Table schema:
CREATE TABLE table_name_6 (design_flow__lpm_ INTEGER, population_served VARCHAR, partner VARCHAR, construction_start VARCHAR)

Question: What is the total Design flow (LPM) with a Partner of app, a Construction Start of 2008 january, and a Population Served larger than 3500?
SQL: SELECT SUM(design_flow__lpm_) FROM table_name_6 WHERE partner = "app" AND construction_start = "2008 january" AND population_served > 3500