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- Integrated process of immediate one-step lime precipitation, atmospheric carbonation, constructed wetlands, or adsorption for industrial wastewater treatment: A reviewPublication . Simão Madeira, Luís Miguel; Carvalho, Fátima; Almeida, Adelaide; Ribau Teixeira, MargaridaThe transition from the linear economy paradigm to the circular economy in industrial wastewater treatment systems is on the global agenda. The search for new simple, eco-innovative, and low-cost processes for treating industrial wastewater, which can also be used by small and medium-sized industries, has been a constant challenge especially when environmental sustainability is considered. So, a new integrated industrial wastewater treatment system has been developed that includes the immediate one-step lime precipitation process (IOSLM) and atmospheric carbonation (AC), followed by constructed wetlands (CWs) or adsorption. The current review provides an overview of industrial wastewater treatment strategies for high- and low-biodegradable wastewater. A background on functionality, applicability, advantages and disadvantages, operating variables, removal mechanisms, main challenges, and recent advances are carried out for each process that makes up the IOSLM+AC+CW/adsorption integrated system. The prospects of the IOSLM+AC+CW/adsorption integrated system are also discussed. Not neglecting the improvements that still need to be made in the integrated treatment system as well as its application to various types of industrial wastewater, this review highlights that this treatment system is promising in industrial wastewater treatment and consequent by-product recovery. The IOSLM+AC integrated system showed that it can remove high amounts of organic matter, total suspended solids, oils and fats, phosphorus, and ammonium nitrogen from industrial effluents. On the other hand, constructed wetlands/adsorption can be alternatives for refining effluents still containing organic matter and nitrogen that were not possible to remove in the previous steps.
- Tunning processes for organic matter removal from slaughterhouse wastewater treated by immediate one-step lime precipitation and atmospheric carbonationPublication . Simão Madeira, Luís Miguel; Almeida, Adelaide; Rosa Da Costa, Ana; Mestre, Ana S.; Carvalho, Fátima; Ribau Teixeira, MargaridaAdsorption using unmodified/modified commercial activated carbons and constructed wetlands (CW) planted with Vetiveria zizanioides were evaluated as tuning processes for lowering chemical oxygen demand (COD) from slaughterhouse wastewater pretreated by the integrated process of immediate one-step lime precipitation and atmospheric carbonation. Powdered and granular activated carbons (PAC and GAC), and PAC and GAC incorporated with iron oxide nanoparticles (PACMAG and GACMAG) were used. COD removal using different adsorbent separation methods (i.e., sedimentation, filtration, or magnetic separation) was also evaluated. The adsorption results indicated that the best adsorbent doses and contact times of the studied adsorbents were 70 g L-1 and 5 min for PAC and PACMAG, and 60 g L-1 and 60 min for GAC and GACMAG. Under optimized conditions, GAC (75.7 +/- 1.0%) and GACMAG (73.5 +/- 2.1%) were more efficient than PAC (59.7 +/- 1.0%) and PACMAG (59.0 +/- 0.0%) in removing COD. The incorporation of iron oxide nanoparticles in GAC and PAC did not affect the adsorption of COD. The Temkin model was the best isotherm model found for PAC and PACMAG, while for GAC and GACMAG was the BET model. Pseudo-order n kinetic model was the best kinetic model found for all the adsorbents tested. There were no significant differences in the removal of COD between filtration and magnetic separations. Phytoremediation results indicated that increased COD removal efficiency occurred when the applied COD mass load decreased or when the bed depth was increased. Maximum COD removals of around 89.9-95.0% were achieved. Vetiveria zizanioides showed no signs of toxicity throughout the trials.
- Immediate one-step lime precipitation and atmospheric carbonation as pretreatment for low biodegradable and high nitrogen wastewaters: A case study of explosives industryPublication . Madeira, Luis; Almeida, Adelaide; Ribau Teixeira, Margarida; Prazeres, Ana; Chaves, Humberto; Carvalho, Fatima; Madeira, Luís Miguel SimãoThe treatment of some industrial wastewaters is complex, since they usually contain complex non-biodegradable organic compounds or toxic compounds which are not easily treatable. These compounds are not removed by biological treatment in wastewater treatment plants and they may affect the removal of ammonium, nitrate, organic nitrogen by these treatment systems. Therefore, this research proposes a new and innovative low-cost and easy-to-apply pre-treatment to treat low biodegradable and high nitrogen wastewaters, using explosive wastewaters as case study. The pre-treatment is composed by immediate one-step lime precipitation (IOSLM) and atmospheric CO2 carbonation (AC) processes. The novelty of the proposed pre-treatment is based firstly on the use of one reactant (hydrated lime) at high concentrations, added in one step, that produces immediately an abundant and insoluble precipitate able to sweep the organic matter and other contaminants from wastewater in a short time and ensure conditions (pH and Ca2+) for the AC process. Secondly, the AC process uses the sludge produced in IOSLM to keep pH high for longer, allowing ammonia removal while simultaneously the pH is reduced by spontaneous reactions with atmospheric CO2. IOSLM results showed 92.1 %, 98.2 % and 100 % of organic matter, oils and fats, and organic nitrogen removals, respectively, for the optimal hydrated lime dose (7.76 g L-1). In AC process 61 % of ammonium nitrogen was removed and pH reduced to 8.1 in 10 days.
- Reutilização de águas resultantes da produção de explosivos: caso de estudo empresa “X”Publication . Madeira, Luís Miguel Simão; Madeira, Luís Miguel Simão; Teixeira, Margarida Ribau; Carvalho, Maria de Fátima Nunes deAs águas residuais resultantes da produção dos explosivos da empresa “X” caraterizam-se físico-quimicamente por conterem uma elevada carga orgânica (5922 mg O2 L-1) com muito reduzida biodegradabilidade (CBO5/CQO = 0,009), concentrações de azoto muito elevadas (1553,9 mg N-NH4+ L-1 e 7233 mg NO3- L-1) e um teor de óleos e gorduras de 285,3 mg L-1. Com objetivo de tratar este efluente, desenvolveu-se um sistema de tratamento, que consistiu na precipitação química em meio básico com Ca(OH)2, carbonatação natural e afinação em zona húmida artificial plantada com Vetivera zizanioides. No processo de precipitação química estudou-se o efeito da dose de cal sobre vários parâmetros físico-químicos, tendo sido escolhida a dose de Ca(OH)2 de 7,76 g L-1 que eleva o pH da água a 10, resulta num efluente límpido e permite atingir remoções de CQO de 92%, óleos e gorduras de 98% e elimina totalmente a matéria orgânica azotada. O sobrenadante obtido apresenta um pH de cerca de 10 e foi neutralizado numa etapa de carbonatação com CO2 atmosférico. Ao fim de 11 dias conseguiu-se a remoção simultânea de 61 % de NH4+, que lhe confere potencialidades para ser utilizado como fertilizante em fertirrega. A etapa de precipitação produziu um precipitado abundante que sedimenta em manto para tempos de retenção hidráulica de 46 minutos com uma percentagem de lamas reduzida, 4,5 %. Adicionalmente foi avaliada a possibilidade de tratamento por zonas húmidas artificais com Vetivera zizanioides sob fluxo sub-superficial vertical, o que permitiu conhecer os processos biológicos envolvidos por análise de vários parâmetros, conhecer as melhores condições operatórias aplicadas para remover maiores cargas mássicas de azoto amoniacal e de nitratos. Apesar de o tratamento proposto ser viável, os resultados evidenciaram que ainda há necessidade de fazer melhorias no tratamento proposto na remoção de azoto amoniacal, matéria orgânica e nitratos.