The efficient biomineralization and adsorption of cadmium (Cd2+) using secretory organo-biominerals (SOBs) produced by screened Alcaligenes faecalis K2.

Cadmium-contaminated wastewater has attracted increasing concerns due to its non-biodegradable properties and high toxicity. To explore eco-friendly and economically feasible strategies, the screened Alcaligenes faecalis K2 were employed for the biomineralization and recovery of Cd2+ from wastewater while producing considerable secretory organo-biominerals (SOBs) as bioadsorbents. At 75 mg/L Cd2+ exposure, 85.5% of Cd2+ was removed by K2, 43.0% of which was fixed in the granular SOBs. SOBs were convenient for separating from the solution. The adsorption capacity of granular sorbent made from SOBs was verified to be greater than 77.1 mg/g. Practically, 89.5% of 75 mg/L of Cd2+ could be stably removed while ereK2 continuously generated SOBs in a moving-bed biofilm reactor (MBBR). To sum up, the production of bioadsorbents can be achieved by K2, while removing Cd with live microorganisms, which was conducive to making full use of materials and improving Cd removal efficiency.

High levels of microplastic pollution in aquaculture water of fish ponds in the Pearl River Estuary of Guangzhou, China.

Microplastics (MPs) have caused great concern worldwide recently due to their ubiquity in the aquatic environment. The current knowledge on the occurrence of MPs in aquaculture fish ponds in a typical estuary system remains meagre. This study investigated the abundance and characteristics (shape, color, size and composition) of MPs in aquaculture water and pond influents in the Pearl River Estuary of Guangzhou, China, using an improved separation method. The bulk sampling and improved separation method by the combination of ethanol and polyaluminum chloride (PAC) significantly increased the MP separation efficiency, especially for particles with size less than <333 µm. The investigation results showed that MPs were detected in all water samples of fish ponds at two experimental stations with abundances of 10.3-60.5 particles/L (S1) and 33.0-87.5 particles/L (S2), respectively. Moreover, the average abundance of MPs in aquaculture water (42.1 particles/L) exhibited higher value than that in pond influents (32.1 particles/L). Most of MPs were colored and fibrous in appearance. MPs with the size range of <1000 µm (56.3-87.7%) prevailed in aquaculture water. MPs with size <333 µm that usually ignored in most studies were detected with percentage of 43.7% at S1station and 33.2% at S2 station, respectively. The small-sized MPs (<100 µm) in aquaculture water (23.7% at S1 station and 14.6% at S2 station) were more abundant than those in pond influents (7.2% at S1 station and 2.5% at S2 station). The main composition of MPs was polypropylene (PP) and polyethylene (PE). These findings indicated a high level of MP pollution in aquaculture fish ponds. The MPs originated from the Pearl River Estuary were accumulated in aquaculture fish ponds. This study provides an insight into MP pollution in aquaculture fish ponds at a typical estuarine system and highlights the load of MPs in the pond influents.