Hydraulic Recycle Ratio Research Articles

APLIKASI BIO-BALL UNTUK MEDIA BIOFILTER STUDI KASUS PENGOLAHAN AIR LIMBAH PENCUCIAN JEAN

The textile industry is one of the most popular industries in Indonesia. Although it’s giving a positive value towards economic value, it also contributes a bed effect towards environmental quality. One of those industries is small-scale laundry industry located in Kelurahan Sukabumi Selatan, West of Jakarta. The lack of land and money, most of the jeans laundry industry throws away their wastewater straight to the river system without any process. The present study describes the application plastic media called bio-ball as a biofilter supporting media for treating of jeans laundry industry wastewater using combined anaerobic and aerobic process. The type of reactor that is used in this research is a continuous flow biological reactor which has total volume 195 litter and divided into 5 zones, i.e. presedimentation , 2 anoxic zone, aerobic zone and post sedimentation zone. Reactor effluent is recirculated into presedimentation zone with hydraulic recycle ratio (HRR) 1:1. Seeding is done in a natural way by directly flowing the domestic wastewater into reactor with retention time 72 hours, until a biofilm layer is formed on the surface of bio-ball media. Acclimatization is done gradually by replacing domestic with laundry jeans wastewater in 72 hours retention time, until domestic wastewater was 100 % replaced, The main research were conducting by continuous operation under condition 72 hours, 48 hours and 24 hours retention time. The result of experiment shows that within the combined anaerobic and aerobic process using bio-ball plastic media under conditions 1 - 3 days retention time, the removal efficiency of COD 78 – 91 %, BOD 85 – 92 %, Total Suspended Solids (TSS) 80 – 93 %, and Colour 48 – 57 % respectively. The longer retention time has resulted in higher removal efficiency

Biological kinetic behaviors and operational performances in aerated and oxygenated systems

AbstractBiological kinetic behaviors of the oxygenated and aerated activated sludge process were studied and compared in both once‐through and constant sludge recycle systems. The models derived by Herbert, Elsworth, and Telling [J. Gen. Microbiol., 14, 601 (1956)] and Ramanathan and Gaudy [Biotechnol. Bioeng., 11, 207 (1969)] were used for the studies of once‐through and constant sludge recycle systems, respectively. Soft drink waste water was used for the growth limiting substrate. Temperature was controlled within 30 ± 2°C. The influent substrate concentration was maintained at 1,000 mg/liter. The experiments were conducted at various dilution rates (from \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{1}{9} $\end{document} to 1/1.0 hr−1), and recycle solids concentration values (from 5,000 to 10,000 mg/liter), with hydraulic recycle ratio, α, at 0.3.Biological kinetic constants were evaluated and compared. It was found that these constants were different for the aerated and oxygenated systems within a certain range of dilution rates studied. The critical dilution rates for diluting out effluent chemical oxygen demand (COD) occurred at 0.1 and 0.2 hr−1in the once‐through operation, and 0.2 and 0.4 hr−1in the sludge recycle operation for aerated and oxygenated systems, respectively. Observed sludge yield values and specific growth rate were varied with the type of aeration and with and without constant sludge recycle concentration applied. Sludge carbohydrates and proteins content in the oxygenation system (cell recycle) were 10.1–21.6% and 35.6–52.2%. Sludge volume index in the air and oxygenation systems varied from 41.4 to 354 and 31.9 to 58.5, respectively.

Conceptual Model for Activated Sludge Processes

The interrelationships between four quantitatively definable characteristics of an activated sludge biomass and three selectable engineering control variables were examined computationally for their effect on effluent quality, reactor biomass, and excess sludge production. It was concluded that the model offers both the designer and the operator a means of predicting and controlling performance of the process. Laboratory pilot plant studies in support of the model has shown its stability in maintaining a “steady state” and its ability in predicting performance of the process. The characteristic properties of the biomass are true cell yield, maintenance coefficient, and the Monod constants, maximum specific growth rate, and saturation constant. The controllable engineering parameters are cell recycle concentration, hydraulic recycle ratio, and mean hydraulic detention time or dilution rate.

Effects of quantitative shock loadings on the constant recycle sludge concentration activated-sludge process.

The reliability of the process of Ramanathau and Gandy (Biotechnical Bioeng., 13, 125 (1971) for the completely mixed activated-sludge process holding the recycle cell concentration, Xr, as a system constant with respect to step changes in hydraluic retention time was investigated. The experiments were run at initial dilution rates of 1/8, 1/6, 1/4, and 1/2 hr-1 treating a soft drink bottling wastewater. The influent substrate concentration was maintained at 1000 mg/liter chemical oxygen demand and the hydraulic recycle ratio at 0.3. The recycle sludge concentration was maintained at about 7000 mg/liter. It was found that the system could accomodate hydraulic shock loads up to 200% positive changes and down to 50% negative changes without disruption of the effluent quality. Shorter retention time of the range studied, from 2 to 8 hr, has the advantage of shorter response time with respect to the response of the concentration of biological solids in the reactor.

