Search

The provision of technologies that can meet increasingly stringent wastewater discharge standards while reducing energy, operation, and maintenance costs is vital to government, local authorities, industry, and the public at large. The air suction flow biofilm reactor (ASF-BR) is a novel batch biofilm technology suitable for treating wastewaters from municipal, industrial, and agricultural sources. This paper presents an investigation into the performance of a laboratory-scale ASF-BR in treating municipal-strength wastewater over two operational periods-Phase 1 and Phase 2. Phase 1 concentrated on organic carbon removal and nitrification, whereas Phase 2 included an anoxic step to achieve denitrification. The operation of the unit was also investigated by monitoring organic carbon and nitrogen in the reactors during a number of treatment cycles. In Phases 1 and 2 (29 and 124 days of steady-state operation, respectively) of this laboratory study, using a municipal-strength synthetic wastewater, the average influent total chemical oxygen demand () was 288 and , whereas the average influent filtered COD () was 127 and , respectively. The average removal rates were 92 and 79% during Phases 1 and 2, respectively. Average nitrogen removals during Phases 1 and 2 of greater than 95% ammonium nitrogen () were achieved. By reducing the number of pumping cycles during the aerobic step, the overall energy consumed was reduced by 37.5% during Phase 2 while achieving similar results. On the basis of these positive initial results, a pilot-scale reactor has been constructed at a local wastewater-treatment facility, and commissioning of the unit is currently underway. [ABSTRACT FROM AUTHOR]

A novel technology suitable for centralised and decentralised wastewater treatment has been developed, extensively tested at laboratory-scale, and trialled at a number of sites for populations ranging from 15 to 400 population equivalents (PE). The two-reactor-tank pumped flow biofilm reactor (PFBR) is characterised by: (i) its simple construction; (ii) its ease of operation and maintenance; (iii) low operating costs; (iv) low sludge production; and (v) comprising no moving parts or compressors, other than hydraulic pumps. By operating the system in a sequencing batch biofilm reactor (SBBR) mode, the following treatment can be achieved: 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and total suspended solids (TSS) reduction; nitrification and denitrification. During a 100-day full-scale plant study treating municipal wastewater and operating at 165 PE and 200 PE (Experiments 1 and 2, respectively), maximum average removals of 94% BOD5, 86% TSS and 80% ammonium-nitrogen (NH4-N) were achieved. During the latter part of Experiment 2, effluent concentrations averaged: 14 mg BOD5/l; 32 mg CODfiltered/l; 14 mg TSS/l; 4.4 mg NH4-N/l; and 4.0 mg NO3-N/l (nitrate-nitrogen). The average energy consumption was 0.46-0.63 kWh/m3treated or 1.25-1.76 kWh/kg BOD5 removed. No maintenance was required during these experiments. The PFBR technology offers a low energy, minimal maintenance technology for the treatment of municipal wastewater. [ABSTRACT FROM AUTHOR]

The objective of this study was to apply hydraulic and chemical oxygen demand (COD) loading rates at the upper limits of the design criteria for buried sand filters to test the sand filter depth design criteria. Over a 274-day study duration, synthetic effluent with a strength of domestic wastewater was intermittently dosed onto two sand filters of 0.2 m diameter, with depths of 0.3 and 0.4 m. Hydraulic and organic carbon loading rates of 105 L m-2 d-1 and 40 g COD m-2 d-1, respectively, were applied to the filters. The filters did not clog and had good effluent removal capabilities for 274 and 190 days, respectively. However, the 0.3 m-deep filter did experience a reduced performance towards the end of the study period. In the 0.3 and 0.4 m-deep filters, the effluent COD and SS concentrations were less than 86 and 31 mg L-1, respectively, and nitrification was nearly complete in both these columns. Ortho-phosphorus (PO4-P) removal in fine sand and laterite 'upflow' filters, receiving effluent from the 0.3 m-deep filter, was 10% and 44%, respectively [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the performance of intermittently loaded, 150 mm-diameter stratified filter columns of 2 depths (0.65 and 0.375 m) comprising different media - sand, crushed glass and soil - in polishing the effluent from a laboratory horizontal flow biofilm reactor (HFBR) treating synthetic domestic-strength wastewater. The HFBR has been successfully used to remove organic carbon and ammonium-nitrogen (NH4-N) from domestic wastewater. In this treatment method, wastewater is allowed to flow over and back along a stack of polyvinyl chloride (PVC) sheets. Biofilms on the sheets reduce organic carbon, suspended matter, and nutrients in the wastewater, but to achieve the quality of a septic tank system, additional treatment is required. In all filters, at a hydraulic loading rate of 100 L m-2 d-1, 40-65% of chemical oxygen demand (COD) and practically 100% of total suspended solids (TSS) were removed, nitrification was complete, and bacterial numbers were reduced by over 80%, with best removals achieved in the soil filters (93%). Soil polishing filters with the depth of 0.65 m performed best in terms of organic carbon, total nitrogen (Tot-N) and bacterial removal. Data from this preliminary study are useful in the design of treatment systems to polish secondary wastewaters with similar water quality characteristics. [ABSTRACT FROM AUTHOR]

