scholarly journals Microalga-Mediated Tertiary Treatment of Municipal Wastewater: Removal of Nutrients and Pathogens

2021 ◽  
Vol 13 (17) ◽  
pp. 9554
Author(s):  
Swati Rani ◽  
Raja Chowdhury ◽  
Wendong Tao ◽  
Linda Nedbalova
Keyword(s):  
Nitrate Uptake ◽  
Municipal Wastewater ◽  
Oxygen Demand ◽  
Biomass Productivity ◽  
Ammonium Uptake ◽  
Plate Count ◽  
Pathogen Inactivation ◽  
Tertiary Treatment ◽  
Waste Stabilization ◽  
Reactor Kinetic

The microalgal strain Chlorella sorokiniana isolated from a waste stabilization pond was used for tertiary treatment of municipal wastewater. Three light:dark (L:D) regimes of 12:12, 16:8, and 24:0 were used for treating wastewater in microalga (A), microalga + sludge (A + S), and sludge (S) reactors. The removal of nutrients (N and P) was found to be the highest in the microalga-based reactor, with more than 80% removal of biochemical oxygen demand (BOD) and 1.2–5.6 log unit removal of pathogens. The addition of sludge improved chemical oxygen demand (COD) removal. Nitrifiers were found to be predominant in the A + S reactor. Algal biomass productivity was more than 280 mg/L/d in all the L:D regimes. The increase in light regime improved nutrient removal and biomass productivity in the algal reactor. Results of the kinetic study showed that (i) nitrifiers had more affinity for ammonium than microalga, and hence, most of the ammonia was oxidized to nitrate, (ii) microalga assimilated nitrate as the primary nitrogen source in the A + S reactor, and (iii) solubilization of particulate organic nitrogen originated from dead cells reduced the nitrogen removal efficiency. However, in the microalga-based reactor, the ammonium uptake was higher than nitrate uptake. Among pathogens, the removal of Salmonella and Shigella was better in the A + S reactor than in the other two reactors (microalga and sludge reactor). Additionally, the heterotrophic plate count was drastically reduced in the presence of microalga. No such drastic reduction was observed in the stand-alone sludge reactor. Kinetic modeling revealed that microalga–pathogen competition and pH-induced die-off were the two predominant factors for pathogen inactivation.

scholarly journals Enhancement of overloaded waste stabilization ponds using different pretreatment technologies: a comparative study from Namibia

2020 ◽  
Vol 10 (4) ◽  
pp. 500-512
Author(s):  
Jochen Sinn ◽  
Susanne Lackner
Keyword(s):  
Municipal Wastewater ◽  
Oxygen Demand ◽  
Uasb Reactor ◽  
Anaerobic Sludge ◽  
Treatment Technology ◽  
Waste Stabilization Ponds ◽  
Stabilization Ponds ◽  
Waste Stabilization ◽  
Sub Saharan ◽  
Anaerobic Sludge Blanket

Abstract Waste stabilization ponds (WSP) are a well-established wastewater treatment technology in Namibia. However, they are often overloaded and we still lack concepts and technologies for improvement. Therefore, this study presents the full-scale implementation of two pretreatment technologies to reduce the inflow of organic and solid loads into a facultative pond. We specifically compared the effects of anaerobic biological and mechanical pretreatment by an upstream anaerobic sludge blanket (UASB) reactor and a 250 μm micro sieve (MS). Not only in Namibia but also in most sub-Saharan countries, there is little experience with these technologies for the treatment of municipal wastewater in small and fast-growing local communities. Both technologies were tested in parallel for a period of 17 months and proved operational. While the UASB achieved better removal results with respect to chemical oxygen demand (COD) and suspended solids (TSS), the MS was more flexible in handling changing inflow patterns and had a much smaller footprint. The average total COD reductions of the MS and the UASB were 22 and 50%, respectively. TSS were removed by 45% with the MS and by 57% with the UASB reactor. Therefore, UASB and MS are viable options for the enhancement of existing WSP to reach better effluent values of the facultative pond.

