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In this study, in situ hybrid sand filters were designed to remove dissolved and suspended contaminants from eutrophic pond. Currently, there are no attempts made to eradicate dissolved as well as suspended contaminants from eutrophic water system in a single step. Monitoring studies revealed that examined pond contain high chlorophyll-acontent (101.8 μg L−1), turbidity (39.5 NTU) and total dissolved solids concentration (0.04 g L−1). Samples were further exposed to extensive water quality analysis, which include examining physicochemical parameters (pH, conductivity, total dissolved solids, salinity, turbidity and chlorophyll-a), metals (Na, K, Ca, Mg, Al, Fe, Cu, Cd, Pb, Zn, Cr, and Ni) and anions (NO3, NO2, PO4, SO4, Cl, F and Br). To tackle pollutants, filtration system was designed to comprise of several components including fine sand, coarse sand/sorbent mix and gravel from top to bottom loaded in fiberglass tanks. All the filters (activated carbon,Sargassumand zeolite) completely removed algal biomass and showed potential to decrease pH during entire operational period of 20 h at 120 L h−1. To examine the efficiency of filters in adverse conditions, the pond water was spiked with heavy metals (Cu, Cd, Pb, Zn, Cr, and Ni). Of the different filter systems,Sargassum-loaded filter performed exceedingly well with concentrations of heavy metals never exceeded the Environmental protection agency regulations for freshwater limits during total operational period. The total uptake capacities at the end of the fifth event were 24.9, 20.5, 0.58, 5.2, 0.091 and 2.8 mg/kg for Cr, Ni, Cu, Zn, Cd and Pb, respectively. [ABSTRACT FROM AUTHOR]

Evolution of filamentous bacteria in two full-scale experimental MBR systems (microfiltration and ultrafiltration) was studied during two years. Sludge Retention Time (SRT) and Hydraulic Retention Time (HRT) were modified and acted as variables, together with temperature and variation in loading. With SRT values between 20 and 35 d and HRT between 31 and 40 h, both MBR systems presented a high density of filamentous bacteria, according to the Filamentous Index (FI) and Simplified Technique of Filamentous Count (STFC). Highest density was achieved when contaminant loads were high and temperature was low. However, the elevated presence of filamentous bacteria did not affect the quality of effluent or the permeability of the membranes. Nocardioform bacteria showed a high degree of adaptation to the characteristics of the system. Predominance of Nocardioforms gave rise to isolated episodes of massive growth at temperatures between 15 and 20°C, which in turn caused episodes of intense foaming whose most significant consequence was a loss in biomass, leading to a slight increase in transmembrane pressure. In the light of these results, FI and STFC should not be considered as suitable tools for predicting operational problems deriving from filamentous bacteria in MBR systems, which could be prevented through identification. [ABSTRACT FROM AUTHOR]

Higher concentrations of ammonium (NH4–N) and iron (Fe) than a standard for drinking are typical characteristics of groundwater in the study area. To remove NH4–N and Fe, the drinking water supply system in this study consists of a series of treatment units (i.e., aeration and sedimentation, filtration, and chlorination); however, NH4−N in treated water is higher than a standard for drinking (i.e., <1.5 mg NH4–N/L). The objective of this study, therefore, is to develop an attached growth system containing a fiber carrier for reducing NH4–N concentration within a safe level in the treated water. To avoid the need of air supply for nitrification, groundwater was continuously dripped through the reactor. It made the system simple operation and energy efficient. Effects of reactor design (reactor length and carrier area) were studied to achieve a high NH4−N removal efficiency. In accordance with raw groundwater characteristics in the area, effects of low inorganic carbon (IC) and phosphate (PO4–P) and high Fe on the removal efficiency were also investigated. The results showed a significant increase in NH4–N removal efficiency with reactor length and carrier area. A low IC and PO4–P had no effect on NH4–N removal, whereas a high Fe decreased the efficiency significantly. The first 550 days operation of a pilot−scale reactor installed in the drinking water supply system showed a gradual increase in the efficiency, reaching to 95−100%, and stability in the performance even with increased flow rate from 210 to 860 L/day. The high efficiency of the present work was indicated because only less than 1 mg of NH4−N/L was left over in the treated water. [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]

