Showing papers on "Trickling filter published in 1999"

Factors Influencing Ultraviolet Disinfection Performance Part II: Association of Coliform Bacteria with Wastewater Particles

Abstract: A technique is described for quantifying the number of particles with embedded coliform bacteria in wastewater samples. This technique was applied to eight different wastewater samples collected from eight significantly different treatment processes (five variations of the activated-sludge process, a trickling filter, an aerated lagoon, and a facultative lagoon). For all treatment process types that did not use chemical coagulants, total number of particles with embedded coliform bacteria correlated linearly with number of residual coliform bacteria following high doses of UV light. Lagoon treatment processes led to the formation of fewer bacteria-associated particles than either the activated-sludge or trickling-filter processes. Chemical coagulants showed a potential to significantly reduce the inactivation fraction of coliform bacteria associated with particles.

A High Performance Biofilter for VOC Emission Control.

Abstract: Biofiltration is a cleaning technique for waste air contaminated with some organic compounds. The advantages of the conventional biofilter over other biological systems are a high-superficial area best suited for the treatment of some compounds with poor water solubility, ease of operation, and low operating costs. It has crucial disadvantages, however; for example, it is not suitable to treat waste gases with high VOC concentrations and it has poor control of reaction conditions. To improve on these problems and to build a high-performance biofilter, three structured peat media and two trickling systems have been introduced in this study. The influences of media size and composition have been investigated experimentally. Peat bead blended with 30% (w/w) certain mineral material with a good binding capacity has advantages over other packing materials, for example, suitable size to prevent blockage due to microbial growth, strong buffering capacity to neutralize acidic substances in the system, and a pH range of 7.0-7.2 suitable for the growth of bacteria. Dropwise trickling system offers an effective measure to easily control the moisture content of the bed and the reaction conditions (pH, nutrient) and to partially remove excess biomass produced during the metabolic processes of microorganisms. The influence of nutrient supplementation has also been investigated in this study, which has revealed that the biological system was in a condition of nutrient limitation instead of carbon limitation. The biofilters built in our laboratory were used to treat waste gas contaminated with toluene in a concentration range of 1 to 3.2 g/m3 and at the specific gas flow rate of 24 to120 m3/m2.hr. Under the conditions employed, a high elimination capacity (135 g/m3.hr) was obtained in the biofilter packed with peat beads (blended with 30% of the mineral material), and no blockage problem was observed in an experimental period of 2-3 months.

Autotrophic denitrification with elemental sulphur in small-scale wastewater treatment facilities

Abstract: An autotrophic denitrification process with elemental sulphur to achieve a high quality effluent with a low concentration of total N was tested at laboratory scale. Two types of wastewater were tested during a period of 10 months. One was a multiple household wastewater obtained from a municipal wastewater treatment plant and the other was a single household wastewater collected from a family. The wastewaters were first treated by primary sedimentation, followed by nitrifying trickling filtration. The nitrified effluents from the trickling filter were further denitrified in an autotrophic denitrification stage. The autotrophic denitrifying reactor was filled with a mixture of elemental sulphur powder and small pieces of limestone. Sulphur was used as an electron donor and CaCO3 in the limestone served as pH buffer. With a hydraulic retention time of 2–3 hours, up to 86 % of total oxidizable nitrogen (TON) was removed from the multiple household wastewater and 75 % from the single household wastewater. The...

Assessment of characteristics and biological treatment technologies of Jordanian wastewater

Abstract: Demand for wastewater treatment facilities will increase as Jordan's population grows. In addition, currently available systems of treatment desperately need upgrades in capacity or supplementary systems; especially in the Amman-Zarqa region. Overall; based on the current wastewater flow rates; approximately 85% of the collected sewerage is treated in stabilization ponds, 10% in trickling filters, and 5% in activated sludge systems.

