Improvement in aerobic sludge digestion through pH control: initial assessment of pilot-scale studies

1987 ◽  
Vol 14 (4) ◽  
pp. 477-484 ◽  
Author(s):  
B. C. Anderson ◽  
D. S. Mavinic
Keyword(s):  
Sodium Bicarbonate ◽  
Hydrated Lime ◽  
Ph Control ◽  
Pilot Scale ◽  
High Rate ◽  
Initial Assessment ◽  
Mixed Liquor ◽  
Solids Retention ◽  
Digestion Efficiency ◽  
The Individual

Waste-activated sludges from an extended-aeration, pilot-scale wastewater treatment facility and a high-rate, full-scale system were aerobically digested in 150 L pilot-scale digesters, operated in a semicontinuous (daily fill-and-draw) mode, at a standard 15-day solids retention time (SRT). To offset the mixed-liquor pH (MLpH) decrease normally encountered in these digesters (as a result of nitrification), hydrated lime and sodium bicarbonate were used in separate experiments to control MLpH in the series pH 6, 7, 8, and 9. Digester performance in the first stage of this work was assessed solely on the basis of reduction in total volatile suspended solids.The extended-aeration type sludge exhibited the greatest improvement in process performance under all pH-controlled conditions. Improvements in digestion efficiency of up to 80% over the uncontrolled reactors were noted. The use of lime resulted in greater digestion enhancement than did sodium bicarbonate with this sludge, without a significant increase in sludge solids production (owing to the low chemical doses required). Digestion efficiency of the high-rate type sludge was little improved (on a relative basis) with either chemical; however, absolute efficiencies in the individual digesters were, in some cases, nearly double those of the comparative extended-aeration sludge digesters. This difference appears to be a function of the process from which the digesting sludge originated, and seems to be influenced by the amount of easily oxidizable, endogenous substrate contained in the biomass. It was concluded that the extended-aeration type sludge was most amenable to enhanced digestion through pH control; as well, cost and process considerations made lime the chemical of choice. Key words: activated sludge, aerobic digestion, hydrated lime, mixed-liquor pH control, nitrification, process enhancement, pilot-scale, sodium bicarbonate.

Effect of solids retention time on the performance and biological characteristics of a membrane bioreactor

2001 ◽  
Vol 43 (11) ◽  
pp. 43-50 ◽  
Author(s):  
N. Cicek ◽  
J. Macomber ◽  
J. Davel ◽  
M. T. Suidan ◽  
J. Audic ◽  
...  
Keyword(s):  
Membrane Bioreactor ◽  
Phospholipid Fatty Acid ◽  
Pilot Scale ◽  
Yeast Cells ◽  
Nitrogen And Phosphorus ◽  
Mixed Liquor ◽  
Gram Positive Bacteria ◽  
Solids Retention ◽  
Biolog Analysis ◽  
Eukaryotic Organisms

The purpose of this study was to compare the performance of a pilot-scale membrane bioreactor (MBR) in the treatment of municipal strength wastewater at solid retention times (SRTs) ranging from 30 days to two days. Cumulative nitrogen and phosphorus mass balances resulted in closures exceeding 90% at each steady state period. Biomass production rate and biomass viability generally increased with decreasing SRT, whereas overall enzymatic activity did not change significantly at most SRTs, but was highest at the two day SRT. Nitrification decreased at two day SRT but did not fail completely. At higher SRTs, nitrification was not noticeably affected by the sludge age. Phospholipid fatty acid (PLFA) analysis showed substantially diverse biomass in the sludge at different SRTs. Different ratios of gram positive bacteria, eukaryotic organisms, and yeast cells were observed in the mixed liquor at varying SRTs. On the other hand, BIOLOG analysis indicated that the overall capacity of the biomass to degrade different carbon substrates did not change significantly at different SRTs. The concentration of metals in the MBR mixed liquor declined steadily with decreasing SRT. The MBR effluent contained negligible amounts of Fe, Zn, Mn, and Co at each condition, indicating the retention of these metals regardless of the SRT.

Behaviour of volatile and nonvolatile suspended solids in the pilot-scale aerobic digestion of waste-activated sludges

1993 ◽  
Vol 20 (1) ◽  
pp. 22-36 ◽  
Author(s):  
B. C. Anderson ◽  
D. S. Mavinic
Keyword(s):  
Suspended Solids ◽  
Ph Control ◽  
Pilot Scale ◽  
Operating Conditions ◽  
Inorganic Materials ◽  
Aerobic Digestion ◽  
Simple Method ◽  
Mixed Liquor ◽  
Sludge Digestion ◽  
Naturally Occurring

