Wastewater Reuse Solutions in Small Communities by Fixed Film Based Package Treatment and Innovation

Transcription

1 Wastewater Reuse Solutions in Small Communities by Fixed Film Based Package Treatment and Innovation Robert S. Reimers 1, Somnath Basu 2, Gary L. Hunter 3, Brady K. Skaggs 4, and Yue Xu 5 1 Texas A&M University, College Station, Texas 2 Headworks International, Inc., Houston, Texas 3 Black and Veatch, Kansas City, Kansas 4 Lake Pontchartrain Basin Foundation (LPBF), New Orleans, Louisiana 5 Paradigm International, Inc., Metairie, Louisiana 4C HSE Conference 2018 San Antonio, Texas April 3 to 5, 2018

2 Background: Wastewater Reuse Reuse of wastewater very important in many communities Treatment plant effluents need advanced treatment Primarily reused water is utilized for irrigation Level of treatment depends upon specific application A few of the common tertiary treatments for reuse are: Polishing residual BOD and TSS in treated effluent from an overloaded plant Nitrification of treated effluent from an operating plant that removes BOD only Replacement of existing septic system to community based small packaged treatment systems

3 Fixed Film Reactors for Wastewater Reuse

4 Double Capacity & Improve Performance in the Same Footprint Existing 10,000m3/d BOD treatment facility can be retrofitted to meet < 2 ammonia nitrification within the same footprint while increasing the treatment capacity to 15,500m3/d

5 Moving Bed Bioreactor (MBBR) Dynamic fixed film process Once through process, no RAS Biomass attached on media surface as fixed film and media suspended in the reactor Reactor contains plastic (HDPE, polypropylene, etc.) media occupying 35% to 60% of empty tank volume Aeration keeps media suspended and provides DO for respiration Aeration system similar to activated sludge process, primarily by air blowers and coarse bubble diffusers Excess growth sloughs off and leaves with effluent Limit influent solids size to <6 mm by influent screen Screen (6 to 10 mm) on the effluent line prevent media loss by carryover Influent Treated Effluent Waste Sludge

6 Disinfection Background: Sources of EDC and PPCP Compounds Natural and Artificial hormones: used and/or excreted by human and animals (e.g., pills, thyroid medicine) Drugs with hormone side effects (e.g., naproxen) Industrial and Household chemicals (e.g., phthalates, fire retardants, solvents, PCBs, Atrazine) Contaminant from industrial and household processes (e.g., PAHs, Dioxins) etc.

7 Disinfection Background : Effects Infertility Sexual underdevelopment Alter or reduced sexual behavior Attention deficit or hyperactivity Altered thyroid or adrenal cortical function Increased incidents of certain cancers Birth defects

8 8 Peracetic Acid

9 Disinfection Process Performance Process Pathogen Inactivation By-Product Formation High Suspended Solids Levels State of the Technology Chlorine Handles bacteria and viruses but problems with spores and protozoa HAA 1, THMs 2, and other halogenated DBPs 3 (over 700 chlorinated organics Low: increases DBPs Practiced over 100 years Ferrate Inactivates all microbes but has concerns with spores Ferric Hydroxide (a micro nutrient) High: No appreciable concern for DBPs Just in the pilot phase with operational issues Peracetic Acid Handles bacteria but has concerns for some viruses, coliphages and protozoa Acetic acid and water High: No appreciable Concern for DBPs Practiced in Europe over the last 15 years (20 plants) but only one to two plants in USA Ultraviolet Irradiation (UV) Inactivates bacteria, viruses and coliphages, protozoa but will not inactivate some spores No residual Low: Reduced due to high TSS levels blocking UV Light Practiced in the wastewater industry for the past 30 years in around 30% of the plants

10 Operational and Cost Information Process Health and Safety Concerns Maintenance Issues Capital Costs for 100 MGD Plant in Million $ O&M Costs and Issues for!00mgd Plant in Million $ Chlorine Cl 2 Gas: Potential for explosion, severe respirator effects. Potential terrorism target. Hypochlorite Moderate occupational exposure risk Cl 2 : Highly corrosive requires handling and safety equipment and training requirements Hypochlorite: Bleach handling less dangerous, slight scaling potential for Onsite Hypochlorite Generation 63.5 for Bulk Hypochlorite 28.9 to 29.5 Low but much higher if dechlorination is required. Ferrate Slight emission of offgases during synthesis and stored feedstock,, bleach handling and alkaline operation conditions. System maintenance requirement higher than normal due to scaling potential has nominal power consumption to operate equipment Peracetic Acid The handling of strong oxidant with standard eye and skin protection System maintenance requirements slightly better than bleach has nominal power consumption to operate equipment UV Low risk of exposure to UV irradiation. High maintenance costs associated with fouling and replacement of lamps and ballasts requires medium power requirements.

