Intertidal Wetland Sediments Research Articles

Aerobic granular sludge inoculant for enhancing high salinity wastewater treatment: Performance and value-added biopolymer recovery

In this study, two lab-scale aerobic granular sludge (AGS) systems, seeded with intertidal wetland sediment (IWS) and activated sludge (AS), were constructed to compare their treatment performances and alginate-like exopolymers (ALE) recovery potential in high salinity wastewater treatment. Both reactors (RIWS and RAS) exhibited excellent total organic carbon (TOC) reduction rates > 95.0 %, while RIWS exhibited an improved total nitrogen (TN) removal than RAS (84.4 % vs 75.7 %). The presence of several inorganic particulates (acted as nucleus) in IWS accelerated the formation of granules in RIWS. The ALE yield of RIWS reached 466.6 ± 52.2 mg/g VSS, which was 1.6 times higher than that of RAS (286.2 ± 5.2 mg/g VSS). Moreover, to illustrate the different ALE recovery potentials, the proposed ALE biosynthesis pathway was also assessed. It was observed that the abundance of function genes encoding ALE biosynthesis of RIWS was significantly higher than that of RAS, revealing its superior ALE recovery potential. This study proposed a novel and effective treatment method for high-salinity wastewater with high potential resource recovery.

Driving force of tidal pulses on denitrifiers-dominated nitrogen oxide emissions from intertidal wetland sediments

Intertidal wetland sediments are an important source of atmospheric nitrogen oxides (NOx), but their contribution to the global NOx budget remains unclear. In this work, we conducted year-round and diurnal observations in the intertidal wetland of Jiaozhou Bay to explore their regional source-sink patterns and influence factors on NOx emissions (initially in the form of nitric oxide) and used a dynamic soil reactor to further extend the mechanisms underlying the tidal pulse of nitric oxide (NO) observed in our investigations. The annual fluxes of NOx in the vegetated wetland were significantly higher than those in the wetland without vegetation. Their annual variations could be attributed to changes in temperature and the amount of organic carbon in the sediment, which was derived from vegetated plants and promoted the carbon-nitrogen cycle. Anaerobic denitrifiers had advantages in the intertidal wetland sediment and accounted for the major NO production (63.8 %) but were still limited by nitrite and nitrate concentrations in the sediment. Moreover, the tidal pulse was likely a primary driver of NOx emissions from intertidal wetlands over short periods, which was not considered in previous investigations. The annual NO exchange flux considering the tide pulse contribution (8.93 ± 1.72 × 10–2 kg N ha–1 yr–1) was significantly higher than that of the non-pulse period (4.14 ± 1.13 × 10–2 kg N ha–1 yr–1) in our modeling result for the fluxes over the last decade. Therefore, the current measurement of NOx fluxes underestimated the actual gas emission without considering the tidal pulse.

Tidal effects on carbon dioxide emission dynamics in intertidal wetland sediments

Understanding the control mechanisms of carbon dioxide (CO2) emissions in intertidal wetland sediments is beneficial for the concern of global carbon biogeochemistry and climate change. Nevertheless, multiple controls on CO2 emissions from intertidal wetland sediments to the atmosphere still need to be clarified. This study investigated the effect of tidal action on CO2 emissions from salt marsh sediments covered by Spartina alterniflora in the Jiaozhou Bay wetland using the static chamber method combined with an infrared CO2 detector. The results showed that the CO2 emission fluxes from the sediment during ebb tides were higher than those during flood tides. The whole wetland sediment acted as a weak source of atmospheric CO2 (average flux: 24.44 ± 16.80 mg C m−2 h−1) compared to terrestrial soils and was affected by the cycle of seawater inundation and exposure. The tidal influence on vertical dissolved inorganic carbon (DIC) transport in the sediment was also quantitated using a two-end member mixing model. The surface sediment layer (5–15 cm) with maximum DIC concentration during ebb tides became the one with minimum DIC concentration during flood tides, indicating the DIC transport from the surface sediment to seawater. Furthermore, aerobic respiration by microorganisms was the primary process of CO2 production in the sediment according to 16 S rDNA sequencing analysis. This study revealed the strong impact of tidal action on CO2 emissions from the wetland sediment and provided insights into the source-sink pattern of CO2 and DIC at the land-ocean interface.

