Saline Ammonia Research Articles

Using plant data to estimate biodegradable COD fractions - case study kwaMashu WWTP.

A modelling study is under way in preparation for a planned upgrade of the capacity of the kwaMashu WWTP in eThekwini, South Africa, from 50 to 80 ML/d. When the configuration of an existing plant is to be changed, the most critical part of the model calibration is the influent wastewater fractionation. However, the constantly varying characteristics of wastewater make experimental determination of an adequately representative set of components difficult, time-consuming and expensive, which constitutes significant barriers to the adoption of modelling by many municipalities. Compliance and process monitoring generate large sets of influent measurements of chemical oxygen demand (COD), free and saline ammonia (FSA), total suspended solids (TSS), etc., but these are insufficient for modelling purposes. In particular, biodegradability is not routinely measured. However, since influent fractionation is designed to predict the fate of material in the wastewater treatment process, it should be possible to infer the fractionation from a combination of influent and plant measurements. This case study demonstrates the application of a pair of modelling tools, a probabilistic influent fractionator and a simplified steady‑state plant‑wide model, to estimate the influent fractionation, together with certain unmeasured or unreliable operational parameters.

Integration of complete elemental mass-balanced stoichiometry and aqueous phase chemistry for bioprocess modelling of liquid and solid waste treatment systems – Part 4: Aligning the modelled and measured aqueous phases

Completely mass-balanced biological, physical and chemical process stoichiometry ensures that the CHONPS material and charge content entering and exiting bioprocess system models is conserved, which is a requirement for pH prediction in integrated physical, chemical and biological process models. Bioprocesses transform the material content from reactants to products, exchanging material between the aqueous, gaseous and solid phases, which cause pH changes in the aqueous phase. By measuring the material content of the aqueous phase, the progress of bioprocesses can be monitored. Alkalinity is an important aqueous-phase property that can be used to track aqueous-phase changes caused by physical, chemical and biological processes. Alkalinity is a stoichiometry property of the components in solution (i.e., a linear function of the amounts present). Its uptake from, and release to, the aqueous phase can both be modelled with bioprocess stoichiometry, and measured in physical bioprocess systems, and so aid in linking the modelled and measured aqueous-phase compositions. Changes in the concentrations of components containing the elements C, H, O, N, P and S result in changes in six weak acid/bases systems in the aqueous phase, all of which affect the total alkalinity. These are: inorganic carbon (IC), ortho-phosphate (OP), free and saline ammonia (FSA), volatile fatty acids (VFA), free and saline sulphide (FSS) and the water itself. Characterization of the aqueous phase to quantify the material content of the aqueous phase containing these six weak acid/base systems using the 5-point titration method is described. While several alkalinity titration based methods are available for anaerobic digestion bioprocess monitoring, only the 5-point titration is sufficiently accurate for aqueous-phase characterization to quantify the aqueous-material content for pH prediction in bioprocess models.

Municipal wastewater management using Vetiveria zizanioides planted in vertical flow constructed wetland

This study investigated wastewater management using Vetiveria zizanioides planted in vertical flow constructed wetland (VFCW). Wastewater from the grit removal chamber and the primary sedimentation tank of Daspoort Wastewater Treatment Works was fed into six-pilot VFCW consisting of 1000-L plastic tanks having 500-mm-deep, 10–15-mm-diameter granite substrate planted with V. zizanioides. Irrigation of macrophytes using effluent from the grit removal chamber and primary sedimentation tanks was done after 3 months of planting and the VFCW monitored. Wastewater samples were collected and analysed using standard procedures. The pollution parameters of the initial sample were total alkalinity 297 ± 27.3 mg/L; COD 627 ± 149.0 mg/L; EC 82.53 ± 5.4 ms/m; free and saline ammonia 36.02 ± 4.1 mg/L, nitrate/nitrite 0.09 ± 0.1 mg/L; pH 7.66 ± 0.4; phosphate 3.07 ± 0.3 mg/L, sulphate 44.57 ± 3.1 mg/L; TDS 551 ± 37.8; TSS 319 ± 34.2 mg/L; and TKN 41 ± 6 mg/L. Percentage removal of 89.57, 98.34% TSS; 98.95, 98.62 free and saline ammonia; 89.87, 91.44% TKN; and 80.65, 58.02% COD for screen and settled wastewater, respectively, was obtained from the VFCW. VFCW using locally available V. zizanioides is a viable alternative for municipal wastewater treatment.