Synthetic dairy wastewater treatment using cross flow medium trickling filter

Abstract: The treatment of synthetic dairy wastewater was carried out using cross flow medium trickling filter of specific surface area 243 m2/m3. The operating variables in this study were hydraulic and organic loading rates. The hydraulic loadings employed in this study were 5, 9, 13 and 17 m3/m2.d for the influent COD concentrations of 427 to 1384 mg/l. It was observed that the relationship between organic removal rate and organic loading rate showed two regions of linear behaviour with the point of inflection at an organic loading rate of 26 g COD/m2.d. Kornegay model was used to evaluate the kinetic coefficients for the system. The results were found to be satisfactory.

Carbon disulfide oxidation by a microbial consortium from a trickling filter

Abstract: Biological oxidation rates of CS2 with a mixed microbial culture obtained from a trickling filter were optimal with 3 mM CS2, pH 7, 30 °C and SO4 2− below 25 g l−1 Degradation rates were 34 mg CS2/gproteinmin and 138 mg H2S/gproteinmin The concentrations of intermediates (H2S, COS and S°) and the product (SO4 2−) of CS2 oxidation were measured The biological oxidation was due principally to Gram negative bacteria

Trickling filter mythology

Abstract: Engineering practice in trickling filter design has been influenced by the propagation of myths as much as by the analysis of data and factual determinations. In this paper, several common myths encountered by the writer in his engineering practice are examined. The myths are tied to source(s) where possible, and then the factual underpinnings (if any) are examined. Common myths include the following: (1) Trickling filter processes are less reliable than activated sludge processes; (2) trickling filters are poor performers in cold weather; (3) trickling filters are more expensive; (4) motorized distributor speed control is always needed; (5) cross-flow media should not be used at total organic loadings exceeding 1.6 kg BOD5/m3⋅d and (6) all media are created equal.

Comparison of the trickling filter models for the treatment of synthetic dairy wastewater

Abstract: This paper describes the design implications of four existing trickling filter models. Experimental data from the treatment of synthetic dairy wastewater was used to evaluate the kinetic parameters. The four trickling filter models were examined for their ability to model the present data. Among the four models studied, Kincannon and Stover model based on the independent variable of surface organic loading rate gave superior results compared to other models.

A Nitrification Model for Mineral-Media Trickling Filters

Abstract: Trickling filters represent the biological treatment component of about 70% of sewage works in the UK. Increasingly, they are being required to achieve a high degree of nitrification consistent with 95 percent compliance with effluent discharge contents as low as 2 mg/l of ammoniacal nitrogen. The available design models for the simultaneous removal of BOD and ammoniacal nitrogen are poor and have led to a lack of confidence in the ability of the process to comply with such standards. This paper describes the development and application of an empirical model based upon the performance of eleven sets of trickling filters at five sites covering a wide range of organic and hydraulic loading.

Treatment of Domestic Wastewater by Enhanced Primary Decantation and Subsequent Naturally Ventilated Trickling Filtration

Abstract: To treat household wastewater, a sequence of ‘primary decantation–trickling filter percolation’ was applied in a lab-scale designed treatment system. Poly-electrolyte was used as coagulant to enhance the primary treatment and charcoal was used as carrier material in the trickling filters. Oxygen was supplied to the trickling filters by means of natural ventilation. In the lab-scale system, the enhanced primary stage removed more than 91% of the suspended solids (SS), and 79% of the total chemical oxygen demand (CODt). The subsequent trickling filtration brought a complete nitrification to the wastewaters at a volumetric loading rate (Bv) of 0.7–1.0 g CODt L-1 d-1. On average, the concentrations of the CODt and SS in the final effluents were about 55 and 15 mg L-1 respectively. With respect to phosphate, physico-chemical removal was the dominant process. About 46–62% of total P was removed from the tested wastewaters. The integrated treatment system also achieved a fair degree of hygienisation. The numbers of total coliforms, fecal coliforms and fecal streptococci were decreased by 2–4 log units. The sludge production of the entire treatment system was about 1.7% (v/v) of the treated wastewater. Only primary sludge was produced; secondary sludge produced in the trickling filters was negligible. The cost savings in terms of minimization of sludge production and aeration energy are estimated to be substantial (i.e. some 50%) relative to a conventional activated sludge system.

