Saline wastewater treatment with purple phototrophic bacteria.

Biological removal of organics, nitrogen and from saline wastewaters is adversely impacted by high salinity, which can be a major concern for treatment of industrial or domestic saline wastewater. In anaerobic treatment systems, sulfidogensis, especially when treating sulfate-rich saline wastewaters (e.g. seawater has 930 mgSO4-S L-1, or 2800 mg L-1 as SO42-) can cause additional biological, operational, and safety issues, due to H2S toxicity. Here, the use of anaerobic purple phototrophic bacteria (PPB) is tested as mediator to treat high salinity domestic wastewater (NaCl), and marine wastewater (Red Sea Salt - high sulfate, potassium, etc.) in a continuous anaerobic infra-red photo bioreactor, operated over 372d. Saline adapted PPB simultaneously removed COD, nitrogen and phosphorus with biomass yields of 0.8 gCOD gCOD-1. Batch activity tests found a broad optimum peak for saline adapted PPB between 30 and 70 mS cm-1, and 50% reduced activity at 140 mS cm-1 (3.5x seawater). For marine wastewater, high sulfate influent concentrations (770 mgSO4-S L-1) did not result in substantial H2S production (<1.6 mgS L-1) over 80 d. When irradiation was removed, sulfide rapidly rose to >90 mgS L-1 and the process failed. The results indicate rapid adaptation to high-salt conditions (both NaCl and marine), and the capacity for PPB to form a combined wastewater treatment/resource recovery process, particularly for salty industrial wastewater.

Simultaneous treatment and single cell protein production from agri-industrial wastewaters using purple phototrophic bacteria or microalgae - A comparison.

Resource recovery, preferably as high value products, is becoming an integral part of modern wastewater treatment, with conversion to heterotrophic or phototrophic/photosynthetic microbes a key option to minimise dissipation, and maximise recovery. This study compares the treatment capacities of purple phototrophic bacteria (PPB) and microalgae of five agri-industrial wastewaters (pork, poultry, red meat, dairy and sugar) to recover carbon, nitrogen, and phosphorous as a microbial product. The mediators have different advantages, with PPB offering moderate removals (up to 74% COD, 80% NH4-N, 55% PO4-P) but higher yields (>0.75 gCODremoved gCODadded-1) and a more consistent, PPB dominated (>50%) product, with a higher crude protein product (>0.6 gCP gVSS-1). The microalgae tests achieved a better removal outcome (up to 91%COD, 91% NH4-N, 73%PO4-P), but with poorer quality product, and <30% abundance as algae.

White and infrared light continuous photobioreactors for resource recovery from poultry processing wastewater - A comparison.

Concentrated wastewaters from agricultural industries represent a key opportunity for the upcycling of organics, nitrogen and phosphorus to higher value products such as microbial protein. Phototrophic or photosynthetic microbes very effectively capture input organics and nutrients as microbial protein. This study compares purple phototrophic bacteria (PPB) and microalgae (photosynthesis) for this purpose, treating real, high strength poultry processing wastewater in continuous photo bioreactors utilising infrared (IR) and white light (WL) respectively. Both reactors could effectively treat the wastewaters, and at similar loading rates (4 kgCOD m-3d-1). The infrared reactor (IRR) was irradiated at 18 W m-2 and the white light reactor (WLR) reactor at 1.5-2 times this. The IRR could remove up to 90% total chemical oxygen demand (TCOD), 90% total nitrogen (TN) and 45% total phosphorus (TP) at 1.0 d hydraulic retention time (HRT) and recover around 190 kg of crude protein per tonne of influent COD at 7.0 kWh per dry tonne-1 light input, with PPB dominating all samples. In comparison, the WLR removed up to 98% COD, 94% TN and 44% TP at 43-90% higher irradiance compared to the PPB reactor. Microalgae did not dominate the WLR and the community was instead a mix of microbes (algae, bacteria, zooplankton and detritus - ALBAZOD) with a production of approximately 140 kg crude protein per tonne influent COD.