6.3 How to design the BSFL process - Humanitarian Sanitation Hub

6.3 How to design the BSFL process

How to estimate the larvae requirement for the treatment process:

Firstly, we need to understand the organic loading rate in kg/d, with the following formula:



Where,

ParameterDescriptionUnit
OLROrganic loading ratekgVS/d
VSTotal sludge volume per daym3
ρDensitykg/m3
CTSConcentration of TS %
CVSConcentration of VS% from TS

Secondly, we need to calculate the number of larvae required to consume the organic material provided per day, using the following formula:



Where,

ParameterDescriptionUnit
 NLNumber of larvae
OLROrganic loading ratemgVS/d
CRConsumption rate mg/larvae/d

How to calculate the area requirements:


After determining the number of required larvae, and based on recommended larvae density, we can estimate the area requirements by dividing the number of larvae by the larvae density.



Where,

ParameterDescriptionUnit
AArea ()m2
NLNumber of larvae
ρLLarvae densitylarvae/m2

How to estimate the larvae production:


Knowing the bio-conversion rate, we can estimate the larvae production by applying the following formula:



Where,

ParameterDescriptionUnit
MLMass of larvaekg/d
OLROrganic loading ratekg/d
BCRConversion rate (%)%

Practice:


Assuming we would like to treat 5 m3 of faecal sludge per day with a total solid content of 20% and VS is 80% from TS, with faecal sludge density of 1,050kg/m3, the consumption rate is identified to be 50 mg/larvae/day and larval density of 13,300 larvae/m2, the bio-conversion rate is 15%.

Firstly, please calculate the expected organic loading rate:


Solution:



Secondly, please calculate the number of larvae required if the consumption rate is estimated to be 50 mg/larvae/day.


Solution:



21,100,000 larvae are required per cycle.


Thirdly, please calculate the required area, if the recommended density is 13,300 larvae/m2.


Finally, please calculate the expected production of larvae, if the bio-conversion rate is assumed to be 15%


x
News