In this paper, two laboratory-scale simulated reed beds were investigated for the purpose of assessing the feasibility and effectiveness of using dewatered alum sludge as a possible substrate for wastewater treatment reed bed systems. One horizontal subsurface flow setup and one vertical flow setup were used. The horizontal flow system was planted with Phragmites australis while the vertical flow system was left unplanted. Thus, the latter was more akin to a sand filter system, but was examined with the potential use as a planted vertical reed bed system. The influent source used was farmyard wastewater. It is expected that the present study will provide the basis for long-term and large-scale trials in realizing the concept of integrating "waste" into treatment processes. Results obtained so far have shown that the dewatered alum sludge holds great promise as a low-cost resource media for use in reed bed treatment systems. Appreciable and stable performance was obtained during the continuous operation at high hydraulic, organic and phosphorus loadings. In particular, both wetlands achieved over 90% phosphorus removal, reflecting the significant advantage of this novel approach over conventional reed bed treatment systems. However, extensive research into possible surface clogging and possible release of some substances from the sludge to the treated effluent is necessary to ensure reliability of the system. This will help to make the alum sludge-based reed bed environmentally and economically justifiable. [ABSTRACT FROM AUTHOR]

Membrane microfiltration (MF) or ultrafiltration (UF) systems of activated sludge is crucial part of a bioreactor process used in municipal wastewater treatment. In this study, both cylindrical and flat sheet ceramic membranes were used to treat municipal wastewaters. The effects of removing water turbidity and coliform bacteria from an artificial wastewater were studied by performing batch experiments by MF and ultraviolet (UV) photolysis of 254 nm wavelength. It was shown that the microfiltration had a high effect of suspended solid removal. However, the effect of bacteria removal was limited so that the rate of cfu removal was approximately 61%. Combined consecutive processes in the treatment (MF/UV and UV/MF) confirmed that a specific porosity of the ceramic filter for bacteria removal was required. The continuous membrane bioreactor (MBR) tests performed by using a MF membrane with the pore size of 0.2 μ m showed that particulate matter and microorganisms found in municipal wastewater could be effectively removed. Turbidity was decreased from 4.50 to 0.05 NTU, with a removal efficiency of greater than 98%. The permeate total suspended solid (TSS) content for the whole run was below 5 mgL- 1. The density of total coliforms was decreased more than four orders of magnitude (from around 1× 105 mL- 1 to less than 5 mL- 1 in the effluent). [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the secondary and tertiary treatment of low-strength domestic wastewater with submerged biological filters (BFs). The experiments were carried out with a two-stage pilot plant consisting of two subsequent filter columns. In the first aerated reactor, the removal of carbon and nitrification was accomplished (secondary nitrification); while, in the second anoxic reactor a post-denitrification process with methanol as external carbon source was performed. During the 3 months of experimental period, in average terms, Total Suspended Solids (TSS) concentrations of 156 mg/L were reduced to 5 mg/L; Chemical Oxygen Demand (COD) concentrations of 179 mg/L were reduced to 43 mg/L. In the secondary nitrification, mean influent NH4+ concentrations of 6.1 mg/L were reduced to average values of 1.8 mg/L. During the post-denitrification, mean influent NO3-. concentrations of 12.0 mg/L were reduced to average values of 6.1 mg/L. The overall process produced a backwashing effluent with an average concentration of about 175 mg/L of TSS. [ABSTRACT FROM AUTHOR]

The objective of this research was to monitor and assess the impact of reclaimed wastewater irrigation on water quality, soil, and rice cultivation by comparing the effects of various wastewater treatment levels on the growth and yield of rice. A randomized complete block design was used for the application methods of the wastewater effluents to paddy rice, with five treatments and six replications. The treatments were: control with groundwater irrigation (GW); irrigation with polluted water form a nearby stream (SW); and three treatments of reclaimed wastewater irrigation at different treatment levels. The three levels of wastewater treatments included wastewater effluents: (i) directly from the wastewater plant (WW); (ii) after passing through a sand filter (WSF); and (iii) after passing a sand filter followed by an ultraviolet treatment (WSFUV). Each plot was 4 × 4 m and was planted with rice (Oryza sativa L. ) in 2002 and 2003. The results indicated that irrigation of rice with reclaimed municipal wastewater caused no adverse effects on the growth and yield of rice. The chemical compositions of the rice from all plots were within the normal ranges of brown rice quality in Korea. No adverse effects were observed on chemical concentrations including the heavy metals Cu, As, Cd, Zn, Hg, and Pb, in either the brown rice or the field. The results showed that treated municipal wastewater can be safely used as an alternative water source for the irrigation of rice, although continued monitoring will be needed to determine the long-term effects with regard to soil contamination and other potential health concerns. [ABSTRACT FROM AUTHOR]