Method for treating an effluent using simultaneous nitrification/denitrification in a trickling filter

Abstract: The invention concerns biological treatment by nitrification/denitrification of an effluent comprising a step which consists in passing said effluent through a biological reactor with micro-organisms fixed on at least a granular material bed provided with means supplying oxygen. The invention is characterised in that it consists in: aerating substantially continuously said granular material bed assembly; measuring at least a parameter representing the oxygen consumption of said fixed micro-organisms and a step which consists in regulating the functioning of said oxygen supply means according to the results of said parameter measuring step and a set value thereof, said method enabling substantially simultaneous nitrification/denitrification of said effluent.

In Situ Bioremediation Technique for Sites Underlain by Silt and Clay

Abstract: An in situ trickling filter system, named Trickling Trench, is being used to treat biodegradable organic compounds at a site underlain by silt and clay. This method provides the containment advantages of pump-and-treat remediation with the low-cost benefits of in situ bioremediation. A design method is presented using a conventional trickling filter analytical model with kinetic coefficients for various organic compounds calculated from published data. Performance monitoring data obtained from the Trickling Trench bioreactor are compared to design predictions.

Method and installations for treating effluents in small communities

Abstract: The invention concerns a method for treating effluents in small communities, that is communities consisting of about 200 to 2000 inh.eq (inhabitant equivalent), characterised in that it consists in: carrying out a biological treatment of the effluent using a trickling filter eliminating matters suspended in the treated effluent, and, simultaneously performing a treatment of the sludge by filtering-composting on filters planted with reeds.

Non-invasive and continuous monitoring of a pilot-scale trickling filter: Weight, off-gas and hydraulic characterization.

Abstract: A pilot-scale trickling filter has been constructed in order to collect experimental data on a fully characterized biofilm system for the selection, development, calibration and corroboration of mathematical models which describe such a system’s dynamic behavior The design of the unit was made such that it allows a full characterization of the relevant model parameters, and an easy monitoring of the system’s performance only using measurements of inflow and outflow By means of an electronic balance, the weight of the filter unit is continuously monitored It is shown that information about the filter’s weight can be used to accurately determine biofilm and hydraulic characteristics Also the off-gas is continuously monitored for CO2 and O2 These measurements allow to establish closed carbon and oxygen mass balances Several short term experiments are conducted to reveal the possibilities of off-gas analysis to monitor, model and control the filter’s performance Two tracer tests were conducted on the filter without and with biofilm NaCl and Thioflavine-S were used as a tracer The hydraulic behavior of the filter without biofilm could be described using an advection-dispersion model If a biofilm was present however, a CSBR (continuously stirred biofilm reactor) approach was found to yield an optimal description of the hydraulics

Method and apparatus for the purification of waste gas of a drying apparatus

Abstract: The exhaust gas enters via an exhaust gas line into a washing apparatus. In the washing apparatus solid matter particles are predominantly separated. The pre-washed exhaust gas flows from the washing apparatus through a droplet removing conduit to a trickling filter device in order to be subjected to an activated sludge treatment for the separating of gaseous contaminants. In order to reduce the point of condensation and accordingly the absolute humidity of the exhaust gas for the activated sludge treatment either fresh air is added through a feed line to the pre-washed exhaust gas or the washing water which is led in a closed circuit through the washing water line of the washing apparatus is cooled in a heat exchanger in a cooling tower. A portion of the washing water of the washing apparatus is led through a first solid matter removing apparatus of which a portion of the filtrate is led to an activated sludge basin located under the trickling filter device. A portion of the water of the activated sludge basin coming from the trickling filter device is led to a second solid matter removing apparatus, of which a portion of the filtrate is led in a counter-move to the washing water of the washing apparatus.

