Ammonia removal from composting leachate using zeolite. I. Characterization of the zeolite

Treatment of secondary urban wastewater with a low ammonium-tolerant marine microalga using zeolite-based adsorption

The low tolerance of marine microalgae to ammonium and hyposalinity limits their use in urban wastewater (UWW) treatments. In this study, using the marine microalga Amphidinium carterae, it is demonstrated for the first time that this obstacle can be overcome by introducing a zeolite-based adsorption step to obtain a tolerable UWW stream. The maximum ammonium adsorption capacities measured in the natural zeolite used are among the highest reported. The microalga grows satisfactorily in mixtures of zeolite-treated UWW and seawater at a wide range of proportions, both with and without adjusting the salinity, as long as the ammonium concentration is below the threshold tolerated by the microalgae (6.3 mg L^-1). A proof of concept performed in 10-L bubble column photobioreactors with different culture strategies, including medium recycling, showed an enhanced biomass yield relative to a control with no UWW. No noticeable effect was observed on the production of specialty metabolites.

A review on the application of nanoporous zeolite for sanitary landfill leachate treatment

This review deals with low-cost nanoporous zeolites for the treatment of sanitary landfill leachate. Organic contaminants and ammoniacal nitrogen are significant parameters in landfill leachate treatment. Adsorption processes are regarded as promising alternative treatment options in this respect. Zeolites are aluminosilicate materials that are widely used in separation, filtration, adsorption and catalysis. Natural zeolite is a low-cost and readily available form of zeolite and is a promising candidate to be used as an ion-exchange material for ammonia and other inorganic pollutant removal from landfill leachate. In this review, adsorption isotherms and kinetic models in batch systems are evaluated and adsorption design parameters of the fixed-bed system are presented. Studies on ammonia removal from landfill leachate via zeolites have been thoroughly investigated. Leachate treatment systems combined with zeolites are presented. Cost of zeolites are also reported in comparison with other adsorbents. The investigated studies demonstrate that activated zeolite can improve the removal of chemical oxygen demand, NH₃-N and colour significantly compared to the case where raw zeolite is used. Moreover, the composite of activated carbon and zeolite is also favorable for ammonia removal according to reported findings, where best adsorptive removal is attained on the composite media (24.39 mg/g).

Sodium adsorption by reusable zeolite adsorbents: integrated adsorption cycles for salinised groundwater treatment

Using Canadian (CMZ), Bear River (BRZ), and St. Cloud (SCZ) zeolites, this study investigates the application of natural and pre-treated zeolites for Na⁺ removal from salinised groundwater. Natural BRZ achieved better Na⁺ removal for initial concentrations of 250-10,000 mg Na⁺/L and had the highest maximum adsorption capacity (14.3 ± 0.4 mg/g) compared to natural CMZ (5.8 ± 0.5 mg/g) and SCZ (5.6 ± 0.7 mg/g). Natural BRZ exhibited a higher cation exchange capacity (CEC), mineralogical purity, and natural abundance of exchangeable calcium. The natural abundance of Na⁺ on CMZ and SCZ may have reduced Na⁺ adsorption. H-form BRZ and H-form CMZ were also prepared through conventional acidic pre-treatment. Acid treatment improved zeolite properties for adsorption (surface area and CEC). Synchrotron-based X-ray scanning transmission microscopy (STXM) indicated that Na⁺ adsorption sites in the H-form zeolites were associated with the mineral framework. However, sorption effluents were highly acidic (pH ∼2) and Al³⁺ leached significantly due to the dealumination induced by acid treatment. Alternatively, hard water softening was cyclically integrated with sodium adsorption as a zeolite treatment to generate Ca/Mg-form CMZ. This integration suggested the feasibility of combining CMZ cycles for water softening and sodium reduction for an extended CMZ lifecycle. Natural CMZ was first used to treat hard water, which enriched the CMZ with Ca²⁺ and Mg²⁺ and increased its subsequent Na⁺ removal rate by over 77%, without producing acidic effluents. The Canadian zeolite adsorbed more sodium when water softening was integrated with sodium removal, which is a repeatable dual-treatment.