The article discusses the potential for ochre to sequester phosphorus in an environmentally sustainable fashion. Ochre deriving from coal mine drainage sites in the United Kingdom displays a high phosphorus retention capacity without highly mobilizing metals, indicating that it can potentially adsorb phosphorus from agricultural wastewaters and be used as a fertilizer. A study focused upon untreated acid mine drainage from an abandoned copper-sulfur mine in a catchment of southeast Ireland. Ochre was mixed with phosphorus-amended water in batch experiments and a maximum adsorption capacity was calculated from the Langmuir equation.

In Ireland, land-spreading is the most widely used method for treating dairy wastewaters. This can be labour intensive and can cause, in some cases, nitrate contamination of groundwater. In this study a simple pilot-scale horizontal flow biofilm reactor (HFBR) with a step-feed was developed and tested at a dairy farm site in County Offaly, Ireland for partial remediation of this soiled water prior to landspreading. During the 122-day study, the top surface plan area (TSPA) hydraulic loading rate was 50 L/m2/day. Influent concentrations averaged: 2904.2mg total chemical oxygen demand (COD)/L, 950mg 5-day biochemical oxygen demand (BOD5)/L and 177.9mg total nitrogen (TN)/L. Between Days 1 and 45 frequent ambient temperatures below 4°C inhibited the build-up of biomass resulting in low removals. From Day 45 the HFBR unit removed 74.9% total COD and 69.6% BOD5, equivalent to TSPA removals of 108.8 g COD/m2/day and 33.1 gBOD5/m2/day. On Sheet 29, by the end of the study, the NH4—N had reduced from 123.1 mg/L in the influent to 37.0 mg/L. TN removal in the reactor averaged 56.0% equating to a TSPA removal rate of 5.0 g TN/m2/day. The HFBR does not require any mechanical aeration, was simple and inexpensive to construct and can provide a robust and economical alternative for the remediation of agricultural soiled water before landspreading. [ABSTRACT FROM AUTHOR]

A novel laboratory bench-scale sequencing batch biofilm reactor (SBBR) system was developed for the treatment of synthetic domestic strength wastewater, comprising two side-by-side 18 l reactor tanks, each containing a plastic biofilm media module. Aerobic and anoxic conditions in the biofilms were effected by intermittent alternate pumping of wastewater between the two reactors. With a media surface area loading rate of 4.2 g chemical oxygen demand (COD)/m².d, the average influent COD, total nitrogen (TN) and ammonium-nitrogen (NH4-N) concentrations of 1021 mg/l, 97 mg/l and 54 mg/l, respectively, reduced to average effluent concentrations of 72mg COD/l, 17.8mg TN/l, and 5.5mg NH4-N /l. Using a similar alternating biofilm exposure arrangement, a 16 person equivalent pilot (PE) plant was constructed at a local village treatment works to remove organic carbon from highly variable settled municipal wastewater and comprised two reactors, one positioned above the other, each containing a module of cross-flow plastic media with a surface area of 100m2. Two different pumping sequences (PS) in the aerobic phase were examined where the average influent COD concentrations were 220 and 237 mg/l for PS1 and PS2, respectively, and the final average effluent COD was consistently less than 125 mg/l - the European Urban Wastewater Treatment Directive limit - with the best performance occurring in PS1. Nitrification was evident during both PS1 and PS2 studies. A 300 PE package treatment plant was designed based on the bench-scale and pilot-scale studies, located at a local wastewater treatment works and treated municipal influent with average COD, suspended solids (SS) and TN concentrations of 295, 183 and 15 mg/l, respectively resulting in average effluent concentrations of 67mg COD/l, 17mg SS/l and 9mg TN/l. The SBBR systems performed well, and were simple to construct and operate. [ABSTRACT FROM AUTHOR]

A stratified sand filter column, operated in recirculation mode and treating synthetic effluent resembling high-strength dairy wastewaters was studied over a 342-d duration. The aim of this paper was to examine the organic, total suspended solids (TSS) and nutrient removal rates of the sand filter, operated in recirculation mode, under incrementally increasing hydraulic and organic loading rates and to propose a field filter-sizing criterion. Best performance was obtained at a system hydraulic loading rate of 10Lm−2 d−1; a higher system hydraulic loading rate (of 13. 4Lm−2 d−1) caused surface ponding. The system hydraulic loading rate of 10Lm−2 d−1 gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3. 7, and 2. 1gm−2 d−1, respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO3-N concentration of 42mgL−1 (accounting for an 86% reduction in total nitrogen (Tot-N)). As the proportional surface area requirement for the sand filter described in this study is less than the recommended surface area requirement of a free-water surface (FWS) wetland treating an effluent of similar quality, it could provide an economic and sustainable alternative to conventional wetland treatment. [Copyright &y& Elsevier]

