Modelling struvite precipitation in anaerobic treatment systems

Loewenthal, R. E.; Kornmüller, U. R. C.; Heerden, E. P. van

doi:10.2166/wst.1994.0592

Cited by 77 publications

(46 citation statements)

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“…This mix of weak and strong acids and bases at different concentrations is evaluated to check if phosphate precipitates with metal cations and ammonia. These processes are well described by Loewenthal et al (1994) and Harding (2009) for determining ionic products of the different cations and anions that make up various minerals in anaerobic digester dewatering liquor. These same principles are applied to the aqueous phase aerobic and anoxic-aerobic digestion at high and low TSS concentrations.…”

Section: Methodsmentioning

confidence: 91%

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The removal of N and P in aerobic and anoxic-aerobic digestion of waste activated sludge from biological nutrient removal systems

M¹,

Ikumi²,

Ekama³

2016

WSA

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Biological nutrient removal (BNR) activated sludge (AS) systems produce a waste activated sludge (WAS) that is rich in nitrogen (N) and phosphorus (P). When this sludge is thickened to 3-6% total suspended solids (TSS) and digested (aerobic or anaerobic), a high proportion of N and P are released to the bulk liquid resulting in high concentrations of ammonia/nitrate and orthophosphate up to several hundred mg/ℓ (without denitrification or P precipitation). This research investigates P removal by P precipitation in anoxic-aerobic digestion of P-rich BNR system WAS. The experimental setup for this work was a lab-scale membrane UCT BNR system fed real settled sewage with added acetate, orthophosphate, and cations Mg and K to increase biological excess P removal. This WAS was fed to batch aerobic digesters at various TSS concentrations, and to two 20-day retention time continuous anoxic-aerobic digesters (AnAerDig) with aeration cycles of 3-h air on and 3-h air off, one fed concentrated WAS (20 g TSS/ℓ ) and the other fed diluted WAS (3 g TSS/ℓ). Nitrogen removal has been discussed in the previous paper. This paper focuses on the P removal by P precipitation observed in the batch tests and continuous systems. The rate of polyphosphate release (b GP ) during batch aerobic digestion at low TSS without P precipitation was found to be 2.5 times faster than the endogenous respiration rate (b G ) of phosphorus accumulating organics (PAO), i.e. b GP = 0.1/d. This rate was then applied to the high-TSS aerobic batch tests and continuous anoxic-aerobic digesters to estimate the P precipitation at various TSS concentrations, with and without additional Mg or Ca dosing. Newberyite (MgHPO 4 ·3H 2 O) and amorphous tricalcium phosphate (ACP or TCP, Ca 3 (PO 4 ) 2 ·xH 2 O) are found to be the most common phosphate precipitates.

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Section: Methodsmentioning

confidence: 91%

“…To determine and quantify which phosphate minerals precipitate, weak acid/base chemistry principles (Loewenthal et al, 1994) were applied to the actual and predicted dewatering liquor (DWL) aqueous phases. Interestingly, struvite was found not to precipitate, most likely due to the complete nitrification of ammonia released in digestion.…”

Section: Introductionmentioning

confidence: 99%

The removal of N and P in aerobic and anoxic-aerobic digestion of waste activated sludge from biological nutrient removal systems

M¹,

Ikumi²,

Ekama³

2016

WSA

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“…Precipitation of struvite is a common phenomenon in anaerobic treatment of both wine distillery and piggery waste waters, and also sludge waste derived from excess biological phosphate removal systems. The reason for this is that these wastes contain higher than usual concentrations of dissolved ortho-phosphates, free and saline ammonia and magnesium ions and these species form the components of mineral struvite [38]. Based on the chemical structure of struvite (MgNH 4 PO 4 _6H 2 O) and the molar fractions of N and P and assuming that all removed P (0.34 g/c.d), the maximum possible N removal is 0.15 g.c.d.…”

Section: Daily Pollutant Contribution/ Pollution Fluxesmentioning

confidence: 99%

Wastewater characteristics in partially sealed cesspit: case study from Beit Dajan, Palestine

Al-Atawneh¹,

Mahmoud²,

Steen³

et al. 2017

Eco-Tech

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Raw domestic wastewater from an individual home was characterised and the water quality was followed after disposal to a partially sealed cesspit over the whole filling period of 4 months. The results revealed that raw wastewater was of medium strength according to the US EPA classification, and was more concentrated than Palestinian municipal sewage. Septage is the water accumulating in the pit, but above the accumulated bottom sludge. The septage was more concentrated than the raw sewage. The specific household water consumption, wastewater generated, septage collected by vacuum truck and septage water infiltration were respectively (59 L/c.d; 100%), (52 L/c.d; 87%), (11 L/c.d; 19%) (Cu, Pb, Mn, Fe and Zn) in septage water were not in compliance with heavy metals concentration limits of the Palestinian regulations for wadi disposal and effluent reuse in agriculture. As a consequence, septage disposal in wadis and agricultural fields is not safe. However, according to municipal regulations, the heavy metals concentrations allow septage to be disposed in the Al-Bireh wastewater treatment plant septage receiving unit, to be further treated in the aerobic system. Regarding nitrogen that is removed in the cesspit, the vast majority will most likely exfiltrate out of the cesspit into the surrounding soil, and might potentially reach 1

