Nutrient removal from pickle industry wastewater by cultivation of Chlorella pyrenoidosa for lipid production

Resource recovery and valorization of food wastewater for sustainable development: An overview of current approaches

The food processing industry is one of the world's largest consumers of potable water. Agri-food wastewater systems consume about 70% of the world's fresh water and cause at least 80% of deforestation. Food wastewater is characterized by complex composition, a wide range of pollutants, and fluctuating water quality, which can cause huge environmental pollution problems if discharged directly. In recent years, food wastewater has attracted considerable attention as it is considered to have great prospects for resource recovery and reuse due to its rich residues of nutrients and low levels of harmful substances. This review explored and compared the sources and characteristics of different types of food wastewater and methods of wastewater treatment. Particular attention was paid to the different methods of resource recovery and reuse of food wastewater. The diversity of raw materials in the food industry leads to different compositional characteristics of wastewater, which determine the choice and efficiency of wastewater treatment methods. Physicochemical methods, and biological methods alone or in combination have been used for the efficient treatment of food wastewater. Current approaches for recycling and reuse of food wastewater include culture substrates, agricultural irrigation, and bio-organic fertilizers, recovery of high-value products such as proteins, lipids, biopolymers, and bioenergy to alleviate the energy crisis. Food wastewater is a promising substrate for resource recovery and reuse, and its valorization meets the current international policy requirements regarding food waste and environment protection, follows the development trend of the food industry, and is also conducive to energy conservation, emission reduction, and economic development. However, more innovative biotechnologies are necessary to advance the effectiveness of food wastewater treatment and the extent of resource recovery and valorization.

Recent updates to microbial production and recovery of polyhydroxyalkanoates

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum.

Aerobic granular sludge treating hypersaline wastewater: Impact of pH on granulation and long-term operation at different organic loading rates

pH is one of the major parameters that influence the granulation and long-term operation of aerobic granular sludge (AGS). In hypersaline wastewater, the impact of pH on granulation and the extent of organic loading rate (OLR) that AGS can withstand under different pH are still not clear. In this study, AGS was cultivated at 3% salinity in three sequencing batch reactors with influent pH values of 5.0, 7.0, and 9.0, respectively, and the OLR was stepwise increased from 2.4 to 16.8 kg COD/m³·d after the granules maturation. The results showed the satisfactory granulation and organic removal under different influent pH conditions, in which the granulation was completed on day 43, 23, and 23, respectively. Neutral influent was the most appropriate for development of salt-tolerant aerobic granular sludge (SAGS), while acidic environment induced the formation of fluffy filamentous granules, and alkaline environment weakened the granule stability. Metagenomic analysis revealed the similar microbial community of neutral and alkaline conditions, with the predominance of genus Paracoccus_f__Rhodobacteraceae. While in acidic environment, fungus Fusarium formed the skeleton of filamentous granules and functioned as the carrier of bacteria including Azoarcus and Pararhodobacter. With the elevation of OLR, SAGSs were found to maintain the compact structure under OLRs of 2.4, 7.2, and 2.4 kg COD/m³·d, and obtain high TOC removal (>95.0%) under OLRs of 7.2, 14.4, and 14.4 kg COD/m³·d, respectively. For hypersaline high-strength organic wastewater, satisfactory TOC removal could also be obtained at broad pH ranges (5.0-9.0), in which neutral environment was the most suitable and acidic environment was the worst. This study contributed to a better understanding of SAGS granulation and treatment of hypersaline high-strength organic wastewater with different pH values.

A comprehensive review on emerging trends in industrial wastewater research

Rapid industrialization is one of the intricate factors that is linked to the depletion of water resources and increased generation of wastewater. Due to various obstructions and impediments, such as ineffective treatment solutions, exorbitant prices, lack of basic amenities, insufficient financial assistance, and technical expertise, sustainable treatment of industrial effluents has become an onerous process in most parts of the world. The majority of current treatment solutions are conventional and outdated, and thus fall short to remove all the contaminants efficiently from the industrial wastewater. Moreover, poorly treated or untreated industrial effluents are indiscriminately dumped into water bodies such as lakes, ponds, and rivers, causing substantial health hazards to humans and animals and serious threats to the aquatic ecosystem. Thus, there is a need for highly efficient, cost-effective, and sustainable technologies for the treatment of industrial wastewater. Employment of microbial technologies such as microbial fuel cells and microalgal technologies, treatment of wastewater can be coupled with the production of bioelectricity and valuable biomass, respectively. Moreover, with nanofiltration and biochar technologies, the efficiency of the overall treatment procedure can be increased to a greater extent. The present review aims to highlight opportunities and challenges associated with some of the emerging trends in industrial wastewater research.