EBP2R – An innovative enhanced biological nutrient recovery activated sludge system to produce growth medium for green microalgae cultivation

Current research considers wastewater as a source of energy, nutrients and water and not just a source of pollution. So far, mainly energy intensive physical and chemical unit processes have been developed to recover some of these resources, and less energy and resource demanding alternatives are needed. Here, we present a modified enhanced biological phosphorus removal and recovery system (referred to as EBP2R) that can produce optimal culture media for downstream micro-algal growth in terms of N and P content. Phosphorus is recovered as a P-stream by diversion of some of the effluent from the upstream anaerobic reactor. By operating the process at comparably low solids retention times (SRT), the nitrogen content of wastewater is retained as free and saline ammonia, the preferred form of nitrogen for most micro-algae. Scenario simulations were carried out to assess the capacity of the EBP2R system to produce nutrient rich organic-carbon depleted algal cultivation media of target composition. Via SRT control, the quality of the constructed cultivation media can be optimized to support a wide range of green micro-algal growth requirements. Up to 75% of the influent phosphorus can be recovered, by diverting 30% of the influent flow as a P-stream at an SRT of 5 days. Through global sensitivity analysis we find that the effluent N-to-P ratio and the P recovered are mainly dependent on the influent quality rather than on biokinetics or stoichiometry. Further research is needed to demonstrate that the system performance predicted through the model-based design can be achieved in reality.

A steady state model for anaerobic digestion of sewage sludges

A steady state model for anaerobic digestion of sewage sludge is developed that comprises three sequential parts – a kinetic part from which the % COD removal and methane production are determined for a given retention time; a stoichiometry part from which the gas composition (or partial pressure of CO,sub>2 ), ammonia released and alkalinity generated are calculated from the %COD removal; and a carbonate system weak acid/base chemistry part from which the digester pH is calculated from the partial pressure of CO 2 and alkalinity generated. From the stoichiometry and weak acid base chemistry parts of the model, for a given % COD removal, the digester gas composition, ammonia released, alkalinity generated and digester pH are com¬pletely defined by the influent sludge composition, i.e. X, Y, Z and A in CXHYOZNA of the hydrolysable organics; volatile fatty acid (VFA) concentration; and pH. For the kinetic part of the model, four hydrolysis kinetic equations were calibrated against 7 to 60 d retention time anaerobic digesters treating two different sewage sludge types, viz. first order; first order specific; Monod; and saturation. Once calibrated against the two sludge type data sets and taking into account experimental error in effluent COD concentration and gas production (i.e. COD mass balance error), each of the four hydrolysis kinetic equa¬tions predicted the % COD removal versus retention time equally well, and predicted COD removal and methane production compared well with measured data. For the different sewage sludge types, viz. a primary and humus sludge mixture from a trickling filter plant, and a “pure” primary sludge, different kinetic rate constants were obtained indicating that the “pure” primary sludge hydrolysed faster and had a lower unbiodegradable particulate COD fraction (f PS'up = 0.33) than the primary and humus sludge mixture (0.36). With the %COD removal known from the hydrolysis part of the model, and again taking experimental error into account (i.e. C and N mass balances error), the stoichiometry and weak acid base chemistry parts of the model predicted the gas composition, effluent free and saline ammonia (FSA) concentration, alkalinity generated and digester pH well for a primary and humus sludge composition of C 3.5 H 7 O 2 N 0.196 . From independent measurement of primary sludge CHON composition, this model estimated composition is within 96%, 100%, 95% and 99% of the average measured composition of C 3.65 H 7 O 1.97 N 0.190 lending strong support to the developed steady state model. Keywords : Anaerobic digestion, steady state model, sewage sludge, hydrolysis kinetics, biodegradability Water SA Vol. 31(4) 2005: 511-528

