Sesuvium portulacastrum-Mediated Removal of Nitrogen and Phosphorus Affected by Sulfadiazine in Aquaculture Wastewater

Plant-based removal of nitrogen (N) and phosphorus (P) from water bodies is an important method for remediation of aquaculture wastewater. In order to acquire knowledge as to how antibiotic residues in wastewater might affect the microbial community and plant uptake of N and P, this study investigated N and P removal by a coastal plant Sesuvium portulacastrum L. grown in aquaculture wastewater treated with 0, 1, 5, or 50 mg/L sulfonamide antibiotics (sulfadiazine, SD) for 28 days and compared the microbial community structure between the water and rhizosphere. Results showed that SD significantly decreased N removal rates from 87.5% to 22.1% and total P removal rates from 99.6% to 85.5%. Plant fresh weights, root numbers, and moisture contents as well as activities of some enzymes in leaves were also reduced. SD changed the microbial community structure in water, but the microbial community structure in the rhizosphere was less affected by SD. The microbial diversity in water was higher than that in the rhizosphere, indicating microbial community differences. Our results showed that the commonly used antibiotic, SD, in aquaculture can inhibit plant growth, change the structure of microbial community, and reduce the capacity of S. portulacastrum plants to remove N and P from wastewater, and also raised alarm about detrimental effects of antibiotic residues in phytoremediation of wastewater.

Influence of Particle Size of River Sand on the Decontamination Process in the Slow Sand Filter Treatment of Micro-Polluted Water

Slow sand filters (SSFs) have been widely used in the construction of water plants in rural areas. It is necessary to find river sand of suitable particle size to improve SSF treatment of micro-polluted water so as to ensure the effective and long-term operation of these plants. In this study, SSF1# (particle size of 0.1–0.5 mm), SSF2# (particle size of 0.5–1 mm), and SSF3# (particle size of 1–1.5 mm) were selected. The physical absorption, CODMn and NH4+-N removal effect, and microbial community were analyzed. According to Langmuir and Freundlich adsorption model fitting, the smaller the particle size of the river sand, the more pollutants are adsorbed under the same conditions. SSF1# has the shortest membrane-forming time, highest CODMn and NH4+-N removal rate, and highest Shannon estimator, indicating that there are more abundant microbial species in the biofilm. Mesorhizobium, Pannonibacter, Pseudoxanthomonas, Aquabacterium, Devosia, and other bacteria have different proportions in each system, each forming its own stable biological chain system. The effluent quality of the three SSFs can meet drinking water standards. However, river sand with a particle size range of 0.1–0.5 mm is easily blocked, and thus the recommended size range for SSF is 0.5–1 mm.

Addition of anaerobic ammonium oxidation bacteria to lower running cost during the membrane bioreactor process treating sewage

Reducing energy consumption or running cost associated with the membrane bioreactor (MBR) process is a serious challenge that needs to be addressed in treating sewage. The addition of anaerobic ammonium oxidation bacteria (AnAOB) to a running MBR has the potential to lower the aeration rate, thus decreasing the running cost in treating sewage. The results obtained showed that owing to addition of AnAOB, TN and NH4+-N removal rates increased by 9.8% and 1.13%, respectively, while the aeration rate decreased by 50%. Additionally, high throughput sequencing and isotope experiments showed that both AnAOB and heterotrophic denitrification bacteria could survive simultaneously and play an important role in nitrogen removal, with AnAOB having a significantly greater contribution. It can be concluded that the addition of AnAOB reduced the running cost of MBR in treating sewage.

Rapid Start-Up of the Aerobic Granular Reactor under Low Temperature and the Nutriment Removal Performance of Granules with Different Particle Sizes

The start-up of the aerobic granular sludge (AGS) process under low temperature is challenging. In this study, the sequencing batch reactor (SBR) was fed with synthetic wastewater and the temperature was controlled at 15 ℃. The main components in the synthetic wastewater were sodium acetate and ammonium chloride. The influent chemical oxygen demand (COD) and NH4+-N concentrations were 300 and 60 mg/L, respectively. The AGS was successfully cultivated in 60 days by gradually shortening the settling time. During the stable operation stage (61–100 d), the average effluent COD, NH4+-N, NO2−-N, and NO3−-N concentrations were 47.2, 1.0, 47.2, and 5.1 mg/L, respectively. Meanwhile, the nitrite accumulation rate (NAR) reached 90.6%. Batch test showed that the smaller AGS had higher NH4+-N removal rate while the larger AGS performed higher NAR. The NH4+-N removal rates of R1 (1.0–2.0 mm), R2 (2.0–3.0 mm), and R3 (>3 mm) granules were 0.85, 0.61, and 0.45 g N/(kg VSS·h), respectively. Meanwhile, the NAR of R1, R2, and R3 were 36.2%, 77.2%, and 94.9%, respectively. The obtained results could provide important guidance for the cultivation of AGS in low-temperature wastewater treatment.

