RESUMO
Urban rainwater runoff is considered to be an important way to transport microplastics into the freshwater. By analyzing the microplastics in rainwater pipelines in different land function areas in Hongshan District (Wuhan, China), the preliminary results of microplastics abundance and characteristics in rainwater pipelines and rainwater pipeline sediments were obtained. The microplastics abundance in water samples was 2.75 ± 0.76 to 19.04 ± 2.96 items/L, the abundance of microplastics in the sediment was 6.00 ± 1.63 to 27.33 ± 4.64 items/100 g. The highest abundance among the samples was in the business district and the lowest in the campus. The microplastics in water samples and sediment samples were mainly fragments, accounting for 44.7% and 57.1%, respectively. The proportion of particle size <1 mm was 75.0% and above. The color of microplastics was diversified, and colored particles occupied over 60.0%. The types of polymers detected were mainly polyethylene, polypropylene and polyester, which were related to the types of polymers widely used in life. This study shows that urban rainwater pipelines is one of the ways for land-based microplastics to migrate to freshwater, and the accumulation of microplastics in stormwater pipe sediments might be an important contributor to microplastics in freshwater area.
RESUMO
Rejected water from sludge processing in wastewater treatment plants (WWTPs) is very harmful due to its high concentration of ammonia nitrogen and phosphorus. It is therefore necessary to find a low-cost and convenient technique to simultaneously remove ammonia nitrogen and phosphorus from rejected water. In this study, natural granular zeolite was modified by NaCl and La(OH)3 to obtain a new material (Na@La-MZP), with several advantages compared with powdered zeolite. Na@La-MZP could remove 92.61% ammonia nitrogen (50 mg/L) and 99.01% phosphate (60 mg/L) at the optimal conditions of dosage 12.5 g/L, initial pH 6.0 and reaction time 12 hours, which enabled the effluent to satisfy the discharge standard (GB 18918-2002) for municipal WWTPs in China. The maximum adsorption capacity of Na@La-MZP was determined as 17.92 mg NH4+-N/g and 9.53 mg P/g by the Langmuir isotherm. Pseudo-second-order kinetics could well illustrate the adsorption process and show that the ammonia nitrogen and phosphate can be degraded by chemical reaction. The characterizations of Na@La-MZP confirmed the removal mechanism of ammonia nitrogen and phosphate. The Na@La-MZP still maintained more than 75% removal efficiency after five reuses. Furthermore, the estimated cost of this treatment method was 0.22 $/m3 rejected water.
Assuntos
Poluentes Químicos da Água , Zeolitas , Adsorção , Amônia , China , Nitrogênio , Fosfatos , Águas Residuárias , ÁguaRESUMO
To evaluate the enhancing of the biological nitrogen removal effectiveness by electromagnetic wave loading on returned sludge in the A/A/O reactor, some experiments were completed with the returned sludge loaded by 2,450 MHz electromagnetic wave. The excess sludge yield and pollutant removal effect of the system were evaluated. Results showed that stronger denitrification effect and less sludge yield were achieved. When 30% of the returned sludge was loaded by electromagnetic wave, the actual denitrification efficiency increased by 7% without dosage. The dissolution of carbon, nitrogen and phosphorus from loaded returned sludge was detected, thus providing the system with a supplemental carbon source of 4.6 g/d SCOD. The specific oxygen uptake rate of the oxic activated sludge increased by 14%, and the denitrification rate of the anoxic activated sludge increased by 29%. Illumina MiSeq analysis showed that the microbial richness increased obviously, and denitrifying bacteria (i.e. Dechloromonas, Zoogloea and Azospira, etc.) were accumulated.
