Enhanced Nutrient Removal Research Articles

Biochar-immobilized Sphingomonas sp. and Acinetobacter sp. isolates to enhance nutrient removal: potential application in crab aquaculture

The frequency of water exchange and reducing the risk of eutrophication to surrounding water bodies have always been water-quality control issues in recirculating aquaculture systems. In this study, maize straw biochar prepared through pyrolysis showed great potential for both bacterial immobilization and pollutant adsorption. Heterotrophic bacterial strains of Sphingomonas sp. PDD-57b-25 and Acinetobacter towneri were isolated in situ from wastewater for pollutant remediation through a 16S rDNA-based method, which has been rarely reported to date. The selected strains had higher ammonia nitrogen (NH4+-N, 63%), nitrite nitrogen (NO2--N, 38%), nitrate nitrogen (NO3--N, 25%) and total phosphorus (TP, 35%) assimilation capacities than those of other widely applied bacteria under similar medium conditions. In addition, more NH4+-N (+16%), NO2--N (+14%), NO3--N (+17%) and TP (+19%) was removed by biochar-immobilized isolated strains than dissociated strains, suggesting their use may provide a means of improving water-quality control in recirculating aquaculture. With specific additions (4 g l-1) of biochar-immobilized Sphingomonas sp. PDD-57b-25 and A. towneri, the dissolved inorganic nitrogen (approximately 0.45 mg l-1) and TP (approximately 0.09 mg l-1) levels were maintained below the clean water threshold for recirculating aquaculture of crab Eriocheir sinensis. Furthermore, the added strains exhibited high bio-safety and were capable of improving the yield and quality of crabs. Results indicate the potential applicability of biochar-immobilized Sphingomonas sp. PDD-57b-25 and A. towneri in agricultural sewage treatments. Further, the experimental methodology developed here may be used for the exploration of new strains for practical aquaculture.

Correlation between operating parameters and removal efficiency for chemically enhanced primary treatment system of wastewater

Background“Chemically enhanced primary treatment” (CEPT) is an approach to wastewater treatment. It can be utilized as a specially designed step in “biological” secondary treatment processes. The aim of this study is to create an empirical model of separation efficiency for wastewater chemically enhanced primary treatment.MethodsThe empirical model is undertaken using the simulation of the data obtained from pilot plant experimental studies using different types of coagulant (FeCl3, alum, lime, and Magna-floc155).The empirical modeling techniques used multivariate regression model. Different values of BOD5, COD, TSS, as well as separation efficiencies for COD and TSS were investigated in accordance to achieve final effluent results that would meet the Egyptian standards limit.ResultsMultiple regression analysis showed that removal efficiencies of COD and TSS can be predicted to be (R2 = 0.973 and 0.978, respectively).ConclusionThe present work provides an approach for using chemically enhanced primary treatment of wastewater. The obtained results showed that the empirical model can predict removal efficiencies with R2 = 0.973, and 0.978 for COD and TSS. The advantage of this model is that it would allow better process control and treatment efficiency. The results show that chemically enhanced primary treatment method can be used as an efficient method in conventional municipal wastewater treatment plants to reduce the organic load of biological treatment and enhance nutrients removal.

Mitigating nutrient accumulation with microalgal growth towards enhanced nutrient removal and biomass production in an osmotic photobioreactor

