Characteristics and performances of microalgal-bacterial consortia in a mixture of raw piggery digestate and anoxic aerated effluent.

The piggery digestate of high ammonia was mixed with the anoxic aerated effluent of high nitrate and phosphorus, to cultivate a microalgal-bacterial consortium for simultaneous pollution removal and resource recovery. The highest removal of total inorganic nitrogen was achieved at 324.77 mg/L in 40% piggery digestate mixed with 60% anoxic aerated effluent, along with the most microalgae biomass production. The crude protein and fatty acids of C14-C20 in microalgae cells were 21.80% and 69.78%, indicating that this mixing strategy could produce abundant microalgal biomass suitable for biofuel generation and animal feed. High-throughput sequencing showed that microbial diversity increased and Paenibacillus, Thiopseudomonas and Pseudomonas were the dominant species promoting microalgal growth. Overall, these results provided a new insight of mixing two types of wastewaters for cultivating microalgal-bacterial consortia, to remove contamination and recover nutrients simultaneously.

Organic degrading bacteria and nitrifying bacteria stimulate the nutrient removal and biomass accumulation in microalgae-based system from piggery digestate.

The microalgae-based system has been applied in anaerobic digestate treatment for nutrient removal and biomass production. To optimize its performance in treating piggery digestate, here, commercial bacterial agents, including organic degrading bacteria (Cb) and nitrifying bacteria (Nb), were inoculated into the microalgae-based system dominated by Desmodesmus sp. CHX1 (D). Reactor DN (inoculated with D and Nb) and DCN (inoculated with D, and Cb to Nb at a ratio of 1:2) have better performance on NH4+-N removal, with a final efficiency at 40.26% and 39.87%, respectively, and no NO3--N or NO2--N accumulations. The final total chlorophyll concentration, an indicator of microalgal growth, reached 4.74 and 5.47 mg/L in DN and DCN, respectively, three times more than that in D. These results suggested that high NH4+-N removal was achieved by the assimilation into high microalgal biomass after the inoculation with functional bacteria. High-throughput sequencing showed that the richness of microbial community decreased but the evenness increased by inoculating functional microorganisms. Microalgae aggregating bacteria were Cellvibrio, Sphingobacterium, Flavobacterium, Comamonas, Microbacterium, Dyadobacter, and Paenibacillus. This study revealed that the inoculation with functional bacteria reconstructed the microbial community which benefited for the microalgal growth and nutrient removal, providing a promising strategy for treating highly-concentrated digestate.

Nutrient removal from piggery wastewater by Desmodesmus sp.CHX1 and its cultivation conditions optimization.

Combination of microalgae cultivation and piggery wastewater treatment has become a hot topic in recent years. Nutrient removal from aerated piggery wastewater (APW) by Desmodesmus sp. CHX1 and the optimization of cultivation conditions were investigated in this study. Results indicated that Desmodesmus sp. CHX1 showed an efficient growth in APW, with specific growth rate of 0.26-0.56 d-1. The biomass yield based on nutrient consumption was 9.65 g biomass/g NH4-N and 209.15 g biomass/g total phosphorus (TP) respectively. Desmodesmus sp. CHX1 performed well in nutrient removal from APW, with ammonium nitrogen (NH4-N) and TP removal efficiency (RE) of 78.46% and 91.66% respectively after 7 days of culture. Nutrient removal process fitted the pseudo-first-order kinetic equations well, with removal rate (RR) constant of 0.24 d-1 for NH4-N and 0.28 d-1 for TP. The optimum conditions for nutrient removal from APW by Desmodesmus sp. CHX1 were light intensity of 150 µmol photons m-2 s-1 in the photoperiod for 24 h when the temperature was set at 35°C with alga cell inoculation concentration of 30%. The removal efficiencies of NH4-N and TP were 88.26% and 95.06% respectively under the optimal conditions after 7 days of culture. Our results can be a good reference for enhancement of microalga production and the nutrient RE and further extend the application of the large-scale piggery wastewater treatment under a controlled environment.

Nitrogen transformations during co-composting of herbal residues, spent mushrooms, and sludge.

Sewage sludge composting is an important environmental measure. The reduction of nitrogen loss is a critical aim of compost maturation, and the addition of spent mushrooms (SMs) and herbal residues (HRs) may be helpful. To evaluate the nitrogen transformations during co-composting of sewage sludge, SMs, and HRs, windrows were constructed in a residual processing plant. Dewatered sewage sludge and sawdust were mixed with SMs and HRs at two proportions on a fresh weight basis, 3:1:1 (sewage sludge:sawdust:SMs or HRs) and 3:1:2 (sewage sludge:sawdust:SMs or HRs). The mixture was then composted for 40 d. Changes in the physicochemical characteristic of sewage sludge during composting were recorded and analyzed. Addition of SMs and HRs accelerated the temperature rise, mediating a quicker composting maturation time compared to control. The addition also resulted in lower nitrogen losses and higher nitrate nitrogen levels in the compost products. Among the windrows, SM and HR addition improved the nitrogen status. The total nitrogen (TN) and nitrogen losses for SM and HR treatments ranged from 22.45 to 24.99 g/kg and from 10.2% to 22.4% over the control values (18.66-21.57 g/kg and 40.5%-64.2%, respectively). The pile with the highest proportion of SMs (3:1:2 (sewage sludge:sawdust:SMs)) had the highest TN level and the lowest nitrogen loss. The germination index (GI) values for all samples at maturity were above 80%, demonstrating optimal maturity. The addition of SMs and HRs augments sewage composting.

Nitrogen interception in floodwater of rice field in Taihu region of China.

A field experiment located in Taihu Lake Basin of China was conducted, by application of urea or a mixture of urea with manure, to elucidate the interception of nitrogen (N) export in a typical rice field through "zero-drainage water management" combined with sound irrigation, rainfall forecasting and field drying. N concentrations in floodwater rapidly declined before the first event of field drying after three split fertilizations, and subsequently tended to return to the background level. Before the first field drying, total particulate nitrogen (TPN) was the predominant N form in floodwater of plots with no N input, dissolved inorganic nitrogen (DIN) on plots that received urea only, and dissolved organic nitrogen (DON) on plots treated with the mixture of urea and manure. Thereafter TPN became the major form. No N export was found from the rice field, but total nitrogen (TN) of 15.8 kg/hm2 was remained, mainly due to soil N sorption. The results recommended the zero-drainage water management for full-scale areas for minimizing N export.

Phosphorus and copper leaching from dredged sediment applied on a sandy loam soil: column study.

In this paper, downward movement of phosphorus and copper as dredged sediment applied on sandy loam soil was studied by column leaching experiments. Three sediment application rate, (i.e., 1, 2 and 5-cm depth of sediments) were applied to the top of the soil columns. Two and a half months leaching experiments were conducted, which include a 15-day un-watered period. Concentrations of phosphorus and copper in the leachate and the vertical distribution of Olsen-P and diethylenetriaminepentaacetic acid (DTPA) extractable Cu in the soil columns were determined. The results showed that, un-watered period could increase the downward movements of phosphorus and copper. Sediment application significantly increased Olsen-P concentration in the top 15 cm of the soil columns, but has not significantly affected that in the deeper soil layer. The 1-cm depth sediment treatment did not increase the DTPA extractable Cu concentration in the whole soil column. The 5-cm depth sediment treatment, however, significant increased the DTPA extractable Cu in the deeper soil layers. This study suggested that the application of dredged sediment laden with P and Cu on sandy loam soil might cause the significant downward movement of phosphorus and copper.