Enhancing phenol removal from waste water by adding powder activated carbon to the lab-scale activated sludge system

In this study, the commercial powder activated carbon (PAC) was added to a bench scale conventional activated sludge (CAS) system to enhance phenol removal. The mixed liquor suspended solid (MLSS) concentration of CAS with adding PAC was stable in all stages of operation, while MLSS concentrations in CAS without PAC addition sharply decreased as the Phenol loading reached 1.8 g phenol/L.day. Higher removal of chemical oxygen demand (COD) and Phenol achieved with the CAS by PAC addition compared with those achieved with CAS without PAC addition. The difference in COD removal efficiency was 7 - 9% in stages 3 and 4 (0.8 and 1.2 g phenol/L.day, respectively), and about 33% in stage 5 (1.8 g phenol/L.day). The advantage of CAS with PAC addition was clearly observed in the highest phenol loading (1.8 g phenol/L.day) because the MLVSS/MLSS ratio of CAS with PAC addition increased and the COD and phenol removal efficiencies kept stable in this stage, while reverse trends were found for CAS without PAC addition. The results indicated that the adaptive ability of the CAS by adding PAC was significantly higher than the CAS without AC addition. This study offers useful preliminary results for applying a hybrid system between CAS and adsorption with PAC for further research and application in future.

Troubleshooting Foaming in Membrane Bioreactor: Review of Foam Analysis, Causes and Remedies

Membrane Bioreactors have proved to be a useful alternative to conventional activated sludge systems for wastewater treatment. Merits of membrane bioreactors include more compact design saving a significant amount of space and lower sludge production due to longer sludge retention time. This system unfortunately has a downside with it comes to excessive foaming. Membrane bioreactors often act as foam traps leading to overflowing, wastage of sludge and difficulty in process control. Pre-Treatment of wastewater has proven to significantly reduce foaming caused by surfactants. Generally, physical methods are considered more economical and operationally convenient compared to conventional techniques including chemical treatment and advanced techniques like biological treatment. Polyaluminium chloride as a coagulant is recommended as a chemical treatment due to economic and effectiveness considerations. It has been concluded that the remedies for foaming issue are case specific and should be determined by the causes of foaming. This paper aims at reviewing techniques to analyse the foaming phenomenon, causes of foaming and its remedies to manage or eliminate foam.

Reduction of Cost and Environmental Impact in the Treatment of Textile Wastewater Using a Combined MBBR-MBR System

A hybrid Moving Bed Biofilm Reactor—Membrane Bioreactor (MBBR-MBR) was developed for the treatment of wastewater from a Spanish textile company. Compared with conventional activated sludge (CAS) treatment, the feasibility of this hybrid system to reduce economic and environmental impact on an industrial scale was conducted. The results showed that, technically, the removal efficiency of COD, TSS and color reached 93%, 99% and 85%, respectively. The newly dyed fabrics performed with the treated wastewater were qualified under the standards of the textile industry. Economically, the values of Capital Expenditure (CAPEX) calculated for the hybrid MBBR-MBR system are profitable because of the reduction in Operational Expenditure (OPEX) when compared with CAS treatment, due to the lower effluent discharge tax thanks to the higher quality of the effluent and the decolorizing agent saved. The result of Net Present Value (NPV) and the Internal Rate of Return (IRR) of 18% suggested that MBBR-MBR is financially applicable for implantation into the industrial scale. The MBBR-MBR treatment also showed lower environmental impacts than the CAS process in the life cycle assessment (LCA) study, especially in the category of climate change, thanks to the avoidance of using extra decolorizing agent, a synthetic product based on a triamine.

Biogas, Solar and Geothermal Energy—The Way to A Net-Zero Energy Wastewater Treatment Plant–A Case Study

Wastewater treatment plants designed to meet the requirements of discharging wastewater to a receiving water body are often not energy optimised. Energy requirements for conventional activated sludge wastewater treatment plants are estimated to range from 0.30 to 1.2 kWh/m3, with the highest values achieved using the nitrification process. This article describes the energy optimisation process of the wastewater treatment plant in Gubin (Poland) designed for 90 000 PE (population equivalent) using renewable energy sources: solar, biogas, and geothermal. At the analysed wastewater treatment plant electricity consumption for treating 1 m3 of wastewater was 0.679 kWh in 2020. The combined production of electricity and heat from biogas, the production of electricity in a photovoltaic system, and heat recovery in a geothermal process make it possible to obtain a surplus of heat in relation to its demand in the wastewater treatment plant, and to cover the demand for electricity, with the possibility of also selling it to the power grid.

Naturally occurring nanoparticles in two biological wastewater treatment plants in Southern California

Naturally occurring nanoparticles (NONPs) in wastewater are generally considered colloids, but their production and size distribution are not well understood. NONPs are more abundant than engineered nanoparticles (ENPs) in wastewater, where they may cause membrane fouling, harbour pathogens, and transport contaminants to the environment. In this study we aimed to understand the seasonal behaviour as well as the quantity and size of suspended particles (both unfiltered and filtered through a 450 nm filter) along two water resource recovery facilities (WRRFs, formerly wastewater treatment plants) located in Southern California. We also investigated the factors that correlate with their occurrence. We found that both of the biological secondary treatments investigated, conventional activated sludge process (ASP) and trickling filter (TF), were more efficient in removing suspended particles larger than 450 nm than they were smaller ones. The results show that current treatment processes are not designed to remove nano-sized particles efficiently. Additionally, there was a significant and direct correlation between influent dissolved chemical oxygen demand (COD) and the abundance of suspended particles both larger and smaller than 450 nm, suggesting that the suspended particles increased with dissolved COD in the WRRFs and thus were biogenically generated during the wastewater treatment.