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Final Report: Comprehensive Evaluation of The Dual Trickling Filter Solids Contact Process
EPA Grant Number: R825427C001Subproject: this is subproject number 001 , established and managed by the Center Director under grant R825427
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Urban Waste Management and Research Center (University New Orleans)
Center Director: McManis, Kenneth
Title: Comprehensive Evaluation of The Dual Trickling Filter Solids Contact Process
Investigators: La Motta, Enrique J. , Josse, Juan
Institution: University of New Orleans
EPA Project Officer: Krishnan, Bala S.
Project Period: June 30, 1997 through May 31, 2000
RFA: Urban Waste Management & Research Center (1998)
Research Category: Targeted Research
Description:
Objective:This project was developed using the full scale treatment plants located in Jefferson Parish, Louisiana, all of them using the trickling filter-solids contact process. A significant part of the project was devoted to a pilot plant investigation using a 2000 gpd pilot plant located at Marrero, LA. The main task was to try to find any relationship between common operating parameters, such as HRT, SRT, FM, hydraulic and organic loadings, and plant performance. No significant correlations could be established, and this led the investigators to conclude that plant performance is affected by other phenomena, such as biological flocculation, that plays a major role on both COD and SS removal.
The main objective of this project is to perform a comprehensive long-term evaluation of the performance of the Marrero, Bridge City, and Harvey wastewater treatment plants, in Jefferson Parish, Louisiana, based on an extended sampling and testing program. Additional objectives are to understand the effect of critical design parameters on the performance of the unit processes and the system as a whole, and to determine the optimum operating conditions.
Municipal Scale Treatment Plants: A sampling program of effluents of each unit process in the Marrero, Bridge City and Harvey full-scale plants was completed. The units sampled included bar rack, primary clarifier, trickling filter, solids contact basin and secondary clarifier. Grab samples were taken from January to July 1998. Between July and December 1998, 24-hour composite samples were taken. Automatic samplers were set up to pump every two hours, during a 24- hour period, into the composite sample tank. They were preserved with sulfuric acid to drop the pH to less than 2. Between January and June 1999, sludge samples were taken at the three plants. Waste activated sludge, primary sludge, sludge as it leaves the digesters, sludge cake and belt press filtrate were also sampled.
The parameters tested on the wastewater samples were total chemical oxygen
demand (TCOD), dissolved chemical oxygen demand (DCOD), total suspended solids
(TSS) and volatile suspended solids (VSS). Flow rates were also recorded at
the time of sampling in the case of grab samples, and average daily flows in
the case of composite samples. The results of the long-term testing were used
to obtain average operating conditions of the unit processes at each plant.
Based on these averages, spreadsheets were developed for each plant to calculate
all operating parameters of each unit process. These values were compared with
typical values published in the literature for the TF/SC process.
Pilot Plant Research: A TF/SC pilot plant was designed, constructed and erected at a location provided by the Marrero wastewater treatment plant, between the two primary clarifiers of the plant. The TF/SC pilot plant consists of an intermittent primary effluent feeding system, a trickling filter, an aerated solids contact tank, a flocculation tank, and a secondary clarifier, all with a design capacity of 2,000 gal/day. The pilot unit is fed by pumping the primary clarifier effluent from one of the primary tanks of the Marrero plant to an elevated 30-gallon constant-head tank. From this tank the water flows by gravity to the trickling filter distribution pipes. A timer-controlled valve opens and closes, so that the flow rate can be adjusted by changing the time that the valve is open. The trickling filter inlet distribution system consists of four properly leveled 2-inch diameter PVC pipes. These pipes are perforated on the sides and allow water overflow uniformly over the top of trickling filter media.