Influence of the Natural Zeolite Particle Size Toward the Ammonia Adsorption Activity in Ceramic Hollow Fiber Membrane

Natural zeolite is widely used in removing ammonia via adsorption process because of its superior ion-exchange properties. Ceramic particle size affects the adsorptivity of particles toward ammonia. In this study, hollow fiber ceramic membrane (HFCM) was fabricated from natural zeolite via phase inversion. The effect of natural zeolite particle size toward the properties and performance of HFCM was evaluated. The results show that the HFCM with smaller particle sizes exhibited a more compact morphological structure with better mechanical strength. The adsorption performance of HFCM was significantly improved with smaller particle sizes because of longer residence time, as proven by the lower water permeability. A high adsorption performance of 96.67% was achieved for HFCM with the smallest particle size (36 μm). These findings provide a new perspective on the promising properties of the natural zeolite-derived HFCM for ammonia removal.

Treatment of de-icing contaminated surface water runoff along an airport runway using in-situ soil enriched with structural filter materials

Airport surface runoff during wintertime contains high concentrations of pavement de-icing fluids (PDFs). Uncontrolled discharge of this runoff poses a potential environmental hazard for the terrestrial and aquatic ecosystem. Several technologies for collection, transportation and treatment of contaminated runoff water are available, mainly technical systems, which require high operation and maintenance efforts. For moderately contaminated runoff, the discharge to a wastewater treatment plant is usually applied. In this study, a passive soil-based filter is proposed to treat the contaminated surface water runoff. The degradation of two PDFs was under investigation, namely Safeway® KA-Hot based on potassium acetate, and urea. The main research objective was to determine the capability of the in-situ soil and a soil based filter using zeolite and perlite as additional filter media to degrade the organic pollutants in the runoff. Column experiments at temperatures between 3 °C and 5 °C were carried out to determine the degradation potential when using 50% in-situ soil mixed with zeolite and perlite. Besides TOC, the nitrogen degradation was also under investigation. Due to the low temperatures, available nutrients are a key factor for the TOC degrading microorganisms. Overall TOC reduction rates were found from 76% up to 98%, with TOC effluent concentrations in the range of 18 to 870 mg·L^-1, depending on the influent concentration. Based on the results, the use of a soil-based filter is a promising, passive, natural based solution for the treatment of de-icing runoff.

Intensified nitrogen transformation in intermittently aerated constructed wetlands: Removal pathways and microbial response mechanism

Nitrogen (N) removal processing in vertical flow constructed wetlands (VFCWs) with different designs often varies greatly. Here, a long term VFCWs study for domestic wastewater treatment was carried out to investigate the impact of intermittent aeration and three construction-waste media (common gravel, red brick and fly-ash brick) on N loss, N retention and microbial community. The total nitrogen (TN) removal was significantly higher in aerated VFCWs (91.31%-93.91%) compared with non-aerated VFCWs (12.22%-53.92%), with the highest removal rate in system VI filled with fly-ash brick. Nitrification/denitrification was the main N sink in aerated VFCWs accounting for 36.79%-55.44%, while media storage (8.47%-48.64%) dominated in non-aerated systems because of nitrification limitation. <16% of the TN removal was uptake by plants, and N₂O emission contributed about 0.08%-0.39%. Microbial study found that functional bacteria increased with intermittently aeration. The analysis revealed the crucial influence of oxygen supply and media on N transformations in VFCWs.

Removal of excess nutrients by Australian zeolite during anaerobic digestion of swine manure

The objective of this study was to investigate the feasibility of using natural and NaCl-treated Australian zeolites to simultaneously remove excess nutrients from anaerobically digested swine manure. Ion adsorption and desorption properties of Australian zeolite during the anaerobic digestion of swine manure were investigated. Two experiments were conducted: the first was an adsorption experiment with multi-component solutions that corresponded with the ionic composition of swine manure digestates. The second experiment determined the effects of zeolite dose rates during anaerobic digestion of swine manure on the removal of N, P and K from solution. Adsorption isotherms confirmed selectivity for K⁺ over NH₄⁺ by Australian natural and sodium zeolites. Therefore, NH₄⁺ removal was considerably reduced when there was simultaneous K⁺ uptake. Natural zeolite desorbed more Ca²⁺ during K⁺ and NH₄⁺ adsorption than sodium zeolite. The ion exchange reaction was independent of the presence of P. P removal was very dependent on the pH of the medium. Natural Australian zeolite was shown to be a potential sorbent for the removal of NH₄⁺, K⁺ and P during the anaerobic digestion of swine manure. However, the application of high concentrations of zeolite at higher pH values (> 7.5) might not be appropriate for anaerobic digestion, because zeolite desorbed more Ca²⁺ ions into the solution at the higher doses of zeolite and then availability of P for microbial growth might be reduced as a result of PO₄^3- precipitation with Ca²⁺ at the higher pH.

