Optimization of a compact on-site stormwater runoff treatment system: Process performance and reactor design.

Stormwater runoff has become a major anthropogenic urban pollution source that threatens water quality. In this study, coagulation-sedimentation, and ammonium ion exchange and regeneration (AIR) modules were coupled as a CAIR system to efficiently treat stormwater runoff. In the coagulation module, 99.3%, 91.7%, and 97.0% of turbidity, total phosphorus, and chemical oxygen demand could be removed at an optimized poly-aluminum ferric chloride dosage of 30 mg/L, and the continuous experiment confirmed that the full load mode was more suitable for its rapid start-up. In the AIR module, dynamic ammonium removal indicated that the breakthrough time decreased with the rising initial concentration and superficial velocity. The Modified Dose Response (MDR) model described the ammonium exchange behavior better than the Thomas and the Bohart-Adams models. Then, a design flow of the ion exchange reactor was constructed by correlating constants in the MDR model with engineering parameters, and the ion exchange reactor was designed for continuous operation of the CAIR system. The average concentrations of chemical oxygen demand, total phosphorus, ammonium nitrogen, and total nitrogen in the effluent of the CAIR system were 7.22 ± 2.26, 0.17 ± 0.05, 1.49 ± 0.01, and 1.62 ± 0.02 mg/L, respectively. The almost unchanged exchange capacity and physicochemical properties after the multicycle operation confirmed the durability of zeolite for ion exchange. Techno-economic analysis suggested that the CAIR system is practically promising for stormwater management with efficient pollutants removal, small footprint, and acceptable operating cost.

Water quality assessment of the Karasu River (Turkey) using various indices, multivariate statistics and APCS-MLR model.

Determining the water quality status of a river and accurately identifying potential pollution sources threatening the river are pillars in effective control of pollution and sustainable water management. In this study, water quality indices, multivariate statistics and absolute principal component score-multiple linear regression (APCS-MLR) were applied to evaluate the water quality of the Karasu River, the main tributary of the Euphrates River (Turkey). For this, 19 water quality variables were monitored monthly at eight stations along the river during one year. Based on the mean dissolved oxygen (DO), electrical conductivity (EC), nitrate-nitrogen (NO3-N), orthophosphate-phosphorus (PO4-P), total phosphorus (TP), ammonium-nitrogen (NH4-N), chemical oxygen demand (COD) and total nitrogen (TN) levels, most stations of the river had "very good" water status according to surface water quality criteria. Spatial cluster analysis (CA) divided eight stations into three regions as clean region, moderate clean region and very clean region. The mean values of Nutrient Pollution Index indicated that the river was "no polluted". Similarly, Water Quality Index and Organic Pollution Index values indicated that the river water quality was between "good" and "excellent". A minimum water quality index (WQImin) consisted of ten crucial parameters was not significantly different with the WQI based on all the 17 parameters. Discriminant analysis (DA) results showed that water temperature (WT), EC, chlorophyll-a (Chl-a), potassium (K), calcium (Ca), NO3-N and COD are the variables responsible for temporal changes, while WT, total dissolves solids (TDS), Chl-a, K, magnesium (Mg), Ca, NH4-N and COD are the variables responsible for spatial changes in the river water quality. Principal component analysis/factor analysis (PCA/FA) identified four potential sources, including anthropogenic, natural, seasonal and phytoplankton. Source apportionment in the APCS-MLR model revealed that seasonal and anthropogenic sources contributed 35.2% and 25.5% to river water quality parameters, respectively, followed by phytoplankton (21.4%) and natural sources (17.9%).

Chemometric and risk assessment of nitrogen composition of atmospheric rainwater from diverse surfaces in Rivers State, Nigeria.