The trickling filter consists of an 8-ft tall PVC tower, which contains 4 modules of cross-flow conventional plastic media obtained from the Harvey wastewater treatment plant. A U-shaped PVC sheet acts as a tray, and collects the effluent at the bottom of the filter and pours it into a 5-gallon tank equipped with a submersible pump. Trickling filter effluent is pumped into a flow-control device from which water flows by gravity into an aerated solids contact chamber. The aerated solids contact (ASC) tank is a 40-gallon polyethylene tank, initially equipped with a coarse bubble air diffusion system. A compressor with 0.8 cfm capacity feeds air to the tank, maintaining a dissolved oxygen concentration of 1.5 mg/L.
The mechanical flocculation unit consists of a 27-gallon conical bottom polyethylene tank. The unit has a retention time of 20 minutes, and is equipped with a vertical shaft and horizontal paddles. Two motors are available, with 20 and 30 rpm. By changing the motors and the number of and size of the paddles, a wide range of velocity gradients could be obtained for flocculation experiments.
The secondary clarifier consists of a 70-gallon conical-bottom polyethylene tank. The inlet structure has a 1.5-inch PVC pipe that discharges upwards into an 8-inch in diameter center-well to dissipate the energy of the incoming water and promote additional flocculation in the center-well. A vertical shaft driven by an AC gear motor moves a bottom scraper. The scraper avoids the formation of clumps that could float. The scraper also allows sludge to flow out of the bottom for recirculation.
The effluent of the secondary clarifier overflows the unit through two ports equipped with launders. The effluent flows into an effluent tank equipped with a submersible pump. The submersible pump operates on a level switch. The level of the effluent tank is maintained by pumping the water into one of the primary clarifiers of the full-scale Marrero plant.
Summary/Accomplishments (Outputs/Outcomes):The Marrero Sewage Treatment Plant: The Marrero plant has the following units: prechlorination, 2 mechanical bar screens and 1 manual bar screen, 2 covered aerated grit chambers, 2 covered primary settling tanks, 2 covered 4"-rock trickling filters, 2 aeration basins, 2 secondary clarifiers, 2 chlorine contact chambers, 3 aerobic sludge digesters, and 2 new belt presses for sludge dewatering. The average flow rate during the testing period was 9.0 MGD, the average influent BOD5 was 146mg/L, and the average TSS was 147 mg/L. Several efforts were made to correlate the final effluent quality, in terms of BOD and SS, with operational parameters commonly used in trickling filter and activated sludge plants (organic loading and hydraulic loading in the TF, F/M ratio, MLSS in the aeration basin, solids retention time). The results were not conclusive in most cases, and no specific trend could be identified.
The Bridge City Sewage Treatment Plant: This plant has a design average flow rate capacity of 7.2 MGD, a peak capacity of 16 MGD, and a maximum hydraulic capacity of 33 MGD. However, the average flow rate is 5.1 MGD. The average total influent BOD5 was 143 mg/L, and the average influent TSS was 186 mg/L. The Bridge City plant has the following units: 2 mechanical bar screens and 1 manual bar screen, 2 aerated grit chambers, 2 primary settling tanks, 2 plastic media trickling filters, 2 aeration basins, 2 secondary clarifiers, 3 aerobic sludge digesters, and 2 belt presses for sludge dewatering. There is no chlorine contact chamber; chlorine is applied on the effluent trough of the secondary clarifiers. Only one trickling filter and one primary clarifier are currently operating. In general, the Bridge City plant operates well and has excellent effluent quality in terms of BOD and TSS. As in the case of the Marrero plant, no correlation could be found between the BOD and SS of the final effluent with organic loading and hydraulic loading in the TF, and F/M ratio, MLSS and solids retention time in the aeration basin.
The Harvey Sewage Treatment Plant: The Harvey plant has 3 mechanical bar screens, 2 aerated grit chambers, 2 primary settling tanks, 1 plastic media trickling filters, 2 aeration basins, 2 secondary clarifiers, chlorination in the effluent line, 2 aerobic sludge digesters, and 2 belt presses for sludge dewatering. The average daily flow rate during the sampling period was 10.6 MGD, and the average influent total BOD5 and SS were 164 mg/L and 171 mg/L, respectively. The average secondary clarifier effluent BOD is 33 mg/L and TSS is 22 mg/L for the sampling period. Efforts to correlate the final effluent quality, in terms of BOD and SS, with typical operational parameters used in trickling filter and activated sludge also failed in this plant, and no specific trend could be identified.
