Upgrading a facultative pond by implanting water hyacinth

Water hyacinth was implanted in one of two existing facultative ponds and both units were operated in parallel under comparable conditions. The ponds were fed with mainly domestic wastewater after pretreatment in anaerobic ponds and operated at a BOD₅-loading of about 48 kg (ha d)⁻¹ and a detention time of 12 days. This paper covers a period of 4 months, from the implantation of the water hyacinths until no further systematic change in the treatment efficiency of the water hyacinth pond was observed. The median effluent concentrations of the facultative pond for SS, COD, TKN and TP were 55, 95, 6.4 and 1.4 mg l⁻¹, respectively. The values for the water hyacinth pond were 12, 26, 2.5 and 0.4 mg l⁻¹, respectively. The average DO effluent concentration of the water hyacinth pond was 1.2 mg l⁻¹, but this still increased slightly as compared to the influent. The study demonstrates that the implantation of water hyacinth is an appropriate option for upgrading facultative ponds. In many cases where more stringent effluent standards are imposed the method may be a suitable alternative to technical treatment processes.     

Phosphorus fractions and profiles in the sediment of shallow Danish lakes as related to phosphorus load,sediment composition and lake chemistry

Depth profiles of sediment dry weight (DW), loss on ignition (LOI), total iron (Fe), total nitrogen (TN), calcium (Ca), total phosphorus (TP), NH₄Cl-P, NaOH-P, HCl-P and Res-P were measured in 32 shallow meso- to hypertrophic Danish lakes and the data compared with that for external phosphorus load (Pex), lake water phosphorus and phytoplankton biovolume. Surface sediment TP was highly and positively correlated to Pex (g P m⁻² y⁻¹) and Fe (mg Fe g⁻¹ DW) (TP = 0.92 + 0.23 Pex + 0.031 Fe, r² = 0.68, P < 0.0001), but not or only weakly related to the other parameters analyzed. NaOH-P in the sediment was significantly and positively correlated to Fe (r² = 0.43) and TP (r² = 0.75), while HCl-P was correlated to Pex (r² = 0.68), TP (r² = 0.28) and to phytoplankton biovolume (r² = 0.35), but not to Ca. On average 4% of the surface sediment TP was NH₄Cl-extractable, 35% NaOH-extractable and 20% HCl-extractable, with the remaining 41% being residual phosphorus (Res-P). At sediment depths below 50 cm the Res-P fraction was greater (63% of TP), while there was still considerable NaOH-P (21% of TP), thus indicating a significant permanent deposition of iron-bound phosphorus. In most sediments a higher surface Res-P and NaOH-P were recorded as compared to depths below 20–30 cm. The presence of a NaOH-P gradient, even in lakes in which P-lake and anthropogenic impact were low, suggests that post-depositional mobility of phosphorus may occur. The Res-P gradient indicates that a major part of the organically bound phosphorus in the upper 10–20 cm of the sediment eventually is mineralized and dissolved.     

Characterizing nutrient dynamics with relation to changes in partial pressure of CO2 in a tropical sewage‐fed aquaculture pond situated in a Ramsar wetland

The changes in nutrient dynamics (nitrate, ammonium, silicate, phosphate and iron concentration) vis‐à‐vis partial pressure of CO₂ in water [pCO₂(water)] from tropical sewage‐fed aquaculture ponds (East Kolkota Wetlands, India) were analysed by means of a microcosm. A significant relationship between these nutrient’s removal from the system and reduction in pCO₂(water) was observed (with few exceptions). These water bodies acted as significant sources of CO₂ in pre‐monsoon and monsoon seasons despite having substantial quantity of chlorophyll‐a to make it a net autotrophic system. The study revealed that if conditions favourable for optimum photosynthesis can be maintained in these ponds, the CO₂ source character of these ponds can be reversed. In the post‐monsoon season, when the pH of the water column was high, the system acted as sink for CO₂ which suggests the use of lime to prevent these systems from becoming hypereutrophic and carbon source at the same time.     