Composting plant leachate treatment by a pilot-scale, three-stage, horizontal flow constructed wetland in central Iran

Handling and treatment of composting leachate is difficult and poses major burdens on composting facilities. The main goal of this study was to evaluate usage of a three-stage, constructed wetland to treat leachate produced in Isfahan composting facility. A pilot-scale, three-stage, subsurface, horizontal flow constructed wetland, planted with vetiver with a flow rate of 24 L/day and a 15-day hydraulic retention time, was used. Removal of organic matter, ammonia, nitrate, total nitrogen, suspended solids, and several heavy metals from Isfahan composting facility leachate was monitored over a 3-month period. Constructed wetland system was capable of efficiently removing BOD₅ (87.3%), COD (74.5%), ammonia (91.5%), nitrate (87.9%), total nitrogen (87.8%), total suspended solids (85.5%), and heavy metals (ranging from 70 to 90%) from the composting leachate. High contaminant removal efficiencies were achieved, but effluent still failed to meet Iranian standards for treated wastewater. This study shows that although a three-stage horizontal flow constructed wetland planted with vetiver cannot be used alone to treat Isfahan composting facility leachate, but it has the potential to be used as a leachate pre-treatment step, along with another complementary method.

Membrane bioreactor technology: a novel approach to the treatment of compost leachate

Compost leachate forms during the composting process of organic material. It is rich in oxidizable organics, ammonia and metals, which pose a risk to the environment if released without proper treatment. An innovative method based on the membrane bioreactor (MBR) technology was developed to treat compost leachate over 39days. Water quality parameters, such as pH, dissolved oxygen, ammonia, nitrate, nitrite and chemical oxygen demand (COD) were measured daily. Concentrations of caffeine and metals were measured over the course of the experiment using gas chromatography - mass spectrometry (GC/MS) and inductively coupled plasma - mass spectrometry (ICP-MS) respectively. A decrease of more than 99% was achieved for a COD of 116g/L in the initial leachate. Ammonia was decreased from 2720mg/L to 0.046mg/L, while the nitrate concentration in the effluent rose to 710mg/L. The bacteria in the MBR system adjusted to the presence of the leachate, and increased 4 orders of magnitude. Heavy metals were removed by at least 82.7% except copper. These successful results demonstrated the membrane bioreactor technology is feasible, efficient method for the treatment of compost leachate.

Zeolites in Wastewater Treatment

The world consumption of natural zeolites is approximately 6.0 Mt annually and is increasing at a fast rate. Natural zeolites are crystalline hydrated aluminosilicates with a framework structure containing pores. The porous zeolite is host to water molecules as well as a variety of positively charged ions. One important property of zeolites is the ability to exchange cations. Owing to their high cation-exchange ability as well as to their molecular sieve properties, natural zeolites have been widely used as adsorbents in separation and purification processes in recent decades. In this chapter we review the recent developments of natural zeolites as adsorbents in wastewater treatment, specifically for the removal of ammonia from wastewater.

Advanced regeneration and fixed-bed study of ammonium and potassium removal from anaerobic digested wastewater by natural zeolite

Highly efficient regeneration of natural zeolite was developed in conjunction with the removal of high concentrations of ammonia and potassium from the reverse osmosis effluent of anaerobic-digested wastewater by fixed-bed ion exchange. The elution and uptake behavior of ammonium and potassium in the fixed bed were studied. Both batch desorption tests and on-column regeneration were conducted to develop an optimum regeneration condition compatible with the wastewater requirements. The effectiveness of ammonium elution increased with increasing alkaline concentration. The increase of salt dose significantly enhanced the ammonium maximum in the elution solution. Complete ammonium elution was achieved in 6 bed volumes (BV) when the alkaline and salt concentrations were respectively 0.1 mol/L and 18.6 g/L at a flow rate of 2.5-3.0 BV/hr. Due to the higher affinity of potassium with natural clinoptilolite, complete potassium elution was not achieved in all cases.