Characteristics of Bacterial and Archaeal Communities in Microbial‐Enhanced Constructed Wetlands under NaCl Stress

AbstractHigh salt concentrations can restrict or inhibit microorganism activity, which can detrimentally influence pollutant degradation. In this study, intertidal wetland sediments (IWS) are introduced into constructed wetlands (CWs) as sources of microorganisms. The richness and evenness of bacterial and archaeal microbial communities in the presence of 150 × 10−3 m NaCl are evaluated by high‐throughput sequencing. The distinction of dominant functional microorganisms in CWs with and without IWS is also analyzed. Anaerolineales and thermomicrobia are the dominant microorganisms in IWS–CWs in the saline condition and are related to methane production. The abundance of Alphaproteobacteria, Myxococcales, and Xanthomonadales, related to dehydrogenation, is relatively high in IWS–CWs. The addition of IWS induces further production of Anaerolineaceae and Geobacteraceae, which is positively correlated with the phosphorus‐accumulating and sulfate‐reducing stages. The dominant archaea phyla in IWS–CWs in the saline condition are Thaumarchaeota (87.5%) and Euryarchaeota (12.2%), which are involved in ammonia‐oxidizing and methane‐producing processes, respectively. These functional microbial communities are beneficial to the degradation and transformation of pollutants in the CWs. Thus, IWS with various halophilic and pollutant‐degrading microorganisms can be considered effective microbial sources to enhance the pollutant removal abilities of CWs.

Novel intertidal wetland sediment-inoculated moving bed biofilm reactor treating high-salinity wastewater: Metagenomic sequencing revealing key functional microorganisms

In this study, two lab-scale moving bed biofilm reactors (MBBR), seeded with intertidal wetland sediment (IWS) and activated sludge (AS), were constructed to compare their performances in treating high-salinity (3%) wastewater. Under a wide range of influent TOC (178–620 mg/L) and NH4+-N (25–100 mg/L), both the MBBRs (Riws and Ras) exhibited excellent TOC removal efficiencies of >95%. Regarding nitrogen reduction, Riws exhibited a significantly superior TN removal efficiency of 90.2 ± 1.8% than that of Ras (76.8 ± 2.9%). A correlation analysis was innovatively conducted comparing the results between metagenomic sequencing and DNA pyrosequencing, and positive linear relationships were found with R2 values of 0.763–0.945. Meanwhile, for illustration of different TN removal performance, nitrogen metabolic pathways were also assessed. Moreover, a list of functional oxidases (EC: 1.13.11.1, EC: 1.13.11.2, EC: 1.13.11.24, EC: 1.13.12.16, EC: 1.4.3.4, EC: 1.16.3.3, EC: 1.14.14.28) was found in IWS, revealing its potential in degradation of recalcitrant organics.

Sulfate removal performance and co-occurrence patterns of microbial community in constructed wetlands treating saline wastewater