复合潜流人工湿地处理城市地表径流研究

以武汉市桃花岛塘和复合潜流人工湿地组合生态处理系统为研究对象，考察了对城市地表径流的处理效果。结果表明，塘和复合潜流人工湿地组合生态系统可以有效净化城市地表径流，对各污染物的去除率：COD为84．0％～85．4％、TP为89．6％～91．8％、TN为92．2％～94．4％、SS为95．8％-97．1％，其中复合潜流人工湿地对COD、TP、TN、SS的去除率分别为69、0％～73．1％、82．6％～86．6％、89．0％～90．4％、64．7％～69．2％，除氮效果独特。在无雨期该生态系统可用于净化湖水，实现了削减污染和保持系统稳定的双重功能，同时还可补给养鱼塘用水。     

Wastewater treatment by reed beds: An experimental approach

The present study consists of assessing the efficiency of a macrophyte (Phragmites australis) system in wastewater purification in an arid climate. The experimental system is made up of three beds differing in length (30, 40 and 50 m) and implanted with Phragmites australis. Wastewater inflow through these beds is horizontal with a flow of 10 l.s⁻¹. Retention time varies between 1 and 4 h. The frequency of irrigation is weekly. The studied parameters are: the organic load (COD and TSS), nutrients (total Kjeldhal nitrogen: TKN and total phosphorus: TP) and the parasitical load (helminth eggs). Water, soil and plants are the three components of the experimental system we analyzed.Results reveal that in the output, the decrease in organic load, nutrients and parasitical load is very sharp in the large bed (COD: 62%, TKN: 43%, TP: 14%, helminth eggs: 93%). However, in the small bed (30 m), the decrease is slight (COD: 48%, TKN: 23%, TP: 5%, helminth eggs: 88%). Concerning parasitical load, the study shows that the three beds are effective in eliminating helminth eggs, even with a very short retention time (1–4 h). The quality of the effluent of the reed bed system should be classified within category B according to WHO guidelines (1989) for crops irrigation.Soil sample analysis from entrance to exit shows a decreasing gradient of nitrogen (N), phosphorus (P), organic carbon (Org.C), organic matter (OM) and parasitical helmith eggs. The gradient becomes more significant in the largest bed with decreasing rate, reaching respectively 49%, 44%, 37%, 40% and 100% for TKN, TP, Org.C, OM and helminth eggs.As for the plant material, the composition of major elements (nitrogen and phosphorus) of Phragmites aerial parts shows the same evolution. While the decreasing rate of nitrogen in the leaves reaches 50% in the largest bed, it does not exceed 8% in the smallest bed. Mean aerial productivity of the studied reed beds was estimated at 134 tons dry weight.ha⁻¹. The aerial biomass exported contains only 5–6% of nitrogen and 10–12% of phosphorus with regard to their load at the influent.     

Biological oxidation of high strength nitrogenous wastewater

A nitrification study was conducted in continuous flow stirred tank reactors using high strength nitrogenous wastewater (concentrated stream from a urea plant mixed with pharmaceutical wastewater). The reactors were operated at different solids retention times (SRT = 10–62.5 d) and hydraulic retention times (HRT = 1.5–2.1 d). Pharmaceutical wastewater was used as an organic carbon source to maintain a COD/TKN ratio of 1. The nitrification achieved at different SRTs varied from 87 to 99%. The nitrogen balance data show that ammonia assimilation and denitrification accounted for 4–53% of the total nitrogen removed. The yield coefficients and decay coefficients were Y_b = 0.5 (COD basis), k_db = 0.07 d⁻¹ (COD basis) for heterotrophs and Y_n = 0.15 (TKN basis), k_dn = 0.06 d⁻¹ (TKN basis) for nitrifiers respectively.     