Study on a fixed zeolite bioreactor for anaerobic digestion of ammonium-rich swine wastes

In this study, a fixed zeolite bioreactor was developed for the anaerobic digestion of ammonium-rich swine wastes (NH(4)(+)-N=3770 mg/l). To investigate the performance of the reactor, a sunken zeolite bioreactor and a bioreactor without zeolite were used as controls. The new bioreactor exhibited good performance, with startup time on the 14th day and methane production of 178.5 ml/g-VS during all 32 days of the experiment at 35°C. This bioreactor significantly shortened startup time, enhanced methane gas yield more than twofold and made COD removal more efficient than under the other models. Furthermore, it reduced the inhibition of high ammonium concentration during the anaerobic digestion of ammonium-rich swine wastes via effective ammonium removal and the immobilisation of microorganisms. Because of its simple structure and good performance, the fixed zeolite bioreactor can be recommended for future use.

Influence of heavy metal supplementation on specific methanogenic activity and microbial communities detected in batch anaerobic digesters

Natural and modified zeolites (0.5-1.0 mm) from the Tasajera deposit in Cuba were used to enhance the anaerobic digestion process of synthetic substrates. Natural zeolites were modified by ionic exchange and by adsorption with nickel, cobalt and magnesium. The experiments were carried out by using an inoculum from a full-scale anaerobic reactor treating winery wastewater. Modified natural zeolites not only enhanced the anaerobic digestion process, but also increased the specific methanogenic activity (SMA) of the sludges. The textural and chemical surface characteristics of the modified zeolites were related to the process performance, volatile fatty acid (VFA) production and microbial communities found in the digesters. For the selected dose of modified zeolites [0.05 g/g of volatile suspended solids (VSS)], the lowest concentration was found for cobalt followed by nickel and magnesium. Based on the analyses of anaerobic biofilms, the heavy metal incorporated into the zeolite was shown to have a great influence on the predominance of species. For example, the presence of nickel and cobalt favoured Methanosaeta, while at the same dose magnesic zeolite stimulated the presence of Methanosarcina and sulfate-reducing bacteria (SRB). In digesters with modified zeolites and metal supplementations the values of SMA were higher than those obtained in the control and natural zeolite digesters.

Ammonium and potassium removal for anaerobically digested wastewater using natural clinoptilolite followed by membrane pretreatment

On the basis of the wastewater characteristic of anaerobically digested wastewater, this work studied the individual and simultaneous adsorption of ammonium and potassium ions by the natural clinoptilolite. Langmuir, Freundlich, Langmuir-Freundlich, and Toth model were employed to fit the experimental isotherm data and the fitting performances of different models were compared. Both the individual and simultaneous adsorption kinetics of ammonium and potassium were studied at various pHs and temperatures. The individual adsorption of ammonium was very fast and potassium uptake was even faster than that of ammonium. The adsorption approached equilibrium within 1h in most cases. Five models, including pseudo-first-order, pseudo-second-order, Vermeulen's model, squared driving force model and Elovich equation were used to fit the individual and simultaneous adsorption kinetics of ammonium and potassium. The validities of the fittings for the ammonium and potassium adsorption kinetics were also evaluated.

An evaluation of reactive filter media for treating landfill leachate

A laboratory bench-scale column study was conducted to evaluate permeable reactive filter materials as a new method for removal of heavy metals and inorganic nitrogen from landfill leachate. Mixtures of sand and peat, blast-furnace slag (BFS) and peat, and Polonite and peat were tested by loading columns with leachate collected from a pond at Tvetaverket Landfill, Sweden. Sand, peat and Polonite represent natural materials. BFS is a by-product from steel-works. The metal treatment efficiencies of the media were assessed and Polonite was found to perform best, where Mn, Fe, Zn and Cu concentrations were removed by 99%, 93%, 86% and 67%, respectively. This material was also able to reduce inorganic N by 18%. The BFS showed good removal efficiency for Cu (66%), Zn (62%), Ni (19%) and Mo (16%). The sand-peat mixture did not demonstrate a promising removal capacity for any of the elements studied with the exception of Cu (25%). The removal of different elements was suggested to be a combination of several factors, i.e. precipitation, ion exchange and adsorption. Prior to full-scale application of reactive filters at a landfill site, matrix selection, filter design and operational procedures must be developed.