Pilot-scale TF/SC Plant: The characteristics of the influent to the pilot plant (primary effluent of the Marrero full-scale plant) are: total COD, 267 mg/L; filtered COD, 97 mg/l; TSS, 147 mg/l; VSS, 113 mg/l; Fixed SS, 34 mg/l; Alkalinity, 252 mg/L as CaCO3; pH, 7.23. During the experimental phase the organic loading to the trickling filter ranged from 18 to 63 lb COD/103 ft3-day. In order to increase the organic loading to the filters, sodium acetate was added to the influent at different rates. The feed at each new concentration was maintained during two weeks; the highest organic loading applied was 160 lb COD/103 ft3-day.
Trickling filter performance, expressed as percent removal of filtered COD, varied with no particular dependency on influent filtered COD. Removal efficiencies averaged 46%, and were not significantly affected by the high organic loading applied. Abundant biological film growth was observed as a result of the high organic loading and the subsequent slough off from the trickling filter. Throughout the experimental phase, mixed liquor concentrations in the solids contact chamber were varied to observe the effect that it could have on the normal operation of the plant. Values ranged from 1,450 to 4,650 mg/L MLSS. Although no statistical model or mathematical relationship between these two variables can be proposed at his time, the lowest secondary effluent TSS values were observed at concentrations around 3,000 mg/L. However, other factors such as the occurrence of flocculation in the system seem to be more relevant.
The results of the experimental phase show that gentle movement of the mixed liquor enhances bioflocculation, thus increasing the entrapment of small particles and, therefore, improving the clarity of the final effluent. It also provides a more stable operation. As indicated, mixing in the ASC tank was enhanced by a submerged centrifugal pump. This, in addition to the effect of coarse-bubble aeration, disrupted the biological flocs, so that the flocculent state of the sludge was very poor as it entered the clarifier. However, the flocculation potential of that sludge was very high and the addition of a flocculation chamber provided a significant reduction in the effluent suspended solids. In a later stage of this research, coarse bubble diffusers were replaced by fine-bubble diffusers, and the internal recirculation with a pump was discontinued. The improvement in the flocculation efficiency was dramatic, to the extent that mechanical flocculation did not significantly improve the final effluent quality. The new diffusers had a pore sizes of 80 microns and an effective bubble size of 0.5 mm.
Conclusions:The summary of findings are as follows:
- Classical activated sludge design parameters like F/M ratio, SRT, MLSS, and organic loading on the TF have no significant effect on effluent quality of the dual TF/SC process.
- Bioflocculation in the solids contact chamber and reflocculation in a center well flocculator in the final clarifier play a significant role in defining effluent quality.
- Optimum performance of the TF/SC dual process relies on low TSS primary effluent, healthy TF and good flocculation in the SC chamber.
- The velocity gradient in mechanical flocculation has no effect on effluent quality within the range studied of 15 to 45 s-1.
- Fine bubble diffusers in the SC chamber provide much better flocculation then coarse bubble diffusers.
- Dissolved oxygen concentrations much lower than 1 mg/L deteriorate effluent quality.
