The question of nitrification in the Passaic River, New Jersey: Analysis of historical data and experimental investigation

Historical NH₄⁺ and NO₃⁻ data from six stations on the Passaic River, New Jersey, were analyzed. The data for five of the stations span 1963 to 1976, and for the sixth station 1947 to 1976. Some of the conclusions reached are as follows:

1. (1) The concentration of NH₄⁺ fluctuated widely, but the trend was towards an increase with time.

2. (2) The concentration of NH₄⁺ was elevated during a period of extreme drought (1963 to 1966).

3. (3) The concentration of NO₃⁻ tended to increase smoothly with time.

4. (4) The concentration of NH₄⁺ increases longitudinally (with downstream travel).

5. (5) The loads (concentration × stream-flow) of both nitrogen species tended to increase with time.

6. (6) Substantial NO₃⁻ enters the stream from non-point sources.

7. (7) The potential for instream nitrification is not fully realized, as represented by elevated levels of NH₄⁺.

Item (7) was puzzling because conditions in the Passaic, especially in the summer, appear to be favorable for nitrification. The point was clarified, in part through an experimental investigation.River water samples, with and without added NH₄Cl, were incubated, and the course of the first step of nitrification was followed through the appearance of NO₂⁻. (The second step of nitrification was inactive during the experimental period.) The added NH₄Cl enhanced nitrification in samples from the uppermost stations (native NH₄⁺-N approximately 0.1 mg l⁻¹, but had little or no effect in samples from the middle and lower reaches (native NH₄⁺-N > 0.5 mg l⁻¹). Consequently, it was inferred that over most of the river's mainstem the growth of NH₄⁺-oxidizing bacteria was not substrate limited. There was also no indication of other nutrient limitations or of the presence of any inhibitors. This led to a projection of a 60-fold increase in the population density of planktonic NH₄⁺-oxidizers over a certain stretch of the river. However, no increase in the most-probable-number (MPN) of NH₄⁺-oxidizing bacteria was observed, which is consistent with item (7). In fact, at the end of a quiescent segment of the river the MPN's were anomalously low. This is attributed to the removal of cells from the water column through settling. This reasoning is extended to suggest that, throughout the river, settling may be the mechanism preventing a response of planktonic nitrifiers to the enrichment with NH₄⁺ from pollution sources. In turn, this could prevent a full expression of the potential for nitrification.The analyses are discussed from a regulatory perspective. It is concluded that the nitrification component of the Passaic's self-purification capacity is overburdened, and first became so in 1953.     

Electrochemical determination of pollutants in sea water: Toxic substances and nutrients

Coastal marine waters have a wide variety of important human uses and therefore must be protected against contamination. The main sources of their pollution (by toxic substances and nutrients) are the discharge of municipal sewage and runoff from agricultural areas. Excessive nutrient enrichment in the form of inorganic nitrogen (NH₄⁺, NO₂^?, NO₃^?) may be directly estimated by the use of ion selective electrodes (ISE), whereas the inorganic phosphorus can only be estimated indirectly. The total content of N, P and heavy metals may be estimated after decomposition of organic substances, using the ISE method in the case of P and N determination and the differential pulse anodic stripping voltammetry (DPASV) method for determining the heavy metals.     

Source identification of nitrous oxide on autotrophic partial nitrification in a granular sludge reactor

Emission of nitrous oxide (N₂O) during biological wastewater treatment is of growing concern since N₂O is a major stratospheric ozone-depleting substance and an important greenhouse gas. The emission of N₂O from a lab-scale granular sequencing batch reactor (SBR) for partial nitrification (PN) treating synthetic wastewater without organic carbon was therefore determined in this study, because PN process is known to produce more N₂O than conventional nitrification processes. The average N₂O emission rate from the SBR was 0.32 ± 0.17 mg-N L⁻¹ h⁻¹, corresponding to the average emission of N₂O of 0.8 ± 0.4% of the incoming nitrogen load (1.5 ± 0.8% of the converted NH₄⁺). Analysis of dynamic concentration profiles during one cycle of the SBR operation demonstrated that N₂O concentration in off-gas was the highest just after starting aeration whereas N₂O concentration in effluent was gradually increased in the initial 40 min of the aeration period and was decreased thereafter. Isotopomer analysis was conducted to identify the main N₂O production pathway in the reactor during one cycle. The hydroxylamine (NH₂OH) oxidation pathway accounted for 65% of the total N₂O production in the initial phase during one cycle, whereas contribution of the NO₂⁻ reduction pathway to N₂O production was comparable with that of the NH₂OH oxidation pathway in the latter phase. In addition, spatial distributions of bacteria and their activities in single microbial granules taken from the reactor were determined with microsensors and by in situ hybridization. Partial nitrification occurred mainly in the oxic surface layer of the granules and ammonia-oxidizing bacteria were abundant in this layer. N₂O production was also found mainly in the oxic surface layer. Based on these results, although N₂O was produced mainly via NH₂OH oxidation pathway in the autotrophic partial nitrification reactor, N₂O production mechanisms were complex and could involve multiple N₂O production pathways.     

