Rock Filter Research Articles

Long Term Performance of a Septic Tank - Rock Filter System

Long Term Performance of a Septic Tank - Rock Filter SystemThe overall performance of rock plant filters in Louisiana has been spotty at best. Previous investigations have found that most Louisiana facilities maintained little or no operational data on which to base rational judgments. This paper summarizes the performance of a septic tank – rock filter system at an interstate rest area on I-49 approximately 40 miles south of Alexandria, Louisiana....Author(s)D. M. GriffinX. YanH. XiangC FletcherR. CrawfordSourceProceedings of the Water Environment FederationSubjectSession 74 - Small Community and Natural Treatment Systems: Small Communities IIDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2002ISSN1938-6478SICI1938-6478(20020101)2002:10L.111;1-DOI10.2175/193864702784164721Volume / Issue2002 / 10Content sourceWEFTECFirst / last page(s)111 - 122Copyright2002Word count356

Meeting stringent environmental and reuse requirements with an integrated pond system for the twenty-first century

AbstractIt is a long sought desire to modernize stabilization pond systems by increasing their efficiency to control malodors, to save land requirements and to improve their effluent quality, particularly for reuse purposes, while still capitalizing on natural energy saving processes such as anaerobiosis and photosynthesis. A full-scale demonstration modern integrated pond system was constructed in the town of Arad (22,000 inhabitants) located in the Negev desert of Israel. The integrated pond system is composed of the following units: (1) anaerobic covered ponds of which one is of the “submerged tent” novel design, including biogas collection and utilization for heating the bottom sludge; (2) two facultative ponds with internal recirculation; (3) a two stage rock filter to biologically remove excess algal biomass from the effluent; (4) three storage reservoirs operating in a sequential array of “fill, stay, draw”, and (5) a seasonal reservoir. The final effluent is aimed at irrigation of various agricultural crops.

Constructed Wetlands for Wastewater Treatment in Colombia

A modular wastewater treatment system has been installed for the Colombian Coffee Growers Federation (FEDERACAFE) at the Fundacion Manuel Mejia residential training centre. This system was designed by the University of Portsmouth, UK, and based on previous experience with the Gravel Bed Hydroponic (GHB) constructed wetland system. The steep topography of the site posed constraints on the design and a modular system composed of a rock filter in gabions for primary treatment, GBH beds for secondary treatment and a pond for tertiary treatment was selected. This system was designed to follow the contours of the site and maximise treatment. The GBH reed bed was planted with Typha angustifolia in early 1997. The system is being monitored by CENICAFE, the research division of FEDERACAFE. Monitoring of the system has shown large BOD removals from more than 350 to less than 20 mg/l. Initial results have also suggested 4 log cycle reductions in indicator bacteria. It is hoped that the success of this system will result in the replication of the treatment process at many villages in the Colombian coffee growing region where conventional sanitation technologies are impractical.

Constructed wetlands for wastewater treatment in Colombia

A modular wastewater treatment system has been installed for the Colombian Coffee Growers Federation (FEDERACAFE) at the Fundacion Manuel Mejia residential training centre. This system was designed by the University of Portsmouth, UK, and based on previous experience with the Gravel Bed Hydroponic (GBH) constructed wetland system. The steep topography of the site posed constraints on the design and a modular system composed of a rock filter in gabions for primary treatment, GBH beds for secondary treatment and a pond for tertiary treatment was selected. This system was designed to follow the contours of the site and maximise treatment.The GBH reed bed was planted with Typha angustifolia in early 1997. The system is being monitored by CENICAFE, the research division of FEDERACAFE. Monitoring of the system has shown large BOD removals from more than 350 to less than 20 mg/1. Initial results have also suggested 4 log cycle reductions in indicator bacteria.It is hoped that the success of this system will result in the replication of the treatment process at many villages in the Colombian coffee growing region where conventional sanitation technologies are impractical.

