Topics. Advanced Wastewater Treatment Processes. US Federal Regulation. Status of Nutrient Regulation in Texas. Texas 2 nd Effluent Limitations

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1 Advanced Wastewater Treatment Processes Kung-Hui (Bella) Chu, P.E. Ph.D. Assistant Professor The Zachry Department of Civil Engineering, Texas A&M University Tel: Topics Regulation: Current & Future Biological Nutrient Removal Nitrification/Denitrification Phosphorus Removal Membrane Bioreactor Emerging Contaminants in Wastewater March 24, 2009 US Federal Regulation Wastewater Characteristics & 2 nd Effluent Discharge Criteria Min 2 nd Eff. Nat. Std. BOD mg/l <30 mg/l TSS 220 mg/l <30 mg/l Total Nitrogen mg/l 3 mg/l NH 4+ -N mg/l Organic-N mg/l Total Phosphorous (as P) 8 mg/l mg/l Total coliforms /100 ml <200 CFU/100mL In 2001, US EPA published water quality criteria for 17 ecoregions. Texas 2 nd Effluent Limitations BOD 5 20 mg/l (30-day average) 10 mg/l (30-day average, enhanced with nitrification) TSS 20 mg/l (30-day average 15 mg/l (30-day average, enhanced with nitrification) No Numerical criteria Residual chorine removed Status of Nutrient Regulation in Texas Current: no numerical criteria for nutrients Future: TCEQ currently considers nutrient controls by 1) applying narrative criteria to address permitted nutrient loadings at sites of concern, 2) developing watershed rules which require nutrient reductions in wastewater discharges in or near specified water bodies, and 3) employing the TCEQ s antidegradation policy to increases in discharge loads of nutrients. The TCEQ also screens phosphorus and nitrate nitrogen and chlorophyll a monitoring data as a preliminary indication of areas of possible concern in the Texas Water Quality Inventory under Section 305(b) of the federal Clean Water Act (CWA). Source:

2 Wastewater Treatment Plant Conventional Activated Sludge Process Screen wastewater For optimized operation conditions BOD Removal : 90%~99.5% TN Removal : 50%~70% (~ mg/l) TP Removal : 70%~90% (~ 6 mg/l) Might not meet future effluent limitations Electron Donor and Acceptor Biological Nutrient Removal (BNR) Using certain types of microorganisms to remove nitrogen and phosphorus in wastewater for us Electron Donor (e - donor) Reduced compounds Organics: Glucose, oils, grease, etc. Inorganics: Fe 2+ Electron Acceptor (e - acceptor) O 2 NO 3 - SO 4 2- CO 2 Biological Nitrogen Removal For N removal: Nitrification (O 2 required) NH 4+ NO 2- NO 3 - Denitrification (no O 2 ) NO 3- N 2 For P removal: (first no O 2 then with O 2 ) Poly P Pi + PAH (polyhydroxybutyrate) Pi + PAH Poly P Nitrification Two major groups of microorganisms NH O 2 NO H + +H 2 O (Nitrosomonas, prefix Nitroso) NO O 2 NO 3 - (Nitrobacter, recently Nitrospira) Long SRT (~ 15 d) and low decay rate ( b = 0.05 day -1 ) θ x, min, nitrifiers = 2.1 days >> θ x, min, heterotrophs = 0.2 days

3 One-Sludge Nitrification One-sludge nitrifiersand heterotrophs coexist. One reactor and one settler for all types of microorganisms. Two-Sludge (Nitrification) Two-sludge Reduce competition between the nitrifiers and the heterotrophs. Two reactors and two settlers. Two different microbial communities, one for each sludge. One-Sludge vs Two-Sludge C/N ratio vs. nitrifier fraction One-sludge little control on incoming toxicants and ph rising sludge problem Two-sludge keep toxicants from 2-stage 1st settler doesn t have rising sludge, 2nd settler might. Good to keep BOD 5 /TKN low for nitrification Denitrification Many heterotrophic and autotrophic bacteria are capable of shifting between oxygen respiration and nitrogen respiration. All denitrifiers are facultative aerobes. G Proteobacteria, such as Pseudomonas, Alcaligenes, Paracoccus, and Thiobacillus. G+ : Bacillus Archaea: Halobacterium Denitrification Dissimilatory reduction of NO 3- or NO 2- to N 2 e- acceptor: NO 3- or NO 2 - e- donor: organics or inorganics (H 2 and reduced sulfur) Possible e- donor sources: sewage organics (effluent) external source (sugars, methanol, acetate, ethanol)