Organic and inorganic nitrogen ions in the environment play important role across environmental matrices. Rainwater samples collected from ambient and different roofing surfaces (zinc, aluminium, asbestos and stone-coated roofing sheets) from selected locations at Ogale, Rumuodomaya/Rumuodome, Diobu and Chokocho within Rivers State, Niger Delta, Nigeria, from April to June, July to August and September to October depicting three regiments of early, mid and late rains. The samples were analysed for Kjeldahl nitrogen, ammonium, nitrate and nitrite using APHA methodology. Quantitative assessment showed that Kjeldahl nitrogen were in range of 0.11 to 28.05 mg/L; ammonium 0.50 to 20.22 mg/L, nitrate from 0.12 to 22.69 mg/L and nitrite from 0.15 to 3.90 mg/L. Parameters decreased from early to late rain, which can be attributed to rain dilution factor potential, wind pattern and emission from anthropogenic sources that influenced the rainwater quality across surfaces. Nitrogen results showed that dry and wet deposition has great impact; atmospheric aerosols and biogeochemical interactions can affect water quality. Monthly variation showed that Ogale had high regression compared to other locations due to close proximity to oil and gas emission and marine contribution. Neutralization factor showed that nitrate-nitrite compounds have strong correlation with ammonium ion. Non-carcinogenic risk assessment using US EPA model showed hazard index less than one (1), thus no associated health effect of nitrate and nitrite in rainwater. In conclusion, it is evident that nitrate/nitrite levels and other nitrogen derivatives in rainwater in crude oil-producing Niger Delta and its continuous consumption can cause negative health outcome.

Reducing nutrient increases diatom biomass in a subtropical eutrophic lake, China-Do the ammonium concentration and nitrate to ammonium ratio play a role?

Response of aquatic organisms to eutrophication have been well reported, while less studies are available for the recovery of eutrophic lakes following a reduction in the external loading, especially for systems where nitrogen is reduced but the phosphorus concentration is maintained high due to internal loading. Diatoms are nitrate (NO3-N) opportunists but can also use ammonium (NH4-N). They may, therefore, be more sensitive to nitrogen reduction than other algae that typically prefer NH4-N. We document the variations of nutrients and diatoms in subtropical, eutrophic Lake Taihu over 28 yr during which a reduction of the external loading resulted from lake management. According to the results of change point analysis, data on environmental variables were divided into two periods (P1: 1992-2006; P2: 2007-2019) with two different seasons (WS: Winter-Spring; SA: Summer-Autumn), respectively. Compared with P1-WS, the concentration of NH4-N decreased significantly whereas NO3-N showed no significant change in P2-WS. In contrast, NH4-N concentrations were low and showed no significant changes in P1-SA and P2-SA and NO3-N decreased significantly in the latter period. Accordingly, NO3-N: NH4-N mass ratios in P1-SA and P2-WS were all significantly higher than those in P2-SA and P1-WS, respectively. The biomass of WS diatom increased significantly and the timing of the peak biomass shifted from P1-SA to P2-WS since 2007. The SEM analysis showed that NO3-N was retained as a statistically significant predictor for diatom biomass in P1-SA and significant effects of windspeed, zooplankton and NH4-N on diatom biomass in P2-WS. Windspeed and zooplankton have further changed the biomass of diatoms in the case of declining inorganic nitrogen. We conclude that the magnitude of vernal suppression or stimulation of diatom assemblages has increased, concomitant with the variations of NH4-N and NO3-N: NH4-N mass ratios. Diatoms response to NH4-N or NO3-N is apparently changing in response to water temperature in this eutrophic shallow lake. Thus, parallel reductions in external nitrogen loading, along with variations in dominant inorganic nitrogen, will stimulate the growth of diatom and therefore increase the total biomass of phytoplankton in still high internal phosphorus loading, which is should be regarded as a good sign of restoration measures.

Assessment of anammox, microalgae and white-rot fungi-based processes for the treatment of textile wastewater.

The treatability of seven wastewater samples generated by a textile digital printing industry was evaluated by employing 1) anammox-based processes for nitrogen removal 2) microalgae (Chlorella vulgaris) for nutrient uptake and biomass production 3) white-rot fungi (Pleurotus ostreatus and Phanerochaete chrysosporium) for decolorization and laccase activity. The biodegradative potential of each type of organism was determined in batch tests and correlated with the main characteristics of the textile wastewaters through statistical analyses. The maximum specific anammox activity ranged between 0.1 and 0.2 g N g VSS-1 d-1 depending on the sample of wastewater; the photosynthetic efficiency of the microalgae decreased up to 50% during the first 24 hours of contact with the textile wastewaters, but it improved from then on; Pleurotus ostreatus synthetized laccases and removed between 20-62% of the colour after 14 days, while the enzymatic activity of Phanerochaete chrysosporium was inhibited. Overall, the findings suggest that all microbes have great potential for the treatment and valorisation of textile wastewater after tailored adaptation phases. Yet, the depurative efficiency can be probably enhanced by combining the different processes in sequence.