Forward osmosis (FO) has great potential for low energy consumption wastewater reuse provided there is no requirement for draw solutes (DS) regeneration. Reverse solute flux (RSF) can lead to DS build-up in the feed solution. This remains a key challenge because it can cause significant water flux reduction and lead to additional water quality problems. Herein, an osmotic photobioreactor (OsPBR) system was developed to employ fast-growing microalgae to consume the RSF nutrients. Diammonium phosphate (DAP) was used as a fertilizer DS, and algal biomass was a byproduct. The addition of microalgae into the OsPBR proved to maintain water flux while reducing the concentrations of NH4+-N, PO43--P and chemical oxygen demand (COD) in the OsPBR feed solution by 44.4%, 85.6%, and 77.5%, respectively. Due to the forward cation flux and precipitation, intermittent supplements of K+, Mg2+, Ca2+, and SO42− salts further stimulated algal growth and culture densities by 58.7%. With an optimal hydraulic retention time (HRT) of 3.33 d, the OsPBR overcame NH4+-N overloading and stabilized key nutrients NH4+-N at ∼ 2.0 mg L−1, PO43--P < 0.6 mg L−1, and COD < 30 mg L−1. A moderate nitrogen reduction stress resulted in a high carbohydrate content (51.3 ± 0.1%) among microalgal cells. A solids retention time (SRT) of 17.82 d was found to increase high-density microalgae by 3-fold with a high yield of both lipids (9.07 g m−3 d−1) and carbohydrates (16.66 g m−3 d−1). This study encourages further exploration of the OsPBR technology for simultaneous recovery of high-quality water and production of algal biomass for value-added products.

Enhanced nutrient removal of simultaneous partial nitrification, denitrification and phosphorus removal (SPNDPR) in a single-stage anaerobic/micro-aerobic sequencing batch reactor for treating real sewage with low carbon/nitrogen

The feasibility of simultaneous partial nitrification, denitrification and phosphorus removal (SPNDPR) process was investigated in a single-stage anaerobic/micro-aerobic sequencing batch reactor for treating real sewage. Partial nitrification was maintained with average nitrite accumulation ratio of 90.3% during 266 days’ operation. Removal efficiencies for NH4+-N (96.3%), total inorganic nitrogen (81.4%), and phosphorus (91.0%) were stably obtained when treated real sewage with low carbon/nitrogen (3.4), with simultaneous partial nitrification and denitrification efficiency of 73.1%. The mechanism analysis revealed that denitrifying glycogen-accumulating organisms (DGAOs) and denitrifying polyphosphate-accumulating organisms (DPAOs) played the main roles in N-removal and P-removal, respectively. Nitrite pathway and optimized use of the organic carbon available in the sewage were keys for the successful performance. Further microbial community illustrating that DGAOs Candidatus_Competibacter, DPAOs Dechloromonas, and ammonia-oxidizing bacteria Nitrosomonadaceae were main functional groups. Notably, sludge granulation was formed under long-term synchronous low dissolved oxygen and low sludge loading conditions, avoiding sludge bulking.

Roles of biochar media and oxygen supply strategies in treatment performance, greenhouse gas emissions, and bacterial community features of subsurface-flow constructed wetlands

Biochar-based subsurface-flow constructed wetlands (CWs) with intermittent aeration (IA) or tidal flow (TF) oxygen supply strategies were established to treat domestic wastewater. The results showed that biochar achieved higher nutrient removal and lower greenhouse gas (GHG) emissions than ceramsite while supporting more diverse bacterial communities and higher abundances of functional taxa. Both IA and TF effectively enhanced nutrient removal, though the latter was more efficient and practical, and aeration conditions greatly influenced nutrient removal efficiency. GHG emissions were decreased by IA but were slightly increased by TF. Both oxygen supply methods significantly shaped the biofilm microbial communities and influenced biodiversity and richness, with observably higher proportions of potential nitrifiers and denitrifiers present in aerated CWs. Overall, biochar-based CWs operated with oxygen supply strategies provide superior treatment of decentralized wastewater.

Metagenomic analysis reveals enhanced nutrients removal from low C/N municipal wastewater in a pilot-scale modified AAO system coupling electrolysis

