Trickling Filter Plant Research Articles

Evaluation of Temperature Effects on Trickling Filter Plant Performance

This paper presents a mathematical-statistical method to help evaluate the temperature effect on BOD and SS residual ratio during and after a trickling filter plant treatment. Mathematical relationships are developed and brought to workable linear forms which are then used for statistical examination by the F test method. The data for this purpose is provided by regular measurements of wastewater quality in a full-scale treatment plant. While settling performance did not respond consistently to temperature changes, the secondary treatment and the overall plant performance provided good correlations with the correct representative temperatures.

Influence of Particulate Organics on the Removal of Dissolved Organics in Fixed-Film Biological Reactors

Very little is known about the interaction between dissolved and particulate organics in the fixed-film biological process used for wastewater purification, although this process has been used for many decades. The mechanisms for the removal of dissolved and particulate organics differ and it has been found that a large fraction of the organics in most wastewaters exists in particulate form. In the experiments described here, the influence of particulate organics on the removal of glucose was studied in laboratory-scale fixed-film reactors. The particles used were starch particles and particles obtained from digested sewage sludge. The result of the experiments showed that for high glucose concentrations and high temperatures the removal of glucose was reduced when particles were adsorbed on the biofilm surface. A dramatic reduction was observed when large amounts of particles were adsorbed. This effect has also been observed in a full-scale trickling filter plant and in pilot trickling filters. At low glucose concentrations and low temperatures, however, a slight increase in glucose removal was observed when organic particles were adsorbed on the biofilm surface.

Nitrification and Phosphorus Removal from Trickling Filter Effluents

Nitrification and simultaneous phosphorus precipitation in a separate activated sludge plant is considered the cheapest alternative for upgrading conventional trickling filter plants. Before upgrading the Herning treatment plant (200,000 PE) a 12 month pilot plant experiment was performed. During operation of the pilot plant, important parameters were investigated, such as excess sludge production, sludge properties, and influence of the large part of chemical sludge when combining separate nitrification and simultaneous precipitation. It was found that a stable process could be operated with a bypass of 20-25% settled raw wastewater. Due to improvements in the sludge characteristics simultaneous precipitation with ferrous sulphate improved the effluent quality with respect to both phosphorus, BOD and suspended solids.

Field evaluation of the treatability of type A zeolite in a trickling filter plant

Type A zeolite is a synthetic aluminosilicate which can be used as a builder in laundry detergents. The treatability of this zeolite in wastewater was evaluated in a trickling filter plant under field conditions. The normal performance of the plant was established during a baseline period of three months, after which the zeolite was added to the raw wastewater for 7 months. The removal of the zeolite by the plant averaged 81% or more at an influent concentration of 10 mg 1 −1. Of the zeolite that passed into the secondary effluent, 92% was removed by a dual-media filter. Removal from raw influent to tertiary effluent was thus 99%. The presence of the zeolite in the wastewater had no effect on the performance of the plant, the production of gas by the anaerobic digester or the concentrations of Pb, Zn and Ni in the effluent.

Preliminary observations on the removal of Taenia saginata eggs from sewage using various treatment processes.

Cattle were grazed for four months on pasture irrigated by effluent from activated sludge plants, a trickling filter plant, from a lagooning process with raw sewage, and then killed and their heart, diaphragm, tongue, and muscles of their head and one forelimb were sliced and examined for Cysticercus bovis. None of the cattle grazed on pasture irrigated with effluent from lagooning were infected compared with 3.3% from the trickling filter plant, 9.0% and 12.5% from the two activated sludge plants and 30.0% of cattle on pastures irrigated with raw sewage. Of the 40 control calves killed at the time the test calves were placed on the various pastures, 2.5% were infected. It appears that modern sewage purification methods do not efficiently remove Taenia saginata from the final effluent and that prolonged settling is necessary before effluent is used to irrigate cattle pastures if C. bovis infection is to be reduced to very low levels.