Soil chemical markers distinguishing human and pig decomposition islands: a preliminary study.

The decomposition of vertebrate cadavers on the soil surface produces nutrient-rich fluids that enter the soil profile, leaving clear evidence of the presence of a cadaver decomposition island. Few studies, however, have described soil physicochemistry under human cadavers, or compared the soil between human and non-human animal models. In this study, we sampled soil to 5 cm depth at distances of 0 cm and 30 cm from cadavers, as well as from control sites 90 cm distant, from five human and three pig cadavers at the Australian Facility for Taphonomic Experimental Research (AFTER). We found that soil moisture, electrical conductivity, nitrate, ammonium, and total phosphorus were higher in soil directly under cadavers (0 cm), with very limited lateral spread beyond 30 cm. These patterns lasted up to 700 days, indicating that key soil nutrients might be useful markers of the location of the decomposition island for up to 2 years. Soil phosphorus was always higher under pigs than humans, suggesting a possible difference in the decomposition and soil processes under these two cadaver types. Our preliminary study highlights the need for further experimental and replicated research to quantify variability in soil properties, and to identify when non-human animals are suitable analogues.

Preparation and evaluation of bis(diallyl alkyl tertiary ammonium salt) polymer as a promising adsorbent for phosphorus removal.

Problems associated with water eutrophication due to high phosphorus concentrations and related environmentally safe solutions have attracted wide attention. A novel bis(diallyl alkyl tertiary ammonium salt) polymer, particularly poly(N1,N1,N6,N6-tetraallylhexane-1,6-diammonium dichloride) (PTAHDADC), was synthesized and characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, mercury intrusion method, and thermogravimetric analysis. The adsorption characteristics in phosphorus were evaluated in dilute solution, and the recycling properties of PTAHDADC were investigated. Results showed that PTAHDADC possessed macropores with a size distribution ranging from 30 to 130 µm concentrating at 63 µm in diameter and had 46.52% of porosity, excellent thermal stability below 530K, and insolubility. PTAHDADC could effectively remove phosphorus at pH = 7-11 and had a removal efficiency exceeding 98.4% at pH = 10-11. The adsorption equilibrium data of PTAHDADC for phosphorus accorded well with the Langmuir and pseudo-second-order kinetic models. Maximum adsorption capacity was 52.82 mg/g at 293 K. PTAHDADC adsorbed phosphorus rapidly and reached equilibrium within 90 min. Calculated activation energy Ea was 15.18 kJ/mol. PTAHDADC presented an excellent recyclability with only 8.23% loss of removal efficiency after five adsorption-desorption cycles. The morphology and structure of PTAHDADC slightly changed as evidenced by the pre- and post-adsorption of phosphorus, but the process was accompanied by the partial deprotonation of the (-CH2)3NH+ group of PTAHDADC. The adsorption was a spontaneous exothermic process driven by entropy through physisorption, electrostatic attraction, and ion exchange. Survey results showed that PTAHDADC was a highly efficient and fast-adsorbing phosphorus-removal material prospective in treating wastewater.

Winter nitrification in ice-covered lakes.

With changes in ice cover duration, nutrient loading, and anoxia risk, it is important to understand the mechanisms that control nitrogen cycling and oxygen depletion in lakes through winter. Current understanding is largely limited to description of changes in chemistry, with few measurements of the processes driving winter changes, how they differ across lakes, and how they are impacted by under-ice conditions. Nitrification is a process which consumes oxygen and ammonium (NH4+), and supplies nitrate (NO3-). To date, nitrification has been measured under ice cover in only two lakes globally. Here, we used 15NH4+ enrichment to measure rates of pelagic nitrification in thirteen water bodies in two ecozones. Our work demonstrates ecologically important rates of nitrification can occur despite low water temperatures, impacting NH4+, NO3- and, most importantly, oxygen concentrations. However, high rates are not the norm. When, where and why is nitrification important in winter? We found that nitrification rates were highest in a eutrophic lake chain downstream of a wastewater treatment effluent (mean: 226.5 µg N L-1 d-1), and in a semi-saline prairie lake (110.0 µg N L-1 d-1). In the boreal shield, a eutrophic lake had nitrification rates exceeding those of an oligotrophic lake by 6-fold. Supplementing our results with literature data we found NH4+ concentrations were the strongest predictor of nitrification rates across lentic ecosystems in winter. Higher nitrification rates were associated with higher concentrations of NH4+, NO3- and nitrous oxide (N2O). While more work is required to understand the switch between high and low nitrification rates and strengthen our understanding of winter nitrogen cycling, this work demonstrates that high nitrification rates can occur in winter.