Evaluation of wastewater nitrogen transformation in a natural wetland (Ulaanbaatar, Mongolia) using dual-isotope analysis of nitrate

The Tuul River, which provides water for the daily needs of many residents of Ulaanbaatar, Mongolia, has been increasingly polluted by wastewater from the city's sewage treatment plant. Information on water movement and the transformation of water-borne materials is required to alleviate the deterioration of water quality. We conducted a synoptic survey of general water movement, water quality including inorganic nitrogen concentrations, and isotopic composition of nitrogen (δ¹⁵N-NO₃⁻, δ¹⁸O-NO₃⁻, and δ¹⁵N-NH₄⁺) and water (δ¹⁸O-H₂O) in a wetland area that receives wastewater before it enters the Tuul River. We sampled surface water, groundwater, and spring water along the two major water routes in the wetland that flow from the drain of the sewage treatment plant to the Tuul River: a continuous tributary and a discontinuous tributary. The continuous tributary had high ammonium (NH₄⁺) concentrations and nearly stable δ¹⁵N-NH₄⁺, δ¹⁵N-NO₃⁻, and δ¹⁸O-NO₃⁻ concentrations throughout its length, indicating that nitrogen transformation (i.e., nitrification and denitrification) during transit was small. In contrast, NH₄⁺ concentrations decreased along the discontinuous tributary and nitrate (NO₃⁻) concentrations were low at many points. Values of δ¹⁵N-NH₄⁺, δ¹⁵N-NO₃⁻, and δ¹⁸O-NO₃⁻ increased with flow along the discontinuous route. Our results indicate that nitrification and denitrification contribute to nitrogen removal in the wetland area along the discontinuous tributary with slow water transport. Differences in hydrological pathways and the velocity of wastewater transport through the wetland area greatly affect the extent of nitrogen removal.     

Analyses and assessment of the spatial and temporal distribution of nitrogen compounds in surface waters

The temporal concentration variations and spatial distribution of nitrogen compounds (nitrate, nitrite, ammonium) in the natural surface waters of Stara Zagora Region, Bulgaria, over a period of 1 year were assessed in the present study. Nitrate‐nitrogen concentrations in all surface water samples, except for the December value – 21.8 mg/L in Zetyovo Reservoir, were within the permissible national quality standards. NO₂ ^–‐N could be classified as a priority pollutant of Chirpan and Zetyovo Reservoirs waters. The greatest extent of NH ₄ ⁺‐N pollution was registered in Chirpan Reservoir surface waters. The correlation study revealed appreciable mutual relationship only between NH₄ ⁺‐N and NO ₂ ^–‐N in the surface waters. The hierarchical cluster analysis (HCA) exhibited divergent apportionment of nitrogen compounds in the surface water bodies.     

Factors affecting nutrient loads in some Iowa streams

The export and concentration of inorganic nitrogen and total phosphorus from 34 watersheds in a northwestern Iowa lake district were measured during March 1971–August 1973. Annual nutrient losses were approximately 0.35 kg ha⁻¹ P. 6.7 kg ha⁻¹ NO₃-N, and 1.0 kg ha⁻¹ NH₃-N. A statistical analysis of the relationship between land-use and plant nutrients was used to determine differences among streams. Animal units in feedlots were significantly correlated with phosphorus and ammonia nitrogen (mg l⁻¹ and kg ha⁻¹ yr⁻¹). Nitrate nitrogen was negatively correlated with the percentage of watershed in marshland. Tile drainage and surface runoff from grasslands, feedlots, cornfields, and soybean fields were analyzed for nitrogen and phosphorus in spring 1974: mean values are given.     

