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Peri-urban aquacultures produce nutritious food in proximity to markets, but poor surface water quality in rapidly expanding megacities threatens their success in emerging economies. Our study compared, for a wide range of parameters, water quality downstream of Bangkok with aquaculture regulations and standards. For parameters not meeting those requirements, we sought to establish whether aquaculture practice or external factors were responsible. We applied conventional and advanced methods, including micropollutant analysis, genetic markers, and 16S rRNA amplicon sequencing, to investigate three family-owned aquacultures spanning extensive, semi-intensive and intensive practices. Canals draining the city of Bangkok did not meet quality standards for water to be used in aquaculture, and were sources for faecal coliforms, Bacteriodes, Prevotella, Human E. coli, tetracycline resistance genes, and nitrogen into the aquaculture ponds. Because of these inputs, aquacultures suffered algae blooms, with and without fertilizer and feed addition to the ponds. The aquacultures were sources of salinity and the herbicide diuron into the canals. Diuron was detectable in shrimp, but not at a level of concern to human health. Given the extent and nature of pollution, peri-urban water policy should prioritize charging for urban wastewater treatment over water fees for small-scale agricultural users. The extensive aquaculture attenuated per year an estimated twenty population equivalents of nitrogen pollution and trillions of faecal coliform bacteria inputs from the canal. Extensive aquacultures could thus contribute to peri-urban blue-green infrastructures providing ecosystem services to the urban population such as flood risk management, food production and water pollution attenuation.

The accumulation of plastic waste in the environment has become a serious environmental problem worldwide. Biodegradable plastics, such as polyhydroxyalkanoate (PHA), could serve as green alternatives to petroleum-based plastics. In this study, a mixed microbial culture was enriched under feast/famine conditions using a sequencing batch reactor (SBR) with acetate as a carbon source. The enrichment could accumulate a maximum PHA concentration of 32.3% gPHA/g mixed liquor suspended solids (MLSS) in the 12 th cycle of SBR operation. The microbial community in this sludge sample was analyzed using 16 S rRNA gene amplicon sequencing (MiSeq). The results showed the dominance of Proteobacteria, represented by Alphaproteobacteria (13.26% of total sequences), Betaproteobacteria (51.37% of total sequences), and Gammaproteobacteria (23.44% of total sequences). Thauera (Betaproteobacteria) had the highest relative abundance, accounting for 48.88% of the total sequences. PHA-accumulating microorganisms in the enrichment were detected using fluorescence in situ hybridization (FISH) and a fluorescent dye, Nile blue A. Alphaproteobacteria and Betaproteobacteria were capable of accumulating PHA, while no Gammaproteobacteria were detected. Thauera spp. from Betaproteobacteria constituted 80.3% of the total PHA accumulating cells. Massive generation of plastic waste has long been considered a worldwide environmental problem. The accumulation of plastic waste and microplastics in the environment can be detrimental to natural ecosystems. Polyhydroxyalkanoate (PHA) is a microbial polymer that can be used in biodegradable plastics, thereby offering a green alternative to nonbiodegradable, petroleum-based plastics. Currently, PHA can be commercially produced using pure cultures of bacteria, such as Cupriavidus necator, Alcaligenes latus, Burkholderia cepacia, and recombinant Escherichia coli 1,2. However, the production costs are still high due to the required sterile processes. Research on PHA production from organic wastewater using mixed microbial cultures has drawn great attention since it can reduce PHA production costs while applying the concept of resource recovery from wastewater. There are several approaches for the enrichment of PHA-accumulating microorganisms in mixed microbial cultures, including creating anaerobic/aerobic, microaerophilic/aerobic, or feast/famine conditions 3. At present, feast/famine conditions can support the highest PHA content (89% gPHA/gMLSS) compared to the other approaches 4. The microbial community is an important factor that can affect PHA production in mixed microbial cultures. Previous research has investigated microbial communities in PHA production systems with mixed microbial cultures under feast/famine conditions. Various molecular techniques have been used, such as a 16 S rRNA gene clone library generation 5 , 16 S rRNA gene amplicon sequencing (MiSeq/HiSeq) 6,7 , polymerase chain reaction-denaturing