The conventional biological nutrients removal process is challenged by insufficient organic carbon in influent. To cross such an organic-dependent barrier, a pilot-scale electrolysis-integrated anaerobic/anoxic/oxic (AAO) process was developed for enhanced removal of nitrogen (N) and phosphorus (P) from low carbon/nitrogen (C/N) municipal wastewater. Average removal efficiencies of total nitrogen (TN) and total phosphorus (TP) in the electrolysis-AAO reached to 77.24% and 95.08% respectively, showing increases of 13.88% and 21.87%, as compared to the control reactor. Spatial variations of N and P showed that NH4+-N removal rate was promoted in aerobic zone of electrolysis-AAO. The intensified TN elimination, which was mostly reflected by abatement of NO3−-N with the concomitant slight accumulation of NH4+-N and NO2−-N, mainly occurred in anoxic2 compartment as the electrons supplied by electrolysis. Furthermore, minor P contents were measured and remained almost unchanged along the reaction units, indicating that chemical precipitation should be the dominant mechanism of P-removal in electrolysis-AAO. From the metagenomic-based taxonomy, phylum Actinobacteria was dramatically inhibited, and phylum Proteobacteria dominated the electrolysis-AAO. Particularly, nitrifying bacteria and multifarious autotrophic denitrifiers were enriched, meanwhile, a significant evolution of heterotrophic denitrifiers was found in electrolysis-AAO compared to control, which was mostly reflected by the inhibition of genus Candidatus Microthrix. Batch tests further confirmed that autotrophic denitrifiers using H2 and Fe2+ as essential electron sinks were mainly responsible for the electrolysis-induced denitrification. Differential metabolic capacities were revealed from the perspectives of functional enzymes and genes, and network analysis allowed insight of microbial taxa-functional genes associations and shed light on stronger relevance between autotrophic denitrifiers and denitrification-associated genes in the electrolysis-AAO system.

Contribution of organic composition and loading to enhance nutrient removal in biological spatial-temporal phase separation

A biological spatial-temporal phase separation system without an additional anaerobic reactor was devised for simultaneous removal of nitrogen and phosphorus. The process was operated at hydraulic retention time (HRT) of 8 h, solids retention time (SRT) of 10 days, and cycle time of 4 h (Anoxic/Anaerobic periods : Aerobic period = 1.5 : 2.5). Three types of influents were examined, namely glucose, glucose/acetate/propionate, and domestic wastewater. They were used to evaluate the contribution of organic composition and loading on the system performance. Nitrogen removal was strongly affected by the organic composition upon low influent C/N ratio. However, for influent C/N of 9.2–11.7 and C/P of 53.0–88.1, nitrogen and phosphorus removal noticeably improved regardless of the organic composition. Biological reactions including nitrification, denitrification, phosphate release and uptake, and PHA synthesis and utilization were clearly observed during the cycle with high organic loading, without any decline on organics removal. Furthermore, significant phosphate release and uptake were successfully accomplished without any nitrate interference and carbon competition under high organic loading. Therefore, organic loading is essential for the simultaneous removal of nitrogen and phosphorus in biological spatial-temporal phase separation.

Small-scale phyco-mitigation of raw urban wastewater integrated with biodiesel production and its utilization for aquaculture

A low-cost small-scale high-rate algal pond (HRAP) was constructed to investigate the synergistic potential of a novel oleaginous microalga, Chlorella sorokiniana for phyco-mitigation, and biodiesel production using raw urban wastewater. An enhanced nutrient removal (97%), total organic carbon (74%), alkalinity (70%) and hardness (75%) from the wastewater was obtained. The microalga dominated in the HRAP as ~90% increase in the dissolved oxygen with high biomass (1.13 g/L) was noted. The microalga biomass showed sufficient lipid content (~31% of dry cell weight) as compared to control (Bold’s Basal media). The total lipid profiling of the microalga cultivated in wastewater showed augmentation in the levels of both storage and neutral lipids with good quality fatty acids composition. Moreover, the sucker fishes grew healthy in the treated wastewater with an increase in body weight.