The application of constant recycle solids concentration in completely mixed oxygen activated sludge process

AbstractFor better operational control of the completely mixed oxygen activated sludge process (CMOAS), a study concerning the kinetics, performance, and operational stability of the Ramanathan‐Gaudy model was conducted. Short‐term experiments were conducted at various dilution rates (1/9, 1/6, 1/3, 1/1.5, and 1/1.0 hr−1) by using two recycle solids concentration values (5000 and 10,000 mg/liter). The influent substrate was an actual industrial organic wastewater (soft drink waste) and its concentration was maintained at 1000 mg/liter COD. The hydraulic recycle ratio, α, was maintained at 0.30.It was found that for CMOAS system with constant recycle cell concentration, a “steady state” with respect to reactor biological solids and effluent COD at different dilution rates could be attained. No appreciable dilute‐out of reactor biological solids and substrate was observed up to the dilution rate of 1 hr−1 for both systems of different XR (5000 and 10,000 mg/liter). For the system of XR = 5000 mg/liter, except the dilution rate of hr−1, the effluent filtrate COD was lower than 100 mg/liter, the aerator biological solids concentration was about 1550 mg/liter, and the COD removal efficiency was higher than 90% for all dilution rates. For the system of XR = 10,000 mg/liter, the effluent filtrate COD was lower than 71 mg/liter, the aerator biological solids concentration was about 2750 mg/liter, and the COD removal efficiency was higher than 90% throughout all the dilution rates selection in the present study. The value of the Sludge Volume Index (SVI) was the range of 37.0 to 58.5 and provided good settleability of sludge. The sludge yield was 0.53 for the system of XR = 5000 mg/liter and 0.57 for the system of XR = 10,000 mg/liter. The carbohydrate and the protein content of the cells were 10.1–21.6% and 35.6–50.6%, respectively.For predicting the reactor biological solid and effluent COD of the CMOAS system by using the Ramanathan‐Gaudy model, two sets of values for the biological kinetic constants should be considered since it provided the best fit of predicted values of the observed values. In the present study, μm = 0.4 hr−1, ks = 92 mg/liter for 1/3 ⩽ D ⩽ 1, and μm = 0.05 hr−1, ks = 11.1 mg/liter for 1/9 ⩽ D < 1/3 were used to calculate the predicted values of reactor biological solid and effluent filtrate COD.

The application of constant recycle solids concentration in activated sludge process.

The applicability of the model derived by Ramanathan and Gaudy (Biotechnol. Bioeng., 11, 207, (1969)) for completely mixed activated sludge treatment holding the recycle solids concentration as a system constant was investigated using an actual industrial organic wastewater. Short-term experiments were conducted at various dilution rates (1/8, 1/6, 1/4, 1/2, 1/1.5 hr-1) for two recycle solids concentration values (5000 and 7000 mg/liter). The influent substrate concentration was maintained at 1000 mg/liter COD and the hydraulic recycle ratio- alpha, was kept at 0.3. It was found that for bottling plant (Pepsi Cola) wastewaters, a steady state with respect to reactor biological solids and effluent COD, at different dilution rates, could be attained, lending experimental evidence to the assumption that a steady state could be reached in developing the model and also affecting the applicability of the model in industrial organic wastewater. The reactor biological solids and effluent COD calculated from the model closely agreed with the observed values at dilution rates lower than 0.5 hr-1. Operation at dilution rates higher than 0.5 hr-1 will washout the biological solids from the reactor and the recycle substrate concentration will be apparent if the concentration of XR were not increased.

Experimental studies on a kinetic model for design and operation of activated sludge processes

AbstractPrevious experimentation in our laboratory has shown that the classical theory developed for continuous growth of pure cultures in completely mixed aerobic systems in which the recycle cell concentration factor, c (where c = XR/X), is a selectable system constant, did not provide a suitable model for the heterogeneous (natural) populations of the activated sludge process. Another model was derived in which the recycle cell concentration, XR was employed as a system constant instead of c, and computational analysis was performed. Laboratory pilot plant experimentation was undertaken in order to determine whether a “steady state” in aerator biological solids concentration, X̄, and substrate concentration, S̄, could be approached under this mode of operation. Studies were performed at various organic feed concentrations holding dilution rate, D, at 0.125 hr−1, hydraulic recycle ratio, α, at 0.25, and XR at 10,000 mg/liter. Also, values of maximum specific growth rate, μmax, and saturation constant, Ks were determined. It was found that the model approached the steady state condition with heterogeneous populations more closely than did the classical model, and the high degree of treatment efficiency predicted by the model was demonstrated experimentally.

Steady‐state model for activated sludge with constant recycle sludge concentration

AbstractIn a previous report it was concluded that steady‐state operation of completely mixed reactors for growth of heterogeneous microbial populations, i.e., activated sludge processes, was extremely difficult to attain if maintenance of a constant sludge recycle ratio, c, was required, and equations were devised in which the concentration of cells in the recycle, xR, rather than the recycle ratio, was constant. In this report the equations are developed and computational analysis shows the effect on substrate and cell concentrations in the reactor of operational variables such as inflowing feed concentration, hydraulic recycle ratio, recycle sludge concentration, dilution rate, and the biological “constants” μm, ks, and Y. The stabilizing effect of operating with constant xR on the dilute‐out pattern is shown.