The aim of this study was to develop a simple biological system that would be suitable for the treatment of dairy parlour wash waters. A novel horizontal-flow biofilm system was designed, constructed and tested in the laboratory for organic carbon and nitrogen removal from a synthetic dairy wastewater with average filtered chemical oxygen demand (COD f ) of 2947.7 mg/L and total nitrogen (TN) of 295.5 mg/L. The novel biofilm system consisted of two reactor units one on top of the other. Each reactor unit comprised a stack of horizontal plastic sheets placed above one another that were supported and separated by vertical plastic cone frustums, which were formed in the sheets during manufacture. The wastewater was pumped onto the top sheet of the top reactor unit at hourly intervals for a 5-minute period and flowed over and back along alternate sheets down through the 2 units. The top unit had 8 plastic sheets and 25 mm high frustums to cater for heavy biofilm growth, and the bottom unit had 17 sheets and 11 mm high frustums for thinner biofilm growth. The organic loading of 57 g COD f /m 2 ·d—based on the plan area of the system—was applied to the top reactor unit. When the reactor process reached pseudo steady-state, about 96% COD f , 71% TN and 100% ammonium nitrogen were removed. Low solids production occurred. The system was simple and easy to construct and operate. [ABSTRACT FROM AUTHOR]

Peat is an abundant resource in Ireland and has the capacity to be used in low-cost, low-maintenance wastewater treatment systems for single houses. In this study four fibrous peat columns, of varying depths were constructed and tested in the laboratory for their capacity to remove contaminants from domestic-strength synthetic wastewater. The four filters had peat depths of 0.3 m, 0.6 m, 0.9 m and 1.2 m. During the 360 day study the filters were intermittently loaded with domestic strength synthetic wastewater at a hydraulic loading rate of 180 l/m 2 ċd. Hydrographs and residence times for each filter were examined as was their ability to remove impurities from the wastewater. Removal of 5-day biochemical oxygen demand (BOD 5 ) and total chemical oxygen demand (COD t ) were ≥96% and 84%, respectively, in all filters with almost complete nitrification (≥99%) being recorded for each filter. The removal of total suspended solids (TSS) was excellent at ≥94% and no clogging was recorded on any filter during the study. For the 0.6 m, 0.9 m and 1.2 m deep filters, total viable counts (TVC) were less than EU surface water directive limits for Class A2 potable water sources. The systems were cheap to construct and very easy to maintain. [ABSTRACT FROM AUTHOR]

Abstract: A laboratory continuous feed biofilm reactor, comprising a bulk fluid reactor, a biofilm plastic module, a feed tank, and pneumatic devices and controls, was operated for a total period of 257 days, including seeding time, to treat domestic-strength synthetic wastewater under increasing ammonium nitrogen () loading rates, ranging from 0.17±0.01 (0.71±0.06gm−2 d−1) to 0.70±0.02kgm−3 d−1 (2.9±0.1gm−2 d−1). The biofilm plastic module was moved vertically in and out of the wastewater in continuous cycles. The maximum removal rate was reached during the maximum loading phase, when a loading rate of 0.70±0.02kgm−3 d−1 (2.9±0.1gm−2 d−1) was applied to the system. During this loading period, the average removal rate was 0.30±0.10kgm−3 d−1 (1.30±0.40gm−2 d−1). [Copyright &y& Elsevier]

Abstract: The design and operation of wastewater treatment systems for single houses, farms, hotels, leisure centres, small communities and small businesses are a challenge to wastewater engineers. In this paper, a pilot-scale system comprising a vertically moving biofilm reactor (VMBR) followed by a stratified sand filter was constructed and its performance was evaluated. The vertically moving biofilm reactor was operated as a sequencing batch biofilm reactor (VMSBBR). The results show that the VMSBBR unit efficiently removed 94.8% of the filtered chemical oxygen demand (CODf) from a synthetic wastewater with the influent CODf of 1096±425mg/l, leaving 45±16mg/l CODf in the effluent, at an organic loading rate of 0.9kg COD/m3 day. After the system had been operated for 133 days, the removal efficiency of orthophosphate (PO4-P) reached 90%. A sand filter polished the effluent from the VMSBBR unit and reduced suspended solids (SS) to 4.4mg/l and total bacterial by 3log10 units. The advantages of the treatment system studied for small wastewater flows include: (1) simple operation and maintenance—sludge was only disposed of once on Day 206 during the 7.5-month study period; clogging, which often happens in other attached-growth biofilm systems, did not take place; (2) efficient removal of COD and phosphorus; and (3) low-energy consumption—the electricity consumption was 4.6kWh/population equivalent (p.e.) year, or 0.6kWh/m3 wastewater treated or 0.6kWh/kg COD removed. [Copyright &y& Elsevier]