The Removal of Salmonellas in Conventional Sewage Treatment Processes

The numbers of salmonellas in raw sewage entering a treatment plant varied hourly and diurnally; their peak concentration preceded the peak influent waste water flow into the plant by about 2 hours. Salmonellas were detected in all raw influent samples collected from 2 sewage works and the mean population level at the daily peak period was 3000 organisms/1. On average. 70–80% of the salmonellas were removed during primary sedimentation when upwards of 74–84% of solids were removed. Biological treatment and secondary sedimentation removed a further 70–100% of the pathogen. Compared with the activated sludge process the trickling filters were less efficient in removing salmonellas and they were adversely affected by increased loading following rainfall. Considering the whole treatment process, the Guildford works with its activated sludge treatment removed an average of 99–83% salmonellas while the Woking works with its trickling filter plant removed an average of 93–04% of the organisms. The large variance in the numbers of salmonellas in the final effluent from the trickling filters suggest that greater emphasis should be placed on the actual quality of the effluent rather than on percentage removal efficiencies.

Pure Oxygen Fixed Film Reactor

The aerobic media trickling filter is compared with other biological processes. It is feasible and functions under organic loadings higher than activated sludge and trickling filter plants. The process is applicable for domestic sewage. Nitrification occurred at combined low organic and hydraulic loadings. Oxygen application rates in this process were comparable to the oxygen activated sludge process. The sludge yield coefficients were approximately the value reported for the high-rate trickling filter, however, the process had higher design organic loadings. A reactor was constructed containing Teflon capillaries pressurized with pure oxygen. With flow outside the Teflon tubings, they became covered with a biological film. Oxygen was provided by diffusion through the walls of the tubing. The device provides more than 90% BOD removal at high organic loadings.

Interactive Computer Design of Wastewater Plants

A program which allows the engineer without computer programming experience to design a sewage treatment plant is described. The program development criteria and user supplied information are briefly described. A design example showing the calculation for upgrading a trickling filter plant is included. The program can be used in the design of a new plant or to model and upgrade an existing facility. A list of the unit operation models currently programmed is given. Other models can be added readily.

Trickling Filter-Activated Sludge Combinations

Activated sludge processes were used on a pilot-plant scale as a means of upgrading trickling filter plants treating domestic wastewater. Parallel use of units provided increased hydraulic capacity and produced effluent BOD concentrations consistently below 25 mg/l. Series activated sludge-trickling filter or trickling filter-activated sludge processes produced effluent BOD consistently below l5 mg/l. This performance was maintained in all cases when operating at organic loadings up to about 50 lb BOD/day/1,000 cu ft (0.80 kg/day/m³) of treatment unit volume.

Airborne coliphages from wastewater treatment facilities.

The emission (from wastewater treatment plants) of airborne coliphages that form plaques on two strains of Escherichia coli was investigated. Two activated-sludge and two trickling-filter plants were studied. Field sampling procedures used large-volume air samplers with recirculation devices. Coliphages were enumerated by a most-probable-number (MPN) procedure. Temperature, relative humidity, windspeed, and presence of sunlight were monitored. Concurrent samples of sewage were taken during each air-sampling run. Average coliphage levels in the airborne emissions of trickling-filter beds and activated-sludge units were 2.84 X 10(-1) and 3.02 X 10(-1) MPN/m3, respectively, for all positive observations, and sewage liquor concentrations from the sources were 4.48 X 10(5) and 2.94 X 10(6) plaque-forming units/liter, respectively, depending upon the E. coli host used for assay. This work establishes minimal airborne-coliphage concentrations from the plants studied. The procedures employed will be useful in evaluating the animal virus levels in these emissions.

Filed Tests on Chlorination of Poliovirus in Sewage

Full-scale field tests on the chlorination of poliovirus in sewage were conducted using the effluent at a small trickling filter plant. A vaccine strain of poliovirus was taken as a model and used to seed the flow to the chlorination basin. Measurements of chlorine residual and of oxidation-reduction potential were compared with reductions in virus concentration. Coliform group bacteria counts were made during each test run. High chlorine residuals were found to significantly reduce virus concentration. With a 10-min contact time, a 99% reduction required a final residual of 21 mg per 1. However, on the basis of the work of other investigators and this field study it appears desirable to use measurements of oxidation-reduction potential instead of chlorine residual for control of sewage chlorination. The number of surviving coliform bacteria was not a reliable indication of effectiveness of virus disinfection.