Integrated chemical/physical and biological processes modeling <BR>Part 2 - Anaerobic digestion of sewage sludges

The development and validation of a two phase (aqueous-gas) integrated mixed weak acid/base chemical, physical and biological processes kinetic model for anaerobic digestion (AD) of sewage sludge are described. The biological kinetic processes for AD are integrated into a two phase subset of the three phase mixed weak acid/base chemistry kinetic model of Musvoto et al. (1997, 2000a,b,c). The approach of characterising sewage sludge into carbohydrates, lipids and proteins, as is done in the International Water Association (IWA) AD model No 1 (ADM1, Batstone et al., 2002), requires measurements that are not routinely available on sewage sludges. Instead, the sewage sludge is characterised with the COD, carbon, hydrogen, oxygen and nitrogen (CHON) composition. The model is formulated in mole units, based on conservation of C, N, O, H and COD. The model is calibrated and validated with data from laboratory mesophilic anaerobic digesters operating from 7 to 20 d sludge age and fed a sewage primary and humus sludge mixture. These digesters yielded COD mass balances between 107 and 109% and N mass balances between 91 and 99%, and hence the experimental data is accepted as reasonable. The sewage sludge is found to be 64 to 68% biodegradable (depending on the kinetic formulation selected for the hydrolysis process) and to have a C,sub>3.5H7O2N0.196 composition. For the selected hydrolysis kinetics of surface mediated reaction (Contois), with a single set of kinetic and stoichiometric constants, for all retention times •free and saline ammonia (FSA), •short chain fatty acids (SCFA), •H2CO3* alkalinity and pH of the effluent stream, and •CO2 and CH4 gases in the gas stream. The measured composition of primary sludge from two local wastewater treatment plants ranged between C3.38H7O1.91N0.21 and C3.91H7O2.04N0.16. The predicted composition is therefore within 5% of the average measured composition providing persuasive validation of the model. Keywords: anaerobic digestion, weak acid/base chemistry, kinetic modelling, sewage sludge Water SA Vol. 31(4) 2005: 545-568

Integrated chemical, physical and biological processes modelling of anaerobic digestion of sewage sludge

The biological kinetic processes for anaerobic digestion (AD) are integrated into a two phase subset of a three phase mixed weak acid/base chemistry kinetic model. The approach of characterising sewage sludge into carbohydrates, lipids and proteins, as is done in the International Water Association (IWA) AD model No 1 (ADM1), requires measurements that are not routinely available on sewage sludges. Instead, the sewage sludge is characterised with the COD, carbon, hydrogen, oxygen and nitrogen (CHON) composition and is formulated in mole units, based on conservation of C, N, O, H and COD. The model is calibrated and validated with data from laboratory mesophilic anaerobic digesters operating from 7 to 20 d sludge age and fed a sewage primary and humus sludge mixture. These digesters yielded COD mass balances between 107-109% and N mass balances between 91-99%, and hence the experimental data is accepted as reasonable. The sewage sludge COD is found to be 32-36% unbiodegradable (depending on the kinetic formulation selected for the hydrolysis process) and to have a C3.5H7O2N0.196 composition. For the selected hydrolysis kinetics of surface mediated reaction (Contois), with a single set of kinetic and stoichiometric constants, for all retention times good correlation is obtained between predicted and measured results for: (i) COD; (ii) free and saline ammonia (FSA); (iii) short chain fatty acids (SCFA); (iv) H2CO3 * alkalinity; (v) pH of the effluent stream; (vi) CO2; and (vii) CH4 gases in the gas stream. The measured composition of primary sludge from two local wastewater treatment plants ranged between C3.38H7O1.91 N0.21 and C3.91H7O2.04N0.16. The predicted composition based on mass balances is therefore within 5% of the average measured composition providing persuasive validation of the model.