Pilot-scale research into the characterization and enhancement of the aerobic digestion of waste-activated sludges was performed. Waste sludge from two sources was aerobically digested at varying operating temperatures; to offset the naturally occurring mixed liquor pH (MLpH) decrease due to nitrification, small amounts of Ca(OH)2 or NaHCO3 were added to maintain target MLpH levels of pH 6, 7, and 8. Results indicated that volatile mass reduction was severely curtailed at low MLpH, but could be significantly improved through MLpH control, with increases of > 100% in performance over the low MLpH reactor noted. However, the process was found to be very "sludge-specific", in that the two test sludges behaved quite differently under similar operating conditions. A separate mass balance on the nonvolatile sludge fraction illustrated the action of the controlling chemicals in terms of reduction in cell lysis; it was also observed that some precipitation of inorganic materials was occurring, depending on chemical type and dose. While it was not possible to suggest an optimized chemical and dose, it was concluded that this process had very real potential for full-scale implementation, as an effective and simple method for rehabilitation of poorly functioning digesters. Key words: aerobic sludge digestion, Ca(OH)2, enhancement, inhibition, mixed liquor pH control, NaHCO3, volatile and nonvolatile suspended solids.

Leadership Enactment for Information System Acceptance: an Explanation from a Sensemaking Perspective

2019 ◽  
pp. 78-106
Author(s):  
Aruna Dayanatha ◽  
J A S K Jayakody
Keyword(s):  
Information System ◽  
User Involvement ◽  
High Rate ◽  
Is Success ◽  
Managerial Leadership ◽  
Individual Level ◽  
System Acceptance ◽  
The Individual ◽  
Leadership Intervention ◽  
Is Failure

Information system (IS) projects have been seen to be failing at an alarmingly high rate. The prevailing explanations of IS failure have had only a limited success. Thus, the time may be right to look at the reasons for IS failure through an alternative perspective. This paper proposes that IS success should be explained in terms of managerial leadership intervention, from the sensemaking perspective. Managers are responsible for workplace outcomes; thus, it may be appropriate to explain their role in IS success as well. The sensemaking perspective can explain IS success through holistic user involvement, a concept which critiques of existing explanations have stated to be a requirement for explaining IS failure. This paper proposes a framework combining the theory of enactment and leadership enactment to theorize managerial leadership intervention for “IS success.” The proposed explanation postulates that the managerial leader’s envisioning of the future transaction set influences the liberation of the follower and cast enactment, while liberating followers and cast enactment constitute manager sensegiving. The managerial leader’s sense-giving influences follower sensemaking. Follower sensemaking, under the influence of managerial sensegiving, will lead to followers’ IS acceptance, and that constitutes IS success at the individual level. Further, collective level IS acceptance constitutes IS adaption/success, and this will influence the leader’s sensegiving, for the next round of sensemaking.

Viability of nematode eggs in high rate algal ponds: the effect of physico-chemical conditions

2000 ◽  
Vol 42 (10-11) ◽  
pp. 371-374 ◽  
Author(s):  
S. Araki ◽  
J. M. González ◽  
E. de Luis ◽  
E. Bécares
Keyword(s):  
Hydraulic Retention Time ◽  
Pilot Scale ◽  
High Rate ◽  
Sterile Water ◽  
Egg Viability ◽  
High Rate Algal Ponds ◽  
Helminth Eggs ◽  
Physico Chemical ◽  
Nematode Eggs ◽  
Chemical Conditions

The viability of Parascaris equorum eggs was studied in two experimental pilot-scale high-rate algal ponds (HRAPs) working in parallel with 4 and 10 days hydraulic retention time respectively. Semi-permeable bags of cellulose (15000 daltons pore size) were used to study the effect of physico-chemical conditions on the survival of these helminth eggs. Three thousand eggs were used in each bag. Replicates of these bags were submerged for 4 and 10 days in the HRAPs and egg viability was compared with that in control bags submerged in sterile water. After 4 days exposure, 60% reduction in viability was achieved, reaching 90% after 10 days, much higher than the 16% and 25% found in the control bags for 4 and 10 days respectively. Ionic conditions of the HRAP may have been responsible for up to 50–60% of the egg mortality, suggesting that mortality due to the ionic environment could be more important than physical retention and other potential removal factors.

On-site and in situ bioremediation of wood-preservative contaminated groundwater

2000 ◽  
Vol 42 (5-6) ◽  
pp. 371-376 ◽  
Author(s):  
J.A. Puhakka ◽  
K.T. Järvinen ◽  
J.H. Langwaldt ◽  
E.S. Melin ◽  
M.K. Männistö ◽  
...  
Keyword(s):  
Iron Oxidation ◽  
Wood Preservative ◽  
Pilot Scale ◽  
High Rate ◽  
Contaminated Groundwater ◽  
Groundwater Temperature ◽  
In Situ Bioremediation ◽  
Contaminated Aquifer ◽  
Fluidized Bed Process

This paper reviews ten years of research on on-site and in situ bioremediation of chlorophenol contaminated groundwater. Laboratory experiments on the development of a high-rate, fluidized-bed process resulted in a full-scale, pump-and-treat application which has operated for several years. The system operates at ambient groundwater temperature of 7 to 9°C at 2.7 d hydraulic retention time and chlorophenol removal efficiencies of 98.5 to 99.9%. The microbial ecology studies of the contaminated aquifer revealed a diverse chlorophenol-degrading community. In situ biodegradation of chlorophenols is controlled by oxygen availability, only. Laboratory and pilot-scale experiments showed the potential for in situ aquifer bioremediation with iron oxidation and precipitation as a potential problem.