Effect of organic sources of nutrients on performance of soybean (Glycine max)

A field experiment was conducted at the Research Farm of ICAR-Indian Institute of Soil Science, Bhopal, India to study the effect of different combinations of organic inputs on performance of soybean [Glycine max (L.) Merr.]. Soybean (cv. JS 335) was grown in a randomized block design with seven treatments and four replications. The treatments studied were organic manure (OM) (T1); biodynamic preparation (BD) (T2); OM+panchagavya (OM+PG) (T3); OM+BD (T4); OM+PG+BD (T5); control (T6); and recommended dose of fertilizers (RDF) (T7). The results of the study revealed that, the treatments with organic manures either alone or in combination with panchagavya and/or biodynamic application improved the performance of soybean crop. The yield of soybean was found comparable and even better (higher 5–13%) with those obtained under RDF, which enhanced nutrient removal by soybean crop by 5–13% with organic combinations. Similarly, the application of organic manures significantly improved the available nutrient status of soil and showed 19–22% and 28–33% higher available N and P, respectively than RDF. Soil enzyme activities, viz. dehydrogenase and alkaline phosphatase increased by 62–72% and 27–35%, respectively under the treatments receiving organic source of nutrients over RDF.

Interaction between Chlorella vulgaris and nitrifying-enriched activated sludge in the treatment of wastewater with low C/N ratio

Abstract Wastewater treatment based on algae-bacteria consortia is expected to find use among other biological processes. In this report, the effects of the inoculation ratios of a Chlorella vulgaris and nitrifier-enriched-activated-sludge (NAS) consortium on nutrient removal, carbon capture, and metabolite generation were investigated under autotrophic conditions. The maximum NH4+-N removal (100%) was observed within 7 days in a photo-bioreactor containing 10% C. vulgaris: 90% NAS (w/w); this consortium is referred to as B10. The maximum PO43--P removal (87.5%) was observed in a pure culture of C. vulgaris after 14 days. Due to the fast nitrification achieved using B10, this system showed the highest nitrate accumulation value of 19.73 mg NO3−-N/L at the end of the experiment. The DO concentration in B10 reached 4 mg/L due to the photosynthetic activity of C. vulgaris, providing appropriate conditions for the NAS. Among all the tested consortium ratios, B90 (90%:10% C. vulgaris/NAS, w/w) showed the highest carbon capture (156 mg), while B10 captured only 43.2 mg of carbon. Furthermore, metabolite analysis showed a positive correlation between the proportion of C. vulgaris and the generation of metabolites in the cultures. A trade-off was observed between nutrient removal and carbon capture in C. vulgaris and NAS co-cultures. Overall, our study shows that the aeration system in conventional nitrification processes could be replaced by a cleaner process based on microalgae, resulting in enhanced nutrient removal, increased carbon capture, reduced metabolite generation, and a decrease in excess sludge production.

Selected aspects of water and sewage management in Poland in the context of sustainable urban development

Abstract Effective water and sewage management is one of the most important enablers of sustainable urban development. In Poland, water and sewage management has been undergoing systematic transformation since the 1990s. This process intensified with Poland’s accession to the European Union in 2004. The aim of the work is to analyse and evaluate water and sewage management in cities in Poland in terms of sustainable development. This was made possible by selecting seven variables from which a summative index (SI) was calculated. The analysis revealed a number of positive changes that have occurred in this field. These were mainly: a decrease in water consumption in households and industry, and an increased share of wastewater treated biologically or using enhanced nutrient removal in total wastewater. An increase in SI was found in 98% of the researched cities. The largest improvement in water and sewage management took place in cities of populations below 100,000 and little industry, and in three large cities, namely Warsaw and Szczecin.

Enhanced Nutrient Removal and Microbial Community Structure in a Step-feed A2/O Process Treating Low-C/N Municipal Wastewater

To resolve the issue of insufficient influent carbon sources in existing municipal wastewater treatment plants (WWTPs) in China, a pilot-scale step-feed A2/O process was used to treat low-C/N (C/N<5) municipal sewage with five different inflow distribution ratios. In this study, the effects of influent flow distribution on the removal efficiencies of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were investigated. The results showed that optimal removal efficiencies of 89.41% for COD, 95.30% for NH4+-N, 83.00% for TN, and 90.09% for TP were obtained at an inflow QPA:QAN:QA distribution ratio of 0.1:0.2:0.3. The activated sludge exhibited excellent settleability characteristics, showing a sludge volume index (SVI)<120 mL·g-1 with an average volatile suspended solids (VSS) total suspended solids (TSS) ratio of 0.84 (Phase 5), and no filamentous bacteria bulking occurred during the 120-day experiment. Moreover, the microbial community structure in the oxic zone was detected by high-throughput sequencing. The results demonstrated that excellent nutrient removal and sludge settling performance of the system were closely related to the enrichment of six types of heterotrophic bacteria, four types of denitrifying bacteria, five types of polyphosphate-accumulating organisms (PAOs), and two types of zoogloea and the elimination of three types of filamentous bacteria.