The migration and transformation of sulfur is closely related to carbon sources. However, knowledge on the co-occurrence patterns of sulfur-related bacteria and other carbon-consuming microorganisms in constructed wetlands (CWs) is limited. In this study, CWs with intertidal wetland sediments (IWS), as microbial inoculant, was constructed to investigate the sulfate and chemical oxygen demand (COD) removal rates, microbial community composition, and co-occurrence network. IWS-enhanced CWs planted with Phragmites australis (PA+) and unplanted ones (CT+) were set up with controls (PA and CT). Results showed that the sulfate removal rate was higher in PA+ (60.60% ± 0.80%) than PA (44.64% ± 2.72%). The sulfate removal rate decreased and that of COD increased in PA+ and PA when the influent sulfate concentrations were raised. Microbial analysis indicated that the numbers of sulfate-reducing bacteria (SRB), sulfur oxidizing bacteria (SOB), and carbon-degrading bacteria improved the removal efficiency of sulfate in PA+ and CT+. The microbial topological pattern revealed that the exchange of matter, energy, and information by microorganisms in PA+ and CT+ was faster than that in PA and CT. The co-occurrence network analysis indicated that SRB (e.g., unclassified Desulfuromonadaceae) harbored negative correlations with denitrifying bacteria (e.g., Thauera, Flavobacterium, and unclassified Burkholderiaceae) because of electron donor competition. However, Flavobacterium and Thauera could cooperate to denitrify through different electron donors to avoid competition. Moreover, Pseudomonas and Amaricoccus had cross-feeding and cooperation in the network when carbon was restricted.

Long-term performance and microbial mechanism in intertidal wetland sediment introduced constructed wetlands treating saline wastewater

Saline wastewater requires a clean and efficient treatment method to avoid frequent public health events and nonpoint source pollution. This study explored intertidal wetland sediment (IWS) as an inoculation source for long-term operation in saline constructed wetlands (CWs). Four CWs planted with Phragmites australis were set up. In two of them, IWS was introduced for saline wastewater treatment (150 mg/L NaCl) and salt-free treatment; and set other CWs as control groups. Nutrient removal rates, microbial community, and functional genus were detected in IWS-introduced CWs and control CWs over three years. The average removal rates of total phosphorus and chemical oxygen demand were 17.37% and 20.35% higher, respectively, in IWS-introduced CWs than in control CWs under a salty environment. No significant difference in NH4+–N removal was observed among all treatments (p > 0.05), and the removal rates in all treatments were above 90%. Results showed that IWS-introduced CWs achieved high levels of halophilic bacteria (Proteobacteria), denitrifying bacteria (Actinobacteria, Gammaproteobacteria), and anaerobic phosphate-accumulating organisms (PAOs) (Alphaproteobacteria, Anaerolineae) in the substrate. The bacterial community of the rhizosphere was dominated by “Pseudonocardiaceae,” “Rhodobacteraceae,” and “Rhizobiaceae” in the IWS-introduced CWs, known as COD-removing bacteria and aerobic PAOs. These bacteria chronically enhanced the pollutant removal performance, salt tolerance, and operational stability of CWs in three years. Overall, microbial augmentation through the IWS as an inoculation source in CWs is effective and has potential in long-term saline wastewater treatment.

Novel Intertidal Wetland Sediment (IWS)-Inoculated MBBR Process Treating High-Salinity Wastewater: Metagenomic Sequencing Revealing Key Functional Microorganisms

Novel Intertidal Wetland Sediment (IWS)-Inoculated MBBR Process Treating High-Salinity Wastewater: Metagenomic Sequencing Revealing Key Functional Microorganisms

Phosphorus removal performance of microbial-enhanced constructed wetlands that treat saline wastewater

The discharge of phosphorus-rich saline wastewater deteriorates the water quality and causes frequent public health incidents. Therefore, this kind of wastewater must be treated using clean and efficient methods. The main objective of this study is to investigate the phosphorus removal performance in constructed wetlands (CWs) with intertidal wetland sediments (IWS) as a new microbial source for treating saline wastewater. IWS was introduced into the substrate of CWs planted with Phragmites australis. CWs without IWS and plants were set as the control groups. The phosphorus removal via plant uptake, substrate accumulation, and microbial transformation were evaluated, and the microbial community was analyzed under salty environment. Results showed that the removal rates in CWs with IWS (89.03% ± 1.47%) were higher than those in CWs without IWS (82.35% ± 1.58%). The microbial analysis revealed that numerous bacteria actively related to phosphorus removal, such as phosphorus-accumulating organisms, denitrifying PAOs, and phosphate solubilizing bacteria, were present in IWS-CWs. These bacteria enhanced the phosphorus removal through microbial transformation. Moreover, the addition of IWS increased the phosphorus loss via substrate accumulation, whereas the phosphorus removal rate via plant uptake decreased. The microbial augmentation of CWs with IWS as a new inoculation source is eco-friendly, economical, and effective and provides the possibility of applying CWs in the field of saline wastewater treatment.

