This work evaluates the use of native microalgae consortia for a dual role: polishing treatment of municipal wastewater effluents and microalgae biomass feedstock potential for biodiesel or biofertilizer production. An initial screening was undertaken to test N and P removal from secondary effluents and biomass production by 12 consortia. A subsequent treatment was performed by selected consortia (01 and 12) under three operational conditions: stirring (S), S + 12 h of daily aeration (S + A) and S + A enriched with CO (S + AC). All treatments resulted in compliance with environmental regulations (e.g. Directive 91/271/EEC) and high removal efficiency of nutrients: 64-79% and 80-94% of total N and PO-P respectively. During the experiments it was shown that pH alkalinization due to microalgae growth benefits the chemical removal of ammonia and phosphorus. Moreover, advantages of pH increase could be accomplished by intermittent CO addition which in this research (treatment S + AC) promoted higher yield and lipid concentration. The resulting dry biomass analysis showed a low lipid content (0.5-4.3%) not ideal for biodiesel production. Moreover, the high rate of ash (29.3-53.0%) suggests that biomass could be readily recycled as a biofertilizer due to mineral supply and organic constituents formed by C, N and P (e.g. carbohydrate, protein, and lipids).

Stabilization lagoons are economic systems that are built for treatment of municipal, industrial and agricultural wastewater; these systems are used in rural communities. Objective of this article is to present the hydrodynamics flow in lagoon system considering 6 screens with 7 channels containing curved forms with slopes suitable to stabilize the flow along each channel, and approach a piston flow. Hydrodynamics of this system with IBER software was analyzed, where was considered the velocity and hydraulic gradient, using Froude number. Also transport of total suspended solids was modelled. Efficiency in the treatment with this design was evaluated, using parameters such as, pH, conductivity, alkalinity, hardness, total solids, dissolved oxygen, redox potential and Chemical Oxygen Demand (COD). Through the results, a homogeneous transport was observed, mainly dissolved oxygen which was concordant with redox potential and COD, also through the curves, short circuits were minimized, avoiding dead zones and making treatment more efficient, finally were possible to comply with regulations of Mexico NOM-001-SEMARNAT-1996 of discharges and the NOM-003-SEMARNAT-1997 for water of agricultural use.

The behavior of a rainwater harvesting system depends on some variables that cannot be controlled, such as precipitation, building roof size and water demand. The selection regarding rainwater tank-size will affect the performance of the system and the cost-bene t ratio. The criterion employed for this selection is based on the need for volume-storage and typically, yield large-sized rainwater-tanks, especially when the amount of rainwater is higher during rainy seasons. This article presents a methodology for modelling the rainwater harvesting, storage, and water consumption, for different con gurations of a set of buildings, called clusters, where all buildings collect, store and same collected water. This methodology allows for analyzing based on different indicators what is the best recommended con guration and tank sizing, based on con guration and storage ratio exhibited, thus avoiding the situation of being underutilized. The proposed methodology is applied to case of study at a university (Mexico). In this study case, the dynamics per day is modeled over a year, considering monthly rainfall averages, over 2 groups made up of 4 buildings with different collecting capabilities and consumption each, allowing for the analysis of 9 cluster con gurations and 4 tank sizing dimensions.The results are analyzed by means of annual indicators such as: the decrease in the volume of water used from the public network, the days of autonomy of the system, and a coe cient R (which relates the volume spilled to the empty volume). This coe cient is then used selection regarding tank sizing and the most recommended cluster con guration.

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Microalgae hold great potential for producing purified high-value products (e.g. pigments and polyunsaturated fatty acids) and represent a source of bioavailable nutrients in aquaculture feeds; however, its production is limited by the high costs of harvesting. Recently, microalgae autoflocculation has been considered a useful solution due to the easy recovery of cell aggregates and natural increase in pH that prevents cell lysis. This work evaluates some cultivation conditions that could contribute to autoflocculation, such as natural pH increase and precipitate formation over the productivity and flocculation of 16 microalgae consortia. Results showed a biomass production of 1.4 to 4.4 dry weight (g L-1) and high flocculation of 81 to ~100%, probably due to Ca3(PO4)2 formation. Moreover, the alkaline pH could have facilitated the assimilation of CO2 and explained the increase of inorganic carbon in the solution obtained. Likewise, results showed a marked descent in electrical conductivity (EC) in solution and high mineral content in the biomass (21.4-35.9%). Finally, this study suggests that the studied culture conditions facilitated microalgae harvest, and the resulting biomass could be a source of bioavailable dietary minerals. Therefore, some of these results might be addressed in future studies with individual microalgae species.