Nitrogenous disinfection byproducts formation and nitrogen origin exploration during chloramination of nitrogenous organic compounds

Formation of nitrogenous disinfection by-products (N-DBPs) of cyanogen chloride (CNCl), dichloroacetonitrile (DCAN) and chloropicrin was evaluated during chloramination of several selected groups of nitrogenous organic (organic-N) compounds, including α-amino acids, amines, dipeptides, purines, and pyrimidines, The intermediates generated, reaction pathways, and nitrogen origin in N-DBPs were explored as well. CNCl was observed in chloramination of all tested organic-N compounds, with glycine giving the highest yields. DCAN was formed during chloramination of glutamic acid, cytosine, cysteine, and tryptophan. Chloramination of most organic-N compounds except for cysteine and glutamic acid generated chloropicrin. Aldehydes and nitriles were identified as the intermediates by negative mode electrospray ionization mass spectrometry during reactions of NH₂Cl and organic-N compounds. Labeled ¹⁵N-monochloramine (¹⁵NH₂Cl) techniques showed that nitrogen in N-DBPs may originate from both NH₂Cl and organic-N compounds and the nitrogen partition percentages vary as functions of reactants and pH.     

Enzymatic NH3-N determination: a specific method for the determination of ammonia in water and sediments

An enzymatic method for the determination of ammonia—nitrogen, not previously applied in water research, is described. The method is specific for NH₃-N, and the risk of hydrolysis of organic nitrogen compounds is very small, because of near neutral pH and low (room) temperature conditions. Differences between results of enzymatic NH₃-N determination and of a distillation method depended on the type of water. The method has been adapted for application in sediment research, where the exchangeable NH₃-N fraction is determined directly, without an extraction procedure. In comparison with this method, direct distillation of sediment samples gave an overestimation of the NH₃-N content of ± 40 per cent.     

Inter-relationships between nitrogen balance, pH and dissolved oxygen in an oxidation ditch treating farm animal waste

The pathways of N in aerobic farm waste treatment systems are discussed in relation to the dissolved oxygen (DO) and pH of the mixed liquor. The change in pH, DO, oxygen uptake rate and nitrogen balance were monitored under steady, and non-steady, state conditions in an oxidation ditch treating undiluted pig waste. A kinetic analysis of the mass balance for nitrogen allowed an interpretation of the fate of nitrogen under different prevailing conditions. Undesirable accumulations of nitrite were noted in the presence of high levels of free NH₃ and HNO₂. The process was self-promoting and was encouraged by the influx of raw waste. Concentrations of 500 mg 1⁻¹ NO₂-N and 1200 mg 1⁻¹ NO₃-N were the maximum values observed and were considered to be the concentrations at which product inhibition arrested nitrifying activity. Attainment of these levels prevented complete nitrification despite an adequate retention time. pH and DO were inversely related probably through nitrification, but pH appeared to be lowered by accumulation of nitrite and nitrate anions, and thus by the balance between nitrification and denitrification. Considerable N loss through denitrification was found to occur despite apparently aerobic mixed liquors. At low DO simultaneous nitrification-denitrification could eliminate 90 per cent of the soluble-N. NH₃ desorption in laboratory cultures was found to be first order in free NH₃ but was not a significant mode of N loss under field conditions.     

Nitrogen gas supersaturation in the recent sediments of lake erie and two polluted harbors

Nitrogen gas distributions in sediment pore water were determined for cores collected in Lake Erie and two nearby harbors. Concentrations of N₂ gas ranged from 11.9 to 37.0 ml l⁻¹ and from 8.9 to 58.3 ml l⁻¹ for open lake and polluted harbor sediments, respectively. Maximum concentrations in the harbor sediments were as high as 3.5 times N₂ saturation calculated for the overlying water. Indirect diffusive flux estimates for nitrogen gas ranged from 20 to 32% of the particulate nitrogen sedimentation rate in Lake Erie. At one location, the amount of nitrogen gas lost by diffusion was calculated to be greater than the nitrogen deposited to the sediments. Nitrogen gas production and diffusive loss from surficial sediments probably represents a major pathway for nitrogen removal from Lake Erie.     