Intertidal wetland sediment as a novel inoculation source for developing aerobic granular sludge in membrane bioreactor treating high-salinity antibiotic manufacturing wastewater

This study proposed a novel approach of cultivating aerobic granular sludge (AGS) using intertidal wetland sediment (IWS) as inoculant in MBR for saline wastewater treatment. Granulation was observed in IWS-MBR during start-up, with increased sludge particle size (3.1–3.3 mm) and improved settling property (23.8 ml/g). The abundant inorganic particulates (acted as nuclei) and distinctive microbial community in IWS contributed to the granules formation. With the help of AGS, IWS-MBR system exhibited excellent TOC reduction of 90.3 ± 6.1% and significant TN reduction of 31.2 ± 5.0%, while the control MBR (Co-MBR) only showed 58.9 ± 7.2% and 10.4 ± 2.7%, respectively. Meanwhile, membrane fouling was mitigated in IWS-MBR, with a longer filtration cycle of 21.5 d, as compared with that of 8.9 d for Co-MBR. Microbial community analysis revealed that abundant functional bacteria associated with granulation and pollutants removal were enriched from IWS and set the basis for AGS formation and the superior treatment performance.

Enhancement of COD removal in constructed wetlands treating saline wastewater: Intertidal wetland sediment as a novel inoculation

This study investigated intertidal wetland sediment (IWS) as a novel inoculation source for saline wastewater treatment in constructed wetlands (CWs). Samples of IWS (5–20 cm subsurface sediment), which are highly productive and rich in halophilic and anaerobic bacteria, were collected from a high-salinity natural wetland and added to CW matrix. IWS-supplemented CW microcosms that are planted and unplanted Phragmites australis were investigated under salty (150 mM NaCl: PA+(S) and CT+(S)) and non-salty (0 mM NaCl: PA+ and CT+) conditions. The chemical oxygen demand (COD) removal potential of IWS-supplemented CWs was compared with that of conventional CWs without IWS (PA(S) and CT(S), PA, and CT). Results showed that the COD removal rate was higher in PA+(S) (51.80% ± 3.03%) and CT+(S) (29.20% ± 1.26%) than in PA(S) (27.40% ± 3.09%) and CT(S) (27.20% ± 3.06%) at 150 mM NaCl. The plants' chlorophyll content and antioxidant enzyme activity indicated that the addition of IWS enhanced the resistance of plants to salt. Microbial community analysis showed that the dominant microorganisms in PA+(S) and CT+(S), namely, Anaerolineae, Desulfobacterales, and Desulfuromonadales, enhanced the organic removal rates via anaerobic degradation. IWS-induced Dehalococcoides, which is a key participant in ethylene formation, improved the plants’ stress tolerance. Several halophilic/tolerant microorganisms were also detected in the CW system with IWS. Thus, IWS is a promising inoculation source for CWs that treat saline wastewater.