Activated sludge treatment of abattoir wastewater—I : Influence of sludge age and feeding pattern

As part of a study to provide data for the design of abattoir activated sludge plants laboratory-scale completely mixed reactors were fed with abattoir wastewater, continuously and intermittently using an 8 h feed, 16 h starvation pattern. The standard biokinetic coefficients and the effluent concentrations of COD. TKN and phosphorus were measured for the continuously fed reactors at sludge ages of 5, 10 and 20 days. Sludge settleability and filterability were also measured.Values obtained for the biokinetic coefficients Y and k_d were within the range of values reported for other substrates but k was lower and k_x higher. Effluent TKN and phosphorus concentrations were low at the three sludge ages, but the COD concentration was high at sludge ages of 5 and 10 days. In contrast to the data reported for many other wastewaters the effect of sludge age on the SVI was small. Intermittent feeding was tested at a single sludge age of 10 days. It produced an effluent and sludge with better and more stable characteristics than those from the continuously fed reactor at the same sludge age.     

Pollutant removal from municipal sewage lagoon effluents with a free-surface wetland

This research project was initiated to refine the knowledge available on the treatment of rural municipal wastewater by constructed wetlands. To determine the treatment capacity of a constructed wetland system receiving municipal lagoon effluents, the wetland was monitored over one treatment season, from May 19 to November 3, 2000. The wetland system consisted of a three-cell free-surface wetland, phosphorus adsorption slag filters and a vegetated filter strip. Bimonthly water samples at the inlet and outlet of each component of the wetland system were analysed for biochemical oxygen demand, nitrate and nitrite, ammonia and ammonium, total Kjeldahl nitrogen (TKN), total suspended solids (TSS), total phosphorus (TP), ortho-phosphate (ortho-PO(4)), fecal coliforms (FCs) and Escherichia coli. The free-surface wetland cells treating the lagoon effluents achieved removals as follows: biochemical oxygen demand (34%), ammonia and ammonium (52%), TKN (37%), TSS (93%), TP (90%), ortho-PO(4) (82%), FCs (52%) and E. coli (58%). The wetland cells reduced total nitrogen, TP and biochemical oxygen demand to levels below the maximum permissible levels required for direct discharge to nearby receiving waters (TN<3.0 mg x L(-1), TP<0.3 mg x L(-1), BOD(5)<3.0 mg x L(-1)). The vegetated filter strip treating the effluents from the wetland cells achieved removals as follows: biochemical oxygen demand (18%), ammonia and ammonium (28%), TKN (11%), TSS (22%), TP (5%), FCs (28%) and E. coli (22%). It may therefore serve as an additional treatment stage further reducing the concentrations of these mentioned parameters. The slag filters reduced TP in the lagoon effluents by up to 99%, and, in this study, were concluded to be effective phosphorus adsorbers.     

Evaluating the input and source of faecal contamination in the cattle farming and forested regions of the Oconee watershed

Sites along Sugar Creek and the Apalachee River were monitored to compare the water quality in cattle farming regions with the forested regions of the Oconee watershed. Dissolved oxygen (6.68 mg/L) and turbidity [23.91 nephelometric turbidity units (NTU)] in Sugar Creek and the Apalachee River were similar. Overall, cattle farming sites along Sugar Creek had higher levels of NO₃^? and PO₄^?3 during the summer months. In contrast, the forested sites on the Apalachee River had elevated concentrations of inorganic nutrients only during spring rain events. The concentration of faecal bacteria was greater in the cattle farming areas compared with the level of faecal bacteria in the forested areas, and microbial source tracking with the bovine‐associated Bacteroides (BoBac) DNA marker indicated that cattle were the major source of faecal bacteria in Sugar Creek.     

Bioassays with Stigeoclonium tenue Kütz. on waters receiving sewage effluents

Stigeoclonium tenue Kützing (Chlorophyceae) was tested as bioassay organism on water receiving effluents of two sewage treatment plants. The PO₄---P and NH₄---N concentration declined with increasing distance from the effluent discharge. Growth potentials were low and inhibited, in assays with undiluted effluents, and relatively high at some distance from the points of discharge. At greater distances growth potentials tended to decrease with increasing distance from the plants. At distant sites nitrogen or phosphorus limitation could be determined. When ratio's of inorganic nitrogen to inorganic phosphorus, N/P, were lower than 7, nitrogen was primary limiting, at ratio's above 10, phosphorus became the limiting factor. Possible growth inhibiting factors in the effluents are discussed.     

