Inception Report on 78 MLD STP Dhandhupura Agra

DINKAR SAXENA

Chartered Engineer (India); M/128465/1 M.I.E., C. Eng., FIPHE, PGDM, E.M.S. Auditor (IEMA, U.K.)

Inception report on 78 MLD STP Dhandhupura Agra Undersigned visited the 78 MLD Dhandhupura site on 27th Dec. 2016, followings are the findings Technical details of STP Design capacity of STP: 78 ML/d Process used is bar screens -grit settling -UASB-Polishing pond. Sludge generated are disposed to Sludge drying beds. Bar screen 2 nos.: 6 x 2.5 x 0.52 m each appears to be working Grit settler channel 3 nos.: 20 x 3.05 x 0.75 m each As all three-grit channel were used during the time of visit performance could not be assessed properly; yet trash bin was full of sellable solids, indicating that system is working properly. #441 sector 16 Sikandra Avas Yojna Sikandra, Agra 282007 +91-562- 2641866 Mo. +919837007304 [email protected] [email protected] web: www.wateronline.co.in

DINKAR SAXENA

Chartered Engineer (India); M/128465/1 M.I.E., C. Eng., FIPHE, PGDM, E.M.S. Auditor (IEMA, U.K.) UASB distribution box As per the attached photo system UASB distribution box is in good shape and working in condition. UASB reactor 6 nos.: 40 x 24 x 5.35 m each designed to operate at maximum of Upflow velocity of 1.5 M / hr at peak, at this flow rate organic loading rate calculated with above operating conditions is 1.3 kg/Cu M/day. Which is safe design. UASB gas collection hoods Gas pipe line was corroded at points and was not connected to Gas holding chamber, thus need required mitigation. Polishing ponds there are 3 nos.: 214 x 93 x 1.25 m, 160 x 129 x 1.25 m, and 162 x 122 x 1.25 m calculated HRT at average flow rate is 23 Hrs.

#441 sector 16 Sikandra Avas Yojna Sikandra, Agra 282007 +91-562- 2641866 Mo. +919837007304 [email protected] [email protected] web: www.wateronline.co.in

DINKAR SAXENA

Chartered Engineer (India); M/128465/1 M.I.E., C. Eng., FIPHE, PGDM, E.M.S. Auditor (IEMA, U.K.)

Observation regarding operations of various units 

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As there is no mechanism to control the flow to UASB during night time, flow drops to almost negligible thus there are chances of sludge settling during quit time, whereas sludge wash out during peak flow. Thus hampering the performance of UASB which needs a constant flow rate for optimum BOD reduction. There is no mechanism by which sludge level inside the reactor can be monitored, it is being operated as per experience of operators. As per the operator of unit, there is no mechanism/ instruction for removal of sludge from polishing pond. Excess sludge accumulation in ponds was observed during the visit, (refer to photograph,) as the main reasons for under performance. This is due to actual HRT being signifyingly much less than the designed HRT, resulting in drop in BOD removal efficiency Please refer to test results table.

Test results Sample was collected by CPCB, followings are results of analysis of composite samples after various stages of treatment (All values in mg/L except pH) Sample point

pH

BOD

COD

TSS

PO4P

efficiency of anaerobic unit in

efficiency of aerobic unit in BOD removal in


DINKAR SAXENA

Chartered Engineer (India); M/128465/1 M.I.E., C. Eng., FIPHE, PGDM, E.M.S. Auditor (IEMA, U.K.) BOD removal in % Raw sewage Outlet of UASB reactors 1-3 (combined) Outlet of UASB reactors 4-6 (combined) Final outlet after polishing ponds

%

7.3

120

424

57

5.67

7.5

56

208

399

6.27

53.33

32.14

7.7

46

224

80

6.39

61.67

17.39

7.4

38

173

71

6.22

Remarks  

Efficiency of UASB can be improved by improving the operating parameter e.g. constant Upflow velocity, VSS: TSS ratio micronutrients etc. overall efficiency of system is low due to poor operation of polishing pond, it is 32.14 % at its maximum whereas it should reach more than 60%.


DINKAR SAXENA

Chartered Engineer (India); M/128465/1 M.I.E., C. Eng., FIPHE, PGDM, E.M.S. Auditor (IEMA, U.K.) Mitigations recommended   

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Maintaining recommended VSS concentration in UASB reactor Proper removal of grit and wasting excess sludge levels of reactor to maintain good VSS/TSS ratio. It is difficult to remove the sludge from the polishing pond, thus there is need of alternate method for required oxygen transfer for achieving the BOR to less than 30 PPM. It is reported that the final effluent TSS and BOD concentrations were not very low for retention times of less than 1 week, but this could be attributed to the presence of algae in the final effluent. Filtered effluent BOD and TSS concentrations were very low. For retention times of more than 1 week, algae were efficiently removed from the liquid phase by the action of predators and algae flocculation and settling, so that a final effluent with a very low BOD and TSS concentrations was produced. To maximise the FC removal efficiency the polishing pond was constructed with the objective of approaching a plug flow regime. However, the observed efficiency was well below the expected value for all retention times, which was attribute to imperfections of the flow regime. From tracer studies, it was established that the dispersion number was in the range of 0.14 to 0.16, which denotes that moderate mixing occurred, even though the pond was designed to avoid mixing as much as possible. Also, the dead volume fraction ranging from 0.12 to 0.15 was quite considerable. Due to these imperfections, the required retention time for an effluent to be used in unrestricted irrigation was produced for a retention time of about 10 days, twice the value of the minimum retention time for a batch or true plug flow pond. Although the plug flow regime could not be approached in practice, the required retention time of 10 days is still very much shorter than the value used in conventional WSPs (20 to 30 days). One of the easy and readily available solution as per the site conditions is to use a Bio tower as there is level difference of nearly 2.5 M in outlet of UASB and Polishing pond. another viable option is to use submersible mixers of required capacity, so that sludge is not able to settle in polishing tank thus required HRT is achieved always. As this option would keep the water in moving state therefore efficiency of oxidation would also increase.

The above observations and opinion is based on the data provided by operating staff and available reports of CPCB. #441 sector 16 Sikandra Avas Yojna Sikandra, Agra 282007 +91-562- 2641866 Mo. +919837007304 [email protected] [email protected] web: www.wateronline.co.in

DINKAR SAXENA

Chartered Engineer (India); M/128465/1 M.I.E., C. Eng., FIPHE, PGDM, E.M.S. Auditor (IEMA, U.K.) As assessed by Dinkar saxena 2-01-2017


Inception Report on 78 MLD STP Dhandhupura Agra

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