trickling filter/solids contact (TF/SC) process, dual treatment, bioflocculation, municipal wastewater treatment. , Geographic Area, Scientific Discipline, Waste, Analytical Chemistry, Ecological Risk Assessment, Municipal, Environmental Chemistry, Ecology and Ecosystems, State, bioflocculation, waste minimization, urban waste, groundwater quality, New Orleans (NO), urban runoff, dual trickling filter, technology transfer, waste management, municipal waste
Relevant Websites:
Progress and Final Reports:
Original Abstract
Main Center Abstract and Reports:
R825427 Urban Waste Management and Research Center (University New Orleans)
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825427C001 Comprehensive Evaluation of The Dual Trickling Filter Solids Contact Process
R825427C002 Issues Involving the Vertical Expansion of Landfills
R825427C003 Deep Foundations on Brownfields Sites
R825427C004 Ambient Particulate Concentration Model for Traffic Intersections
R825427C005 Effectiveness of Rehabilitation Approaches for I/I Reduction
R825427C006 Urban Solid Waste Management Videos
R825427C007 UWMRC Community Outreach Multimedia Exhibit
R825427C008 Including New Technology into the Investigation of Inappropriate Pollutant Entries into Storm Drainage Systems - A User's Guide
R825427C009 Investigation of Hydraulic Characteristics and Alternative Model Development of Subsurface Flow Constructed Wetlands
R825427C010 Beneficial Use Of Urban Runoff For Wetland Enhancement
R825427C011 Urban Storm and Waste Water Outfall Modeling
R827933C001 Development of a Model Sediment Control Ordinance for Louisisana
R827933C002 Inappropriate Discharge to Stormwater Drainage (Demonstration Project)
R827933C003 Alternate Liner Evaluation Model
R827933C004 LA DNR - DEQ - Regional Waste Management
R827933C005 Landfill Design Specifications
R827933C006 Geosynthetic Clay Liners as Alternative Barrier Systems
R827933C007 Used Tire Monofill
R827933C008 A Comparison of Upflow Anaerobic Sludge Bed (USAB) and the Anaerobic Biofilm Fluidized Bed Reactor (ABFBR) for the Treatment of Municipal Wastewater
R827933C009 Integrated Environmental Management Plan for Shipbuilding Facilities
R827933C010 Nicaragua
R827933C011 Louisiana Environmental Education and Resource Program
R827933C012 Costa Rica - Costa Rican Initiative
R827933C013 Evaluation of Cr(VI) Exposure Assessment in the Shipbuilding Industry
R827933C014 LaTAP, Louisiana Technical Assistance Program: Pollution Prevention for Small Businesses
R827933C015 Louisiana Environmental Leadership Pollution Prevention Program
R827933C016 Inexpensive Non-Toxic Pigment Substitute for Chromium in Primer for Aluminum Sibstrate
R827933C017 China - Innovative Waste Composting Plan for the City of Benxi, People's Rupublic of China
R827933C018 Institutional Control in Brownfields Redevelopment: A Methodology for Community Participation and Sustainability
R827933C019 Physico-Chemical Assessment for Treatment of Storm Water From Impervious Urban Watersheds Typical of the Gulf Coast
R827933C020 Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region
R827933C021 Characterizing Moisture Content Within Landfills
R827933C022 Bioreactor Landfill Moisture Management
R827933C023 Urban Water Issues: A Video Series
R827933C024 Water Quality Modeling in Urban Storm Water Systems
R827933C025 The Development of a Web Based Instruction (WBI) Program for the UWMRC User's Guide (Investigation of Inappropriate Pollutant Entries Into Storm Drainage Systems)
R827933C027 Legal Issues of SSO's: Private Property Sources and Non-NPDES Entities
R827933C028 Brownfields Issues: A Video Series
R827933C029 Facultative Landfill Bioreactors (FLB): A Pilot-Scale Study of Waste Stabilization, Landfill Gas Emissions, Leachate Treatment, and Landfill Geotechnical Properties
R827933C030 Advances in Municipal Wastewater Treatment
R827933C031 Design Criteria for Sanitary Sewer System Rehabilitation
R827933C032 Deep Foundations in Brownfield Areas: Continuing Investigation
R827933C033 Gradation-Based Transport, Kinetics, Coagulation, and Flocculation of Urban Watershed Rainfall-Runoff Particulate Matter
R827933C034 Leaching and Stabilization of Solid-Phase Residuals Separated by Storm Water BMPs Capturing Urban Runoff Impacted by Transportation Activities and Infrastructure
R827933C035 Fate of Pathogens in Storm Water Runoff
R87933C020 Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region