A comparison of toxicity tests conducted in the laboratory and in experimental ponds using cadmium and the fathead minnow (Pimephales promelas)

Acute toxicity tests were conducted in the laboratory with fathead minnows (Pimephales promelas) to determine the 96-h LC₅₀ of cadmium under three conditions: (1) in laboratory water, (2) in water from experimental ponds, and (3) in pond water underlain by sediment. Cadmium was then applied at doses equivalent to the estimated LC₅₀ values to 0.07-ha ponds containing caged fathead minnows. A cadmium ion selective electrode, ultrafiltration, and equilibrium calculations were used to determine cadmium speciation, and several water quality characteristics were measured to correlate differences in mortality between test systems (laboratory and field) with observed differences in water quality. The LC₅₀ estimates (mg l⁻¹) for the bioassays were 4.39 for the laboratory water, 3.52 for the pond water with sediment, and 2.91 for the pond water. Concentrations of Cd²⁺ decreased and those of cadmium in the particulate (> 1.2 μm) and 300,000 mol. wt (0.018–1.2 μm) fractions increased over the 96-h; cadmium in these fractions was believed to consist of colloidal sized CdCO₃ precipitates. Concentrations of Cd²⁺ decreased at different rates between test systems, regulated by the degree of CdCO₃(s) supersaturation which in turn depended on pH and total metal concentrations. Differences in toxicity in the laboratory tests were attributed to differences in water hardness and Cd²⁺ concentrations. Mortality of fathead minnows was low (0–10%) during the 96-h test period in the ponds due to the higher pH, which produced supersaturated conditions resulting in the rapid formation of nontoxic CdCO₃ precipitates and a more rapid decrease in Cd²⁺ concentrations as compared to the laboratory bioassays.     

A comparison of phosphorus retention in lakes determined from mass balance and sediment core calculations

Phosphorus retention (TP_acc) was determined in 7 lakes in Ontario, Canada from mass balances and from the direct measurement of phosphorus accumulation in the sediments. Phosphorus retentions determined using the mass balance technique ranged between 20 ± 4.0 and 95 ± 23 mg/m²/yr and were slightly lower than those calculated by multiplying sediment total phosphorus (TP) concentrations by sediment accumulation rates (49 ± 14 to 148 ± 37 mg/m²/yr). The lower TP_acc values measured using the mass balance approach may result from the underestimation of external TP inputs. Alternatively, it is suggested that in the more acidic lakes, a decrease in TP concentrations in the lakewaters and/or a decrease in TP export from the catchment may have resulted in a decrease in TP_acc through time. Thus, relatively higher TP_acc values would be calculated using the sediment approach (since TP_acc values calculated from the sediment data are averaged over a greater number of years than those calculated from the mass balance data).Provided several cores are collected from the lake, the direct measurement of sediment TP and sediment accumulation rates for estimating TP_acc may be a suitable alternative to mass balances, especially in situations where it is not possible to measure all inputs of TP to the lake.     

Urban Water Journal: Special Issue on Transients

Retention/detention basins are commonly used to remediate runoff from road surfaces in an attempt to remove contaminants before these materials enter adjacent waterways. However, the efficiency of such devices in removing contaminants is not well known, especially for Australian conditions. The efficiency of a retention/detention device adjacent to a major motorway in Sydney (Australia) was assessed for total suspended solids (TSS), a suite of trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn), nutrients (TP, TKN, NO_x, TN) and faecal coliforms. The mean removal efficiency of Cu, Pb, Mn and Zn was 23, 41, 43 and 41%, respectively, whereas the mean reduction in Cr, Fe and Ni concentrations was only 0, 3 and 1%, respectively. TSS in stormwater entering the retention/detention basin was highly variable resulting in large variations in removal efficiencies (range: ?12 to 93%; mean: 40%). The mean removal efficiency of Kjeldahl nitrogen (TKN) and total nitrogen (TN) was high (56 and 28%, respectively) in contrast to total NO_x and total phosphorus (TP) (?42 and ?5%, respectively). Faecal coliform was low to very low (<5000 cfu/100 ml) and removal efficiency was 16 to 68%. Possible leaching of fine terrigenous particles from the gravel bed of the retention/detention basin may have contributed to the increase in Cr, Fe and Ni concentrations in effluent stormwater.     

