Shaukat Farooq

Performance evaluation of slow sand filters using fuzzy rule-based modelling

The main objective of this study is to evaluate and predict the performance of slow sand filters used for wastewater treatment. The uncertainties in the control parameters and processes require fuzzy sets to be used when modelling system performance. Fuzzy logic if–then rules were used to build a model for the removal efficiency (total coliforms) of slow sand filters. The data were collected from three pilot-scale slow sand filters at the Alkhobar (Saudi Arabia) wastewater treatment plant. The removal efficiency of filters was modelled using three input control parameters—filtration rate, sand bed depth and grain size. Based on available data, fuzzy logic if–then rules were established. The fuzzy rule-based model was validated using experimental data of three case studies reported in the literature. The results were also compared with a multiple regression model. A possibilistic risk analysis was performed using optimal removal efficiency of the slow sand filters. The risk is estimated with respect to non-compliance of unrestricted agricultural reuse standards (100 total coliform/100 ml). In addition to slow sand filters, post- or pre-chlorination of wastewater is recommended to improve wastewater quality for conforming agricultural reuse standards.

Comparative response of mixed cultures of bacteria and virus to ozonation

Abstract The ozone disinfection studies were performed using five cultures of organisms: i.e. a yeast Candida parapsilosis . an acid-fast organism Mycobacterium fortuitum, Salmonella typhimurium, Escherichia coli and poliovirus to determine their relative resistance to ozone in a given completely mixed continuous flow system. Studies were conducted in both clean aqueous system and secondary wastewater effluent. Their resistance to ozone in both cases was observed in the following order: M. fortuitum > poliovirus type 1 Mahoney strain > C. parapsilosis > E. coli > S. typhinturium .

Activated carbon adsorption in oxidizing environments

Abstract Molecular oxygen-induced enhancement in the adsorption capacity of GAC was investigated thoroughly from sorbate types point of view. Isotherm studies on phenol, o-cresol, and 4-nitrophenol at 23°C showed a 20–163% increase in retention capacities with the incremental capacity increasing with decreasing equilibrium concentrations. The incremental capacity was strongly dependent on the DO to GAC mass ratio and the adsorptive capacity under anoxic conditions. The phenomenon was observed when oxidizing agents such as hydrogen peroxide and potassium permanganate were used instead of molecular oxygen. GC-MS analysis performed on GAC extracts suggested polymerization of adsorbates on the carbon surface as a potential reason for this enhancement phenomenon. Four different aliphatic compounds namely chloroform, bromoform, 1,1,1 trichloromethane, and 1,1,2,2 tetrachloroethane were also studied. The results showed no significant effect on the adsorptive capacity of GAC for those aliphatics due to dissolved oxygen existence in the test environment. Significant enhancement was found in the case of wastewater samples from both domestic and industrial sources.

Disinfection of wastewaters: high-energy electron vs gamma irradiation

Abstract A study was undertaken to examine the sensitivity of a wastewater population of coliphage, total coliforms and total flora present in raw sewage and secondary effluent after irradiating with similar doses delivered by a high-energy electron beam and y -radiation. The electron beam study was conducted on a large scale at the Virginia Key Wastewater Treatment Plant, Miami, Fla. The facility is equipped with a 1.5 MeV, 50 mA electron accelerator, with a wastewater flow rate of 8 ls −1 . Concurrent y-radiation studies were conducted at laboratory scale using a 5000 Ci, 60 Co y -source. Three logs reduction of all three test organisms were observed at an electron beam dose of 500 krads, while at least four logs reduction were observed at the same dose utilizing the y-source.

Phenol degradation by pseudomonas aeruginosa

Abstract Bench scale batch reactors were used to acclimatize and selectively enrich phenol degrading microorganisms, using raw domestic sewage as a seed of heterogeneous culture. During acclimatization process, phenol was used as the sole carbon source and the feed concentration was varied from 20 mg/l to 500 mg/l. After the acclimatization, which was attested by low effluent phenol (<1 mg/l), samples where taken from the sludge as well as the effluent and bacteriologically analyzed. It was found that Pseudomonas aeruginosa to be the predominant microbail species for phenol degradalion in this particular case.