Nitrogen transformations and retention in planted and artificially aerated constructed wetlands

Nitrogen (N) processing in constructed wetlands (CWs) is often variable, and the contribution to N loss and retention by various pathways (nitrification/denitrification, plant uptake and sediment storage) remains unclear. We studied the seasonal variation of the effects of artificial aeration and three different macrophyte species (Phragmites australis, Typha angustifolia and Phalaris arundinacea) on N processing (removal rates, transformations and export) using experimental CW mesocosms. Removal of total nitrogen (TN) was higher in summer and in planted and aerated units, with the highest mean removal in units planted with T. angustifolia. Export of ammonium (NH₄⁺), a proxy for nitrification limitation, was higher in winter, and in unplanted and non-aerated units. Planted and aerated units had the highest export of oxidized nitrogen (NO_y), a proxy for reduced denitrification. Redox potential, evapotranspiration (ETP) rates and hydraulic retention times (HRT) were all predictors of TN, NH₄⁺ and NO_y export, and significantly affected by plants. Denitrification was the main N sink in most treatments accounting for 47-62% of TN removal, while sediment storage was dominant in unplanted non-aerated units and units planted with P. arundinacea. Plant uptake accounted for less than 20% of the removal. Uncertainties about the long-term fate of the N stored in sediments suggest that the fraction attributed to denitrification losses could be underestimated in this study.     

Effect of ammonium on the hydraulic conductivity of geosynthetic clay liners

Hydraulic conductivity and swell index tests were conducted on a conventional geosynthetic clay liner (GCL) containing sodium-bentonite (Na-B) using 5, 50, 100, 500, and 1000 mM ammonium acetate (NH₄OAc) solutions to investigate how NH₄⁺ accumulation in leachates in bioreactor and recirculation landfills may affect GCLs. Control tests were conducted with deionized (DI) water. Swell index of the Na-B was 27.7 mL/2 g in 5 mM NH₄⁺ solution and decreased to 5.0 mL/2 g in 1000 mM NH₄⁺ solution, whereas the swell index of Na-B in DI water was 28.0 mL/2 g. Hydraulic conductivity of the Na-B GCL to 5, 50, and 100 mM NH₄⁺ was low, ranging from 1.6–5.9 × 10^?11 m/s, which is comparable to the hydraulic conductivity to DI water (2.1 × 10^?11 m/s). Hydraulic conductivities of the Na-B GCL permeated with 500 and 1000 mM NH₄⁺ solutions were much higher (e.g., 1.6–5.2 × 10^?6 m/s) due to suppression of osmotic swelling. NH₄⁺ replaced native Na⁺, K⁺, Ca²⁺, and Mg²⁺ in the exchange complex of the Na-B during permeation with all NH₄⁺ solutions, with the NH₄⁺ fraction in the exchange complex increasing from 0.24 to 0.83 as the NH₄⁺ concentration increased from 5 to 1000 mM. A Na-B GCL specimen permeated with 1000 mM NH₄⁺ solution to chemical equilibrium was subsequently permeated with DI water. Permeation with the NH₄⁺ converted the Na-B to “NH₄-bentonite” with more than 80% of the exchange complex occupied by NH₄⁺. Hydraulic conductivity of this GCL specimen decreased from 5.9 × 10^?6 m/s to 2.9 × 10^?11 m/s during permeation with DI water, indicating that “NH₄-bentonite” can swell and have low hydraulic conductivity, and that the impact of more concentrated NH₄⁺ solutions on swelling and hydraulic conductivity is reversible.     

Adsorption of ammonium to activated sludge

The adsorption of ammonium (NH₄⁺) to the sludge floc matrix has been investigated in two activated sludge treatment plants. When activated sludge was extracted in 1 N KCl the extractable amounts were between 0.5 and 1.3 mg NH₄⁺-N/l higher than the dissolved ammonium concentration at dissolved ammonium concentrations between 1 and 6 mg NH₄⁺-N/l. The difference between the extractable and the dissolved ammonium, the exchangeable ammonium, thus represented 18–30% of the dissolved ammonium concentration. A part of this, around 0.5–0.6 mg NH₄⁺-N/l was not exchangeable under the actual operational conditions in the treatment plants due to a slow desorption kinetics, but seemed to be accessible for nitrification under prolonged aeration. The highest observed amount of adsorbed ammonium corresponded to 0.4–0.5 mg NH₄⁺-N/gSS. Adsorption of ammonium should be investigated in more details and included in models for nitrogen mass balances for activated sludge.     