Carbon oxidation and nitrification of dairy wastewater in a trickling filter

Abstract: In this investigation a single stage cross flow medium trickling filter was used to study the combined carbon oxidation and nitrification of synthetic dairy wastewater. The synthetic dairy wastewater was prepared to have influent TKN concentration of 30, 60 and 90 mg/1 at various COD concentrations (30–298 mg/1). The effect of organic loading rate on TKN removal was studied for three different hydraulic loading rates of 5,9 and 13 m3/m2.d. Within an organic loading rate of 0.39 kg COD/m3.d the TKN removal efficiency was observed to be more than 60%. The TKN removal percent showed a decreasing trend with increase in COD/TKN ratio. For organic load greater than 1.39 kg COD/m3.d the nitrate production was completely eliminated.

Low-rate trickling filter effluent: characterisation and crossflow filtration

Abstract: The low-rate trickling filter is the most common biological treatment process used in small and medium sized sewage works in the UK. It produces an inconsistent effluent quality, which has traditionally been related to seasonal changes in solids accumulation, grazing activity and sloughing of microbial film. The final effluent solids and, organic matter content is then too high for discharge or reuse. Given the increasingly stringent effluent standards, both in terms of quality and consistency, tertiary treatment is often required. This study was designed to investigate the key parameters affecting the performance of low-rate trickling filters and the characteristics of their effluents in terms of contaminant size, which might influence the efficiency of crossflow filtration as a tertiary treatment for the trickling filter. [Continues.]

Biodegradation of methyl tertiary butyl ether (MTBE) using a granular activated carbon trickling filter

Abstract: A pilot scale trickling filter was constructed using granular activated carbon (GAC) as the packing medium and inoculated with a microbial culture known to degrade MTBE. The packing dimensions were 0.076 m in diameter and 0.22 m deep. The unit operated with recycling flow for two months before a biofilm was observed on the GAC. After two additional months the biofilm had visibly spread throughout the packing. A few pieces of GAC were placed in a sealed bottle with MTBE-contaminated water and nutrients. Headspace analysis performed over 14 days confirmed that MTBE degradation was occurring. The trickling filter was converted to continuous flow and operated for one month at a nominal flow rate of 0.1 L/min and a hydraulic loading rate of 32 m{sup 3}/m{sup 2}-d. Samples were collected for analysis at the spray nozzle and at the bottom of the trickling filter. Fractional removal varied with influent MTBE concentration, temperature and liquid flow rate. Percent MTBE removal was as high as 85%. A mechanical failure resulted in the trickling filter bed drying and percent removal dropping to less than 1 percent. However, the system recovered within five days.

Upgrading a trickling filter wastewater treatment plant to biological nutrient removal standard

Abstract: The Selfs Point Wastewater Treatment Plant in Hobart was upgraded to biological nutrient removal standard in early 1997. The upgrade incorporated the existing trickling filter and anaerobic digesters. The new nutrient removal capability is provided by the BioDenipho process, and is supported by prefermentation and alum dosing of the digested sludge sidestream. This study reviews the development of wastewater treatment processes and the history of sewage treatment and collection in Hobart leading to this upgrade. All of the major processes at the Plant are reviewed as to how each impacts and is impacted by nutrient removal processes. Results from the first 18 months of operation of the plant following commissioning of nutrient removal are discussed, along with some of the factors affecting performance. Prefermentation has been found to be critical in achieving good biological phosphorus removal. A solids residence time of 5 days in a combined activated primary tank and sidestream prefermenter system has provided good performance. Use of existing rock trickling filters in a combined carbonaceous removal and nitrification role has permitted a smaller BNR reactor volume and a plant with greater flexibility for treating high influent loads or flows. The anaerobic digestion of phosphorus rich activated sludge led to a solubilisation of about 30% of the phosphorus entering the digesters. Alum dosing of the digested, sludge prior to the belt filter press at 1 to 1 1:1 molar (Al:P) ratio has been effective at reducing return of phosphorus to the main process to less than 1%.