Seasonal variation of nutrient salts and heavy metals in mangrove (Avicennia marina) environment, Red Sea, Egypt.

In the Egyptian Red Sea coast, nutrient salts, major ions, and heavy metals ion concentrations were examined in mangroves and the results were compared to respective concentrations in a reference area. Water samples were collected during the four seasons of 2012 from three different mangrove regions, Safaga, Abo Gheson, and El Quseer, besides, a mangrove free region, Marsa Alam. A temporal variation in the chemical composition of seawater of the mangrove and reference regions was recorded. Phosphorous and nitrogen forms were measured and calculated. Fe, Mn, Cu, Zn, Ni, Cr, Cd, and Pb ions were measured in water samples. Redfield nitrogen to phosphorous ratio explained the oligotrophic nature of the Red Sea. Ca and Mg ions besides total alkalinity showed negligible variations. The relatively greater concentration values of ammonium, 242.11 µg/l, dissolved inorganic nitrogen, 315.55 µg/l, and oxidizable organic matter, 0.4 mg-O2/l, may be caused by the impact of mangroves. Seawater contamination by heavy metals was assessed, using the metal index, in the mangrove regions which, compared to the reference region, were highly contaminated. Analysis of variance showed no significant variation among mangrove stations. Principal component analysis suggested that El Quseer and Safaga, mangrove regions, were contaminated by metal ions. Safaga possessed the highest concentration of Cd and Zn ions, while the highest concentrations of Mn, Cu, Ni, and Pb ions were observed at El Quseer. This may be attributed to industrial and shipping activities. It is concluded that the mangrove ecosystem along the Red Sea highly affects marine environment.

Using a mixture of wastewater and seawater as the growth medium for wastewater treatment and lipid production by the marine diatom Phaeodactylum tricornutum.

This study was conducted to evaluate the potential of the marine diatom Phaeodactylum tricornutum in nutrient removal coupled with biodiesel production using different ratios of mixed municipal wastewater (MW) and seawater (SW) as the growth medium. The results indicated that P. tricornutum exhibited high nutrient removal efficiency with the ratios of MW: SW = 1:1 and MW: SW = 2:1, e.g. 87.7-89.9% for chemical oxygen demand (COD), 82.2-86.7% for total nitrogen (TN), 96.0-97.0% for total phosphorus, and 76.9-84.2% for ammonium (NH3-N). Significantly higher biomass and lipid productivity were obtained with aeration. The highest lipid productivity of P. tricornutum was 54.76 mg/L/day, which was obtained with a two-step cultivation using the ratio of MW: SW = 1:1 by diluting half of the mixture and bubbling with 5% CO2 during the second step. These results suggested that the marine diatom P. tricornutum exhibited great potential for using mixed wastewater for wastewater treatment and biodiesel production.

Evaluation of the adsorption of ammonium-nitrogen and phosphate on a granular composite adsorbent derived from zeolite.

To remove the extra ammonium-nitrogen (NH3-N) and phosphorus (P) from contaminated water, a novel granular adsorbent (GAZCA) was fabricated with zeolite powders and Al-Mn binary oxide (AMBO) via the compression method. The SEM-EDS and mapping and XRD results illustrated the microstructure of GAZCA: the homogeneous aggregation of zeolite and AMBO nanoparticles with their crystal integrity and the uniform distribution of Al/Mn/Si/O elements on the adsorbent surface. FTIR and XPS results demonstrated the existence of impregnated sodium cations and hydroxyl groups, which were responsible for the removal of NH3-N and P, respectively. The results of BET analysis and compression tests exhibited a high surface area (14.4 m2/g) and a satisfactory mechanical strength of GAZCA. Kinetic adsorption results showed a fast adsorption rate for NH3-N and P, and mutual inference was not observed between the adsorption kinetics of NH3-N and P in the bi-component system. The adsorption isotherm results demonstrated that the maximum adsorption capacities of NH3-N and P were calculated as 12.9 mg/g and 9.3 mg/g via the Langmuir model, respectively. In the bi-component system, the adsorption capacities of NH3-N and P were maintained at low and moderate concentrations and decreased at high concentrations due to the blockage effects of NH4MnPO4·H2O precipitates. The removal efficiency of NH3-N could be maintained in a wide pH range of 4~10, while P adsorption was inhibited at alkali conditions. The solution of sodium bicarbonate (0.4 M) was used for the regeneration of saturated adsorbents, which permitted GAZCA to keep 98% and 78% of its adsorption capacity for NH3-N and P even after three regeneration and reuse cycles. Dynamic experiments illustrated that a satisfactory performance was obtained for the in situ treatment of simulated N- and P-contaminated water by using a column reactor packed with GAZCA, thus further confirming its great potential for the control of eutrophication.