Utilisation de la clinoptilolite en potabilisation des eaux—elimination de l'ion NH4+Clinoptilolite in drinking water treatment for NH4+ removal

The objective of this study is to develop a technique to remove ammonium ion from water intended for potable purposes. An ion exchange method is used with a selective ion exchanger, a natural cation zeolite, clinoptilolite. Glass columns (Fig. 1) are used for laboratory experiments. These experiments show that the NH₄⁺ exchange capacity is very small compared to its total capacity 2.17 meq g^?1; its value depends essentially on the NH₄⁺ initial concentration and less on the Ca²⁺ concentration in the influent water. Figure 3 illustrates the practical exchange capacity relative to the initial concentration of ammonium ion for a soft water (Ca²⁺ = 35–50 mg l^?1). We were particularly interested in waters weak in ammonium ion concentration (NH₄⁺ = 1–3 mg l^?1). In this case and for ～1 and 2 mg l^?1 NH₄⁺ concentration in water, the practical capacity is only 0.06 and 0.108 meq g^?1 respectively. The leakage is smaller than the ECC limit (European Community Council) for drinking waters (NH₄⁺ ? 0.5 mg l^?1) and the treated volume of water to breakthrough, defined at 0.5 mg l^?1 of NH₄⁺, is ?720 BV (BV = bed volume) in both cases.In another way Fig. 6 shows that hard waters (due to Ca²⁺ ions) are more difficult to treat than soft waters. The practical capacity is smaller than before and the NH₄⁺-leakage is greater. To lessen NH₄⁺-leakage to less than 0.5 mg l^?1 for soft waters down-flow and up-flow, regeneration is used. Figure 7 shows that up-flow regeneration is more attractive than down-flow regeneration.Cycle reproducibility (Figs 4 and 5) shows that the regeneration conditions satisfied our requirements: in this case, the salt consumption is 180 eq of salt per eq of NH₄⁺ eliminated. This prompted us to try to reuse the regenerant (with NH₄⁺ ion). An increase of NH₄⁺-leakage is noticed in the presence of an NH₄⁺-residual in the regenerant. This increase is more significant with down-flow regeneration.After these laboratory experiments, we carried out a semi-industrial pilot-plant. Our objective was first to verify the laboratory results and secondly to study clinoptilolite behaviour relative to the time it was used. Two plexiglass columns comprise the pilot-plant shown in Fig. 9; soft water is used for these experiments. The first column is regenerated with fresh salt solution. The cycles obtained, considering their initial NH₄⁺-concentration, are reproduced in Fig. 10. For 2 mg l^?1 NH₄⁺ in the influent water, the leakage is about 0.2 mg l^?1 and the treated volume to breakthrough (0.5 mg l^?1 of NH₄⁺) is about 750 BV. The second column is regenerated with a recycled solution. The quality of the cycles decreases with the number of reuse of the regenerant as shown in Fig. 11. Nevertheless, it is interesting to note that after 3 reuses, the performance decrease is only 25% and the leakage, although it increases is smaller than 0.5 mg l^?1.Pilot results allowed us to propose a treatment of 30,000 m³ day^?1; the cost per cubic meter water treated, relative to NH₄⁺-removal, is about 0.165 FF (0.033 US $) for a plant and 0.77 FF (0.014 US $) for the same plant at the seaside. Using two serial columns decreased the cost by about 40–50%.     

The changes of bamboo pulping waste water residuals in biological treatment process

The residuals of the bamboo pulping wastewater were analysed systematically. The COD (chemical oxygen demand) decreased significantly by adding appropriate coagulant (1.5 kg/m³ 10% Al₂ (SO₄)₃ as coagulant and 2 mg/L anionic PAM as coagulant aid) to the effluent in secondary sedimentation tank. The study found that hydrolytic bacteria in primary sedimentation tank and balancing tank may increase the ratio of BOD/COD and promote the release of ammonia nitrogen (NH₃‐N), which was benefit to further degradation of organic pollutants by aerobic biological treatment. Through optimizing biochemical process and adjusting contents of nitrogen, phosphorus, and mineral elements, the effects of wastewater treatment has been greatly enhanced and the quality of discharged water could met the new national standard GB3544‐2008.     

