Evaluation of Roughing and Slow Sand Filters for Water Treatment

The present study examined the potential of someroughing filter media, prepared from locally availablematerials in removing organic matter and turbidityfrom surface water. Also, the study included testingthe efficiency of roughing filter followed by slowsand filter in minimizing the suspended load on thesubsequent water treatment steps. Based onmicroorganisms removal and turbidity data, filtermedia consisted of three layers of gravel ranked topamong six of the media tested, showing 84–100%removal for chlorophyll ‘a’ green algae, blue-greenalgae, diatoms, total algal count, bacterial count (at22 and 37 °C), total coliforms, faecal coliform,faecal streptococci, yeast and Candida albicans.Using slow sand filter after roughing filter improvedthe percentage removal of turbidity, where it reachedup to 83% after roughing filter while it reached 92%after slow sand filter. From the view point ofaesthetic quality of the filtered water, the resultsof the analyzed physico-chemical parameters showed nochange before and after the use of the roughing andslow sand filters.     

Treatment of Septic Effluent for Fecal Coliform and Nitrogen in Coarse-textured Soils: Use of Soil-only and Sand Filter Systems

Groundwater effluent sample collectors(zero-tension lysimeters) were installed directlybelow the drainfields of three residential onsitetreatment systems in the Clover/Chambers Creek aquiferregion of Pierce County near Tacoma, WA. The use of asplit effluent delivery system from the septic tank,where half the effluent was delivered under pressureto a normal native soil-only filter system and halfwas delivered to a sand filter system, allowed thedirect comparison of the two commonly-utilized septicsystems for treatment levels. Septic tank effluent(from the septic tank) and percolating water (between0.3 and 0.9 m beneath the effluent distributionlines) was collected between May 1991 and April 1994on 30 occasions. Samples were analyzed for fecalcoliform bacteria, nitrate, nitrite, ammonium andtotal reduced (Kjeldahl) nitrogen. Results of thisstudy indicate that the use of sand filters greatlyincreased removal of fecal coliform bacteria and totalnitrogen. Soil-only filter systems had an average of91% removal of fecal coliforms and 47%of total N; whereas sand filter systems had an averageof 99.8% removal of fecal coliforms and 80% of total N.     

Application of Reclaimed Wastewater in the Irrigation of Rosebushes

The use of reclaimed wastewater in agriculture can be a solution for regions with water shortages or low rainfall periods; besides fulfilling the crop's water needs, it would also promote the recycle of nutrients. However, care should be taken regarding soil salinization, especially in closed environments such as greenhouses for the cultivation of ornamental plants. The domestic effluents are rich in sodium which can accumulate on soil and cause soil sealing. This study evaluated the use of effluents from anaerobic filters and intermittent sand filters in the production of rosebushes (Rosa hybrida “Ambiance”). The crop yield of the rosebushes irrigated with reclaimed wastewater exceeded the one obtained with traditional cultivation, reaching a value 31.8 % higher when employing nitrified effluent originated from intermittent sand filters, with no difference in the product quality. The salinity levels are below the critical limits found in the literature; however, there was a significant increase compared to the irrigation with drinking water.     

Bacteriological Changes Associated with Granular Activated Carbon in a Pilot Water Treatment Plant

Bacteriological analysis were performed on collected water samples from a conventional water treatment pilot plant in Cincinnati, Ohio in which granular activated carbon (GAC) has been used as the final process to assess the impact of GAC on the bacteriological quality and incidence of antibiotic resistant bacteria in water produced. Heterotrophic bacterial counts (HPC) at 20 °C was stabilized at 10² to 19⁴ cfu mL^-1 and did not markedly differ at different water treatment processes. On the other hand, slight reduction in HPC was observed for the effluent produced from sand filter and GAC contactors. Effluents produced from both the sand filter and GAC contactors showed 2 log reduction in coliforms count. Fecal coliform showed the same rate of reduction as a result of sand filtration, while it reached undetectable numbers in the effluent of GAC contactors. Subculturing the isolated strains in tryptic soy broth revealed that 61.3, 61.5, 12.6 and 8.5% of HPC at 28 °C, total coliforms and fecal coliform, respectively were non-culturable. In this case, R2A or R3A broth was used as subculturing media. The incidence of coliform resistant strains among isolates varied significantly according to the source of water samples. Multiple antibiotic resistance (MAR) was not always high in the same samples in which the overall resistance was high. The species composition varied considerably in different water samples. Selection for bacteria exhibiting resistance to antibiotic or antibiotics was observed under some experimental conditions using different doses of chlorine. The antibiotic resistance character was mostly transferable. As a conclusion, the use of GAC has no observable adverse effect on the bacteriological quality of the water produced from the pilot plant under investigation.     