Impact of environmental variables on fouling bryozoan species in the Eastern Aegean Sea.

Bryozoans are the major component of marine macro-fouling communities. In the study, the relations between bryozoan species and environmental variables were investigated at seven stations along the Aegean coast in August and December 2015. Constant bryozoan species in both sampling periods were Bugula neritina, Amathia verticillata, Shizoporella errata, Cryptosula pallasiana and Celleporaria brunnea. Their relationship with physico-chemical variables (Temperature, salinity, pH, dissolved oxygen, ammonium, nitrite and nitrate nitrogen, orthophosphate phosphorous, total phosphate, chlorophyll-a) were analysed by means of logistic regression analysis. The result showed that temperature with B. neritina; NH4-N, oPO4-P and TPO4-P with A verticillata; dissolved oxygen concentrations with S. errata and C. brunnea were positively related (p < 0.05).

Vertical flow wetlands and hybrid systems for the treatment of landfill leachate.

Landfill leachates contain a variety of toxic compounds, which makes them one of the most difficult types of wastewater to be treated. An alternative "green" technology for leachate treatment is the use of constructed wetlands (CWs). The aims of this study were to select macrophytes and substrates to be used in vertical flow wetlands (VFWs) and to evaluate the performance of hybrid systems composed by a VFW and a horizontal subsurface flow (HSSW) or a free water surface flow (FWSW) wetlands for the treatment of a high ammonium concentration landfill leachate. In microcosms scale experiments, Typha domingensis, Scirpus californicus, and Iris pseudacorus were studied to assess their tolerance to raw and diluted leachate. Substrate selection for VFWs was evaluated using different layers of light expanded clay aggregate (LECA), coarse sand, fine sand, and gravel. Contaminant removals were higher in planted than in unplanted wetlands. Plants did not tolerate the raw effluent but showed a positive effect on plant growth when exposed to the diluted leachate. T. domingensis and I. pseudacorus showed higher contaminant removal ability and tolerance to landfill leachate than S. californicus. VFW with LECA + coarse sand showed the best performance in removal efficiencies. Hybrid system composed by VFW-FWSW planted with T. domingensis presented the best performance for the treatment of landfill leachate with high concentrations of ammonium.

Soil nutrient heterogeneity affects the accumulation and transfer of cadmium in Bermuda grass (Cynodon dactylon (L.) pers.).

There have been no studies demonstrating the correlation between soil nutrient heterogeneity and cadmium (Cd) absorption of Bermudagrass. In this study, a pot experiment was carried out to study the correlation between them. The purpose is to find soil nutrient factors which are conducive to improving the Cd absorption and translocation. The eighth group had the largest total number of surviving plants, the highest Fv/Fo value (3.24) and the best growth characteristics. The fifth group had the lowest total number of surviving plants, Fv/Fo (2.47) and the worst growth. The Cd content of the fifth group (36.11 mg kg-1) was close to the eighth group (35.72 mg kg-1), but the two groups had significant differences in plant height, stem node length and stem node number (P < 0.05). The eighth group showed the highest contents of nitrate nitrogen (NO3--N), available potassium and urease activity. The fifth group showed the lowest NO3--N content, but the highest ammonium nitrogen (NH4+-N) and available phosphorus content. There was significant difference of the Cd bioconcentration factors (BCF) and translocation factor (TCF) between the fifth and the eighth group although they had the similar total soil Cd content (P < 0.05). The fifth group had the highest BCF and TCF. RDA analysis indicated the BCF and TCF were positively correlated with soil NH4+-N and available phosphorus and negatively correlated with soil NO3--N. The results demonstrated that soil NH4+-N and available phosphorus were important soil ecological factors to enhance Cd absorption and translocation of bermudagrass.

Nitrogen deposition affects both net and gross soil nitrogen transformations in forest ecosystems: A review.

