The food-water quality nexus in periurban aquacultures downstream of Bangkok, Thailand

Abstract

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 Dilemmas of Water Quality and Food Security Interactions in Low- and Middle-Income Countries

“…Fish production can be affected by algae blooming. Fish farmers in the downstream areas of Bangkok in Thailand used herbicides to avoid algae blooms which could intoxicate their fish with cyanotoxins (Mrozik et al, 2019). However, neither exceedance of herbicide residues concentrations nor the presence of pathogens in shrimps were reported (Mrozik et al, 2019).…”

“…Fish farmers in the downstream areas of Bangkok in Thailand used herbicides to avoid algae blooms which could intoxicate their fish with cyanotoxins (Mrozik et al, 2019). However, neither exceedance of herbicide residues concentrations nor the presence of pathogens in shrimps were reported (Mrozik et al, 2019). In general, In the Nile delta in Egypt, pesticide residues were found in water and sediment samples, but the levels of pesticide residues in fish did not exceed the maximum residue limits (Shalaby et al, 2018).…”

“…In intensive aquaculture next to feed, pesticides, herbicides and fertilizers are used (Mrozik et al, 2019). For example, in the production of tilapia and shrimp in Thailand, fertilizers are used during the pond preparation to stimulate photosynthetic production.…”

Valorisation of agricultural waste derived biochars in aquaculture to remove organic micropollutants from water – experimental study and molecular dynamics simulations

“…In South Asia, aquaculture plays a major role in the rural economy, accounting for example for 2% of total GDP in Thailand ( Sugiyama et al, 2004 ). However, recently the Thai aquaculture industry has suffered a major decline, which is related to problems with novel diseases and water quality ( Mrozik et al, 2019 ). To deal with diseases and algae blooms farmers may resort to the use of antibiotics (i.e.…”

“…The main aim of this work was to establish the sorption properties of biochars produced from different agricultural waste materials with different methods for the removal of different organic micropollutants from water. The organic micropollutants selected for the assessment of biochar sorption properties represented a range of typical antibiotics, pesticides and common pharmaceuticals that are used in aquaculture and agriculture in South Asia or may be found in wastewater ( Mrozik et al, 2019 ). Experimental studies were supported by molecular dynamics simulation.…”