Performance of Intermittently Operated Sand Filters: A Comparable Study,Treating Wastewaters of Different Origins

The purpose of this research was to determine the efficiency of sand filters to remove several common pollutants, found in most wastewaters. In order to achieve this objective, Plexiglas columns of 1 m height were used. The columns were filled with river sand and loaded with real or synthetic wastewaters, corresponding to different origins, following an intermittent feeding schedule. The effect of addition of inoculum to the synthetic wastewaters was also examined and the results were compared with the uninoculated columns. The inoculum consisted of 20 ml addition of activated sludge from the aeration tank of a large-scale wastewater treatment plant. Samples of the inlet and outlet of these columns were analyzed for common parameters (TSS, COD, NH₄-N, NO₂-N, NO₃-N, TN, PO₄-P and pH). At the end of each experimental serie, sand samples from different column heights were obtained and observed, using a Scanning Electron Microscope (SEM). The SEM micrographs demonstrated the existence of microorganisms through out the column depth. The analysis of effluent show significant reduction of COD (more than 50% for the majority of wastewaters that were used) and PO₄-P (more than 40%), as compared with the initial loading. Ammonification occurred and by increasing the number of loadings, nitrification was subsequently observed. Denitrification was not found to take place, due to the lack of anoxic conditions.     

An investigation of the pathogenic and non-pathogenic free-living amoebae from the root zone method of wastewater treatment

Pathogenic and non-pathogenic free-living amoebae from the Root Zone Method (RZM) of wastewater treatment were investigated. Ten reed beds planted on four different substrate types were compared for their efficiency of removal of free-living amoebae. Reed beds planted on coarse substrates generally gave the highest removal rates (up to 100%) while those planted in soil gave the lowest (60.4%). Possible reasons for differences in removal efficiencies are discussed. Thirteen species representing nine genera of free-living amoebae were isolated; these included three species of Acanthamoeba (A. astronyxis, A. polyphaga and A.rhysodes) all of which were pathogenic for mice. The implications for RZM design of the presence of potentially pathogenic free-living amoebae in the effluent are discussed.     

Efficiency of Bark, Activated Charcoal, Foam and Sand Filters in Reducing Pollutants from Greywater

Greywater is a potential resource of water that can be improved to meet the quality needed for irrigation. This study evaluated the performance of bark, activated charcoal, polyurethane foam and sand filters in removing biochemical oxygen demand (BOD₅), surfactants, phosphorus, nitrogen and microbial indicators from greywater during start-up and steady state. In column experiments, 0.6?m high filters (diameter 20?cm) were fed for 113?days with artificial greywater at a hydraulic loading rate of 0.032?m³?m^?2?day^?1 and an organic loading rate of 0.014?kg BOD₅ m^?2?day^?1. Bark and activated charcoal efficiently reduced the concentrations of organics (BOD₅), surfactants (methylene blue active substances??MBAS), total phosphorus (Tot-P) and total thermotolerant coliform numbers, while sand and foam were less efficient. Bark, activated charcoal, foam and sand reduced influent BOD₅ by 98, 97, 37 and 75?%; MBAS by >99, >99, 73 and 96?%; Tot-P by 97, 91, 36 and 78?%; and total nitrogen by 19, 98, 13 and 5?%, respectively. BOD₅ and MBAS were efficiently reduced directly from start-up by bark and activated charcoal, while foam needed 30?days to achieve about 50?% reduction in BOD₅. Bark was the most efficient filter in reducing thermotolerant faecal coliforms (2.4 log₁₀), while foam achieved the lowest reduction (0.5 log₁₀). Overall, bark and activated charcoal filters appeared to be the most suitable filters for improving greywater quality to reach irrigation quality in terms of organic matter reduction. Performance of these filters under higher and fluctuating loadings and the long-term sustainability of the filter materials need further investigation.     

