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Combined flocculants with low ecological risk are urgently required in water supply and wastewater treatment in China. A novel flocculant was thus developed under the condition of low ecological risk (noted as CAS). The experiments to examine wastewater treatment performance of the new product showed that there was favourable performance in the flocculation process in contrast to commercial flocculants in treating kaolin suspensions, municipal effluent and domestic wastewater. Flocculation performance included the turbidity removal rate, sediment character and a decrease in COD (chemical oxygen demand). The sediment time of flocculation is short and the removal rate of turbidity treated by CAS is high compared with PAC (polyaluminum-chloride), PAM (polyacrylamide) and the combined addition of PAC and PAM. The optimal concentration required to affect flocculation processes is dependent on kaolin concentration and the character of the wastewater within the range examined. It also showed that CAS is effective to treat wastewater with high turbidity.
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PMID:Flocculation performance of a novel synthesized flocculant with low ecological risk. 1527 20

This study focuses on the practical application of high concentration powdered activated carbon coupled membrane bio-reactor to domestic wastewater reclamation. The study was conducted in three parts, such as analysis of secondary domestic wastewater effluent, design and operation parameter evaluation and reclaimed water quality estimation for stream restoration. The organic concentration was 25.2-80.2 mgCOD(Cr)/L for the effluent of three domestic wastewater treatment plants. Around 50-75% of the COD was low molecular substances less than 1,000 which were quite biodegradable. The sawdust PAC was estimated to be proper adsorbent for the organics in the secondary effluents. Its Freundlich constant, K value was 5.847 and 1/n, 0.36. Using a system consists of single reactor with high concentration PAC (80 g/L) and submerged hollow fiber MF membrane module with nominal pore size of 0.1 microm, design and operation parameters were obtained, such as HRT of the bioreactor (2.5 hr), PAC concentration (80 g/L), the initial flux (less than 0.5 m/day) and intermittent suction cycle (12 min. suction and 3 min. idling). Organic removal by the system was high enough to produce reclaimed water for urban stream restoration The effluent organic concentration was at the level of 2 mg/L in terms of TOC (around 5 mg/L as COD(Cr)). Substances with molecular weight cut off < 1,000 were removed mostly by adsorption and biodegradation. Those above 1,000 were rejected at PAC cake layer on the membrane and gradually degraded by microorganisms during extended contact.
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PMID:Domestic wastewater reclamation by submerged membrane bioreactor with high concentration powdered activated carbon for stream restoration. 1534 88

A study was conducted to examine the potential of jute processing waste (JPW) for the treatment of wastewater contaminated with dye and other organics generated from various activities associated with jute cultivation and fibre production. Adsorption studies in batch mode have been conducted using dye solution as an adsorbate and JPW as an adsorbent. A comparative adsorption study was made with standard adsorbents such as powdered and granular activated carbon (PAC and GAC, respectively). A maximum removal of 81.7% was obtained with methylene blue dye using JPW as compared to 61% using PAC and 40% using GAC under similar conditions. The adsorption potential of JPW was observed to be dependent on various parameters such as type of dye, initial dye concentration, pH and dosage of adsorbent. The batch sorption data conformed well to the Langmuir and Freundlich isotherms. However, lower BOD (33.3%) and COD (13.8%) removal from retting effluent was observed using JPW as compared to 75.6% BOD removal and 71.1% COD removal obtained with GAC.
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PMID:Use of jute processing wastes for treatment of wastewater contaminated with dye and other organics. 1608 72

This study focuses on comparing the performance of submerged membrane bioreactor (SMBR) and submerged membrane adsorption bioreactor (SMABR) over a period of 20 days at a hydraulic retention time (HRT) of 3.1h. The effects of PAC on critical flux and membrane fouling were also investigated. The SMABR exhibited better results in terms of mixed liquor suspended solids (MLSS) growth, DOC removal (over 96%), COD removal (over 95%), transmembrane pressure (TMP) and oxygen uptake rate. Nearly 100% of bacteria and 100% of total coliforms were removed in both systems. The addition of PAC could maintain the critical flux at a lower TMP value (7.5 kPa), while irreversible fouling caused by PAC occurred when the filtration flux exceeded critical flux.
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PMID:Comparison of the performance of submerged membrane bioreactor (SMBR) and submerged membrane adsorption bioreactor (SMABR). 1749 3

Catalytic thermal treatment (thermolysis) accompanied with coagulation was used for the removal of COD and color of composite wastewater from a cotton textile mill. CuSO4, FeSO4, FeCl3, CuO, ZnO and PAC were used as catalytic agents during thermolysis. Homogeneous copper sulphate at a mass loading of 6 kg/m3 was found to be the most active. Similarly during coagulation aluminum potassium sulphate [KAl(SO4)(2).16H2O] at a coagulant concentration of 5 kg/m3 was found to be the best among the other coagulants tested, namely, commercial alum, FeSO4, FeCl3 and PAC. During thermolysis, a reduction in COD and color of composite wastewater of about 77.9 and 92.85%, respectively, was observed at pH 12. Coagulation of fresh composite waste using aluminum potassium sulphate resulted in 88.62% COD reduction and 95.4% color reduction at pH 8. Coagulation of the supernatant obtained after treatment by catalytic thermolysis resulted in overall reduction of 97.3% COD and close to 100% color reductions at pH 8 at a lesser coagulant concentration of 3 kg/m3. The results reveal that the application of coagulation after thermolysis is most effective in removing nearly 100% of COD and color at a lower dose of coagulant. The sludge thus produced would contain lower inorganic mass coagulant and can be used as a solid fuel with high calorific value of about 16 MJ/kg, close to that of Indian coal.
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PMID:Treatment of composite wastewater of a cotton textile mill by thermolysis and coagulation. 1764 51

