulting substance fluxes into and out of the biofilm and the biomass activity regarding nitrification are illustrated with the help of experimental investigations with plastic media trickling filters, rotating biological contactors and different aerated biofilters. The results of experiments with these systems in tertiary nitrification applications reveal process limitations and technical measures to enhance nitrification performance in each system. In a case study, a comparison between the different biofilm processes and activated sludge alternatives showed that biofilm systems may lead to remarkably smaller reactor volumes, but high energy consumption due to unfavorable oxygen utilization. [ABSTRACT FROM AUTHOR]

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 NH 3 –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. Image 1 • 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 kg N m−3 d−1. • Bamboo woodchip filters achieved denitrification rates up to 0.03 kg N m−3 d−1. • Scrap iron filter removed 126 g P m−3 d−1 with 23.2 g P kg−1 Fe capacity. [ABSTRACT FROM AUTHOR]