A pilot bioretention system with commercial activated carbon and river sediment-derived biochar for enhanced nutrient removal from stormwater.

Bioretention is an effective technology for urban stormwater management, but the nutrient removal in conventional bioretention systems is highly variable. Thus, a pilot bioretention column experiment was performed to evaluate the nutrient control of systems with commercial activated carbon and river sediment-derived biochar. Significant chemical oxygen demand (COD) and total phosphorus (TP) leaching were found with the addition of activated carbon and biochar, but total nitrogen (TN) leaching was significantly improved when activated carbon was used as the medium. During a semi-synthetic runoff experiment, the bioretention systems containing two types of fluvial biochar showed relatively better COD and TN control (average mass removal efficiencies and cumulative removal efficiencies) than commercial activated carbon. However, the average TP mass removal efficiency with commercial activated carbon (95% ± 3%) was significantly higher than biochar (48% ± 20% and 56 ± 14%). The addition of biochar in the media increased the nitrogen removal efficiency, and the addition of activated carbon significantly increased the phosphorous removal efficiency. Therefore, both biochar and activated carbon are effective materials for bioretention, and fluvial biochar provides an alternative approach to comprehensively utilize river sediment.

Performance evaluation of modified bioretention systems with alkaline solid wastes for enhanced nutrient removal from stormwater runoff

Bioretention systems have been found to be potential candidates for the removal of various pollutants/nutrients from rainfall or stormwater runoff. Despite bioretention has been widely developed for the removal of nutrients from stormwater, effective removal of both phosphorus and nitrogen is still a challenge. Hence, in this study, bioretention systems modified by alkaline solid waste media have been reported for the effective removal of nutrients. Six different types of solid wastes were first assessed using leaching and adsorption tests, and then the bottom ash from a refuse incineration plant was selected as a modifier. The bottom ash was mixed with soil to form a special media as the filter layer in the bioretention systems. The nutrient removal efficiencies of the modified bioretention systems were evaluated and also compared with those of the unmodified control. For this purpose, the design of the modified filter media with a saturated zone was combined to enhance the simultaneous removal of nitrogen and phosphorus. The effect of different rainfall intensities and nutrient concentrations in stormwater runoff on the removal efficiency of nutrients was evaluated. The results indicated that the modified bioretention with bottom ash modified soil media and saturated zone could exhibit the excellent removal efficiency of nitrogen and phosphorus from stormwater runoff. The extent of removal of total nitrogen, total Kjeldahl nitrogen, and total phosphorus was found to be 58–70%, 66–82% and 82–97%, respectively. The performed correlation analysis showed that the bioretention cell using the special media could simultaneously enhance the removal of phosphorus and nitrogen. As a part of this study, the adsorption isotherms of phosphorus removal by the modified bioretention systems have also been determined. Finally, the implications and opportunities for deploying modified bioretention systems for optimizing water-energy nexus and stormwater management were illustrated. In overall, this study demonstrated that the modified bioretention systems could substantially enhance the removal efficiencies of nutrients from stormwater runoff.