The pilot plant study comprised the construction and monitoring of a new vertically moving biofilm system (VMBS) for treating municipal wastewater. The system operated on site for 11 months. The biofilm module in this system, consisting of high surface area plastic media, was vertically and repeatedly moved in cycles up into the air and down into the wastewater. The vertical movement of the biofilm module supplied sufficient oxygen for the removal of the organic carbon in the wastewater. The overall physical oxygen transfer coefficient (Kla) measured at the cycle speed of six cycles per minute was 2.53 per hour. During the pilot study, dissolved oxygen (DO) concentrations in the bulk fluid were in the range of 1.5–5 mg/l. It was found that the areal removal rate of filtered chemical oxygen demand (COD) was up to 35 g COD/(m2 day) and the bulk fluid volumetric filtered COD removal rate was 2.62 kg COD/(m3 day). The field experiment showed that clogging commonly found in other biofilm systems did not occur in this system. The power consumption was in the range of 0.09–0.25 kWh/m3 wastewater flow, 0.40–2.19 kWh/kg COD removal and 1.24–1.74 kWh/kg BOD removal. The new biofilm system offers potential for reduced reactor volumes, energy saving, simple construction and easy operation. [Copyright &y& Elsevier]

Four moving-medium biofilm reactors treating wastewater were reviewed in this paper: the rotating biological contactor (RBC), the moving bed biofilm reactor (MBBR), the vertically moving biofilm reactor (VMBR) and the fluidized-bed reactor (FBR). The RBC process has been applied widely. MBBR is a good process for upgrading current wastewater treatment systems. VMBR is suitable for treating small wastewater flows. FBR can maximize pollutant removals and minimize sludge production. [ABSTRACT FROM AUTHOR]

Discusses the efficacy of an experimental biofilm system for the removal of nitrogen from synthetic wastewater. Types of reactors included in the system; Experiments carried out in the different reactors; Data from experiments; View that the experimental biofilm system was simple to construct and operate.

Abstract: A horizontal flow biofilm reactor (HFBR) designed for the treatment of synthetic wastewater (SWW) was studied to examine the spatial distribution and dynamics of nitrogen transformation processes. Detailed analyses of bulk water and biomass samples, giving substrate and proportions of ammonia oxidising bacteria (AOB) and nitrite oxidising bacteria (NOB) gradients in the HFBR, were carried out using chemical analyses, sensor rate measurements and molecular techniques. Based on these results, proposals for the design of HFBR systems are presented. The HFBR comprised a stack of 60 polystyrene sheets with 10-mm deep frustums. SWW was intermittently dosed at two points, Sheets 1 and 38, in a 2 to 1 volume ratio respectively. Removals of 85.7% COD, 97.4% 5-day biochemical oxygen demand (BOD5) and 61.7% TN were recorded during the study. In the nitrification zones of the HFBR, which were separated by a step-feed zone, little variation in nitrification activity was found, despite decreasing in situ ammonia concentrations. The results further indicate significant simultaneous nitrification and denitrification (SND) activity in the nitrifying zones of the HFBR. Sensor measurements showed a linear increase in potential nitrification rates at temperatures between 7 and 16°C, and similar rates of nitrification were measured at concentrations between 1 and 20mg NH4-N/l. These results can be used to optimise HFBR reactor design. The HFBR technology could provide an alternative, low maintenance, economically efficient system for carbon and nitrogen removal for low flow wastewater discharges. [Copyright &y& Elsevier]

Abstract: The performance of a 10L sequencing batch reactor (SBR) treating slaughterhouse wastewater was examined at ambient temperature. The influent wastewater comprised 4672±952mg chemical oxygen demand (COD)/L, 356±46mg total nitrogen (TN)/L and 29±10mg total phosphorus (TP)/L. The duration of a complete cycle was 8h and comprised four phases: fill (7min), react (393min), settle (30min) and draw/idle (50min). During the react phase, the reactor was intermittently aerated with an air supply of 0.8L/min four times at 50-min intervals, 50min each time. At an influent organic loading rate of 1.2g COD/(Ld), average effluent concentrations of COD, TN and TP were 150mg/L, 15mg/L and 0.8mg/L, respectively. This represented COD, TN and TP removals of 96%, 96% and 99%, respectively. Phase studies show that biological phosphorus uptake occurred in the first aeration period and nitrogen removal took place in the following reaction time by means of partial nitrification and denitrification. The nitrogen balance analysis indicates that denitrification and biomass synthesis contributed to 66% and 34% of TN removed, respectively. [Copyright &y& Elsevier]