Phosphorus Forms in Sediments of a River-Dominated Estuary

Estuaries are biologically productive transition zones between land and sea that play a vital role in transforming, recycling, and sequestering nutrients and organic matter, thus influencing nutrient loading to coastal systems. Yet, the processes involved in phosphorus (P) transformation and cycling among inorganic and organic P forms are poorly known in estuaries. To better understand the potential for P transformation and sequestration, we identified P forms and estimated their contributions to total P in intertidal wetland sediments of a river-dominated estuary (Columbia River, Oregon, USA) using solution 31P nuclear magnetic resonance spectroscopy (P-NMR). Inorganic P forms dominated sediment P extracts throughout the estuary, with orthophosphate accounting for 71–84% of total extracted P. However, biologically-derived inorganic and organic P forms were also detected. Polyphosphates were found in sediment extracts throughout the estuary, contributing as much as 10% of extracted P. Similar to other wetlands, orthophosphate monoesters and diesters made approximately equal contributions (~ 20%) to total extracted P. However, monoesters (e.g., phytate) were more abundant in sedimentary environments characterized by low organic matter content, while diesters (e.g., DNA) were more abundant in sedimentary environments with high organic matter, regardless of salinity. Collectively, the data show strong evidence for P transformation in sediments of a large, river-dominated estuary, which influences its transport to the coastal Pacific Ocean via the expansive Columbia River plume.

Pretreatment of saline antibiotic wastewater using marine microalga

A green microalga Chlorella sp. isolated from marine environment was investigated for its potential to pretreat saline antibiotic wastewater containing amoxicillin (AMX). Through Biolog EcoPlate assay, the Chlorella sp. showed its unique carbon source metabolic patterns under autotrophic condition. In addition, the microalga could effectively remove AMX (>99%) under initial AMX concentrations ranging from 10 to 150 mg/L through a treatability test. In the continuous AMX treatment using a lab-scale membrane photobioreactor (MPBR), a stable AMX removal efficiency of 85.6 ± 3.8% was observed. Moreover, with the aid of a subsequent bacterial treatment, the microalgal-bacterial process (the Chlorella sp. pretreatment followed by either intertidal wetland sediment or activated sludge) can achieve simultaneous AMX removal of >99% and total organic carbon (TOC) removal of ∼80%. In general, the microalgal pretreatment showed its great potential in effective removal of antibiotic residues, which could greatly enhance the overall treatment efficiency of saline antibiotic wastewater.

Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state.

A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes that the bulk volume of sediment equates to the sum of self‐packing volumes of organic and mineral components or BD = 1/[LOI/k1 + (1‐LOI)/k2], where k1 and k2 are the self‐packing densities of the pure organic and inorganic components, respectively. The model explained 78% of the variability in total BD when fitted to 5075 measurements drawn from 33 wetlands distributed around the conterminous United States. The values of k1 and k2 were estimated to be 0.085 ± 0.0007 g cm−3 and 1.99 ± 0.028 g cm−3, respectively. Based on the fitted organic density (k1) and constrained by primary production, the model suggests that the maximum steady state accretion arising from the sequestration of refractory organic matter is ≤ 0.3 cm yr−1. Thus, tidal peatlands are unlikely to indefinitely survive a higher rate of sea‐level rise in the absence of a significant source of mineral sediment. Application of k2 to a mineral sediment load typical of East and eastern Gulf Coast estuaries gives a vertical accretion rate from inorganic sediment of 0.2 cm yr−1. Total steady state accretion is the sum of the parts and therefore should not be greater than 0.5 cm yr−1 under the assumptions of the model. Accretion rates could deviate from this value depending on variation in plant productivity, root:shoot ratio, suspended sediment concentration, sediment‐capture efficiency, and episodic events.

Evidence of Nitrogen Loss from Anaerobic Ammonium Oxidation Coupled with Ferric Iron Reduction in an Intertidal Wetland.

Anaerobic ammonium oxidation coupled with nitrite reduction is an important microbial pathway of nitrogen removal in intertidal wetlands. However, little is known about the role of anaerobic ammonium oxidation coupled with ferric iron reduction (termed Feammox) in intertidal nitrogen cycling. In this study, sediment slurry incubation experiments were combined with an isotope-tracing technique to examine the dynamics of Feammox and its association with tidal fluctuations in the intertidal wetland of the Yangtze Estuary. Feammox was detected in the intertidal wetland sediments, with potential rates of 0.24-0.36 mg N kg(-1) d(-1). The Feammox rates in the sediments were generally higher during spring tides than during neap tides. The tidal fluctuations affected the growth of iron-reducing bacteria and reduction of ferric iron, which mediated Feammox activity and the associated nitrogen loss from intertidal wetlands to the atmosphere. An estimated loss of 11.5-18 t N km(-2) year(-1) was linked to Feammox, accounting for approximately 3.1-4.9% of the total external inorganic nitrogen transported into the Yangtze Estuary wetland each year. Overall, the co-occurrence of ferric iron reduction and ammonium oxidation suggests that Feammox can act as an ammonium removal mechanism in intertidal wetlands.