4 One-Sludge Denitrification: Biomass Storage and Decay One-sludge Denitrification: Predenitrification Mechanisms for P Removal Process Configurations for P Removal Source: Stensel, 2001, WEFTEC BNR: Nutrient Removal Efficiency What s New? Membrane Bioreactors (MBR)

5 Membrane & Membrane Bioreactor Developed 40 years ago Used commercially in Japan for 30 years Needs for high quality water Source: Filtration + Separation January/February (1):32-35 Conventional WWTP vs. MBR Principle Configurations of MBR Technologies Based on Membrane Process Mode Diffusion Extraction Rejection Process Configuration Immersed Sidestream Can be Airlift or Pumped Membrane Configuration Hollow fibre Flat Plate Multitubes Process Configuration Membrane Configuration Source: Trends in Biotechnology (2):

6 Source: Trends in Biotechnology (2): Source: Trends in Biotechnology (2): Advantage of MBR Low space required. Maintain higher biomass concentration, volumetric loading rates, and less sludge production. Greater control of longer SRT & HRT allow for retention and degradation of slowly biodegradable contaminant. Higher rate of nitrification and denitrification. High quality treated effluent. in Biotechnology (2): Disadvantage of MBR Higher operation and energy cost Membrane lifetime and replacement Membrane fouling problem Source: Meng et al. Water Research (2009), DOI: /j.waters

7 What s Hot? Emerging Contaminants Source: Meng et al. Water Research (2009), DOI: /j.waters Endocrine-Disrupting Compounds Endocrine Disrupting Compounds (EDCs) Endocrine system regulates important biological functions Growth Development Reproduction eating/sleeping fetus, puberty reproductive system Chemicals (synthetic or natural) mimic or act like hormones Population decline Abnormal reproductive system Feminization Reproduction failure One of top six research priorities identified by EPA s Office of Research and Development in Estrogens and PPCPs in Environment Found in sediments, rivers, lakes, drinking water, treated wastewater, and groundwater. PPCPs Considered as environmental pollutants recently More than 80 different classes (Daughton and Ternes, 1999) Hormones and many other pharmaceuticals were detected in 108 (80% of 139) US rivers surveyed by USGS in (Koplin et al ES &T). Frequently detected compounds Caffeine Insect repellents Hormones Fire retardants Plasticizers Prozac, antidepressant OH HO 17β-estradiol OH C CH HO 17α-ethynyl estradiol sample locations Diltiziam Verapamil (antiarrhythmic)

8 Wastewater: A major source of EDCs / PPCPs Wastewater Treatment Plant Reclaimed Eco-health impacts Individual usage Intentional disposal: flushing expired drugs into toilets Adapted from Ternes (April 2000) Estrogen removal varies among WWTPs Eff (ng/l) Removal (%) 17 β estradiol Estrone Estriol α-ethynyl estradiol from Lai et al. (2000), Johnson and Sumpter (2001) and Ying et al. (2002). Adapted from Ternes (April 2000) Drugged drinking water (EHP,2000) Water treatment Wastewater Treatment Plant (WWTP) Improve estrogen removal through biodegradation Our Current Research 14 estrogen-degrading isolates were phylogenetically diverse. 7 uncultivable estrogen degraders were detected by Q-FAST assay % of added 14 C-17β-estradiol was mineralized into 14 CO 2 in 24 hours in activated sludge samples (Layton et al. 2000). The first 17β-estradiol-degrading culture, Novosphingomonas sp. ARI-1, was isolated from activated sludge (Fujii et al. 2002). => Biodegradation can be a major removal mechanism Estrogens can be biodegraded effectively 3 patterns of estrogen degradation were observed. Application of ARI-1 for estrogen removal is challenging. Mineralization of estrogen might involve many microbes. Source: Yu et al ES &T, 41: Questions?