THE CHALLENGES OF DESIGNING, PERMITTING AND BUILDING A 1,200 GPM PASSIVE BIOREACTOR FOR METAL MINE DRAINAGE WEST FORK MINE, MISSOURI

An active underground lead mine produces water having a pH of 8.0 with 0.4 to 0.6 mg/L of Pb and 0.18 mg/L of Zn. A full-scale 1,200 gpm capacity bioreactor system was designed and permitted based on a phased program of laboratory, bench and pilot scale bioreactor testing; it was constructed in mid-1996. The gravity flow system, covering a total surface area of about five acres (2 ha), is composed of a settling basin followed by two anaerobic bioreactors arranged in parallel which discharge into a rock filter polishing cell that is followed by a final aeration polishing pond. The primary lead removal mechanism is sulfate reduction/sulfide precipitation. The discharge has met stringent in-stream water quality requirements since its commissioning. The system was designed to last about 12 years, but estimates suggest a much longer life based on anticipated carbon consumption in the anaerobic cells.

A prototype small swine waste treatment system for land limited and tropical application

A prototype of a 300-pig waste treatment system was constructed at the animal research farm of the University of Hawaii. The system includes a solid/liquid separation (12 m3), two anaerobic reactors (10 m3 each), one aeration unit (20 m3) and one combined rock bed filter with the aquatic plant reactor (20 m3). Based on the current results of a 240-pig operation, the methane gas production and TS reduction are 0.75 m3/m3/day and 72.7%, respectively, at the loading rate of 3.09 kg TS/m3/day. The aeration unit provides a TCOD and NH3-N reduction of 94% and 91%, respectively. The rock filter achieves a TCOD, NH3-N and NO3-N reduction of 32.8%, 26.8% and 68.4%, respectively. The annual cost for each of the treatment component is presented. It is very useful for the application of each treatment unit for the various needs of each pig farm.

A prototype small swine waste treatment system for land limited and tropical application

A prototype of a 300-pig waste treatment system was constructed at the animal research fart of the University of Hawaii. The system includes a solid/liquid separation (12 m3), two anaerobic reactors (10 m3 each), one aeration unit (20 m3) and one combined rock bed filter with the aquatic plant reactor (20 m3). Based on the current results of a 240-pig operation, the methane gas production and TS reduction are 0.75 m3/m3/day and 72.7%, respectively, at the loading rate of 3.09 kg TS/m3/day. The aeration unit provides a TCOD and NH3-N reduction of 94% and 91%, respectively. The rock filter achieves a TCOD, NH3-N and N03-N reduction of 32.8%, 26.8% and 68.4%, respectively. The annual cost for each of the treatment component is presented. It is very useful for the application of each treatment unit for the various needs of each pig farm.

Upgrading waste stabilization pond effluent by rock filters

Pilot-scale rock filters were constructed at the outlet of a large waste stabilization pond facility in Jordan. Their viability in upgrading the ponds' effluent was studied over a period of eleven months. This was done through studying the efficiency of four different types of locally available inexpensive materials placed in six filters and configured in three trains. The efficiency of each filter and the three combinations was evaluated. Results show that the filters can reduce the ponds' effluent content of TSS and BOD5 by 60%, TFCC by a maximum of 94% and T-P by 46%. This was achieved with a loading of 0.033-0.044 kgTSS/m3.d at an average temperature of 25 °C. Of the four media, the wadi gravel medium (3-23 cm) performed best. It was concluded that rock filters constitute a promising upgrading technique for pond effluent.

Upgrading pond effluents: an overview

A synopsis of the performance data and design concepts for methods used to upgrade wastewater stabilization pond effluents is presented. The following methods are discussed: intermittent sand filters, rock filters, microstrainers, constructed wetland systems, water hyacinths and duckweed, land application, hydrograph controlled release technique, and others. Cost information is given for the most commonly used methods.