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“…These in turn dictate, indirectly via pH or through direct inhibition, the rate of many biological processes including nitrification/denitrification, uptake/release of phosphorus and anaerobic digestion , Ganigué et al 2010, Hellinga et al 1999, Lopez-Vazquez et al 2009, Van Hulle et al 2007). Furthermore, the weak acid-base system impacts on other physicochemical processes such as chemical precipitation, spontaneous minerals precipitation and stripping of carbon dioxide and ammonia (Loewenthal et al 1995), as also highlighted in Figure 1.1. Current standardized biological models in the wastewater sector such as the ASM and ADM series (Batstone et al 2002, Henze et al 2000 contain limited and simplistic descriptions of physicochemical reactions (Batstone 2009.…”

Section: Figure 11 -Major Physicochemical Processes Occurring In a Tmentioning

confidence: 99%

“…The proton balance required the quantification of the total concentration of protons or pH as an input (Loewenthal et al 1995). Similarly, the charge balance sometimes requires the calculation of residual charge as an input (Batstone et al 2002), unless all ionic components in the wastewater are known.…”

Section: Algebraic Equation Setmentioning

confidence: 99%

Dynamic modelling of minerals precipitation in wastewater treatment

Mbamba¹

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In wastewater treatment, there is an increasing focus on nutrient and energy recovery and a reduction in energy consumption to counter climate change. Because of this, integrated mathematical modelling platforms are required to support plant-wide developments making use of emerging, resilient and environmental-friendly technologies. A reliable model description of a wastewater treatment plant should include both biology and physico-chemistry. However, existing standard models used across the wastewater sector have a biological focus with over-simplified descriptions of important physicochemistry, especially with minerals precipitation which is a very important class of physicochemical reactions.As part of development of a more widely applicable physicochemical framework, this thesis sought to identify a suitable minerals precipitation modelling approach that could give reasonable results in mainstream use with wastewater treatment. This research aim was approached in three steps. Firstly a review of available modelling approaches suggested a simple equilibrium kinetic-based modelling approach could be feasible. This approach was then validated in a simple system of calcite in synthetic solutions using pH titration experiments with the reliable Constant Composition Method (CCM).Further statistical analysis focused on clarifying key environmental factors that influence calcite precipitation to determine whether these are necessary to include in a model. Secondly, the proposed model approach was further tested on different types of wastewater and for multiple parallel precipitation reactions. Experiments included dynamic titration or aeration with synthetic wastewater and real wastewater. Thirdly, the general physicochemical modelling approach was implemented in a plant-wide platform together with standard biological models, namely activated sludge model No 2 (ASM2d) and Anaerobic Digestion Model No. 1 (ADM1). The plant-wide model evaluation compared simulations with real data from a full-scale wastewater treatment plant, and used steadystate, dynamic and scenario analyses to test the model performance.Experimental evidence for calcite precipitating in synthetic aqueous solutions, suggested that minerals precipitation kinetics could be reliably described with a 1 st order dependency on mineral Further testing for multi-species systems in real wastewater indicated that precipitation was dominated by the mineral struvite, forming together with varied and minor amounts of calcium phosphate and some calcium carbonate. Kinetic rate coefficients (kcryst), which were statistically fitted, were generally in the range 0.35-11.6 h -1 with 95% confidence intervals of 10-80% relative.The results confirmed that the baseline model approach provided a statistically good fit of measured pH, dissolved calcium, magnesium, total inorganic carbon and phosphate. With this application, the precipitation modelling approach offered the advantage of only requiring a minimal number of empirical fitted parameters (kcryst values), res...

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Modelling struvite precipitation in anaerobic treatment systems

Cited by 77 publications

References 0 publications

The removal of N and P in aerobic and anoxic-aerobic digestion of waste activated sludge from biological nutrient removal systems

The removal of N and P in aerobic and anoxic-aerobic digestion of waste activated sludge from biological nutrient removal systems

Wastewater characteristics in partially sealed cesspit: case study from Beit Dajan, Palestine

Dynamic modelling of minerals precipitation in wastewater treatment

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