Nutrient discharges to Biscayne Bay, Florida: trends, loads, and a pollutant index

Changes in land use, management practices, and environmental conditions may all lead to detectable differences in nutrients transported to aquatic systems. Biscayne Bay, an oligotrophic estuary in southeastern Florida, requires minimal phosphorus and nitrogen inputs and here we quantified the effects of continued watershed development. Nutrient (nitrate/nitrite-nitrogen [NO_X-N], total ammonia nitrogen [NH₃-N], and total phosphorus [TP]) water quality data (1992-2006) from six monitoring sites were evaluated using trend analysis, load estimation, and a new Pollutant Empower Density (PED) index. The PED index assesses the effect of discharged pollutants relative to the background productivity of aquatic environments. NO_X-N, NH₃-N, and TP concentrations declined or exhibited no change at most sites, with only six instances of significantly (p < 0.1) increasing trends. Load estimates revealed higher NO_X-N loads in the southern, agricultural section of the watershed and higher NH₃-N and TP loads in the urbanized northern and central areas. NO_X-N loads from site MW04 (south) were the highest for all sites while site LR06 (north) had the highest NH₃-N and TP loads. Of the evaluated canal discharges, PED index values also suggested that canal discharges from these two sites (MW04 and LR06) had the greatest potential for impact in the bay. Overall, water quality is generally improving but canal discharges are coupled with land use activities in adjacent drainage areas. Trend analysis, load estimation, and the PED index can be used together to provide a more holistic interpretation of water quality, which is necessary for optimizing resources to meet watershed management goals.     

Measuring the trophic status of ponds: Relationships between summer rate of periphytic net primary productivity and water physico-chemistry

The monitoring of the water quality is a major environmental concern and specific method of assessment needs to be addressed for ponds. Among threats on freshwater, eutrophication remains an important and widespread problem. To assess if the trophic state of ponds can be significantly predicted by physico-chemical surrogates, parallel measurements of water physico-chemistry and of summer rates of periphytic net primary productivity (NPP) were performed on a set of nine lowland Swiss ponds representing the whole spectrum of trophic states.The developed methods to measure periphytic NPP on artificial substrates give similar values between the pseudo-replicates and are functional for ponds. The winter concentration of total nitrogen (TN) in the water is a significant predictor of the average summer rates of NPP while in submerged macrophyte beds total phosphorus (TP) is a better predictor. Rates of NPP measured in open water were most often higher and water transparency lower than in macrophyte beds, highlighting the positive influence of macrophytes on water quality and a possible co-occurrence in a pond of contrasting conditions when submerged species are present. This emphasizes the importance of maintaining or restoring submerged macrophyte stands in ponds to improve the water quality.     

Wastewater quality and pollutant loads in combined sewers during dry weather periods

An observatory of urban pollutants was created in Paris in order to assess, at the urban catchment scale, the quality of sanitary sewage and pollutant loads during dry weather periods in the Paris combined sewer. Investigations were carried out for six urban catchments (varying from 42 to 2580 ha) focusing on a wide range of parameters, including: suspended solids (SS), chemical and biochemical oxygen demand (COD and BOD₅), total organic carbon (TOC), total Kjeldahl nitrogen (TKN), heavy metals (Cd, Cu, Pb, Zn), and aliphatic and polycyclic aromatic hydrocarbons (AHs and PAHs). Despite the marginal intra-site variability of some pollutants, which serves to reflect the impact of point sources, this work attests to the spatial homogeneity, at the physical scales considered, of wastewater quality and pollutant loads within the Paris combined sewer network. These results imply that similar production and transfer processes are occurring within sewers during dry weather periods and strongly suggest that data obtained on one specific catchment could be extrapolated to smaller or larger catchments that display quite similar land use and sewer characteristics.     