Nitrogen (N) deposition has rapidly increased and is influencing forest ecosystem processes and functions on a global scale. Understanding process-specific N transformations, i.e., gross N transformations, in forest soils in response to N deposition is of great significance to gain mechanistic insights on the linkages between global N deposition and N availability or loss in forest soils. In this paper, we review factors controlling N mineralization, nitrification and N immobilization, particularly in relation to N deposition, discuss the limitations of net N transformation studies, and synthesize the literature on the effect of N deposition on gross N transformations in forest ecosystems. We found that more than 97% of published papers evaluating the effect of N deposition (including N addition experiments that simulate N deposition) on soil N cycle determined net rates of mineralization and nitrification, showing that N deposition significantly increased those rates by 24.9 and 153.9%, respectively. However, studies on net N transformation do not provide a mechanistic understanding of the effect of N deposition on N cycling. To date, a small number of studies (<20 published papers) have directly quantified the effect of N deposition on gross N transformation rates, limiting our understanding of the response of soil N cycling to N deposition. The responses to N deposition of specific N transformation processes such as autotrophic nitrification, heterotrophic nitrification, dissimilatory nitrate reduction to ammonium, N mineralization, and N immobilization are poorly studied. Future research needs to use more holistic approaches to study the impact of N deposition on gross N transformation rates, N loss and retention, and their microbial-driven mechanisms to provide a better understanding of the processes involved in N transformations, and to understand the differential responses between forest and other ecosystems.

Effect of phenanthrene on the physicochemical properties of earthworm casts in soil.

Earthworms have been widely studied as bioindicators of soil health for their important role in sustaining soil structure and functions. Many soil contaminants such as phenanthrene have been confirmed to exert adverse effects on earthworms' growth, reproduction, behaviors and biochemical conditions. However, their effects on the properties of earthworm casts have been little studied. In the present study, the effect of different doses of phenanthrene (PHE) (0, 2, 5, 10, 20 mg/kg) on the six physicochemical properties and Fourier transform infrared spectroscopy (FTIR) spectra characteristics of earthworm casts was assessed in artificial soil in a laboratory. 1) Residual concentration of PHE in soils and casts increased with the increasing exposure concentrations and followed the order of casts > soil, concluding that Kow values are the important factor affecting the distribution of hydrophobic organic contaminants (HOCs) in soil and casts; 2) Earthworms produced casts with improved total organic carbon (TOC) (15-19%), NH4+-N (550-800%), total available phosphorus (TAP) (300-450%), cation exchange capacity (CEC) (about 15%) and available potassium (AK) (7-12.6%) compared to that in unpolluted soil, indicating that earthworms still have the ability to play the role of ecological engineers even in polluted soil; 3) The sensitivity of different properties of casts to phenanthrene varies, the order of sensitivity being (most sensitive first) NH4+-N ( triggered as 2 mg/kg of exposure concentrations) > AK (5 mg/kg) > Olsen-P (10 mg/kg) > TOC = pH= CEC (no response within the range of exposure concentrations). NH4+-N content in casts shows a clear dose-response relationship when the exposure exceeds 2 mg/kg, indicating that the index might be a potential sensitive biomarker to provide early warning for soil pollution. 4) FTIR spectra showed that the constitution of casts from earthworms in PHE-spiked soil was not significantly alternated. However, FTIR spectra revealed that the concentrations of C-O of polysaccharide in casts increased with the elevated exposure concentrations, indicating that intensities of C-O of polysaccharide at 1032 cm-1 of casts might be also a potential biomarker for the early-warning of soil pollution. This study advances the knowledge of earthworm ecology in polluted soil, and further extends the scope of earthworm casts as a potential biomarker in soil pollution assessment.

Biochar additions alter phosphorus and nitrogen availability in agricultural ecosystems: A meta-analysis.