Atmospheric NH3 and NO2 concentration and nitrogen deposition in an agricultural catchment of Eastern China

To assess the atmospheric environmental impacts of anthropogenic reactive nitrogen in the fast-developing Eastern China region, we measured atmospheric concentrations of nitrogen dioxide (NO₂) and ammonia (NH₃) as well as the wet deposition of inorganic nitrogen (NO₃⁻ and NH₄⁺) and dissolved organic nitrogen (DON) levels in a typical agricultural catchment in Jiangsu Province, China, from October 2007 to September 2008_. The annual average gaseous concentrations of NO₂ and NH₃ were 42.2 μg m⁻³ and 4.5 μg m⁻³ (0 °C, 760 mm Hg), respectively, whereas those of NO₃⁻, NH₄⁺, and DON in the rainwater within the study catchment were 1.3, 1.3, and 0.5 mg N L⁻¹, respectively. No clear difference in gaseous NO₂ concentrations and nitrogen concentrations in collected rainwater was found between the crop field and residential sites, but the average NH₃ concentration of 5.4 μg m⁻³ in residential sites was significantly higher than that in field sites (4.1 μg m⁻³). Total depositions were 40 kg N ha⁻¹ yr⁻¹ for crop field sites and 30 kg N ha⁻¹ yr⁻¹ for residential sites, in which dry depositions (NO₂ and NH₃) were 7.6 kg N ha⁻¹ yr⁻¹ for crop field sites and 1.9 kg N ha⁻¹ yr⁻¹ for residential sites. The DON in the rainwater accounted for 16% of the total wet nitrogen deposition. Oxidized N (NO₃⁻ in the precipitation and gaseous NO₂) was the dominant form of nitrogen deposition in the studied region, indicating that reactive forms of nitrogen created from urban areas contribute greatly to N deposition in the rural area evaluated in this study.     

Utilisation de la clinoptilolite en potabilisation des eaux—elimination de l'ion NH4

The objective of this study is to develop a technique to remove ammonium ion from water intended for potable purposes. An ion exchange method is used with a selective ion exchanger, a natural cation zeolite, clinoptilolite. Glass columns (Fig. 1) are used for laboratory experiments. These experiments show that the NH₄⁺ exchange capacity is very small compared to its total capacity 2.17 meq g⁻¹; its value depends essentially on the NH₄⁺ initial concentration and less on the Ca²⁺ concentration in the influent water. Figure 3 illustrates the practical exchange capacity relative to the initial concentration of ammonium ion for a soft water (Ca²⁺ = 35–50 mg l⁻¹). We were particularly interested in waters weak in ammonium ion concentration (NH₄⁺ = 1–3 mg l⁻¹). In this case and for 1 and 2 mg l⁻¹ NH₄⁺ concentration in water, the practical capacity is only 0.06 and 0.108 meq g⁻¹ respectively. The leakage is smaller than the ECC limit (European Community Council) for drinking waters (NH₄⁺ 0.5 mg l⁻¹) and the treated volume of water to breakthrough, defined at 0.5 mg l⁻¹ of NH₄⁺, is 720 BV (BV = bed volume) in both cases.In another way Fig. 6 shows that hard waters (due to Ca²⁺ ions) are more difficult to treat than soft waters. The practical capacity is smaller than before and the NH₄⁺-leakage is greater. To lessen NH₄⁺-leakage to less than 0.5 mg l⁻¹ for soft waters down-flow and up-flow, regeneration is used. Figure 7 shows that up-flow regeneration is more attractive than down-flow regeneration.Cycle reproducibility (Figs 4 and 5) shows that the regeneration conditions satisfied our requirements: in this case, the salt consumption is 180 eq of salt per eq of NH₄⁺ eliminated. This prompted us to try to reuse the regenerant (with NH₄⁺ ion). An increase of NH₄⁺-leakage is noticed in the presence of an NH₄⁺-residual in the regenerant. This increase is more significant with down-flow regeneration.After these laboratory experiments, we carried out a semi-industrial pilot-plant. Our objective was first to verify the laboratory results and secondly to study clinoptilolite behaviour relative to the time it was used. Two plexiglass columns comprise the pilot-plant shown in Fig. 9; soft water is used for these experiments. The first column is regenerated with fresh salt solution. The cycles obtained, considering their initial NH₄⁺-concentration, are reproduced in Fig. 10. For 2 mg l⁻¹ NH₄⁺ in the influent water, the leakage is about 0.2 mg l⁻¹ and the treated volume to breakthrough (0.5 mg l⁻¹ of NH₄⁺) is about 750 BV. The second column is regenerated with a recycled solution. The quality of the cycles decreases with the number of reuse of the regenerant as shown in Fig. 11. Nevertheless, it is interesting to note that after 3 reuses, the performance decrease is only 25% and the leakage, although it increases is smaller than 0.5 mg l⁻¹.Pilot results allowed us to propose a treatment of 30,000 m³ day⁻¹; the cost per cubic meter water treated, relative to NH₄⁺-removal, is about 0.165 FF (0.033 US $) for a plant and 0.77 FF (0.014 US $) for the same plant at the seaside. Using two serial columns decreased the cost by about 40–50%.     