Advances in high rate anaerobic treatment: staging of reactor systems

2001 ◽  
Vol 44 (8) ◽  
pp. 15-25 ◽  
Author(s):  
J.B. van Lier ◽  
F.P. van der Zee ◽  
N.C.G. Tan ◽  
S. Rebac ◽  
R. Kleerebezem
Keyword(s):  
Cost Effective ◽  
Anaerobic Treatment ◽  
High Rate ◽  
Extreme Conditions ◽  
Waste Streams ◽  
Textile Processing ◽  
Anaerobic Wastewater Treatment ◽  
Anaerobic Reactors ◽  
Wide Acceptance ◽  
Solids Retention

Anaerobic wastewater treatment (AnWT) is considered as the most cost-effective solution for organically polluted industrial waste streams. Particularly the development of high-rate systems, in which hydraulic retention times are uncoupled from solids retention times, has led to a world-wide acceptance of AnWT. In the last decade up to the present, the application potentials of AnWT are further explored. Research shows the feasibility of anaerobic reactors under extreme conditions, such as low and high temperatures. Also toxic and/or recalcitrant wastewaters, that were previously believed not to be suitable for anaerobic processes, are now effectively treated. The recent advances are made possible by adapting the conventional anaerobic high-rate concept to the more extreme conditions. Staged anaerobic reactor concepts show advantages under non-optimal temperature conditions as well as during the treatment of chemical wastewater. In other situations, a staged anaerobic - aerobic approach is required for biodegradation of specific pollutants, e.g. the removal of dyes from textile processing wastewaters. The current paper illustrates the benefits of reactor staging and the yet un-exploited potentials of high-rate AnWT.

Tilapia rearing with high rate algal pond effluent: ammonia surface loading rates and stocking densities effects

2018 ◽  
Vol 78 (1) ◽  
pp. 49-56
Author(s):  
I. A. Sánchez ◽  
R. K. X. Bastos ◽  
E. A. T. Lana
Keyword(s):  
Weight Gain ◽  
Oxygen Demand ◽  
Pilot Scale ◽  
Ammonia Nitrogen ◽  
High Rate ◽  
Surface Loading ◽  
Loading Rates ◽  
Total Weight Gain ◽  
Low Weight ◽  
Total Ammonia

Abstract In two pilot-scale experiments, fingerlings and juvenile of tilapia were reared in high rate algal pond (HRAP) effluent. The combination of three different total ammonia nitrogen (TAN) surface loading rates (SLR1 = 0.6, SLR2 = 1.2; SLR3 = 2.4 kg TAN·ha−1·d−1) and two fish stocking densities (D1 = 4 and D2 = 8 fish per tank) was evaluated during two 12-week experiments. Fingerlings total weight gain varied from 4.9 to 18.9 g, with the highest value (equivalent to 0.225 g·d−1) being recorded in SLR2-D1 treatment; however, high mortality (up to 67%) was recorded, probably due to sensitivity to ammonia and wide daily temperature variations. At lower water temperatures, juvenile tilapia showed no mortality, but very low weight gain. The fish rearing tanks worked as wastewater polishing units, adding the following approximate average removal figures on top of those achieved at the HRAP: 63% of total Kjeldahl nitrogen; 54% of ammonia nitrogen; 42% of total phosphorus; 37% of chemical oxygen demand; 1.1 log units of Escherichia coli.

scholarly journals Mudra (shishu) – an effective scheme in startups

2019 ◽  
Vol 9 (4) ◽  
pp. 222-226
Author(s):  
K.C. Kavipriya
Keyword(s):  
Economic Development ◽  
Individual Development ◽  
High Rate ◽  
Small Scale ◽  
Poor People ◽  
Employment Opportunities ◽  
The People ◽  
The Individual ◽  
The Right ◽  
Small Scale Industries

Economic Development of a country depends upon the individual development; Creation of more Employment opportunities is the right way to strengthen our Economy. By way of strengthening Small scale units, ultimately more people will get Employment. More over Small scale Industries required less amount of Capital. These are the main reasons to start the scheme MUDRA. The scheme MUDRA was launched in the year 2015 by Government of India. In India most of the people are depending upon small scale businesses as their source of livelihood. Most of the individuals depend on un-organised sectors for loans and other credit facilities which have high rate of interest along with unbearable terms and conditions. Ultimately it will lead these poor people to fall in debts. This paper is an attempt to educate the readers about MUDRA Yojana.

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