Upgrading waste stabilization pond effluent by rock filters

Pilot-scale rock filters were constructed at the outlet of a large waste stabilization pond facility in Jordan. Their viability in upgrading the ponds' effluent was studied over a period of eleven months. This was done through studying the efficiency of four different types of locally available inexpensive materials placed in six filters and configured in three trains. The efficiency of each filter and the three combinations was evaluated. Results show that the filters can reduce the ponds' effluent content of TSS and BOD5 by 60%, TFCC by a maximum of 94% and T-P by 46%. This was achieved with a loading of 0.033–0.044 kgTSS/m3.d at an average temperature of 25 °C. Of the four media, the wadi gravel medium (3–23 cm) performed best. It was concluded that rock filters constitute a promising upgrading technique for pond effluent.

Upgrading pond effluents: An overview

A synopsis of the performance data and design concepts for methods used to upgrade wastewater stabilization pond effluents is presented. The following methods are discussed: intermittent sand filters, rock filters, microstrainers, constructed wetland systems, water hyacinths and duckweed, land application, hydrograph controlled release technique, and others. Cost information is given for the most commonly used methods.

A bench-scale rock-plant filter investigation

Three bench-scale rock filters containing 0.6 m of gravel were used in this investigation. Two of the filters were planted withSagittaria Iancifolia andScirpus validus, while the third filter was an unvegetated control filter. The wastewater directed through these systems was a synthetic mixture containing nutrient broth as the carbon source. An 80-day experiment was run on the filters using eight combinations of two flow rates and four influent biochemical oxygen demand (BOD5) concentrations, each combination remaining constant for ten days. These combinations resulted in BOD5 surface loadings from 4.63-30.96 g/day/m(2). From other studies of batch and continuous flow rock-plant filter systems, the first-order BOD5 reaction rate constant was found to decrease exponentially with detention time. In this study, however, little correlation was found between BOD5 loading rate and removal percentages, which averaged 69%, 57%, and 47% for theScirpus, Sagittaria, and control systems, respectively. This is probably due to the relatively small change in detention times studied and the short time period of each loading rate. Oxidation/reduction potential (ORP) and dissolved oxygen (DO) measurements within these systems indicated that no free oxygen was available at any depth. Total Kjeldahl nitrogen (TKN) removal was higher in the plant systems relative to the control, with theScirpus system achieving a higher overall removal than theSagittaria system.

Investigation of crushed rock filters for dam embankment : Chai Huat Khor; Heng Kee Woo J geotech engng div ASCEV115, N3, March 1989, P399–412

Investigation of crushed rock filters for dam embankment : Chai Huat Khor; Heng Kee Woo J geotech engng div ASCEV115, N3, March 1989, P399–412

Investigation of Crushed Rock Filters for Dam Embankment

A laboratory investigation of crushed rock filters is made to evaluate the filter criteria needed for the sandy clays and silts of tropical residual soils. The ability of a downstream filter to seal a concentrated leak through a dam core is assessed. Behavior of the broad, graded, sandy, impervious soils are dominated by the fines fraction. The filter criteria is well represented by D15 of filters and d85* of base soils. The derived criteria, D15/d85*⩽12 is conservative for judging the acceptability of crushed rock filters as protective filters. The filtering ability of graded filters is sensitive to the grading below the 15% size. The effects of remolding and saturation on the soil properties deserve consideration in the design of filters for the tropical residual soils. The Atterberg Limits of the soils have no significant influence on the needed protective filter.

A Critical Look at Rock Filters

Rock filters have been used for more than a decade to remove algal cells from the effluents of sewage lagoons. Previous studies have provided estimates of the serviceable life of rock filters as long as 43 and 55 years. Using mass balance considerations and realistic assumptions concerning the biodegradable fractions of solids and sludge solids-moisture compositions reveal that the serviceable life of these filters will be much shorter.