Spatial analysis of water quality trends in the Han River basin, South Korea

Spatial patterns of water quality trends for 118 sites in the Han River basin of South Korea were examined for eight parameters-temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended sediment (SS), total phosphorus (TP), and total nitrogen (TN). A non-parametric seasonal Mann-Kendall's test determined the significance of trends for each parameter for each site between 1993 and 2002. There are no significant trends in temperature, but TN concentrations increased for the majority of the monitoring stations. DO, BOD, COD, pH, SS, and TP show increasing or decreasing trends with approximately half of the stations exhibiting no trends. Urban land cover is positively associated with increases in water pollution and included as an important explanatory variable for the variations in all water quality parameters except pH. Topography and soil factors further explain the spatial variations in pH, COD, BOD, and SS. BOD, COD, SS, and TP variations are consistently better explained by 100m buffer scale analysis, but DO are better explained by the whole basin scale analysis. Local water quality management or geology could further explain some variations of water quality. Non-point-source pollution exhibits strong positive spatial autocorrelation as measured by Moran's I, indicating that the incorporation of spatial dimensions into water quality assessment enhances our understanding of spatial patterns of water quality. The spatial regression models, compared to ordinary least square (OLS) models, always better explain the variations in water quality. This study suggests that spatial analysis of watershed data at different scales should be a vital part of identifying the fundamental spatio-temporal distribution of water quality.     

Element dynamics of oak ecosystems on acid-sulphurous mine soils in the Lusatian lignite mining district (Eastern Germany)

Seepage water chemistry and input–output budgets of major ions are investigated within an oak chronosequence (Quercus petraea Liebl., 3 years; Quercus rubra L., 26 and 37 years) on acid-sulphurous soils of lignite mining. Due to declining intensity of weathering and deep percolation, the leaching rates of Fe, Al, Mn, Mg, Ca, NH₄ and SO₄-S from soil decline drastically within 34 years. Moreover, an enrichment of NH₄-N, NO₃-N, PO₄-P and K can be noticed, resulting from the accumulation of living biomass.     

Investigation of Lake Sapanca water pollution,Adapazari, Turkey

Lake Sapanca has been the only source of drinking and recreational water for the city of Adapazari, Turkey. This paper reports a study of the variation of nutrient loading and trophic state of the lake, and also water quality parameters of Lake Sapanca compared to those of the neighbouring Lake Iznik. Through one year, samples were taken every three months from 15 different points on the streams feeding and draining off the lake. Nitrate, NO₂‐N, NH₃‐N, TKN, PO₄‐P concentrations on the 12 streams fe and three draining off points were determined. Then, loading, discharge, and accumulation amounts of nitrogen and phosphorus causing eutrophication were calculated and the trophic state of the lake was determined. A simple model was used to analyse the response of Lake Sapanca when the phosphorus loading rate was changed. Through this model, the variation of different parameters (t, M, K, Q, V and A) with respect to phosphorus concentration (C) was studied to identify effects and results. The consequences of an eutrophic state and measures to protect the lake are also discussed.     

Application of response surface methodology for simultaneous carbon and nitrogen (SND) removal from dairy wastewater in batch systems

The application of batch systems to the direct treatment of dairy wastewater was investigated. Batch experiments were conducted to study the organics removal and simultaneous nitrification and denitrification (SND) process. The experiment was conducted by varying four independent parameters (mixed liquor suspended solids, chemical oxygen demand [COD]/N ratio, aeration time and cycling time), using a central composite design under response surface methodology. The process responses of five dependent parameters (COD, Total kjehldahl nitrogen (TKN), NO₃ ^?, effluent NO₃ ^? and effluent total nitrogen) were studied, and in each case, the percentage removal in batch runs was determined with each process displayed in contour plots. Finally, after optimizing the process conditions, the best treatment of dairy wastewater under optimized conditions was established and the responses were shown. This study shows that microbial granules cultivated under the alternating aerobic/anaerobic conditions in batch systems could efficiently remove organic carbon and convert all the ammonium to nitrogen gas.