Biochar is a carbon (C) rich product of thermochemical conversion of organic material that is used as a soil amendment due to its resistance to decomposition and its influence on nutrient dynamics; however, individual studies on biochar effects on phosphorus (P) and nitrogen (N) have proven inconsistent. Herein, we performed a meta-analysis of 124 published studies to evaluate the influence of biochar on available P, microbial biomass P (MBP), and inorganic N (NO3--N and NH4+-N) in global agricultural ecosystems. Overall, the results showed that biochar applications significantly increased surface soil available P by 45% and MBP by 48% across the full range of biochar characteristics, soil type, or experimental conditions. By contrast, biochar addition to soil reduced NO3--N concentrations by 12% and NH4+-N by 11%, but in most cases biochar added in combination with organic fertilizer significantly increased soil NH4+-N compared to controls. Biochar C:N ratio and biochar source (feedstock) strongly influenced soil P availability response to biochar where inorganic N was most influenced by biochar C:N ratio and soil pH. Biochar made from manure or other low C:N ratio materials, generated at low temperatures, or applied at high rates were generally more effective at enhancing soil available P. It is important, however, to note that most negative results were observed in short-term (<6 months) where long-term studies (>12 months) tended to result in neutral to modest positive effects on both P and N. This meta-analysis indicates that biochar generally enhances soil P availability when added to soils alone or in combination with fertilizer. These findings provide a scientific basis for developing more rational strategies toward widespread adoption of biochar as a soil amendment for agricultural P and N management.

Stable and efficient partial nitritation granular sludge reactor treating domestic sewage at low temperature.

The success of combined partial nitritation (PN) and anammox process treating low-strength domestic wastewater depends on achieving a stable and efficient PN. In this study, desirable PN for domestic sewage with low temperature of 11.8-16.9 °C was achieved in a granular sludge reactor operated in anaerobic/aerobic (A/O) mode. Average nitrite accumulation ratio of 97.3% was obtained with an effluent nitrite/ammonium ratio of 1.2 for influent ammonium of 39.3-78.7 mg·L-1. Quantitative microbial analysis and activity batch test showed that nitrite oxidizing bacteria (NOB) were effectively suppressed, while ammonium oxidizing bacteria (AOB) were dominant. For the efficient suppression of NOB, A/O mode, aerobic phosphorus uptake and granular sludge could play important roles. Furthermore, high AOB activity was obtained with an average ammonium oxidation rate of 11.6 mg N·L-1·h-1, which could be due to the abundant psychrotolerant microorganisms, increased content of extracellular polymeric substances and relatively high dissolved oxygen condition of the reactor.

Enhancement of Organic Matter Removal in an Integrated Biofilm-Membrane Bioreactor Treating High-Salinity Wastewater.

High salinity can strongly inhibit microbial activity and decrease the sedimentation ability of activated sludge. The combination of biofilm and membrane bioreactor is a practical approach towards effective removal of pollutants and low fouling rate. An integrated biofilm-membrane bioreactor (BMBR) treating mustard tuber wastewater was investigated. An average COD removal efficiency of 94.81% and ammonium removal efficiency of 96.84% were achieved at an organic load of 0.5 kg COD/(m3·d). However, the reactor showed a relatively low efficiency in total nitrogen and soluble phosphorus removal due to the lack of anaerobic environment. The increase of influent organic load resulted in a performance degradation because a balance between the degradation ability and pollution has been reached. Images of scanning electron microscopy revealed that halophilic bacteria were the dominant microbe in the system that leads to a loose sludge structure and declined settling properties. It was found that membrane fouling was the consequence of the interaction of microbial activities and NaCl crystallization.

Microalgae cultivation and nutrients removal from sewage sludge after ozonizing in algal-bacteria system.

The feasibility of growing algae in concentrated wastewater generated from sludge ozonation for simultaneous nutrients removal and biomass production was studied. The effects of bacteria addition into microalgae on nutrients removal, biomass yield and settleability, the growth rate of algae and concentrations of extracellular polymeric substances (EPS) and soluble microbial products (SMP) were investigated. The results showed that the growth rate of algae in algal-bacteria system (0.2182) was improved than in algae-only system (0.1852), while both of them are comparable with others reported previously. And the addition of bacteria enhanced COD, NH4+-N, TN and TP removal rate by 23.9 ±â€¯3.3%, 27.7 ±â€¯3.6%, 16.6 ±â€¯1.8% and 14.9 ±â€¯2.2%, respectively. And 32.8 ±â€¯0.7% of the TN and 50.3 ±â€¯1.8% of the TP were recycled from ozonated sludge-supernatant (OSS) being absorbed into algal-bacterial biomass. The algal-bacteria system also demonstrated advantages on biomass settleability and heavy metals removal. Finally, the mechanism involving matter exchange and algal-bacteria system on OSS treatment in this study were discussed through evaluation of nutrients, SMP and EPS contents, nitrogen and phosphorus balance.