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Protein‐dependent aquaculture generates large amounts of nutrient‐rich residuals; a feasible way to develop sustainable production systems is to integrate Decoupled Aquaponic Systems (DAPS) with residual water bioprocesses, to combine Photoautotrophic Biofloc Technology (P‐BFT) aquaculture and hydroponic horticulture. This study describes the characteristics of residual water from Oreochromis niloticus aquaculture performed with P‐BFT inoculated with Chlorella microalgae, reared during the nursery (180 fish m3) and grow‐out (55 fish m3) phases. The experiment included five treatments: photoautotrophic BFT inoculated with Chlorella sp. (M), C. sorokiniana 2714 (CV), and C. sorokiniana 2805 (CS), and chemoautotrophic (Q) and heterotrophic (H) as controls. Elemental characteristics in liquid and solid residual fractions (15 macro‐ and micronutrients) were compared among treatments and against Hoagland & Arnon solution with hydroponics and used in Nutrient Film Technique (NFT) hydroponic horticulture including five plant species: lettuce (Lactuca sativa), pak‐choi (Brassica rapa subsp. chinensis), rocket (Eruca sativa), spinach (Spinacia oleracea) and basil (Ocimum basilicum). The physicochemical parameters were ideal for O. niloticus and plants. The relationship between N:P was ideal until weeks 16–22 in the photoautotrophic treatments, compared with hydroponic solutions. Micronutrient content was greater in the solid than a liquid fraction. The best BFT effluent regarding fish and plant growth was photoautotrophic treatments. Oreochromis niloticus BFT aquaculture in photoautotrophic mode using microalgae Chlorella inoculations provided residual water beneficial to hydroponic horticulture in DAPS located in coastal arid zones where freshwater is scarce, improving aquaculture performance and reusing water and nutrients.

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Phosphorous (P) and nitrogen (N) residuals fromLitopenaeus vannamei and N and P retention by L. vannamei were studied at three protein levels and with two protein sources: fish meal with plant protein (AVD) and plant protein with squid meal as an attractant (VD). A protein retention bioassay began with shrimp that were 1.5-2.5 g, and nutrient release bioassays were conducted with shrimp of two sizes (4.5 and 8.5 g). Both bioassays were conducted at: 30 AE 0.5°C, [O 2 ] > 4 mg L À1 , and 38 UPS. Total P residuals were significantly higher for AVDs than for VDs (P < 0.05), particularly those with a high dietary protein level. The particulate P fraction was the predominant form of P. Total N and inorganic dissolved N, mainly in ammonia form, significantly increased (P < 0.05) with dietary protein level and shrimp size, regardless of the protein source. VDs resulted in significantly greater P retention (P < 0.05) than AVDs, without significantly affecting growth rates or survival. P retention as well as N retention decreased with increasing protein supplementation level, independently of the protein source used (P > 0.05). This study shows that the substitution of fish meal with plant protein (soybean meal and wheat flour) improves P retention in L. vannamei.

Wastewater from poultry-processing plants can be challenging to treat, partially because of the antimicrobial processing aides such as peracetic acid (PAA) and cetylpyridinium chloride (CPC) which suppress nitrifying bacteria. The objective of this research was to test the effects of adding microalgae, PAA, and CPC on nitrification in poultry-processing wastewater. Batch experiments were designed to test two different green algae along with PAA or CPC in a set of full-factorial experiments. The presence of C. sorokiniana increased nitrate production up to 2.7-fold compared to cultures without algae, but this effect was only statistically significant in one of the experiments. The measurement of nitrate was confounded by the fact that this alga consumes both nitrite and nitrate. Carrying out the experiment with A. protothecoides (which does not consume nitrite or nitrate) resulted in 4–9-fold higher peak nitrate concentrations compared to cultures without algae (p < 0.005). These improvements were more than enough to overcome the negative suppressive effects of PAA and CPC. The results suggest that incorporation of algae into engineered treatment systems for poultry-processing wastewater could improve the function of nitrifying bacteria, enabling potential water reuse in hydroponic plant irrigation.