Sewage Treatment by Waste Stabilization Pond Systems

2018 ◽  
Vol 3 (1) ◽  
pp. 7-14
Author(s):  
J. Kenneth, R. S. Suglo
Keyword(s):  
Management Practices ◽  
Sewage Treatment ◽  
Oxygen Demand ◽  
Wastewater Management ◽  
Stabilization Pond ◽  
Waste Stabilization Pond ◽  
Quality Guidelines ◽  
Waste Stabilization ◽  
High Reduction ◽  
Wastewater Samples

Sewage generated in Ghana is commonly discharged into the environment without any form of treatment to reduce the degree ofcontamination and mitigate potential public health and environmental issues. Although some attempts have been made in someparts of Ghana to utilize the waste stabilization pond (WSP) system to treat domestic sewage, the ponds often fail to achievetheir purpose due to lack of basic maintenance and supervision. To assess the utility of the WSP system for treating sewage,wastewater samples were collected from the raw sewage, anaerobic, facultative and maturation ponds of WSPs at Obuasi inGhana, and analyzed for physicochemical and microbiological contaminants. The results show that the final pond effluent meetsrecommended microbiological and chemical quality guidelines. The waste stabilization pond system demonstrates high removalefficiencies of wastewater contaminants. The biochemical oxygen demand, total suspended solids, nitrate and faecal coliformsreduction efficiencies of 97.3%, 97.6%, 83.3% and 99.94% respectively are highly significant, and compare well with reportedremoval efficiencies in the literature. Additionally, the ponds have high reduction efficiencies for heavy metals and pathogenicmicroorganisms. The wastewater treatment system complies with standard wastewater management practices, and provides auseful method for treating and disposing wastewater in Ghana.

Costs of tertiary treatment of municipal wastewater by rapid sand filter with coagulants and UV

2003 ◽  
Vol 3 (4) ◽  
pp. 145-152 ◽  
Author(s):  
H. Heinonen-Tanski ◽  
P. Juntunen ◽  
R. Rajala ◽  
E. Haume ◽  
A. Niemelä
Keyword(s):  
Total Phosphorus ◽  
Municipal Wastewater ◽  
Pilot Scale ◽  
Treated Wastewater ◽  
Tertiary Treatment ◽  
Sand Filter ◽  
Physico Chemical ◽  
Bathing Waters ◽  
Filtration Unit ◽  
Microbial Groups

Municipal treated wastewater has been tertiary treated in a pilot-scale rapid sand filter. The filtration process was improved by using polyaluminium coagulants. The sand-filtered water was further treated with one or two UV reactors. The quality changes of wastewater were measured with transmittance, total phosphorus, soluble phosphorus, and somatic coliphages, FRNA-coliphages, FC, enterococci and fecal clostridia. Sand filtration alone without coagulants improved slightly some physico-chemical parameters and it had almost no effect on content of microorganisms. If coagulants were used, the filtration was more effective. The reductions were 88-98% for microbial groups and 80% for total phosphorus. The wastewater would meet the requirements for bathing waters (2,000 FC/100 ml, EU, 1976). UV further improved the hygiene level; this type of treated wastewater could be used for unrestricted irrigation (2.2 TC/100 ml, US.EPA 1992). The improvement was better if coagulants were used. The price for tertiary treatment (filtration + UV) would have been 0.036 Euro/m3 according to prices in 2001 in 22 Mm3/a. The investment cost needed for the filtration unit was 0.020 Euro/m3 (6%/15a). Filtration with coagulants is recommended in spite of its costs, since the low transmittance of unfiltered wastewater impairs the efficiency of the UV treatment.

scholarly journals Assessment of Microplastics in a Municipal Wastewater Treatment Plant with Tertiary Treatment: Removal Efficiencies and Loading per Day into the Environment

Water ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1339
Author(s):  
Javier Bayo ◽  
Sonia Olmos ◽  
Joaquín López-Castellanos
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plant ◽  
Municipal Wastewater ◽  
Removal Rate ◽  
Treatment Plant ◽  
Source Control ◽  
Municipal Wastewater Treatment ◽  
Tertiary Treatment ◽  
Stable Performance ◽  
Wastewater Samples

