Nguyen Phuoc Dan

Pilot study on the removal of TOC, THMs, and HAAs in drinking water using ozone/UV–BAC

AbstractThe contaminated water is a main source of many waterborne diseases such as cholera, typhoid, etc. causing many serious public health crises, especially in developing countries with the low hygiene condition. In Vietnam, previous studies have reported that industrial and domestic waste cause adverted pollution on Saigon River that supplies water for 30% of 10 million residents in Ho Chi Minh City. Annual monitoring water quality data during 2006–2011 showed that concentration of ammonia and organic matter has been significantly increased and over the allowable limit (COD > 10 mg/L). In order to reduce these pollutants in the finished water and for disinfection, a large dose of chlorine (about 3–6 mg/L) needs adding in the treatment process at Tan Hiep water treatment plant. A negative effect of using too much chlorine is the formation of disinfection by-products (DBPs) such as trihalo-methanes (THMs) and haloacetic acids (HAAs). The concentration of THMs in finished water of Tan Hiep plant ranged ...

Laboratory-scale membrane up-concentration and co-anaerobic digestion for energy recovery from sewage and kitchen waste.

This study assessed an alternative concept for co-treatment of sewage and organic kitchen waste in Vietnam. The goal was to apply direct membrane filtration for sewage treatment to generate a permeate that is suitable for discharge. The obtained chemical oxygen demand (COD) concentrations in the permeate of ultrafiltration tests were indeed under the limit value (50 mg/L) of the local municipal discharge standards. The COD of the concentrate was 5.4 times higher than that of the initial feed. These concentrated organics were then co-digested with organic kitchen wastes at an organic loading rate of 2.0 kg VS/m(3).d. The volumetric biogas production of the digester was 1.94 ± 0.34 m(3)/m(3).d. The recovered carbon, in terms of methane gas, accounted for 50% of the total carbon input of the integrated system. Consequently, an electrical production of 64 Wh/capita/d can be obtained when applying the proposed technology with the current wastes generated in Ho Chi Minh City. Thus, it is an approach with great potential in terms of energy recovery and waste treatment.

The Challenges of Water Governance in Ho Chi Minh City

Population growth, urbanization, pollution, and climate change pose urgent water challenges in cities. In this study, the sustainability of integrated water resources management in Ho Chi Minh City (HCMC) was evaluated using the City Blueprint approach. The City Blueprint is a set of 24 dedicated indicators divided over 8 categories (i.e., water security, water quality, drinking water, sanitation, infrastructure, climate robustness, biodiversity and attractiveness, and governance including public participation). The analysis showed that the rapid increase of water use for urban, industrial, and agricultural activities in HCMC has resulted in depletion of groundwater and severe pollution of both groundwater and surface water. Surface water quality, groundwater quality, biodiversity, and the sanitation of domestic and industrial wastewater are matters that need serious improvement. Current and future water supply in HCMC is at risk. HCMC can cope with it, but the 7 governance gaps as described by the Organisation for Economic Co-operation and Development (OECD) are major obstacles for HCMC. Rainwater harvesting, pollution reduction, as well as wastewater reuse are among the practical options. Wastewater reuse could lower the water stress index to 10%. The window to do this is narrow and rapidly closing as a result of the unprecedented urbanization and economic growth of this region.

Status and strategies on solid waste management in Ho Chi Minh City

As a result of rapid industrialisation and uncontrolled urbanisation, solid waste generation rate has increased significantly in Ho Chi Minh City (HCMC). At present, about 6000 tons of solid waste is generated daily from activities in HCMC. Meanwhile, solid waste management and disposal facilities have not reached to extent to satisfy the need. Solid waste is not sorted at the sources. Some critical issues arise from these landfills such as emission of bad odour, land sliding, land subsidence and pollution of receiving waters. Therefore, at the initial stage, a master plan should be focused on an effective waste management planning.

Low flux submerged membrane bioreactor treating high strength leachate from a solid waste transfer station

A submerged membrane bioreactor was employed to treat high strength leachate generating from a solid waste transfer station. The reactor was operated at low fluxes of 1.2; 2.4; 3.8 and 5.1 LMH. The organic loading rate (OLR) ranged from 2 to 10 kg COD/m(3)day. Results show that 97% removal efficiency of COD at flux of 2.4 LMH. The highest removal of ammonia nitrogen and total nitrogen was 92.0 ± 1.5% and 88.0 ± 2.0% respectively at flux of 3.8 LMH. Fouling rates were observed to be 0.075; 0.121; 3.186 and 6.374 kPa/day for the fluxes of 1.2; 2.4; 3.8 and 5.1 LMH, respectively. Membrane fouled very slowly at low flux operation. The sustainable flux was identified to be less than 2.4 LMH for treating high strength leachate. It reveals less fouling was able to achieve for high strength wastewater by reducing the membrane flux.