Oxygen‐induced enhancement of the adsorpttve capacity of activated charcoal

Abstract Adsorption isotherms for phenol and o‐cresol on activated charcoal at neutral pH and several dissolved oxygen concentrations were conducted at 23°C. Significant improvement in capacities were observed with increasing dissolved oxygen concentrations for the two adsorbates. These statistically‐significant additional capacities were not due to biological activities but merely due to surface chemical reactions. The improvement in capacity was directly related to the amount of oxygen per unit mass of GAC.

Modeling of an ozone-wastewater system's kinetics

Abstract The mass transfer of ozone into aqueous solution is important in both disinfection and reduction of organic matter, i.e. the more ozone transferred into the solution the better the disinfection and the less the amount of organic matter left in the effluent. The mathematical model proposed by Sheffer and Esterson (Wat. Res.16, 383, 1982) for an ozone-tap water system is modified to predict the amount of ozone input required for a given ozone residual, and COD in an actual ozone-wastewater system. Knowing the amount of ozone needed as input to obtain a specific ozone residual in a given wastewater can prevent wastage of ozone and conserve energy for a required degree of treatment. The values of ozone mass transfer rate kLa (1.243 min−1), ozone decomposition rate k1 (0.087 min−1) and ozone reaction rate k2 [0.091 (l/mg) 1 2 min−1] obtained by using the proposed model are similar to the values reported in the literature.

Secondary Effluent Treatment by Slow Sand Filters: Performance and Risk Analysis

The objective of this study is to examine the reuse of wastewaterfor beneficial purposes. To accomplish this objective, the efficiency of slow sand filters in removing total coliforms (TC) was studied using a probabilistic method. Three pilot scale slowsand filters were constructed at Alkhobar wastewater treatment plant, Dhahran, Saudi Arabia. The removal efficiency of filters was estimated under different operating control parameters, which included filtration rate (q), sand bed depth (d) and sand grain size (c). The Type III extreme value distribution best fitted theremoval efficiency data. A multiple linear regression analysis was performed to develop a relationship for mean removal efficiency as a function of control parameters. The predicted mean response and experimental results of previous studies werecompared to validate the empirical regression model. The controlparameters and influent concentrations of total coliform were used in Monte Carlo (MC) simulations for calculating the reliability index (β). The reliability index and corresponding risk were calculated for lognormally distributedsafety margins (SM). An effluent standard of 100 total coliform/100 mL was defined as capacity of the filter to ascertainthe risks of exceedence, which was approximately less than 50 for95% of the time. Pre and/or post disinfection would be necessaryto meet the stipulated effluent standards for unrestricted agriculture use.

Tertiary treatment of sewage effluent via pilot scale slow sand filtration

Abstract In view of limited information available about the performance of actual size slow sand filtration as a tertiary process in sewage treatment a pilot scale study was conducted over a period of one year using the secondary treated effluent from North Aramco Wastewater Treatment Plant, Dhahran, at a flow rate of 0.16 m hr‐1 (2L min‐1) to determine the process efficiency. Two sizes of local sand, i.e., effective size (ES) = 0.31, uniformity coefficient (UC) = 2.00; and ES = 0.56, UC = 1.64, were evaluated in terms of removal of major pollution parameters such as organic matter, micro‐organisms and nutrients. Effective range of the filter depth was also investigated by conducting the experiments at three different depths of the sand bed, i.e., 135, 105, and 55 cm for each size of the sand. It was found that removals of BOD, COD, standard plate counts, nitrate, phosphate and sulphate vary from 79–92%, 40–60%, 88–93%, 17–30%, 8.3–84%, and 5–10%, respectively, at various sand depths for two different siz...

Start‐up of sequencing batch reactors for toxic wastewater treatment

Abstract The start‐up of sequencing batch reactors (SBR) for the treatment of phenol‐bearing wastewater was achieved in about a week without any seeding, using the culture present in raw sewage only. The mixed liquor suspended solids (MLSS) concentration was grown to about 3000 mg/1 without showing any inhibition effects at phenol concentrations as high as 800 mg/1. The effluent concentrations of phenol were consistently less than 0.5 mg/1 during most of the start‐up phase. The response of the SBR to shock loadings of phenol at concentrations up to 1600 mg/I was favorable and over 75% phenol removal was maintained at a hydraulic retention time of 1 day.