Comparison of physical characteristics and dewatering behaviour between granular and floccular sludges generated from the same sewage source

Aerobic granular sludge can improve the efficacy of wastewater treatment in existing sequencing batch reactors (SBRs) compared to conventional floccular sludge. Despite the well known advantages of increased capacity, reduced reactor footprint and enhanced nutrient removal, many performance characteristics of granular and floccular sludges have not been directly compared, in particular for sludges generated from treating the same sewage source. In this study we investigated the microstructure, microbial composition, settling and dewatering properties of granular and floccular sludge generated from the same sewage sources. Cryo-scanning electron microscopy analysis indicated that the granular and floccular sludges had a significantly different internal network structure, with flocs being much more open and porous than granules. Sulphur deposits were clearly visible on the surfaces of granules, which was complemented by the enrichment of some sulphur oxidising bacterial species compared to floccular sludge, as assessed by Next Generation Sequencing (NGS). Dewatering measurements showed, as expected, that the settling velocity of granules was much faster than flocs at solids concentrations below the gel point. At at higher solids concentrations above the gel point, however, both flocs and granules form a similar gelled network structure with no significant difference in dewaterability. We used the dewatering properties in process models to predict the impact of granulation on thickener and filter throughput. Overall, this work highlights the biological, structural and physical differences and similarities between granular and floccular sludges with the outcome being improved settling for granules but no significant difference in downstream dewatering properties that pertain to filtration processes.

Enhanced nutrient removal in bioretention systems modified with water treatment residuals and internal water storage zone

Bioretention systems modified with water treatment residuals and internal water storage zone are effective for removal of N, P, TSS, COD, and heavy metals in rainfall runoff.

Trace organic contaminant removal in six full-scale integrated fixed-film activated sludge (IFAS) systems treating municipal wastewater

Trace organic contaminants (TrOCs) often pass through conventional activated sludge wastewater treatment plants (CAS-WWTPs) and are discharged into surface waters, where they can threaten aquatic ecosystems and human health, largely due to the hormone disrupting effects of certain TrOCs. The integrated fixed-film activated sludge (IFAS) process is a cost-effective means of upgrading CAS-WWTPs by adding free-floating carrier media, which promotes biofilm formation in the well-mixed suspended growth reactors, providing a potential niche for slow-growing microorganisms. Although IFAS upgrades are typically aimed at enhancing nutrient removal, limited bench- and pilot-scale data indicate that TrOC removal may also be improved. However, only limited reports which focus on a small number of compounds in individual full-scale IFAS-WWTPs have been published to date, and no data is available regarding the removal of estrogenic activity in full-scale IFAS-WWTPs. In this study, six full-scale IFAS-WWTPs were surveyed to quantify TrOC and estrogenic activity removal. Twenty-four hour composite samples of secondary influent and effluent (pre-disinfection) were analyzed for total suspended solids (TSS), chemical oxygen demand (COD), ammonia, total nitrogen (TN), total phosphorus (TP), estrogenic activity, and 98 TrOCs. The biomass distribution between the suspended growth phase (i.e. mixed liquor) and IFAS media was also assessed. All IFAS-WWTPs performed well in terms of TSS, COD, and ammonia removal. TN removal varied in accordance with nitrate removal. Total solids per liter of wetted reactor volume ranged from 2.5 to 7.6 g, with 40–60% attached to media. TrOCs with no detection (17) and those with high median removal (23, ≥90% average removal) were observed. Other TrOCs had lower and more variable removal efficiencies. Qualitative comparison with CAS literature shows potentially higher IFAS removal efficiencies for a number of compounds including several which have been previously indicated in bench- or pilot-scale studies (atenolol, diclofenac, gemfibrozil, DEET, 4-nonylphenol, and 4-tert-octylphenol), as well as the chlorinated flame retardants TCIPP and TDCIPP. Effluent estrogenic activity was found to be similar to that reported for full-scale CAS-WWTPs. These results provide the first survey of multiple full-scale IFAS-WWTPs employing mobile plastic carrier media in terms of basic chemical endpoints (removal of ammonia, TN, TP, and COD), the distribution of solids within the systems, and the removal of TrOCs and estrogenic activity.