Change of groundwater chemistry from 1896 to present in the Mid-Levels area, Hong Kong

In this study, groundwater quality information collected in 1896 (well waters), 1980/1981 (piezometric and seepage samples) and 2002/2003 (seepage samples) in the regions centered by the Mid-Levels area, Hong Kong Island, was compared to illustrate how groundwater quality has changed over a century and the processes controlling it. As shown by saline ammonia and nitrate levels in the late nineteenth century, groundwater was severely polluted by widespread and obvious leakage from poorly designed wastewater collection systems, although groundwater was still a drinking water source for local residents. The extremely high residual chlorines in groundwater demonstrated that large doses of disinfection agents were added to wells at that time. In view of the decline in saline ammonia and nitrate levels, groundwater became less organically polluted in the 1980s probably due to significant improvement of the design of underground sewers. However, more leakage from sources such as salty flushing water and fresh water pipes emerged in the past few decades which added complexity to groundwater chemical systems. Some chemicals were used to identify possible locations of leakages. The temporal variations of the distribution of these chemicals over the area may shed light on the rate of leakage. Leakage from service pipes seems to have improved from the early 1980s to 2002/2003. However, the area is still suffering from widespread and small-scale leakage from service pipes. More efforts should be paid to control small leakages in the future. The findings will be instructive to various government organizations such as the Water Supplies Department and Drainage Services Department to identify possible locations of unobvious leakages in the area.

The performance of constructed wetlands for, wastewater treatment: a case study of Splash wetland in Nairobi Kenya

AbstractThe performance of a constructed wetland for wastewater treatment was examined for four months (December 1995 to March 1996). The study area, hereby referred to as the Splash wetland, is approximately 0·5 ha, and is located in the southern part of Nairobi city. Splash wetland continuously receives domestic sewage from two busy restaurants. Treated wastewater is recycled for re‐use for various purposes in the restaurants. Both wet and dry season data were analysed with a view of determining the impact of seasonal variation on the system performance. The physical and chemical properties of water were measured at a common intake and at series of seven other points established along the wetland gradient and at the outlet where the water is collected and pumped for re‐use at the restaurants. The physico‐chemical characteristics of the wastewater changed significantly as the wastewater flowed through the respective wetland cells. A comparison of wastewater influent versus the effluent from the wetland revealed the system's apparent success in water treatment, especially in pH modification, removal of suspended solids, organic load and nutrients mean influent pH = 5·7 ± 0·5, mean effluent pH 7·7 ± 0·3; mean influent BOD5 = 1603·0 ± 397·6 mg/l, mean effluent BOD5 = 15·1 ± 2·5 mg/l; mean influent COD = 3749·8 ± 206·8 mg/l, mean effluent COD = 95·6 ± 7·2 mg/l; mean influent TSS = 195·4 ± 58·7 mg/l, mean effluent TSS = 4·7 ± 1·9 mg/l. As the wastewater flowed through the wetland system dissolved free and saline ammonia, NH4+, decreased from 14·6 ± 4·1 mg/l to undetectable levels at the outlet. Dissolved oxygen increased progressively through the wetland system. Analysis of the data available did not reveal temporal variation in the system's performance. However, significant spatial variation was evident as the wetland removed most of the common pollutants and considerably improved the quality of the water, making it safe for re‐use at the restaurants. Copyright © 2001 John Wiley & Sons, Ltd.

