SR0085076_OWTS - Laserfiche WebLink

Home Browse Search

Grenclar,pesign Appendix 3A: Example Design for a School (Application Type 3) Advarl Treatment for Removal of Organics and Nitrogen with cBOD5,TSS, and TN Discharge Limits Example: High School with cafeteria,gymnasium,and sports fields. System is to be discharged to a pressurized drainfield and permit require- ments include organic(cBOD5 and TSS)and total nitrogen (TN)discharge limits. Establishing a Design Basis Flows School facilities include cafeteria and gym with seating for 800.Due to their weekly flow characteristics,schools are a perfect application for the use of equalization tankage to evenly distribute the flows over the week. Flow equalization provides a consistent,stable loading of the treatment system,as well as slightly reduces the system size. Table 3A-1: Flows Source Max.Day Design Flow Per Unit(gpd) Max.Day Design Flow(gpd) 400 students 25 10,000 60 Employees 15 900 School event seating,800 5 4,000 Total 14,900'or 10,5002 For Average Day Design Flow,use the five-day average flow of 10,900 gpd 2 If using Flow Equalization,see below Determine the Design Average Day Flow using Flow Equalization to reduce treatment capacity requirement: (10,900 gpd x 4 days) + (14,900 gpd x 1 day) + (4,000 gpd x 1 day) + (0 gpd x 1 day) Equalized Design Day Flow,QE = 6 days3 = 10,416 gpd,use 10,500 gpd 'Allowing for one day for recovery(see pages 12-13) Discharge Type Pressurized drainfield. Influent(Primary Treated Effluent) and Permit Parameters Table 3A-2: Influent and Permit Parameters BODS(mg/L) TSS(mg/L) TKN(mg/L) TN(mg/L) Alkalinity(mg/L) Primary Treated Effluent(Ave/Max) 280/350 50/100 160/200 N/A 120 Discharge Permit Requirement(30-day Average) 20 20 N/A 20 N/A Other Design Considerations Seasonal use Most school applications see regular flows five days per week during the school year. For high schools there may be 1-2 days per week that see significant additional flows associated with sporting events or other activities. Flows during the summer months are typically only a frac- tion of the usage while school is in session.Flow equalization and a corresponding downsizing of the treatment facility is typically in order. Temperature effects Seasonally low temperatures may impact performance of a treatment system. For nitrogen sensitive applications,there may be a need to address waste stream temperature effects.This is especially true for systems with significant nitrogen removal requirements. Alkalinity needs Ensuring that the pH remains above 7 at all times is critical for ammonia sensitive applications.Therefore alkalinity addition should be includ- ed if influent alkalinity is insufficient to buffer the process. NDA-ATX-1 Orenco Systems®•800-348-9843•+1 541-459-4449•www.orenco.com Rev.8,©10/20 Page 34 of 38