The impact of the art-ICA control technology on the performance, energy consumption and greenhouse gas emissions of full-scale wastewater treatment plants

Advanced real time – Instrumentation, Control, and Automation (Art-ICA) controllers are an advanced control solution for biological nutrient removal wastewater treatment plants. Art-ICA has been previously shown to be capable of enhancing nutrient removal performance in BNR plants, at lower energy expenditures. However, the impact that this control solution has on the greenhouse gas emissions from full-scale wastewater treatment plants has not previously been addressed. This work addresses the effect of art-ICA on the performance, energy consumption and greenhouse gas emissions of two full-scale WWTPs, Chelas and Castelo Branco (Portugal). The raw wastewater, nitrous oxide emissions, energy consumption and water discharges were quantified in two independent trains operated under different operational modes, conventional operation and art-ICA control. The implementation of the art-ICA strategy improved the effluent quality and reduced the operational costs, resulting in a better performance of these WWTPs. The art-ICA controllers activation led to a reduction of 54% and 7–10% of the total nitrogen effluent and in the specific energy consumption, respectively. Moreover, process control with art-ICA did not have a negative impact on the N2O emissions of the plants, and contributed to lower global warming potential by the facilities. The lower indirect carbon dioxide production due to lower energy consumption contributes to the observation that art-ICA control is environmentally preferable to conventional control.

Biochar fails to enhance nutrient removal in woodchip bioreactor columns following saturation

Denitrifying bioreactors are edge-of-field structures that remove excess nitrogen (N) from intercepted agricultural drainage by supporting the activity of denitrifying microorganisms with a saturated organic carbon substrate. Although these bioreactors successfully mitigate N export, the typical woodchip systems have little effect on phosphorus (P), which is also often present in environmentally harmful quantities in drainage waters. Currently, the evidence that amending woodchip bioreactors with biochar enhances both N and P removal rates is mixed, but more work is required to test this hypothesis under controlled conditions. To determine the effect of biochar amendment on nitrate (NO3-N) and phosphate (PO4-P) removal in woodchip bioreactors, three media types—aged woodchips (W), 10% (B10) and 30% (B30) biochar by volume—were tested under different operational conditions during five-day laboratory trials with horizontal, flow-through columns. Nutrient removal was observed under different flow rates yielding hydraulic residence times of 3, 6, and 12 hours with four formulations of simulated agricultural drainage, all combination of 16.1 or 4.5 mg L−1 NO3-N and 1.9 or 0.6 mg L−1 PO4-P. Each unique treatment with respect to media type, HRT, and influent formulation was tested in triplicate using independent columns. All treatments successfully removed NO3-N, but PO4-P removal was inconsistent. Cumulative NO3-N removal efficiencies ranged 15–98% with an average removal rate of 11.0 g m−3 d−1; biochar amendment enhanced removal only in response to sufficiently high loading rates. Cumulative PO4-P removal efficiencies ranged from 66% removal to 170% export of the influent load; biochar addition was associated with increased export. These results indicate that pine-feedstock biochar poses a substantial increase to PO4-P leaching risk and only modestly enhances NO3-N removal given sufficiently high loading.

Cultivation of Chlorella vulgaris in manure-free piggery wastewater with high-strength ammonium for nutrients removal and biomass production: Effect of ammonium concentration, carbon/nitrogen ratio and pH

Ammonia toxicity is a major disadvantage of microalgal growth when high-strength ammonium wastewaters like manure-free piggery wastewater (MFPW) were used as microalgal growth medium. In the present study, the effect of ammonium concentration, carbon/nitrogen ratio, and pH on ammonia toxicity of Chlorella vulgaris cultivated in the MFPW and nutrients removal was investigated. The three important parameters affected ammonia toxicity of C. vulgaris and nutrients removal of the MFPW significantly. The ammonium concentration of the MFPW could be decreased by air stripping. Microalga grew best at a carbon/nitrogen ratio of 25:1 with the maximum biomass concentration of 3.83 g L−1, the highest cell viability of 97%, and the removal of 100% ammonia, 95% of total phosphorus, and 99% of chemical oxygen demand. Ammonia toxicity was alleviated by pH control. The application of the established strategies can enhance nutrients removal of the MFPW while mitigating ammonia toxicity of C. vulgaris.