Application of Integrated Chemical - Physical Processes Modelling to Aeration Treatment of Anaerobic Digester Liquors

A three phase (aqueous/solid/gas) mixed weak acid/base kinetic model developed by Musvoto et al. is applied to simulate the physical and chemical processes that occur on aeration of anaerobic digester liquors. Included in the model are the kinetic reactions for (i) weak acid/base dissociations (water, carbonate, ammonium, phosphate, and short-chain fatty acids), (ii) precipitation of struvite, newberyite, amorphous calcium phosphate, calcium and magnesium carbonate, (iii) ion pair formation and (iv) stripping of CO2 and NH3 gases. To generate data for model application, batch aeration tests were conducted on two anaerobic digester liquors from (i) a spent wine upflow anaerobic sludge bed (UASB) digester and (ii) a sewage sludge anaerobic digester. In the batch tests pH, Ca, Mg, PO4-P, free and saline ammonia (FSA) and H2CO3* alkalinity (from which inorganic carbon is calculated) were measured. After establishing from the literature values for (i) weak acid/base equilibrium constants (pKa), (ii) weak acid/base kinetic rate constants (Kra), and (iii) ion pair stability constants (pKST), and trial and error determination of (iv) mineral solubility products (pKSP) (within the range reported in the literature), (v) ion pair kinetic rate constants (KrIP), (vi) mineral precipitation rate constants (Kppt) and (vii) gas stripping rates (KrG), a good correlation between predicted and measured data was obtained for all the parameters for both liquors. The solubility product values for the minerals that precipitated were the same for both liquors and fall in the range of values quoted in the literature, but the specific precipitation rate constants of the minerals differed for the two liquors.

Dynamics of benthic macroinvertebrates in created wetlands receiving wastewater

This paper presents results of a study on the status and dynamics of benthic macroinvertebrates in a wetland constructed for wastewater treatment in Nairobi (Kenya), conducted for 16 weeks during the period between December 1995 and March 1996. Seventeen species of macroinvertebrates were recorded in the wetland. Species richness in the wetland was 9.6 ± 1.3 while species diversity index was 0.466. Mean pH and dissolved oxygen increased gradually from the intake point to the outlet while the BOD5, suspended solids and free and saline ammonia decreased as the wastewater flowed throughout the wetland. The benthic macroinvertebrate community was poorly developed while microbial community appeared to be well developed. It was evident that the community structure improved with the purification of wastewater along the wetland. As discussed in the paper, aquatic benthos are crucial to wetlands ecosystems function and they are potential indicators of health of these ecosystems.

Integrated chemical–physical processes modelling—II. simulating aeration treatment of anaerobic digester supernatants

A three phase (aqueous/solid/gas) mixed weak acid/base kinetic model is developed to simulate the physical and chemical processes that occur on aeration of anaerobic digester supernatant. Included in the model are the kinetic reactions for (i) weak acid/base dissociations (water, carbonate, ammonium, phosphate, and short-chain fatty acids), (ii) precipitation of struvite, newberyite, amorphous calcium phosphate, calcium and magnesium carbonate and (iii) stripping of CO 2 and NH 3 gasses. A preliminary validation of the model is done using data available in the literature. The model was then applied to simulate batch aeration tests on two anaerobic digester supernatants from (i) a spent wine upflow anaerobic sludge bed digester and (ii) a sewage sludge anaerobic digester. In the batch tests pH, Ca, Mg, PO 4-P, free and saline ammonia (FSA) and H 2CO 3 ∗ Alkalinity (from which inorganic carbon is calculated) were measured. After establishing (i) the minerals most likely to precipitate viz. struvite (MgNH 4PO 4), newberyite (MgHPO 4), amorphous calcium phosphate (ACP), CaCO 3 and MgCO 3 and trial and error determination of (ii) the solubility products, (iii) specific precipitation rate constants and (iv) the specific gas stripping rates, a good correlation was obtained for all the parameters for both supernatants. The solubility product values for the minerals that precipitated were the same in both supernatants, and fall in the range of values quoted in the literature but the specific precipitation rate constants of the minerals were different in the two supernatants. Compared to the equilibrium chemistry approach to modelling three phase mixed weak acid/base systems, the kinetic approach facilitates (i) integration of the weak acid/base model with biological kinetic models and (ii) determination of solubility products and precipitation rates in an integrated manner for a number of minerals simultaneously from a single batch test.