This study investigates the removal of microplastics from wastewater in an urban wastewater treatment plant located in Southeast Spain, including an oxidation ditch, rapid sand filtration, and ultraviolet disinfection. A total of 146.73 L of wastewater samples from influent and effluent were processed, following a density separation methodology, visual classification under a stereomicroscope, and FTIR analysis for polymer identification. Microplastics proved to be 72.41% of total microparticles collected, with a global removal rate of 64.26% after the tertiary treatment and within the average retention for European WWTPs. Three different shapes were identified: i.e., microfiber (79.65%), film (11.26%), and fragment (9.09%), without the identification of microbeads despite the proximity to a plastic compounding factory. Fibers were less efficiently removed (56.16%) than particulate microplastics (90.03%), suggesting that tertiary treatments clearly discriminate between forms, and reporting a daily emission of 1.6 × 107 microplastics to the environment. Year variability in microplastic burden was cushioned at the effluent, reporting a stable performance of the sewage plant. Eight different polymer families were identified, LDPE film being the most abundant form, with 10 different colors and sizes mainly between 1–2 mm. Future efforts should be dedicated to source control, plastic waste management, improvement of legislation, and specific microplastic-targeted treatment units, especially for microfiber removal.

Water quantity and quality assessment on a tertiary treatment wetland in a tropical climate

2014 ◽  
Vol 71 (4) ◽  
pp. 511-517 ◽  
Author(s):  
Guangzhi Sun ◽  
Tanveer Saeed ◽  
Guangxin Zhang ◽  
Nagaratnam Sivakugan
Keyword(s):  
Oxygen Demand ◽  
Field Testing ◽  
Tropical Climate ◽  
Surface Flow ◽  
Quality Analysis ◽  
Treated Wastewater ◽  
Wetland Soil ◽  
Tertiary Treatment ◽  
Wet Season ◽  
Treatment Wetland

This study aimed to assess the quantity and quality of water in a surface flow constructed wetland in Australia's far north Queensland. Owing to tropical climate in the region, the wetland provided dual functions: retention of a treated wastewater for zero discharge during the dry season and tertiary treatment prior to discharge during the wet season. Rainfall data, permeability of wetland soil, evaporation, inflow and outflow were analysed in a water balance analysis; the results showed that based on a 72-year-average rainfall pattern, daily wastewater inflow of 85 m3/d is the maximum this wetland can cope with without breaching its discharge certificate. In water quality analysis, the K-C* model was used to predict changes of biochemical oxygen demand (BOD, suspended solids (SS), total nitrogen (TN), total phosphorus (TP) and faecal coliforms (FC) in the wetland. Model predictions were compared with field sampling results. It was found that the wetland was effective in removing FC (>99.9%), TN (70.7%) and TP (68.2%), for which the predictions by the K-C* model were consistent with field testing results. However, significant disparities between the predictions and testing results were found for BOD and SS. A revised K-C* equation was proposed to account for the internal generation of organics in constructed wetlands with a long retention time.

Floating geomembrane covers for odour control and biogas collection and utilization in municipal lagoons

2000 ◽  
Vol 42 (10-11) ◽  
pp. 291-298 ◽  
Author(s):  
C. J. DeGarie ◽  
T. Crapper ◽  
B. M. Howe ◽  
B. F. Burke ◽  
P. J. McCarthy
Keyword(s):  
Control System ◽  
Municipal Wastewater ◽  
Treatment Plant ◽  
Anaerobic Treatment ◽  
Organic Load ◽  
Stabilization Pond ◽  
Waste Stabilization ◽  
Odour Control ◽  
Lagoon Systems ◽  
Anaerobic Lagoons

The use of anaerobic lagoons as the first pond in waste stabilization pond systems in tropical and warm-temperature climates is considered a highly cost-effective and practical way to treat municipal wastewater. These anaerobic ponds, designed with hydraulic residence times of up to six days, can effect BOD5 removals of 60 to 80%. The subsequent aerobic stabilization pond surface area is greatly reduced over systems designed without anaerobic treatment up front due to the organic load reduction occurring anaerobically. In lagoon systems with mechanical aeration, operation costs can be greatly reduced. While odour is a concern with anaerobic treatment, anaerobic ponds treating municipal wastewater can be designed to be relatively odour-free given sufficiently low wastewater sulfate concentrations. However, when sulfate concentrations are high, or when odour control or greenhouse gas emissions are significant issues, or when the wastewater is relatively high in organic strength resulting in commercial production of methane gas, anaerobic lagoons can be covered, and the biogas collected and burned both to produce energy and reduce emissions and odour. The City of Melbourne treats approximately 50% of its municipal wastewater at the Western Treatment Plant in waste stabilization ponds designed with anaerobic ponds as the first pond in the system. Each of three pond systems at the Western Treatment Plant receives an average dry weather flow of 120,000 m3/d with an average strength of 400 mg/L BOD5. This paper describes the design, installation and commissioning of two 3.9 hectare floating, self draining, geomembrane covers on the anaerobic section of two of these lagoon systems. Biogas collection and utilization were an important part of the installation. A description of how the biogas is collected, the quantities generated and an overview of the control system used to operate the biogas handling facility is also included. Particular emphasis was placed on maximizing biogas utilization in design of the biogas control system.

