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1.
Sci Total Environ ; 813: 151875, 2022 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-34826471

RESUMO

Phosphorus, a limited resource, is also an environmental pollutant that should be removed from wastewater and ideally reused. A pilot-scale facility was set up and used to precipitate and recover phosphorus from wastewater. The return activated sludge in a hydrolysis tank was flocculated and separated and the solid material returned to the hydrolysis tank; the flocculation process did not harm the microorganisms. Phosphate in the reject water was precipitated with different calcium salts and the phosphorus-containing precipitate recovered. The precipitate consisted mainly of phosphate and calcium, and under 5% of the final product consisted of iron and aluminum. Around 20% of the precipitate was organic material. The pilot-scale test was supplemented with bench-scale tests using calcium salt, magnesium salt, and NaOH/KOH. Without the addition of calcium ions, phosphate could be precipitated by increasing pH to 9.5, resulting in a concentration of phosphorus in the reject water of under 2 mg/L. If calcium salt was added (Ca:P ratio of 2:1), it was possible to remove phosphate at pH 9 (<1 mg/L). In general, the concentration of dissolved phosphate was 8-10 mg/L lower after precipitation when calcium salt was used compared with all other tested salts. This difference increased if additional phosphate was added to the sludge. The bench- and pilot-scale experiments yielded comparable data. At the pilot-scale facility, it was possible to remove 90% of the phosphate by adding calcium salt and regulating the pH to 8.5.


Assuntos
Fósforo , Águas Residuárias , Precipitação Química , Hidrólise , Fosfatos , Esgotos , Eliminação de Resíduos Líquidos
2.
Biotechnol Lett ; 39(11): 1689-1698, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28849363

RESUMO

OBJECTIVE: To assess the effect of small temperature increases in mesophilic sludge-based digesters in order to develop and evaluate strategies for improving the biogas production in full-scale digesters. RESULTS: Methane production was strongly affected by small temperature differences, and this result was consistent across samples from 15 full-scale digesters. The specific methane yield varied between 42 and 97.5 ml g VS-1 after 15 days of incubation at 35 °C, and improved when increasing the digester temperature to 39 °C. Only a limited quantity of additional gas was required to balance out the cost of heating and a positive energy balance was obtained. Further increases in temperature, in some cases, negatively affected the production when operated at 42 °C compared to 39 °C. CONCLUSIONS: Small temperature increases should be applied to mesophilic sludge-based digesters to optimize the biogas production and is applicable to digesters operated in the lower mesophilic temperature range.


Assuntos
Reatores Biológicos/microbiologia , Metano/biossíntese , Esgotos/microbiologia , Anaerobiose , Biocombustíveis , Temperatura
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