Research on the treatment efficiency and coagulation experiments was done using a new compound flocculation agent SE in printing and dyeing wastewater. Taking COD and chromaticity color as indexes, We did research on the coagulation efficiency under different condition of SE dosage, pH value, settling time, and agitation speed, and then we did comparative experiments between SE and PAC, SE and PFS. The experiments show that SE can effectively remove COD and chromaticity color. The four parameters namely pH of 8 - 10, settling of 30 min, agitation of 75 r/min and dosage of 155 mg/L were chosen, the COD and chromaticity color removal rate were recorded as high as 83% and 94% respectively, and the optimum effluent COD and chromaticity color were 155 mg/L and 37 respectively. Compared with PAC and PFS, SE produced bigger and more compact floc, settling time was shorter, the amount of mud and chemical dosage were less, and effluent quality was much better. The results show that SE is a high-effective and practical compound coagulant agent.
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PMID:[Experimental research on printing and dyeing wastewater treatment through new compound flocculation agent]. 1767 37

The particles from carwash wastewater were separated by a hollow fiber membrane aided by a enhanced coagulation and activated carbon. This study demonstrated that the addition of KMnO(4) to coagulant (PAC) could enhance the efficiency of coagulation, which helped reduce clogging of the ultrafiltration membrane and activated carbon. The existence of LAS can loosen the gel layer on the membrane and improve the flux. Adsorption of particles such as organic matter and oil is the main reason causing membrane flux decrease. When carwash wastewater was pretreated, the permeation flux of membrane showed a higher value. LAS, odour and colour are removed by GAC adsorption treatment at last. The COD, BOD, LAS and oil of reuse water was 33.4 mg/L, 4.8 mg/L, 0.06 mg/L and 0.95 mg/L, respectively.
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PMID:Reuse of carwash wastewater with hollow fiber membrane aided by enhanced coagulation and activated carbon treatments. 1807 86

Electrocoagulation with aluminum electrodes was used to treat the vegetable oil refinery wastewater (VORW) in a batch reactor. The effects of operating parameters such as pH, current density, PAC (poly aluminum chloride) dosage and Na(2)SO(4) dosage on the removal of organics and COD removal efficiency have been investigated. It has been shown that the removal efficiency of COD increased with the increasing applied current density and increasing PAC and Na(2)SO(4) dosage and the most effective removal capacity was achieved at the pH 7. The results indicate that electrocoagulation is very efficient and able to achieve 98.9% COD removal in 90 min at 35 mAcm(-2) with a specific electrical energy consumption of 42 kWh(kgCOD(removed))(-1). The effluent was very clear and its quality exceeded the direct discharge standard.
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PMID:Electrocoagulation of vegetable oil refinery wastewater using aluminum electrodes. 1822 28

Al2 (SO4), FeCl3, PAC and PAFC were used to coagulate the effluent of MSW incineration leachate after biochemical treatment, and mathematical models for COD removal were set up as well. The results show that COD removal rates are 20%, 17%, 30% and 40% respectively with addition of 500 mg x L(-1) Al2 (SO4)3, FeCl3, PAC and PAFC alone at pH 6. The < 2 000 fraction contains mainly dissolved organics from the leachate after biochemical treatment. Moreover, according to the analysis of Zeta potential and transmission electron microscope (TEM), the main mechanisms of the leachate coagulation can be explained as electrical neutralization, netting and bridging. As a matter of fact, compared to inorganic coagulants, the poly coagulants show higher capacity on these three functions.
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PMID:[Mechanism of coagulation treatment to leachate from MSW incineration]. 1829 Apr 85

A composite inorganic polymer coagulant, polyferric aluminum chloride (PFAC) was prepared by using hydrochloric pickle liquor and calcium aluminate as main materials. The optimum conditions for preparing PFAC with the hydrochloric pickle liquor and the calcium aluminate were studied. The coagulation performance of PFAC was investigated by studying the turbidity, COD, total phosphate (TP) and NH(3)-N removal efficiency in municipal sewage treatment. Results indicated that the effective composition, basicity (simplified as B, B=[OH]/(3[Fe(T)+Al(T)])x100%), coagulation performance and stability of PFAC were affected by calcium aluminate dosage, reaction time, reaction temperature and stabilizing agents. The COD and turbidity removal efficiency of PFAC was better than that of PFS and FeCl(3), and the TP and NH(3)-N removal efficiency of PFAC was much better than that of PFS, FeCl(3) and PAC. PFAC not only possessed a good coagulation performance, but also had good stability when stored.
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PMID:Characteristic of a novel composite inorganic polymer coagulant-PFAC prepared by hydrochloric pickle liquor. 1857 91


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