Swine wastewater treatment by combined process of iron carbon microelectrolysis-physical adsorption-microalgae cultivation

Combined treatments were designed based on iron-carbon micro-electrolysis treatment (ICME), physical adsorption (PA) with zeolite (Z) or vermiculite (V) and microalgae cultivation (MC, C. vulgaris) for removing pollutants from swine wastewater (SW), herein are ICME + MC (IM), ICME + Z + MC (IZM) and ICME + V + MC (IVM). Results showed that the minimum total nitrogen (TN) of 43.66 mg L−1, NH4+-N of 1.33 mg−1 and total phosphorus (TP) of 0.14 mg−1 were obtained by IVM, while the minimum chemical oxygen demand (COD) was 105 mg−1 via IM. During the process of combined treatments, ICME contributed most to the removal of TN (84.52% by IZM), TP (97.78% by IVM and IZM) and COD (62.44% by IVM), and maximum NH4+-N removal (55.64%) was obtained by MC procedure in IM process. Vermiculite performed better than zeolite during all the combined treatments. Besides, the maximum cell dry weight (CDW, 0.74 g−1) of C. vulgaris was obtained by IM on day 13. The results provide an efficient integrated method for swine wastewater treatment.

The potential of seaweed cultivation to achieve carbon neutrality and mitigate deoxygenation and eutrophication

Carbon neutrality has been proposed due to the increasing concerns about the consequences of rising atmospheric CO2. Previous studies overlooked the role of lost particle organic carbon (POC) and excreted dissolved organic carbon (DOC) from seaweed cultivation in carbon sequestration, that is to say, long term carbon storage in the oceanic sediments and in the water. This study assessed the potential of seaweed cultivation to achieve carbon neutrality of China by 2060 using a new method that included lost POC and excreted DOC. Based on the seaweed production in the years 2015-2019 in China, harvested seaweed removed 605,193 tonnes of carbon, 70,304 tonnes of nitrogen and 8,619 tonnes of phosphorus from seawaters annually; farmed seaweed sequestrated 343,766 tonnes of carbon and generated 2530,558 tonnes of oxygen annually. Among the seven farmed seaweeds, Gracilariopsis lemaneiformis has the highest capacities for carbon removal (9.58 tonnes ha-1 yr-1) and sequestration (5.44 tonnes ha-1 yr-1) and thus has the smallest cultivation area required to sequestrate 2.5 Gt CO2 that is annually required to achieve China's carbon neutrality goal by 2060. The O2 generated by seaweed cultivation could increase dissolved oxygen in seawaters (0-3 m deep) by 21% daily, which could effectively counteract deoxygenation in seawaters. Gracilariopsis lemaneiformis also has the highest N removal capacity while Saccharina japonica has the highest P removal capacity. To completely absorb the N and P released from the fish mariculture, a production level or a cultivation area two and three times larger (assuming productivity remains unchanged) would be required. This study indicates that seaweed cultivation could play an important role in achieving carbon neutrality and mitigating deoxygenation and eutrophication in seawaters. Cultivation cost could be offset to some extent by increased sales of the harvest parts of the seaweed for food and biofuel.

A biosurfactant-producing yeast Rhodotorula sp.CC01 utilizing landfill leachate as nitrogen source and its broad degradation spectra of petroleum hydrocarbons

In this study, a biosurfactant producing strain, Rhodotorula sp. CC01 was isolated using landfill leachate as nitrogen source, while olive oil was determined as the best sole carbon source for producing biosurfactants. The biosurfactant produced by Rhodotorula sp. CC01 was characterized as glycolipids with a critical micelle concentration of 70 mg/L, which showed stability over a wide range of pH (2–12), salinity (0–100%), and temperature (20–100°C). During the cultivation process, the surface tension decreased from 51.87 to 28.20 mN/m in 15 h, and the removal efficiency of NH4+-N reached 84.2% after 75 h cultivation with a maximum NH4+-N removal rate of 3.92 mg·L-1·h−1. In addition, Rhodotorula sp. CC01 has proven to be of great potential in remediating petroleum hydrocarbons, as revealed by chromogenic assays. The findings of this study prove a cost-effective strategy for the production of BS by yeast through the utilization of landfill leachate.

Evaluation of various preparation methods of oil palm fiber (OPF) biochar for ammonia-nitrogen (NH3-N) removal

The aim of this study is to develop a oil palm based biochar for the selective removal of NH3-N in low concentration from aquaculture wastewater. In this study, three different preparation methods of biochar were evaluated for the adsorption of NH3-N from synthetic aquaculture wastewater. The three methods are pyrolysis, activation with acid before pyrolysis and activation after pyrolysis with numerous oxidizing agents. In the 1st method, various biochars have been prepared at different pyrolysis temperatures (300 – 500 °C) and holding time (0.5 – 2 hr). The maximum removal efficiency of 50 % was achieved at preparation condition of 300 °C and 2 hr. In the 2nd method, the acid activated raw OPF was pyrolyze at 300 °C, 1 hr. The maximum removal was lower compared to the 1st method without acid treatment. In the 3rd Method, the optimized biochar from the 1st method was activated with different activating agents such as, HNO3, HCl, H3PO4, H2SO4, CH3COOH and H2O2 at 100 °C for 2 hr. It was noticed that activation after pyrolysis did not show any improvement in the removal of NH3-N from synthetic aquaculture wastewater. Characterization of optimized samples were carried out to investigate the adsorption mechanism process of NH3-N. The 1st method (pyrolysis) was the best which reported the highest (50 %) removal of NH3-N. Pyrolyzed OPF is a potential adsorbent for NH3-N.