Novel biofilm reactor for denitrification of municipal wastewater

2018 ◽  
Vol 78 (7) ◽  
pp. 1566-1575 ◽  
Author(s):  
S. S. Rathnaweera ◽  
B. Rusten ◽  
K. Korczyk ◽  
B. Helland ◽  
E. Rismyhr
Keyword(s):  
Carbon Source ◽  
Municipal Wastewater ◽  
Low Cost ◽  
Oxygen Demand ◽  
Pilot Scale ◽  
Biofilm Reactor ◽  
Treated Wastewater ◽  
Removal Rates ◽  
Good Filter ◽  
Solids Removal

Abstract A pilot-scale CFIC® (continuous flow intermittent cleaning) reactor was run in anoxic conditions to study denitrification of wastewater. The CFIC process has already proven its capabilities for biological oxygen demand removal with a small footprint, less energy consumption and low cost. The present study focused on the applicability for denitrification. Both pre-denitrification (pre-DN) and post-denitrification (post-DN) were tested. A mixture of primary treated wastewater and nitrified wastewater was used for pre-DN and nitrified wastewater with ethanol as a carbon source was used for post-DN. The pre-DN process was carbon limited and removal rates of only 0.16 to 0.74 g NOx-N/m²-d were obtained. With post-DN and an external carbon source, 0.68 to 2.2 g NO3-Neq/m²-d removal rates were obtained. The carrier bed functioned as a good filter for both the larger particles coming with influent water and the bio-solids produced in the reactor. Total suspended solids removal in the reactor varied from 20% to 78% (average 45%) during post-DN testing period and 9% to 70% (average 29%) for pre-DN. The results showed that the forward flow washing improves both the DN function and filtration ability of the reactor.

scholarly journals Municipal Wastewater Treatment Using a Packed Bio-tower Approach

2020 ◽  
pp. 42-50
Author(s):  
Klaus Doelle ◽  
Qian Wang
Keyword(s):  
Wastewater Treatment ◽  
Flow Rate ◽  
Municipal Wastewater ◽  
Oxygen Demand ◽  
Pilot Scale ◽  
Continuous Operation ◽  
Growth Media ◽  
Municipal Wastewater Treatment ◽  
Bacteria Growth ◽  
Tower System

The study tested a designed and built pilot scale packed bio-tower system under continuous operation using pre-clarified municipal wastewater. Performance was evaluated by measuring the removal of chemical oxygen demand and nitrogen ammonia. The pilot scale packed bio-tower system had a diameter of 1209 mm (4 ft.) and a height of 3,962 mm (13 ft.) and contained Bentwood CF-1900 bacteria growth media with a surface area of 6,028.80 ft² (560.09 m²). The municipal residential sewage was fed into a 1,481 l (375 gal.) recirculation reservoir at a temperature of 15°C (59.0°F) and a flow rate between 7,571 l/d (2000 gal/d) and 90,850 l/d (24,000 gal/d) and recirculated through the bio-tower with a fixed recirculation rate of 75.7 l/min (20 gal/min). The influent COD value reduction achieved is between 63.4% and 84.8%, whereas the COD influent value varied between 87 mg/l and 140 mg/l. The influent NH3-N reduction achieved was between 99.8% and 91.8% whereas the influent NH3-N value was between 28.8 mg/l and 18.6 mg/l  at a flow rate between 7571 l/d (2000 gal/d) and 90,850 l/d (24,000 gal/d).

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