Investigation of intertidal wetland sediment as a novel inoculation source for anaerobic saline wastewater treatment.

Biological treatment of saline wastewater is considered unfavorable due to salinity inhibition on microbial activity. In this study, intertidal wetland sediment (IWS) collected from a high saline environment was investigated as a novel inoculation source for anaerobic treatment of saline pharmaceutical wastewater. Two parallel lab-scale anaerobic sequencing batch reactors (AnSBR) were set up to compare the organic removal potential of IWS with conventional anaerobic digested sludge (ADS). Under steady-state condition, IWS reactor (R(i)) showed organic reduction performance significantly superior to that of ADS reactor (R(a)), achieving COD removal efficiency of 71.4 ± 3.7 and 32.3 ± 6.1%, respectively. In addition, as revealed by fluorescent in situ hybridization (FISH) analysis, a higher relative abundance of methanogenic populations was detected in R(i). A further 16S rRNA gene pyrosequencing test was conducted to understand both the bacterial and archaeal community populations in the two AnSBRs. A predominance of halophilic/tolerant microorganisms (class Clostridia of bacteria, genera Methanosarcina, and Methanohalophilus of archaea) in R(i) enhanced its organic removal efficiency. Moreover, several microbial groups related with degradation of hardly biodegradable compounds (PAHs, n-alkenes, aliphatic hydrocarbons, and alkanes, etc.) were detected in the IWS. All these findings indicated that IWS is a promising inoculation source for anaerobic treatment of saline wastewater.

Dynamic Evaluation of Intertidal Wetland Sediment Quality in a Bay System

Intertidal wetlands are fragile ecological systems vulnerable to changing environmental conditions. Using the Rapid Assessment Approach, intertidal wetland sediments were dynamically evaluated in the Deep Bay, South China in terms of monitored benthic macroinvertebrates. The observation and expectation ratio indicated variations of intertidal wetland sediment quality had taken place at certain ecologically sensitive areas, such as the Mai Po Marshes. Series of dynamic models were used to simulate the behavior of certain environmental variables (i.e. cadmium, copper, lead and zinc accumulation rates) that might have adverse effect on the growth of benthic macroinvertebrates, and hence interpreted the results of the ecological assessment. The changes of sediment quality were primarily due to anthropogenic activities and were further attributed largely to the industrial discharged heavy metals which were unevenly distributed and heavily accumulated at some sensitivity areas (i.e. Futian National Natural Reserve and Mai Po Marshes) with help of sediment deposition altered by long-term tidal flow actions in Deep Bay.

Rapid Assessment of Intertidal Wetland Sediments

Urbanization of coastal areas poses a severe threat to ecologically valuable intertidal wetlands. This paper presents a pragmatic approach called Rapid Assessment for Intertidal Wetland Sediments (RAITWS) for evaluating the sediment quality of intertidal wetlands. RAITWS involves construction of reference groups, selection of a subset of environmental variables, matching of test sites to reference groups, prediction of the benthic fauna community structure (e.g. of macroinvertebrates) at test sites, evaluation of the Observation to Expectation ratio (O/E ratio), quantification of environmental variables with series of dynamic numerical models, and interpretation of the O/E findings. The proposed method extends the existing rapid biological assessment approach from static to dynamic applications. In particular, RAITWS provides a fast method of assessing intertidal wetland sites which are undergoing ecological change due to nearby coastal development.