Transport and Attenuation of Microbial Tracers and Effluent Microorganisms in Saturated Pumice Sand Aquifer Material

Land disposal of treated human and animal effluent through pumice sand soils is a common practice around Rotorua, in the central North Island of New Zealand. There is increasing concern about the possibility of contamination of shallow pumice sand aquifers associated with this practice. In this study, we investigated the transport and attenuation of F-RNA bacteriophages and Escherichia coli in saturated pumice sand aquifer media using a field tracing experiment, and laboratory batch and column studies. The influence of dissolved organic carbon on microbial transport was also investigated by conditioning the 18 cm-long column with ultrafiltered sewage. The CXTFIT curve-fitting program was used to model the experimental data and to determine transport and attenuation parameters. Batch studies showed more than 90% adsorption of both microbial indicators onto pumice sand. High mass removal of microbial indicators was shown in the field (>99% for phage MS2 and E. coli at 2 m down gradient of the injection well; not detected at 6 m) and in the ‘clean sand’ column (65% for phage MS2 and 90% or E. coli). These results suggest that uncontaminated pumice is an effective sorbent capable of retaining microbial contaminants due to high surface area and porosity. However, in the column, with additional dissolved organic carbon, phages showed a progressive reduction in mass removal and retardation between experiments (93%, 75%, and 63% removal; retardation factor: 3.5, 2.5 and 1.2). This suggests that the organic matter competed with phages for the sorption sites, thus promoting phage transport. As a result, viral transport rates may be significantly greater in contaminated compared with uncontaminated pumice sand aquifers.     

Efficiency of Mesocosm-Scale Constructed Wetland Systems for Treatment of Sanitary Wastewater Under Tropical Conditions

Subsurface-flow constructed wetlands technology (SSFW) has been used successfully for treating sanitary wastewater throughout North America and Europe. However, treatment wetland technologies have not been used extensively in the tropics. To advance tropical studies, a pilot-scale SSFW was constructed on the campus of the University of the Atlantic in Barranquilla, Colombia. The systems performance was monitored from January to July of 2009. The treatment system consisted of a 760-L septic tank followed by three mesocsom-scale subsurface-flow constructed wetlands in parallel arrangement. Clarified wastewater was batch loaded to each unit at a rate of 53 L/m²/day to affect a hydraulic retention time of approximately 3 days. One of the treatment units served as a non-planted control (gravel only), while the other two treatment units were planted with either Eriochloa aristata or Eleocharis mutata. The objective of this study was to evaluate the comparative efficacy of the treatment units (planted vs. unplanted), with respect to their abilities to augment treatment of septic tank effluent (sanitary wastewater). Monitored parameters included plant biomass, oxidation?Creduction potential, chemical oxygen demand (COD), temperature, dissolved oxygen, pH, ammonia?Cnitrogen (NH ₄ ⁺ ?CN) nitrate?C and nitrite?Cnitrogen (NO₃?CN, NO₂?CN), phosphates (PO ₄ ^? ), and coliform bacteria. Total biomass (dry matter) was 2.84 and 0.87 Kg/m² for E. aristata and E. mutata, respectively. Redox potential in the plant rizospheres averaged ?172 mV (±164.1) in E. aristata, 29 mV (±251.1) in E. mutata, and 32 mV (±210.5) in the unplanted control. COD removal was superior in planted vs. non-planted systems (>75% vs. 47%). Ammonia and total phosphorus removal averaged 69% and 85%, respectively, in planted systems versus 31% and 59% in the unplanted system. Removal of total and fecal coliforms averaged 96%. Results of this pilot study revealed that SSFW technology in the tropics can provide significant removal of organic matter, nutrients, and bacteria from clarified sanitary wastewater.     