Modelling struvite precipitation in anaerobic treatment systems

Struvite precipitation is common in waste water systems containing high concentrations of dissolved orthophosphates, free and saline ammonia and magnesium ions, such as in anaerobic fermentation systems, often leading to severe fouling. It appears that a reduction of the partial pressure of CO2, ie. pCO2 is a trigger mechanism for struvite precipitation. An algorithm was developed, based on equilibrium chemistry, to quantitatively predict the struvite precipitation potential of the water in such a process. This was then extended, to predict the change in state together with precipitation potential due to chemical perturbations, particularly variations of pCO2. Experimental verification of the algorithms is presented.

A technique for the measurement of total ammonia in small volumes of seawater and haemolymph

Abstract A rapid and precise technique combining flow-injection analysis and gas-diffusion is described for the measurement of total ammonia (NH3 + NH4 +) in small volumes (100–450 μl) of seawater and diluted haemolymph. Calibration of the method with seawater ammonia standard solutions in the range 1.0–50.0 μmol ammonia l-1 (n=8), and with saline ammonia standard solutions in the range 5.0–50.0 μmol ammonia l-1 (n=6)gave linear calibration curves (r=O.999 in each case) with precision in the range 0.2–3.0%. Precision of measurement of ammoniain samples of seawater and diluted haemolymph was 0.9–3.3% (n=11–13). The lower limit of detection is 0.20 μmol ammonia l-1. Thirty determinations can be made per hour.

The Production of Easily Dyed Wool ‐ An Evaluation of Saline Ammonia Scouring

Treatment of wool with dilute ammonia solutions containing salt for short times at low temperatures modifies the wool to make it readily dyeable at 50–70°C. A saline ammonia scouring procedure to produce an easily dyed wool has been developed and has been evaluated both as a scouring procedure with particular preservation of wool quality and as a means of producing wool that can be dyed at 50–70°C. A short‐time dyeing cycle for Lanasol (CGY) dyes is considered in detail.

Biochemistry of water-logged soils: Part I. The effect of water-logging on the different forms of nitrogen, on the reaction, on the gaseous relationships, and on the bacterial flora

Rothamsted and Indian soils were water-logged in the absence of freshly decomposing organic matter.Nitrogen changes: Water-logging resulted in:(1) A distinct increase in the free and saline ammonia content.(2) A significant though only slight diminution in the nitric nitrogen.(3) No marked loss of ammonia by volatilisation or otherwise in the gaseous form: nor considerable variation in the nitrites: nor any observable diminution in the total nitrogen.Reaction: Water-logging resulted in an increase in alkalinity; the increase in pH value was closely correlated with the corresponding increase in ammonia.Gaseous relations: Water-logging resulted in:(1) No release of any soluble reducing matter capable of absorbing dissolved oxygen.(2) No appreciable carbon dioxide production.(3) An absorption of dissolved oxygen from the surface water. An equation has been worked out expressing the concentration gradient of dissolved oxygen with depth.Bacterial numbers:From bacterial counts on water-logged soils it was found that:(1) There was significant though slight decrease in bacterial numbers on Thornton's Agar.(2) Very few colonies were obtained by plating aerobically (and fewer still anaerobically) on Giltay's Agar. None of the organisms appearing on the plates brought about any nitrate reduction in soils.(3) The total counts on gelatine plates also showed some decrease. The numbers of gelatine-liquefiers on the other hand did not vary. There was no evidence to suggest that the increased production of ammonia was due to the activity of the gelatine-liquefiers.Agency responsible for ammonia formation:The results indicate that the formation of ammonia in water-logged soils is not due to biological action. It is suggested that the action is due to an enzyme.