Fouling mitigation in a submerged membrane bioreactor treating dyeing and textile wastewater

Abstract The present study aims to assess the treatment efficiency and membrane fouling propensity of a submerged membrane bioreactor (MBR) treating dyeing and textile wastewater by introducing Powder-Activated Carbon (PAC) and Alum (called “fouling reducer”). The treatment performance and fouling behavior of MBR when adding PAC and Alum were compared to those of the control MBR. The components of dyeing and textile wastewater were fluctuated with Chemical oxygen demand (COD), color, and turbidity of 500–2,500 mg/L, 370–2,700 Pt-Co, and 50–370 NTU, respectively. The Mixed Liquor Suspended Solids (MLSS) concentration in an MBR fluctuated from 6,000 to 9,000 mg/L. The mixed liquor volatile suspended solids (MLVSS) to MLSS ratio was 0.76. The organic loading rate was operated in the range of 1.4–1.7 kg COD/m3 d. In the control MBR (without the addition of a fouling reducer into the bioreactor), the results showed that the MBR could only remove the color at a maximum efficiency of 50% and COD of 60–94% during...

Performance of wetland roof with Melampodium paludosum treating septic tank effluent

AbstractWetland roof (WR) system was developed to apply for building terrace and top roof in the urbanized area of Ho Chi Minh City. This study aims to improve the green area of the city and to treat domestic wastewater through a shallow horizontal subsurface constructed wetland that is located in a household roof. The pilot-scale unit of horizontal subsurface flow WR system with Melampodium paludosum, an indigenous emerging plant in Vietnam, was experimented at the average hydraulic loading rate (HLR) of 338 m3/ha d (∼36 kg COD/ha d) corresponding to HRT of 18 h. The treatment performance was not significantly different for rainy and sunny days at various HLRs. It was observed that the average removal efficiency of COD was 77–78% or 20–28 kgCOD/ha d for both sunny and rainy days. It is apparent that nutrient removal was greatly achieved as indicated by TN removal efficiency of 88–91% or 17–20 kg TN/ha d. In addition, TP removal reached 72–78% or 1.6 kg TP/ha d for different HLRs. The treated effluent cou...

Nutrient removal by different plants in wetland roof systems treating domestic wastewater

AbstractThis study evaluated nutrients removal from domestic wastewater by five plants in wetland roof systems (WR). The study plants include Arachis duranensis (1), Evolvulus alsinoides (2), Cosmos Bipinnuatus (3), Cyperus alternifolius Linn (4), and Philodendron hastatum (5). The WRs were acclimatized at hydraulic loading rates (HLR) of 220 m3/ha d and operated at HLR of 300 m3/ha d. The plants (1), (2), (4), and (5) had the ability to grow under the rooftop conditions with domestic wastewater as a nutrient source while the plant (3) was not suitable and dead after 20 d of operation. Generally, A. duranensis (1) and C. alternifolius Linn (4) were the most suitable plants treating domestic wastewater under the conditions of WR. The average phosphorus removal efficiencies of (1) and (4) were approximately 75 and 89%, respectively, while the average nitrogen removal efficiencies were 69 and 92%. The phosphorus accumulation in plants (1) and (4) during operation was 20.4 and 29.4%, respectively, while the n...

Impact of nitrogen loading rates on nitrogen transformation for anaerobic effluent from latex processing industry

This study evaluated the influence of nitrogen loading rates on fate of nitrogen treating anaerobic effluent from latex processing industry using a novel acryl-fibre biomass carrier-bio-fringe (BF) in a swim-bed reactor. At NLR of 0.5 kg N/m³.day, 60% to 70% TKN was converted and the nitrogen ratio N-NO2 / (NO2 + NO3) reached 80% to 90%. At NLR of 1 kg N/m³.day, conversion efficiency of TKN increases by 80% to 95% and the ratio reached 80% to 95%. However, this ratio decreased by 40% to 60% due to the influent alkalinity reduction. At increased NLR of 1.5-2 kg N/m³.day, nitrite and nitrate reduced less than 20 mg N/L. This is due to an increase in NLR and amount of alkalinity available. Reactor pH as high as 8.2-8.6 produced high free ammonia (FA) concentration restricting nitrite production. The COD removal efficiencies were 80-90% and 85-95% at NLR of 0.5-1 kg N/m³.day, respectively. This reduced 75-88% at an increased NLR of 1.5-2 kg N/m³.day.

Study of swim-bed technology for COD removal and nitrification for latex wastewater treatment

COD removal and nitrification by swim-bed technology using a novel carrying acryl-fibre biomass carrier (biofringe) was conducted to investigate its effectiveness for latex wastewater treatment. The influent taken from a rubber factory contained 2,000 to 3,500 mg/l COD, 150 to 300 mg/l ammonia-N and 250 to 500 mg/l TKN. The quality of latex wastewater is unstable, depending on seasonal latex production. The results showed that COD removal and nitrification efficiency were high at the volumetric loading rates (VLRs) equal and less than 1.0 kg COD/m³/d, corresponding to 0.13 kg N/m³/d. COD removal and nitrification efficiency were above 90% and 73%, respectively. At the VLR of 2 kg COD/m³/day (0.24 kg N/m³/d), nitrification efficiency was reduced to 56%, while COD removal were still above 90%. At the VLR as high as 3 kg COD/m³/d (0.4 kg N/m³/d), low COD removal and nitrification efficiency were observed, 86% and 20%, respectively. Biomass concentration increased as the increase of VLRs. Total biomass was 6,800 mg/l and 7,900 mg/l at VLRs of 2 and 3 kg COD/m³/d, respectively.