11 EDC Production during Chlorination as noted at New Orleans Eastbank Plant Stage in the Wastewater Plant Estrogenic Activity in ng/l as E2 equivalents/l Comments and Observations Wastewater Influent Wastewater Effluent before Chlorination 99.6 Reduction of activity by 47 % due to aerobic degradation of EDC compounds Chlorinated Effluent Increased the EDC activity by almost 30 % due to production if chlorinated organics

12 Comparative Properties PAA NaOCl Efficacy High High Efficacy ph>8, High Lower NH 3 Oxidizes H 2 S Yes Yes Degraded by UV C No Yes, T 1/2 45 mins Contributes Na + No 1.8 lb NaCl/gallon Aquatic toxicity Very Low High Field test kit Yes Yes

13 Efficacy of PAA to Inactivate Indicator Microorganisms in Secondary Effluents Indicator Microorganisms Inactivation in Log Reduction Dosage in mg/l Exposure Time in minutes Total coliforms 2 to to 2 16 to 27 Comments Fecal coliforms 3 1 to 2 16 to 20 Effluent level are below regulatory levels at 1mg/L E. coli 2 to to 4 10 to 20 Enterococci 2 to to 3 15 to 20

14 EDC Activity Comparing PAA to Cl 2 Process Stage Chlorination PAA Processing Comments Secondary Effluent ,7 Treated Effluent Impact 149% Increase 30% Decrease 179 % reduction of EDC activity with the usage of PAA, which should have been higher.

15 Disinfection By-Products (DBPs) (ppb) DBPs in ppb Before Disinfection After Chlorination After PAA Treatment Dichlorobromomethane Dibromochloromethane Chloroform Bromoform Bromoform (Laboratory Study) < ug/l with Cl 2 dosage of 5 mg/l 70 ug/l with Cl 2 dosage of 10 mg/l < 10 with PAA dosages of 2,3 and 4 mg/l) Dibromochloromethane (Laboratory Study) < ug/l with Cl 2 dosage of 5 mg/l 21 ug/l with Cl 2 dosage of 10 mg/l < 5 with PAA dosages of 2,3 and 4 mg/l)

16 Ferrate Ferrate (Fe +6 ) is a strong oxidant, which can be utilized in reacting with refractory organics, inactivate pathogens, odor control, and assist the coagulation process. Producing the ferrate in a liquid form drops cost to around 1.5 dollars per pound. This liquid form can produced on site and is able to integrate with hypochlorite systems utilized in many existing plants in the United States. Currently, the City of New Orleans, Louisiana and Cocca Beach, Florida are assessing this technology since it is viable in many wastewater reuse projects to reduce DBPs.

17 Disinfection treatment: Ferrate Iron species w/ +6 oxidation state Strong oxidant under acidic condition Selective oxidant under basic condition Work as disinfectant, oxidant and coagulant Effected by ph, temp, NOM, etc

18 ng E2 equivalent/l Effect of ferrate treatment on estrogenic activity in the whole wastewater effluent (TOC=11) after 30 minutes contact time (6.01) 61.05% (61.05) 47.39(54.18) 41.31(60.06) Ferrate dose ppm ng E2 equivalent/l(%reduction)

19 Drivers for Conversion to PAA and Ferrate Chlorine Toxicity 4 Chlorine DBPs 6 Need to add dechlorination High Operating Cost High Chlorine Demand Disinfection Capacity 5 3 Need to replace chlorination with UV Need to increase disinfection capacity New contact tank New UV system High Capital Cost Higher Chlorine Dose PAA and Ferrate can be the potentially economical disinfection alternative