Removal of Chromium, Copper, and Nickel from an Electroplating Effluent Using a Flocculent Brewer’s Yeast Strain of Saccharomyces cerevisiae

The release of heavy metals in aquatic systems due to the discharge of industrial wastewaters is a matter of environmental concern. Heat-inactivated cells of a flocculent strain of Saccharomyces cerevisiae were used in the bioremediation, in a batch mode, of a real electroplating effluent containing Cu, Ni, and Cr. In this approach, no previous reduction of Cr(VI) to Cr(III) was required. Cr(VI) was selectively removed (98%) by yeast biomass at pH 2.3. At this pH, Cr(VI) is mainly in the form of HCrO ₄ ^? and yeast surface is surrounded by H⁺ ions, which enhance the Cr(VI) interaction with biomass binding sites by electrostatic forces. Subsequently, pH of the effluent was raised up to 6.0; this pH maximizes the efficiency of cations removal since at this pH the main binding groups of yeast cells are totally or partially deprotonated. The passage of effluent through a series of sequential batches, at pH 6.0, allowed, after the third batch, the removal of Cu(II), Ni (II), Cr total, and Cr(VI) in the effluent to values below the legal limit of discharge. The strategy proposed in the present work can be used in plants for the treatment of heavy metals rich industrial effluents containing simultaneously Cr(VI) and Cr(III).     

Utilization of created wetlands to upgrade small municipal wastewater treatment systems

Created wetlands offer a low cost, low maintenance, and practical alternative for upgrading secondary municipal wastewater treatment systems. The removal efficiencies, effects of seasonal temperature variations, and effects of increased loading rates on contaminant removal within such a system was studied by Auburn University researchers at a created wetland site in Hurtsboro, Alabama. The 0.16 ha system consisted of a two cell wetlands planted with cattails (Typha latifolia), bulrush (Scirpus validus), arrow duck potatoes (Sagitaria latifolis), burr reeds (Spargaminum eurycarpun), water pennywort (Hydrocotyl ranunculoides), and parrotfeather (Myriophyllum brasiliense). Testing occurred from January through September of 1988 at hydraulic loading rates of 169, 289, and 345 m³ ha^?1 d^?1. The monthly average total suspended solids influent: effluent mg L^?1 concentration ratio during the study period was 135:19 while the monthly average total BOD₅ influent: effluent mg L^?1 concentration ratio was 38:8. Once the system stabilized, the monthly average total BOD₅ effluent concentration remained essentially constant over the range of average BOD₅ loading rates employed in this study. Total Kjeldahl N removal was more effective at loading rates of 2.6 kg ha^?1 d^?1. The monthly average influent: effluent TKN mg L^?1 concentration ratio was 15:4.     

Pulp and Paper Mill Effluent Treated by Combining Coagulation-Flocculation-Sedimentation and Fenton Processes

Pulp and paper industries face serious environmental challenges, especially with regard to the conservation of water resources. Chemical thermal mechanical pulping (CTMP) is a process of pulping that combines chemical and mechanical pulping. This reduces the volume of water used in the process. But on the other hand, CTMP generates an effluent with high concentration of organic matter and is difficult to treat. This study evaluated the efficiency in the combination of physicochemical pretreatment by coagulation-flocculation-sedimentation (CFS) process and advanced oxidation process (AOP) by Fenton in sequence to treat CTMP effluent of a Brazilian industry. At first, the best treatment conditions for this type of effluent were determined. To evaluate the efficiency, pH, chemical oxygen demand, biochemical oxygen demand, total organic carbon, lignin contents, color, total phenolic contents, turbidity, and solids were measured before and after treatment. The acute toxicity on Daphnia magna was also determined. The treatment with CFS showed better results in the removal of solids and Fenton in the removal of recalcitrant compounds, such as lignin, demonstrating the need to use them in sequence. Combining CFS and Fenton to treat CTMP effluent allowed to achieve a removal efficiency of 95% for TOC, 61% for COD, and 76% for lignin contents.     

