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1.
Chemosphere ; 263: 128332, 2021 Jan.
Article in English | MEDLINE | ID: mdl-33297261

ABSTRACT

This research comparatively investigates the biotoxicity of landfill leachate effluent from acclimatized and non-acclimatized sludge two-stage activated sludge (AS) systems. Both AS systems were operated with two leachate influent concentrations: moderate (condition 1) and elevated (condition 2). The biotoxicity of AS effluent of variable concentrations (10, 20, and 30% (v/v)) was assessed by the mortality rates of common carp (Cyprinus carpio) and glutathione-S-transferase (GST) enzyme activity. The treatment efficiency of the acclimatized sludge AS system for organic and inorganic compounds and nutrients (BOD, COD, TKN, NH4+, PO43-) were 75-96% under condition 1 and 79-93% under condition 2. The non-acclimatized sludge AS system achieved the treatment efficiency of 70-91% under condition 1 and 66-90% under condition 2. The acclimatized sludge AS system also achieved higher biodegradation of trace organic compounds, especially under condition 1. The effluent from acclimatized sludge AS system was less toxic to the common carp, as evidenced by lower mortality rates and higher GST activity. The findings revealed that the acclimatized sludge two-stage AS system could be deployed to effectively treat landfill leachate with moderate concentrations of compounds and trace organic contaminants. The acclimatized sludge AS is an efficient wastewater treatment solution for developing countries with limited technological and financial resources.


Subject(s)
Carps , Water Pollutants, Chemical , Animals , Antioxidants , Bioreactors , Sewage , Water Pollutants, Chemical/analysis , Water Pollutants, Chemical/toxicity
2.
Sci Total Environ ; 724: 138275, 2020 Jul 01.
Article in English | MEDLINE | ID: mdl-32408458

ABSTRACT

This research comparatively investigates the effect of landfill leachate effluent of two biological treatment schemes on germination of Lactuca sativa and Vigna radiata. The treatment schemes are two-stage activated sludge (AS) and two-stage membrane bioreactor (MBR) systems with acclimatized seed sludge. The AS and MBR are operated under two concentrations of landfill leachate influent: moderate (condition 1) and elevated (condition 2). The results show that, under condition 1, the AS and MBR efficiently remove 80-96% of organic compounds and nutrients and 81-100% of harmful micropollutants. Under condition 2 with elevated influent concentration, MBR is more effective in biodegrading micropollutants than the AS system. The germination rate (GR) and germination seed index (GSI) of L. sativa and V. radiata germinated with AS and MBR effluent from condition 1 are 100% and 1.29-1.56. Under condition 2, the GR and GSI with AS effluent are reduced to 80% and 0.65-0.77, while those with MBR effluent are 100% and 1.27-1.38. Quantitative real-time polymerase chain reaction (qPCR) analysis indicates that the bacterial community in the MBR is more abundant than in the AS, especially ammonia oxidizing bacteria, Nitrobacter, and Nitrospira, which aid heterotrophic bacteria in biodegradation of micropollutants and promote the growth of heterotrophs. The bacterial abundance and community composition render the MBR scheme more operationally suitable for elevated landfill-leachate influent concentrations. By comparison, the MBR system is more effective in removal of micropollutants than the AS, as evidenced by higher GR and GSI. The technology also could potentially be applied to water reclamation. A lack of technological and financial resources in many developing countries nevertheless precludes the adoption of MBR despite higher pollutant removal efficiency. An alternative solution is the use of acclimatized seed sludge in AS system to enhance treatment efficiency, especially in influent with low concentrations of micropollutants. In addition, the seed germination results suggest the possibility of water reuse in agriculture.


Subject(s)
Sewage , Water Pollutants, Chemical/analysis , Biodegradation, Environmental , Bioreactors , Germination , Membranes, Artificial , Seeds/chemistry , Waste Disposal, Fluid
3.
Chemosphere ; 230: 606-615, 2019 Sep.
Article in English | MEDLINE | ID: mdl-31128507

ABSTRACT

This research investigates the effect of hydraulic retention time (HRT) on micropollutant biodegradation of two-stage activated sludge (AS) system augmented with acclimatized sludge treating low-micropollutants wastewater. The experimental wastewater was a mixture of landfill leachate and agriculture wastewater, and HRT was varied between 24, 18, and 12 h. The results showed that, under 24 h HRT, the micropollutant biodegradation efficiencies were 87-93% for bisphenol A (BPA), 2,6-di-tert-butyl-phenol (2,6-DTBP), di-butyl-phthalate (DBP), di-(ethylhexyl)-phthalate (DEHP); 75-81% for carbamazepine (CBZ), diclofenac (DCF); and 88% for N,N-diethylmeta-toluamide (DEET). The degradation efficiencies were similar under 18 h HRT: 87-93% for BPA, 2,6-DTBP, DBP, DEHP; 75-80% for CBZ, DCF; and 80% for DEET. However, the efficiencies substantially declined under 12 h HRT: 71-93%, 55-60%, and 50%, respectively. Importantly, the findings revealed that HRT plays a crucial part in micropollutant biodegradation of bioaugmented AS system. More specifically, too short an HRT (12 h) results in low micropollutant removal efficiency, and too long an HRT (24 h) contributes to low daily throughput and high treatment operation cost. As a result, moderate HRT (18 h) is operationally and economically optimal for bioaugmented AS system treating low-micropollutants wastewater.


Subject(s)
Microbial Consortia , Sewage/microbiology , Wastewater/chemistry , Water Pollutants, Chemical/analysis , Water Purification/methods , Biodegradation, Environmental , Bioreactors , Time Factors , Wastewater/microbiology
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