Question

15 ml of waste sample was collected from MBBR and was added directly into a 300 ml BOD incubation bottle. The initial DO of the diluted sample was 98.8 mg/L and the final DO after 5 days was 31.9 mg/L. The corresponding initial and final DO of seeded dilution water was 119.9 and 70.4 respectively. What is the 5-day BOD ($BOD_{5}$) of the wastewater sample?

Answer 1

ske an ge sry4 ev Nice to be in touch again but now on a different platform. I always appreciate your pertinent comments in various groups on LinkedIn.

Knowing that TDS = total dissolved solids, the first step is to remove all non-mineral dissolved solids by advanced biological treatment (without adding any chemicals other than nutrients if/as required). This results in ultra-low TOC, COD, BOD, TSS, turbidity (NTU) and SDI (silt density index) which minimizes irreversible fouling and power consumption of NF/RO membranes and doubles their economic lifetime. In the second step, some of the minerals could be removed by precipitation and/or air stripping. Finally after UF/cartridge pre-filtration and conditioning, the remaining TDS is retained by partial or full RO filtration as needed. I would like to add that some minerals such as sulfates, nitrates, ammonia, ... can also be removed in the first step by advanced biological treatment. In this way, we develop, design and realize tailored high grade water reuse systems with over 90% overall water recovery = less than 10% water loss at the lowest operating and lifecycle cost. Depending on the scale/capacity and on the quality of the source water the treatment steps 1 and 2 could be skipped as to minimize investment cost.