Effects of salinity on the simultaneous anammox and denitrification process: performance, sludge morphology and shifts in microbial communities

In this study, the long-term effects of different salinities on the performance, sludge morphology and shifts in microbial communities were studied in a simultaneous anammox and denitrification (SAD) process at a C/N ratio of 0.5. Stable nitrogen removal efficiencies of 86.96 and 84.58% and nitrogen removal rates of 0.95 and 0.93 kg (m3 d)-1 could be achieved under low (25 mmol l-1) and moderate (50 mmol l-1) salinity, respectively. However, the performance collapsed when the system was exposed to high salinity (100 mmol l-1). The content of extracellular polymeric substances increased as salinity increased, which resulted in larger sizes of granular sludge under low and moderate salinities. Nevertheless, high salinity shock disintegrated granular sludge, thereby decreasing the average granule size. The Illumina-Miseq sequencing results revealed that Candidatus Jettenia was the sole salinity-tolerant AnAOB genus during the entire operation, whereas the main denitrification bacterial genera shifted from Denitrisoma under low salinity to Denitrisoma, Thauera and Ignavibacterium under high salinity. The results of this study provide a comprehensive and practical evaluation of the SAD process for organic nitrogen-rich saline wastewater treatment.

Nutrients recycling and biomass production from Chlorella pyrenoidosa culture using anaerobic food processing wastewater in a pilot-scale tubular photobioreactor

Microalgae cultivation in anaerobic food wastewater was a feasible way for high biomass production and nutrients recycling. In this study, Chlorella pyrenoidosa culture on anaerobic food wastewater was processed outdoors using a pilot-scale tubular photobioreactor. The microalgae showed rapid growth in different seasons, achieving high biomass production of 1.83-2.10 g L^-1 and specific growth rate of 0.73-1.59 d^-1. The biological contamination and dissolved oxygen were controlled at suitable levels for algal growth in the tubular photobioreactor. Lipids content in harvested biomass was 8.1-15.3% of dried weight, and the analysis in fatty acids revealed high quality with long carbon chain length and high saturation. Additionally, algal growth achieved effective pollutants purification from wastewater, removing 42.3-53.8% of COD_Cr, 82.6-88.7% of TN and 59.7-67.6% of TP. This study gave a successful application for scaled-up microalgae culture in anaerobic food processing wastewater for biodiesel production and wastewater purification.

Determination of the potential of pickle wastewater as feedstock for biopolymer production

Food industry wastewater (FIWW) streams with high organic content are among the most suitable and inexpensive candidates for polyhydroxyalkanoate (PHA) biopolymer production. Due to its high organic acid content, pickle industry wastewater (PIWW), can be considered as one of the prospective alternatives to petroleum-based polymers for PHA production. In this context, this study aimed to investigate the production of PHA with enriched microbial culture using PIWW. Two laboratory scale sequencing batch reactors (SBRs) were operated under aerobic dynamic feeding conditions at a sludge retention time of 8 days, with a total cycle duration of 24 hours. SBRs were fed with peptone mixture and PIWW. In-cycle analysis and batch respirometric tests were performed to evaluate PHA storage together with biodegradation kinetics. In-cycle analysis showed that maximum PHA content was 1,820 mgCOD/L, corresponding to 44% in the biomass (ratio of chemical oxygen demand (COD) to volatile suspended solids) for PIWW. Experimental results were also confirmed with activated sludge model simulations. As for the PHA composition, hydroxybutyrate was the major fraction. Model simulations proposed a unique conversion-degradation-storage pathway for the organic acid mixture. This paper presents a novel insight for better understanding of PHA biopolymer production using high saline FIWW.