Rate constants of reactions of ozone with organic and inorganic compounds in water—III. Inorganic compounds and radicals

Second-order rate constants for reactions of ozone with 40 inorganic aqueous solutes are reported. Included are compounds of sulfur (e.g. H₂S, H₂SO₃, HOCH₂SO₃H), chlorine (e.g. Cl⁻, HOCl, NH₂Cl, HClO₂, ClO₂), bromine (e.g. Br⁻, HOBr), nitrogen (e.g. NH₃, NH₂OH, N₂O, HNO₂) and oxygen (e.g. H₂O₂), as well as free radicals (e.g. O₂⁻, OH^•). Most of these compounds exhibit an increase in rate constant with increasing pH corresponding to their degree of dissociation. Rate constants are based on ozone consumption rates measured by conventional batch-type or continuous-flow methods (10⁻³-10⁺⁶ M⁻¹ s⁻¹ range) and determinations of stoichiometric factors. Also listed are data determined by pulse-irradiation techniques using kinetic spectroscopy (10¹⁰ M⁻¹ s⁻¹ range). Additional literature data are reviewed for completeness. Results are discussed with respect to water treatment and environmental processes.     

Nutrient inputs from submarine groundwater discharge (SGD) in Masan Bay, an embayment surrounded by heavily industrialized cities, Korea

In order to estimate the magnitude of submarine groundwater discharge (SGD) and the associated nutrient fluxes in Masan Bay on the southern coast of Korea, we measured the concentrations of ²²⁶Ra and nutrients in seawater, brackish groundwater, and stream water in May and August 2006. Gauging unidentified nutrient fluxes through SGD is very important in this bay since diatom red tides have been occurring from April to October every year since the 1980s. Based on a ²²⁶Ra mass balance model, the submarine inputs of coastal groundwater were estimated to be 4.8 × 10⁶ and 5.7 × 10⁶ m³ d^− 1 (61 and 71 L m^− 2 d^− 1) in May and August, respectively, which were approximately 840% and 540% of the surface water discharge into the bay. The fluxes of dissolved inorganic phosphorus (DIP) and silicate (DSi) through SGD were 2-3 fold higher than those via stream water, while the fluxes of dissolved inorganic nitrogen (DIN) were comparable to those from surface waters during both sampling periods. Nutrient fluxes through stream waters relative to those from SGD were more significant in the inner part of the bay, which appears to be due to the direct influence of heavily polluted stream waters. Our study shows that the large and continuous supply of inorganic nutrients through SGD may play an important role in eutrophication and the occurrence of red tides in this bay, which should be taken into consideration in the environmental management of the bay.     

Long term partial nitritation of anaerobically treated black water and the emission of nitrous oxide

Black water (toilet water) contains half the load of organic material and the major fraction of the nutrients nitrogen and phosphorus in a household and is 25 times more concentrated, when collected with a vacuum toilet, than the total wastewater stream from a Dutch household. This research focuses on the partial nitritation of anaerobically treated black water to produce an effluent suitable to feed to the anammox process. Successful partial nitritation was achieved at 34 °C and 25 °C and for a long period (almost 400 days in the second period at 25 °C) without strict process control a stable effluent at a ratio of 1.3 NO₂-N/NH₄-N was produced which is suitable to feed to the anammox process. Nitrite oxidizers were successfully outcompeted due to inhibition by free ammonia and nitrous acid and due to fluctuating conditions in SRT (1.0-17 days) and pH (from 6.3 to 7.7) in the reactor. Microbial analysis of the sludge confirmed the presence of mainly ammonium oxidizers. The emission of nitrous oxide (N₂O) is of growing concern and it corresponded to 0.6-2.6% (average 1.9%) of the total nitrogen load.