Abstract
With a conceptual shift in sewage treatment from ‘waste pollution’ to ‘vehicle of resource and energy recovery’ and the further intensification of the energy crisis, the separation and recovery of carbon resources from discharged sewage has gained increasing recent attention in the field of water treatment. The ultra-short Solids Retention Time (SRT) activated sludge process (SRT ≤ 4 d) is highly efficient for separating organic matter and improving the energy recovery rate in wastewater treatment plants, but the effluent quality is relatively poor. If organics in the ultra-short SRT effluent can be reduced further to separate and recover carbon resources, the process may soon replace the traditional activated sludge process. We conducted physical adsorption carbon recovery experiments in an ultra-short SRT (SRT = 2 d) activated sludge system using three carbon nanotubes. Considering that Chemical Oxygen Demand (COD) arises from a mixture of organic compounds, and because humic acid (HA) makes up a large fraction of the effluent and can cause great environmental harm, further experiments were conducted on the adsorption of HA in the effluent COD to three nanotubes. This study proposes a novel method to completely remove organics from the effluent from ultra-short SRT activated sludge processes and reveals nanotube adsorption properties and mechanisms.
Highlights
Recent years have seen a worldwide conceptual shift in sewage treatment from ‘waste pollution’ to ‘vehicle of resource and energy recovery.’ Organic matter in sewage contains 1.5–1.9 kW·h·m−3 of chemical potential, which is nearly 10 times the energy consumption of sewage treatment[1,2]
Previous studies have demonstrated that the secondary effluent Soluble COD (SCOD) from municipal wastewater treatment plants still contains some refractory organics, such as humic acid (HA), fulvic acid (FA), and synthetic organic compounds
In tests of adsorption capacity variation and Chemical Oxygen Demand (COD) removal rate, the organic matter adsorption rate was high initially owing to the number of effective adsorption sites
Summary
Recent years have seen a worldwide conceptual shift in sewage treatment from ‘waste pollution’ to ‘vehicle of resource and energy recovery.’ Organic matter in sewage contains 1.5–1.9 kW·h·m−3 of chemical potential, which is nearly 10 times the energy consumption of sewage treatment[1,2]. The ultra-short Solids Retention Time (SRT) activated sludge process (SRT ≤ 4 d) developed from section A of the traditional Absorption Biodegradation (AB) process is highly efficient in separating organic matter from water and improving the sewage plant energy recovery rate The process it poised to become the leading wastewater treatment technology, but currently produces relatively poor effluent quality, with a Total Chemical Oxygen Demand (TCOD) at around 70 mg·L−1. Physical adsorption is the simplest advanced wastewater treatment method for some degree of DOM removal; adsorption is highly efficient, has little environmental impact, occupies little space, and uses recyclable adsorbents in contrast to chemical treatment methods New carbon materials, such as carbon nanotubes (CNTs), based on traditional adsorbents (such as activated carbon and diatomite) have gained attention in synthetic adsorbent research in recent years. The DOM-to-CNT adsorption mechanisms remain poorly understood
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