Tertiary treatment of the liquid fraction of pig manure with Phragmites australis

Since 2003, the pig industry in Flanders (Belgium) is obliged to process a portion of the nutrient overproduction. In general, pig manure processing occurs as follows: i) separation into liquid and solid fractions, ii) conversion of the solid fraction to an exportable product (e.g. composting) and iii) reduction of nutrient contents in the liquid fraction before discharge into surface water or spreading on arable land. The aim of this study was to evaluate the potential of constructed wetlands (CWs) planted with Phragmites australis to reduce nitrogen (N), phosphorus (P) and chemical oxygen demand (COD) in the liquid fraction to levels below discharge criteria. In addition, the removal efficiency of heavy metals (Cu, Zn) present at elevated levels in the liquid fraction was evaluated. A greenhouse experiment was conducted with subsurface flow (SSF) reed beds (2 × 0.125 × 0.11 m) filled with sand, loam, clayey sand or expanded clay (argex). The liquid manure load was set at 1 mm per day. Removal efficiencies varied between 64–75% for COD, 73–83% for N and 71–92% for P, depending on the matrix material used. However, effluent levels still remained significantly above the Flemish legal discharge criteria of 2 mgl^?1, 15 mgl^?1 and 125 mgl^?1 for P, N and COD respectively.     

Identification of an Assemblage of Indicator Organisms to Assess Timing and Source of Bacterial Contamination in Groundwater

Bacterial contamination of drinking water wells is a commonproblem in many rural areas. Some of this contamination may berelated to manure spreading or housing of livestock; another source is on-site septic systems. Current indicator organisms are able to detect the presence of fecal contamination, but where there may be more than one potential source of fecal material, the current indicators are unable to ascertain the origin. This laboratory investigation was undertaken to determine the longevity and reliability of a selected suite of indicator organisms. Total coliform, fecal coliform, fecal streptococci and Clostridium perfringens were monitoredin a simulated contaminated groundwater environment for 6 months. All four indicator organisms were present at the end of6 months. The number of fecal streptococi bacteria decreased most noticeably, allowing assessment of relative age of contamination. C. perfringens was found to be a reliableindicator of contamination from animal manure. Fecal material from 28 different animals and three septic systems were assessed for the presence of the indicator organisms. Totalcoliform, fecal coliform and fecal streptococci were present in the fecal material of all animals tested including reptiles.C. perfringens was detected in feces from all but two of the animals assessed. Using an assemblage of indicator organisms provides more information regarding source and timingof contamination than just testing for total coliform and fecalcoliform bacteria.     

Evaluation of sugar beet pulp efficiency for improving the retention of copper in stormwater basin

Purpose

Sugar beet pulp (SBP) has been shown to be a promising low-cost sorbent for the removal of metals from contaminated waters. The objective of this study was to investigate the impact of SBP addition to horizontal-flow gravel filters in increasing the copper (Cu) retention ability of stormwater basins.

Material and methods

Small-scale gravel filters filled with 6 kg of a sand–sediment mix (SS) were used to experimentally treat Cu-contaminated water under conditions that represented an intense storm event. Sugar beet pulp efficiency was assessed by adding 100 g of raw SBP. Two ways of applying SBP were tested: (1) mixed with SS into the gravel filter or (2) packed at the outlet in a PVC column. Eluates were characterized by their volume, pH, Cu and dissolved organic carbon (DOC) concentrations.

Results and discussion

When placed at the outlet, SBP fixed 73 % of the Cu remaining in solution and increased the overall retention capacity of the gravel filter to 99.4 %. Conversely, when SBP was mixed with SS, the outflowing water carried higher concentrations of Cu and DOC. Complementary batch experiments underlined the crucial role of DOC in the decline of Cu sorption ability observed when SS and SBP were mixed. Geochemical calculations suggested that DOC (assumed to be pectins) promotes the mobilisation of Cu from SS by complexing it in porewater.

Conclusions

Accompanied with careful guidance, SBP has the potential of removing dissolved Cu from contaminated water in gravel filters. Protocols for SBP preparation and conditions of use should be established so as to promote its sorption efficiency and decrease its release of Cu-complexing compounds like pectins.     

Microbiological Quality and Antibiotic Resistance Analysis of a Brazilian Water Supply Source

Water samples of the Passaúna River, Curitiba/Paraná (Brazil), were analyzed to determine total and thermotolerant coliform counts and Escherichia coli in order to provide information on human impacts on the water supply. Samples were collected and analyzed monthly, from March 2006 to February 2007, at five different locations along the river, and the multiple tube method was used to obtain total and thermotolerant coliform counts. The results varied from 130 MPN/100 mL to 1.6?×?10⁶ MPN/100 mL for total coliforms, while for thermotolerant coliforms the variation was between 40 MPN/100 mL and 5?×?10⁵ MPN/100 mL. The E. coli strains isolated from the samples were tested with 13 different antibiotics to determine their antibiotic resistance. The isolated strains were constantly sensitive to seven of the 13 antibiotics tested, and resistant to at least one of the other antibiotics. The results indicated that two factors could influence the increased contamination on this river, viz., seasonality parameters and domestic wastewater discharges. The determination of antibiotic resistance indices aimed to provide information on the anthropogenic influence. Only one of the locations investigated was considered critical due to the anthropogenic influence, with significant impacts from irregular domestic wastewater discharges.     

