Backwash Sludge Research Articles

Characteristics and utilization of biologically aerated filter backwashed sludge

An investigation on the characteristics of biologically aerated filter (BAF) backwashed sludge and its biological flocculation performance were carried out by a bench-scale experiment. The bio-flocculation ability of backwashed sludge, the combined coagulation efficiency of chemical coagulant FeCl3, Al2 (SO4)3 and biological sludge, and the properties of the settled sludge produced in the pretreatment process were investigated, respectively. The results showed that the backwashed sludge had preferable biological flocculation performance, biological activity and a complex biota. It was observed that the treatment efficiency would be improved greatly whether by using the backwashed sludge or combined using chemical coagulant and biological sludge in the enhanced domestic wastewater pretreatment process. The removal efficiency of COD, SS and TP were improved about 40%, 40% and 75% than that of the comparisons, respectively, when backwashed sludge dosage was 76 mg and FeCl3 dosage was 30 mg/L domestic wastewater. A promising property of settling and dewatering of the secondary sludge produced in the bio-chemically enhanced coagulation process was also revealed.

Comparing cost and process performance of activated sludge (AS) and biological aerated filters (BAF) over ten years of full sale operation

In the early 1990s, the Wastewater Treatment Plant (WWTP) of Frederikshavn, Denmark, was extended to meet new requirements for nutrient removal (8 mg/L TN, 1.5 mg TP/L) as well as to increase its average daily flow to 16,500 m(3)/d (4.5 MGD). As the most economical upgrade of the existing activated sludge (AS) plant, a parallel biological aerated filter (BAF) was selected, and started up in 1995. Running two full scale processes in parallel for over ten years on the same wastewater and treatment objectives enabled a direct comparison in relation to operating performance, costs and experience. Common pretreatment consists of screening, an aerated grit and grease removal and three primary settlers with chemical addition. The effluent is then pumped to the two parallel biological treatment stages, AS with recirculation and an upflow BAF with floating media. The wastewater is a mixture of industrial and domestic wastewater, with a dominant discharge of fish processing effluent which can amount to 50% of the flow. The maximum hydraulic load on the pretreatment section as a whole is 1,530 m(3)/h. Approximately 60% of the sewer system is combined with a total of 32 overflow structures. To avoid the direct discharge of combined sewer overflows into the receiving waters, the total hydraulic wet weather capacity of the plant is increased to 4,330 m(3)/h, or 6 times average flow. During rain, some of the raw sewage can be directed through a stormwater bypass to the BAF, which can be modified in its operation to accommodate various treatment needs: either using simultaneous nitrification/denitrification in all filters with recirculation introducing bottom aeration with full nitrification in some filters for storm treatment and/or post-denitrification in one filter. After treatment, the wastewater is discharged to the Baltic Sea through a 500 m outfall. The BAF backwash sludge, approximately 1,900 m(3) per 24 h in dry weather, is redirected to the AS plant. Primary settler sludge and the combined biosolids from the AS plant are anaerobically digested, with methane gas being used for generation of heat and power. On-line measurements for the parameters NO3, NO2, NH4, temperature as well as dissolved oxygen (DO) are used for control of aeration and external carbon source (methanol). Dosing of flocculants for P-removal is carried out based on laboratory analysis and jar tests. This paper discusses the experience gained from the plant operation during the last ten years, compiling comparative performance and cost data of the two processes, as well as their optimisation.

Long Term Full Scale Comparison of Activated Sludge (AS) with Biological Aerated Filter (BAF)

The Wastewater Treatment Plant (WWTP) of Frederikshavn, Denmark, was extended in the early nineties to increase its average daily flow to 4,5 MGD (16,500 m³/d) and meet new requirements for nutrient removal (8 mg/l TN, 1,5 mg TP/l). A parallel biological aerated filter (BAF) was the selected as the most economical upgrade of the existing activated sludge plant (AS), and started up in 1995. Running two full scale processes in parallel on the same wastewater and treatment objectives for over ten years enabled a direct comparison in relation to operating performance, costs and experience. After screening, a combined grit and grease chamber and 3 primary settlers, the effluent is pumped to the bio-treatment, consisting of AS with recirculation (Modified Lutzack-Ettinger – MLE) and an upflow BAF with floating media. The wastewater is a mixture of industrial and domestic wastewater, with a dominant discharge of fish processing effluent which can amount to 50 % of the flow. The maximum hydraulic load on the pretreatment section as a whole is 10 MGD (1,530 m3/h) . Approx. 60% of the sewer system is combined with a total of 32 overflow structures. To avoid the direct discharge of combined sewer overflows into the receiving waters, the total hydraulic capacity of the plant is increased during rain to 27 mgd (4,330 m³/hour) or 6 times average flow. During rain, this is achieved by directing some of the raw sewage through a stormwater bypass to the BAF and switching all six BAF to full nitrification. After final biotreatment, the wastewater is conveyed through a 500 m sea outfall. The operation of the BAF can be modified to accommodate various treatment needs: - either using simultaneous nitrification/denitrification in all filters with recirculation - bottom aeration with full nitrification in all filters for stormwater treatment - or post-denitrification in 1 filter. On-line measurements for the parameters NO3, NO2, NH4 and PO4 as well as dissolved oxygen (DO) are used for control of aeration and for addition of flocculants for P-removal and external carbon source (methanol). The BAF backwash sludge, approx. 0.5 MGD (1.900 m³/d) once every 24 h in dry weather, is redirected to the AS plant. Sludge from primary settlers and the combined biosolids from the AS plant are anaerobically digested, with methane gas being used for generation of heat and power. This paper discusses the experience gained from the plant operation during the last ten years, compiling comparative performance and cost data of the two processes.