A pilot plant was constructed with eight elements of an Asahi microfiltration (MF) membrane—a total filtration surface area of 56 m 2 . Performance of the plant was examined in preparation of a secondary sewage effluent without coagulant for reverse osmosis membrane treatment. Production at different permeate flux was tested for evaluation of the changes in transmembrane pressure (TMP) and specific permeate flux (SPF) with time. Clean-in-place (CIP) was conducted when TMP reached a value about 2 atm after each test. For permeate flux of 48, 55, 61 and 66 L m -2 h -1 , the ceiling TMP was reached after filtration for approximately 420, 200, 225, and 195 h, respectively. The corresponding cumulative permeate volumes were 1130, 620, 765, 720 m 3 before a CIP was necessary. The SPF decreased quickly with increases in permeate flux and the corresponding half-SPF times were 147, 89, 75 and 39 h for the respective flux studied. The membrane fouling tolerance was greater at a lower than at a higher flux. Analysis of the performance data suggests that run of the MF plant at higher permeate flux with more frequent and quick CIP might produce more water. The optimal filtration durations were found to be 12, 8, 7 and 3 days for permeate flux of 48, 55, 61 and 66 L m -2 h -1 , respectively. Prolonged filtration after the optimal interval without CIP may not maximise the economical benefit. [ABSTRACT FROM AUTHOR]

In this research the characteristics of fresh wastewater were studied by filtration of organic material and nutrients. Besides the short-term dissolving of phosphorus was determined. The size fractions of oxygen demand for 7 days (BOD 7 ), total organic carbon (TOC), phosphorous (P) and nitrogen (N) were separated to 0.1 μm. Most of the phosphorous, nitrogen and organic carbon was under 0.1 μm fractions. Most of the biological oxygen demand was over 12 μm fractions although the fraction under 0.1 μm was 37%. The amount of phosphorus over 0.45 μm increased 25% after 3 days' storage. [ABSTRACT FROM AUTHOR]

Controlled experiments were carried out in a mesoscale subsurface flow sand filter treating municipal wastewater from a single household. The system consisted of a 50 cm high vertical flow column (pre-filter) with unsaturated flow and a 3 m long horizontal sub-surface flow unit (main filter) with saturated flow. Fluxes of nitrogen and carbon were analyzed in 4 different operating conditions (low and high loading, with and without the prefilter unit). Water samples were taken from the inlet, the outlet and within the sand filter at different depths and locations and analysed for water quality (Tot N, NO3-N, NH4-N, TOC, DOC, CODcr, BOD5, SS, PH, and EC) and dissolved gas content (N²O, CH4, and CO2). Emissions of N2O, CH4, and CO2 were measured with the closed- chamber technique adjacent to water quality sampling points. The results show that prefiltering in a vertical, unsaturated flow column changed the incoming ammonium to nitrate during low loading. During high loading part of the ammonium nitrified in the pre-filter was lost by denitrification. Within the horizontal main filter there were two pathways for the incoming nitrate: denitrification and dissimilatory nitrate reduction to ammonium (DNRA). [ABSTRACT FROM AUTHOR]

Microbial community structure was assessed in a horizontal subsurface flow planted sand filter treating domestic wastewater with molecular and culture-based methods. The diversity and spatial distribution of the microbial community was investigated using a PCR-DGGE (eubacterial and archaeal primers, ammonia-oxidizing bacteria, and ammonium monooxygenase specific primers), and spread plate and MPN counts. Significant differences were found in the spatial distribution of the microbial community structure. Data analysis revealed that different components of the microbial community possessed different spatial distribution patterns within the filter bed and depending on community type, relationships with soil chemical, and microbiological parameters varied. The most important spatial pattern in microbial community structure within the constructed wetland was related to the depth gradient, followed by differences between inflow and outflow. A comparison of a number of heterotrophic bacteria between inlet and outlet pipes as well as between two sampling depths showed no significant differences. In addition, the variation of the abundance of ammonia-oxidizing bacteria demonstrated no clear spatial pattern. [ABSTRACT FROM AUTHOR]

We studied an experimental horizontal subsurface-flow planted sand filter in Kodijärve, Estonia. We measured the microbial biomass, nitrogen immobilization, potential nitrification, soil respiration, multiple carbon source utilization patterns of the microbial consortia of the soil samples, the carbon, nitrogen, and phosphorus content of the soil samples, the water quality and physicochemical indicators in water sampling wells as well as emissions of CO2, N2, NO2, and CH4 from the two beds (the dry bed and the wet bed) in the wetland. The potential nitrification of the upper layer of the dry bed could not be attributed primarily to autotrophic nitrification, or the nitrifying bacteria in this layer could be facultative heterotrophs, whereas autotrophic nitrification is predominant in the upper layer of the wet bed. It also was found that changing aeration conditions in the lower layer of the dry bed have resulted in a lower diversity of the microbial community and led to a relative depletion of easily degradable soil carbon resources. [ABSTRACT FROM AUTHOR]