Question 6 of 18: Industrial Waste Survey

Question 6: Industrial Waste Survey (10 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

An industrial waste survey is the systematic data-gathering exercise that underlies any waste-management or pretreatment design decision, and it is normally built from five components. (1) Plant/process inventory. This documents every process, unit operation and raw material used on-site, via process flow diagrams, material balances and production schedules. It is important because waste characteristics and quantities cannot be interpreted, let alone reduced, without knowing which process actually generates them — it is the map the rest of the survey is organized around. (2) Flow measurement. This quantifies the wastewater (and other waste-stream) flow rate at each source and at the combined discharge point, typically continuously over at least one full production cycle to capture batch and shift variability. It is important because treatment and conveyance systems are sized on peak and average flow, and a flow that is under-measured (e.g. missing a batch dump) undersizes the whole downstream system. (3) Sampling and analysis (waste characterization). This determines the chemical/physical composition of each stream — BOD, COD, TSS, pH, temperature, nutrients, metals, and any process-specific or hazardous constituents — using a sampling program (grab vs. flow-proportional composite) matched to how variable the stream actually is. It is important because treatment technology selection and discharge-permit compliance both depend on knowing exactly what is present, not just how much. (4) Water/material balance. This reconciles measured inputs (raw water, raw materials) against measured outputs (product, waste streams, evaporation/losses) to confirm the survey data is internally consistent and to identify unaccounted-for losses. It is important because it is the single best check that the flow and sampling data (components 2 and 3) are actually complete and correct, and it directly identifies waste-minimization/water-reuse opportunities. (5) Regulatory and cost review. This compiles the applicable discharge permit limits, sewer-use bylaw limits and current treatment/disposal costs. It is important because the survey's ultimate purpose is a management or treatment recommendation, and that recommendation has to be judged against what is legally required and what it will cost, not against the raw waste data alone.