Rapid start-up of biofilters for removal of ammonium, iron and manganese from ground water

Research Article| November 01 2004 Rapid start-up of biofilters for removal of ammonium, iron and manganese from ground water Tamara Štembal; Tamara Štembal 1University of Zagreb, Faculty of Chemical Engineering and Technology, Marulićev trg 19, HR-10000 Zagreb, Croatia Search for other works by this author on: This Site PubMed Google Scholar Marinko Markić; Marinko Markić 1University of Zagreb, Faculty of Chemical Engineering and Technology, Marulićev trg 19, HR-10000 Zagreb, Croatia Search for other works by this author on: This Site PubMed Google Scholar Felicita Briški; Felicita Briški 1University of Zagreb, Faculty of Chemical Engineering and Technology, Marulićev trg 19, HR-10000 Zagreb, Croatia Search for other works by this author on: This Site PubMed Google Scholar Laszlo Sipos Laszlo Sipos 1University of Zagreb, Faculty of Chemical Engineering and Technology, Marulićev trg 19, HR-10000 Zagreb, Croatia E-mail: laszlo.sipos@zg.htnet.hr Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2004) 53 (7): 509–518. https://doi.org/10.2166/aqua.2004.0040 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Twitter LinkedIn Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll JournalsThis Journal Search Advanced Search Citation Tamara Štembal, Marinko Markić, Felicita Briški, Laszlo Sipos; Rapid start-up of biofilters for removal of ammonium, iron and manganese from ground water. Journal of Water Supply: Research and Technology-Aqua 1 November 2004; 53 (7): 509–518. doi: https://doi.org/10.2166/aqua.2004.0040 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Spontaneous formation of the active layer in biological filters for removal of iron, manganese and ammonium from ground water usually takes a few months. Inoculation of the new filters with well-established filter material is a common start-up procedure. An operational approach for inoculation of new filters using backwash sludge, instead of filter material, is elaborated here. The sludge is obtained from an already well-established biofilter used for removal of iron, manganese and ammonium. This procedure reduces the start-up time of the filters to 2 weeks only. The successful application of the described start-up procedure was demonstrated in two new plants treating ground water of different qualities. In one of these plants, the ground water contained increased concentrations of iron, manganese and ammonium, and in the other, only manganese concentration was increased. ammonium removal, biofilters, ground water, iron removal, manganese removal, start-up procedure This content is only available as a PDF. © IWA Publishing 2004 You do not currently have access to this content.

Water treatment plant residuals management

Water treatment plants produce enormous amounts of sludge. Due to increased environmental concern, recently, there is considerable amount of pressure on the water authorities for the safe disposal of the sludge. Currently, the most acceptable form of disposal is sanitary landfilling, which requires sludge to be dewatered to 20-40% of solids. One of the most commonly used dewatering techniques is sand drying beds. This process is popular because of its reliability, ease of use and low cost. However, one of the basic concerns with this process is the requirement of a large area of land. This could be overcome by chemical conditioning of the sludge, which can accelerate the dewatering rate substantially. At this stage, however, there are no guidelines for the design of the sand drying beds for treating chemically conditioned sludges. This study is conducted to investigate the design and performance of sand drying beds for treating chemically conditioned water treatment plant (WTP) sludge. Experiments are conducted using laboratory scale sand drainage columns. The results indicate that the drainage rates, after adding polymer, increased by 9 times for clarifier sludge and 20-25 times for filter backwash sludge. Thus, the land area requirement for sand drainage bed can be drastically reduced through polymer addition. Optimal dose of polymer is found to be between 3 and 6 kg/t of dry solids, with dilute sludges requiring high dosages. The cake solids concentration increased from 3 to 12% as the polymer dose increased from 0 to 16 kg/t of dry solids. The variation of drainage rates and cake solids with solids/hydraulic loading rates are found to vary depending on the type of sludges and polymers. The filtrate quality is found to be independent of polymer dose and solids loading rates.

Water treatment plant residuals management

Water treatment plants produce enormous amounts of sludge. Due to increased environmental concern, recently, there is considerable amount of pressure on the water authorities for the safe disposal of the sludge. Currently, the most acceptable form of disposal is sanitary landfilling, which requires sludge to be dewatered to 20.40% of solids. One of the most commonly used dewatering techniques is sand drying beds. This process is popular because of its reliability, ease of use and low cost. However, one of the basic concerns with this process is the requirement of a large area of land. This could be overcome by chemical conditioning of the sludge, which can accelerate the dewatering rate substantially. At this stage, however, there are no guidelines for the design of the sand drying beds for treating chemically conditioned sludges.This study is conducted to investigate the design and performance of sand drying beds for treating chemically conditioned water treatment plant (WTP) sludge. Experiments are conducted using laboratory scale sand drainage columns. The results indicate that the drainage rates, after adding polymer, increased by 9 times for clarifier sludge and 20-25 times for filter backwash sludge. Thus, the land area requirement for sand drainage bed can be drastically reduced through polymer addition. Optimal dose of polymer is found to be between 3 and 6 kg/t of dry solids, with dilute sludges requiring high dosages. The cake solids concentration increased from 3 to 12% as the polymer dose increased from 0 to 16 kgA of dry solids. The variation of drainage rates and cake solids with solids/hydraulic loading rates are found to vary depending on the type of sludges and polymers. The filtrate quality is found to be independent of polymer dose and solids loading rates.