Submerged rock filter evaluation using an oxygen consumption criterion for closed recirculating systems

The supply of dissolved oxygen for the bacteria has been observed to be the principal factor limiting the carrying capacity of submerged rock filters used in high density recirculating culture systems. Oxygen concentrations in a submerged rock filter must not fall below 2 mg liter −1 if complete nitrification is to be assured. A mass balance on oxygen is used to develop relationships defining the rock volume and flow rates required for the nitrification beds used in blue crab ( Callinectus sapidus Rathbun) shedding systems. These relationships are used to examine the impact of various filter configurations on performance. Of the six designs evaluated, those employing recirculation with supplemental aeration are shown to be the most successful. Under the conditions imposed in this analysis, it was observed experimentally that 1 m 3 of 2 cm limestone could support bacterial consumption of 1·2 kg O 2 day −1 without limitations from other parameters. Elimination of oxygen limitation leads to filter failure by physical clogging or pH decline. Further improvements in carrying capacity can be realized by solids removal which is shown to reduce oxygen demand in a submerged rock filter tested on blue crabs by approximately 30%. The criterion developed is applicable to a wide variety of culture systems.

Automatic Determination of Filter Efficiency in Recirculating Systems

The efficiency of a biological filter is easily measured by determining the amount of oxygen consumed by bacteria biomass in the filter. Monitoring oxygen consumption under various loading regimes provides insight into the operational capabilities of a given filter configuration and provides a rational basis for designing intensive culture systems. A configuration for continuous monitoring of dissolved oxygen in submerged rock filters used in recirculating systems is presented. Reliability of dissolved oxygen measurements is assured by using a centralized probe location and a standards tank. Functional relationships, derived from the monitoring data, are used to assist in filter design.

Chemical addition for accelerated biological filter acclimation in closed blue crab shedding systems

Heavy loading of commercial crab shedding systems is a major problem at the beginning of the softshell crab season if the biological filters are not properly acclimated. Thus methods that can be used to accelerate filter acclimation in a commercial setting are desirable. Experimental shedding systems with submerged rock filters impacted by media size, commercial additives containing nitrifying bacteria, and chemical addition were examined. Filters acclimated with crabs took 35 days to adjust to base line water quality conditions. The filters demonstrated the ability to be increased to full design loading if acclimated with 25% of the shedding system design. Filter media size and addition of concentrated nitrifying bacteria did not have any significant effect on acclimation time of the nitrification beds. Addition of ammonia to simulate loading acclimated a biological filter without the use of animals, but did not shorten the acclimation time. The most promising avenue of research is the addition of ammonia and nitrite in combination to stimulate growth in both species of nitrifying bacteria simultaneously. Nitrite addition during startup of a biological filter reduced the acclimation period by 10 days (or 28%).

Well Screen Study Scrutinized

The author of this letter comments that the study described by Dennis Williams in “Modern Techniques in Well Design” (Journal AWWA, September 1985) appears to be restricted to a single manufacturer's product. He also questions statements concerning high efficiency wells in uncased rock aquifers, filter packs, specific discharge versus critical well radius, natural development, and trade‐off between length of screen and available drawdown. Kelly concludes by stating that Williams did not appear to draw on previous extensive research on wells. Williams responds by pointing out that the study included six commercially available screens. He states that the comment regarding high efficiency wells was made only as a comparison. Williams comments that the procedure of determining the minimum length of screen only enhances well design criteria by providing a minimum check point on screen length. He remarks that previous research was evaluated for the study, but he believes some of the conclusions did not reflect sound well design criteria.

Upgrading Lagoon Effluents with Rock Filters

Rock filtration is an effective, low-cost unit process for removing algae from effluents and correspondingly upgrading lagoon treatment. Sedimentation is the primary mechanism of algal removal within rock filter. A mathematical model of the sedimentation mechanism indicated that total suspendedsolids (TSS) removal efficiency is a function of the distribution of algal settling velocities, the hydraulic retention time, and the effective settling distance in the rock filter. Weekly average effluent biochemical oxygendemand (BOD\d5) and TSS from the Veneta, Ore, lagoon-rock filter treatment facility did not exceed 20 mg/L over a 1-yr study period. Settling rates of algae from the Veneta lagoon averaged about 0.05 m\dy. A linear relationship between TSS removal efficiency and hydraulic loading rate was demonstrated.