Column Studies on Nitrate Removal from Potable Water

Biological processes can achieve nitrate removal from groundwater. The sulfur/limestone autotrophic denitrification by Thiobacillus denitrificans was evaluated with three laboratory-scale column reactors. The optimum sulfur/limestone ratio was determined to be 2:1 (mass/mass). Different hydraulic retention times were used during the column tests to examine nitrate removal efficiencies. Under an HRTs of 13 h, nitrate concentration of 60 mgNO₃ ^--N L^-1 was reduced to less than 5 mg NO₃ ^--N L^-1. On a higher HRT of 26 h the nitrate removal efficiency was close to 100% for all nitrate-nitrogen loading rates. Different initial nitrate-nitrogen concentrations (30, 60, and 90 mg NO₃ ^--N L^-1) were used in the study. Column tests showed that the nitrate-nitrogen loading rate in this study was between 50 to 100 g NO₃ ^--N m^-3 d^-1 to obtain a removal efficiency of 80–100%. It was found that approximately 6 mg SO₄ ^2- was produced for 1 mg NO₃ ^--N removed. Nitrite-nitrogen in all cases was less than the maximum allowable concentration of 1 mg NO₂ ^--N L^-1. Effluent pH was stable in the range of 7 to 8; the effluent dissolved oxygen was less than 0.15 mg L^-1 and the oxidation-reduction potential in all columns was in the range of –110 to –250 mV.     

Constructed Wetlands Treating Runoff Contaminated with Nutrients

The aim was to assess the role of Phragmites australis (Cav.) Trin. ex Steud. in experimental, mature, and temporarily flooded vertical flow wetland filters treating urban runoff rich in organic matter. During the experiment, ammonium chloride was added to sieved concentrated road runoff to simulate primary treated urban runoff contaminated with nitrogen. Five days at 20°C N-allylthiourea biochemical oxygen demand (BOD) and chemical oxygen demand removal efficiencies were relatively lower for planted than unplanted filters. Moreover, there was no significant difference for BOD removal for all filters under fluctuating inflow concentrations of sulfate. The nitrogen removal performances of planted filters were more efficient and stable throughout the seasons compared to those of unplanted filters. A substantial load of nitrogen (approximately 500 mg per filter) was removed by harvesting P. australis. Plant uptake was the main removal mechanism for nitrogen during high concentrations (10 mg/L) of ammonia-nitrogen in the urban runoff.     

Treatment of Total Dissolved Solids from Plastic Industrial Effluent by Halophytic Plants

Eight halophytic plant species, Avicennia marina, Avicennia alba, Bruguiera gymnorrhiza, Lumnitzera racemosa, Rhizophora mucronata, Rhizophora apiculata, Suaeda maritima, and Xylocarpus moluccensis were evaluated for the removal ability of total dissolved solids (TDS) from plastic industrial effluent. All halophytic plants could tolerate and survive when grown in wastewater with high TDS. Among the test plants, S. maritima showed the highest TDS removal capability and was selected for further study. S. maritima had ability not only for TDS removal, but also for reduction of pH, electrical conductivity, and salinity from wastewater effluent under soil conditions. S. maritima did not exhibit symptoms such as necrosis and leaf tip burn during the experimental period. These results indicated that S. maritima has tolerance to high TDS and salinity. However, S. maritima responded to high TDS stress by producing proline and total sugar in the roots, stems, and leaves which indicated that this plant can adapt to wastewater with high TDS. In addition, silicon (Si) and calcium (Ca) were increased in the leaves due to plant stress from TDS. Therefore, S. maritima is suitable halophytic plants for treatment of TDS contaminated wastewater.