Effluent Treatment - Tips for Logbook

IETS/WWTP – Tips on IETS-Logbook

An Industrial Effluent Treatment System (IETS) and Sewage Treatment System are delicate biotechnical equipment. Their biochemical dynamics often varies not according to mechanical equations that we prompt them to. Occasionally we encounter systems upset and expensive rectification work. Bulking, foaming and other symptom of ‘shock-loading’ are common challenges in IETS operation. These fluctuations are usually not caused by the system, instead, by us, the originators of effluents and sewage. How do we ensure consistent performance? How do we use those monitoring data to predict suitable settings when we know of a changed influent quality/quantity is about to enter our IETS? Hence, rule of the thumb – communication between effluent originator (releaser) and the IETS Operation Team must be established and always interacting. A good communication between them would complement the purpose of this IETS Logbook.

The table below is a brief sample of the IETS Logbook. Several important columns need to be added as it’s rather inconvenient to assemble them all in this restricted space. Discussion about each column is as follows;

Column	Purpose	Rationale/Remarks
Date Q0 & Time Q0	The date and time when the batch of influent enters the IETS.	The countdown of the RT (Wrt) begins at this point
Q0	The influent flow-rate	Read as Time Q0 for the Logbook
Prate	The production rate or throughput as at Date Q0 & Time Q0	Varying production rates and activities generates a varying quantity and quality of effluent
Wrt	The total retention time of the IETS from entry point up to discharge point	Good to verify actual and designed retention time. Any variation should be investigated systematically.
Weather	Ensure consistency in the weather condition during influent and effluent samplings.	Sampling in the rain is not accepted and usually produce rogue data.
Indicative Parameters (reactants)	A concise tabulation of all the concerned parameters.	Please split each parameter into two halves for ‘influent’ and ‘effluent’

Column	Purpose	Rationale/Remarks
‘influent’	This is the influent sampling as it enters the IETS prior treatment – also known as raw effluent	Influent samples shall be sent for analysis for all concerned parameters and serves as a comparative data that indicates IETS treatability.
‘effluent’	Effluent sampling after undergoing IETS treatment scheme and taken at final discharge point.	The data represent what treatment quality that the IETS has achieved and for serving as evidence in its legal compliance.
Q	This the flow-rate recorded after considering the Wrt as sampling at final discharge point is being done.	Represents the true batch that enters the IETS are being treated and discharged.
Remarks	To record identity of sampling personnel, time and date samplings are being done and identity of analytical lab	As part of judicial record; since sampling and analytical chemist is regarded as ‘expert witnesses’ in related legal proceedings. (In Malaysia)

Date Q0

Time Q0

Q0 L/hr

Prate unit/day

Wrt

Weather Condition

Indicative Parameters (reactants) = C (mg/L)

Q L/hr

Remarks

COD

SS

D.O

PH

BOD

METALS

10th August 2007

11.00 am

25

150

5

Windy sunny

70

60

5.0

7.5

30

Zn: 0.18

24.5

In-situ & sampling date 15th Aug 2007 by Ms. X

Note: The Retention Time (W_rt) of the system is an important factor of accuracy for this logbook and succeeding its mass-balance calculations, thus, ensuring accurate predictions. If the W_rt is known to be 48 hours, then, the flow-rate reading Q₀ shall be taken 48 hours prior sampling at the final discharge point and its corresponding discharge flow-rate Q. This shall represent the batch of influent entering the IETS is the same batch that undergoes treatment and finally discharged. The column for Indicative Parameters (reactants) = C should also be expanded to accommodate its input and output data i.e. each cell of the parameter be split into two halves for this purpose. Creativity in utilizing Excel Spreadsheet is what I envisage.  

The above insertions only serve as a starting guide. Please observe those figures involved in the mass-balance calculation as displayed below. However, this equation applies best for continuous-flow WWTP. For, batch system the dC/dt should equals to Zero, again presumably. The W_rt is the total retention time of the WWTP.

Note:

1. 2 units of current-value flow-meters are required. One is installed just before entering the WWTP scheme (after the grid chamber, macerators, etc.) and the other just before or at the legalized final discharge point.
2. In-situ analytical or instrumental analyzer shall help in determining major parameters such as COD, pH and D.O.
3. The conceptual Mass-balance equation is; dC/dt x V = Q₀ C_o – QC + [-kC]V 

Where;

                   V = the fixed volume retained in the WWTP (preferably in L) or m³

                Q₀ = influent (entering) effluent flow-rate in L/hr

                  Q = effluent (discharging/leaving the WWTP) flow-rate in L/hr

                 C_o = concentration of ‘reactant’ entering the WWTP in kg/m³ or mg/L

                  C = concentration of ‘reactant’ leaving the WWTP in kg/m³ or mg/L

                  K = 1^st order reaction rate coefficient, T^-1 i.e. 1/hr or 1/day

So, adequate data shall enable more accurate prediction of treatment settings such as dosing rate, aeration strength, pumps settings, etc. That’s all folks. Best wishes in implementing this invaluable technique.