Solidification/stabilization of Dewatered Sludge with Multi-Component Solidifying Agents

This work experimentally examined the optimal proportioning of sludge curing agent for dewatered sludge curing on solidified sludge,two components sludge curing agent consisted of cement and slag,and three components consisted of cement,slag and inorganic salt. The results showed that,increasing of curing ages could increase unconfined compressive strength and reduce moisture content for solidified sludge. For the test of two components,the biggest unconfined compressive strength of the solidified sludge achieved to 543. 72 kPa and the minimum moisture content achieved to 3. 56% of 21 d. The optimum proportion of the sludge curing agent of two components is sludge: cement: slag = 1 ∶ 0. 05 ∶ 0. 2 which selected by Design-expert. It could rapidly increasing the unconfined compressive strength of solidified sludge when added three components sludge curing agent( sludge: cement: slag: MgSO4= 1 ∶ 0. 05 ∶ 0. 2 ∶ 0. 03) on sludge curing. The results showed that,curing ages of 7 d,the unconfined compressive strength could achieve to 126. 74 kPa,which was more than 11 times comparison with the solidified sludge curing by two components curing agent. Two or three components sludge curing agent all could stabilize the heavy metals on solidified sludge and the leaching of heavy metals was below the government standard,while the stability of the heavy metals was superior for three components sludge curing agent.

Occurrence and discharge of pharmaceuticals and personal care products in dewatered sludge from WWTPs in Beijing and Shenzhen

This study mainly focused on the occurrence of pharmaceutical and personal care products(PPCPs)in sewage dewatered sludge and their discharges through sludge disposal from wastewater treatment plants(WWTPs).The data were obtained and calculated from seven PPCPs in dewatered sludge collected from 12WWTPs in two typical cities,Beijing and Shenzhen in China.Four of seven PPCPs,diclofenac acid,carbamazepine,mefenamic acid and N,N-diethyl-m-toluamide were detectable in dewatered sludge from Beijing and Shenzhen with concentration up to 4240,11,060,92 and 219μg/kg respectively.While,the other three compounds,trimethoprim,chloramphenicol and bezafibrate were not detected in collected samples from these two cities.The highest discharge of diclofenac acid and carbamazepine were 1023 g/d and 494 g/d respectively.In addition,the total discharge of these four detected PPCPs from each plant ranged from 5 to 1092 g/d in Beijing and 4e497 g/d in Shenzhen.Thus,PPCP discharge through sludge disposal cannot be neglected,and further research on transfer of PPCPs during sludge disposal onto agriculture land and influence of sludge application is required and essential.

Nitrogen removal from sludge dewatering effluent through anaerobic ammonia oxidation process

Anaerobic ammonia oxidation（Anammox） process is a novel and promising wastewater nitrogen removal process. The feasibility of transition of Anammox from denitrification and the performance of lab-scale Anammox biofilm reactor were investigated with sludge dewatering effluent. The results showed that Anammox process could be successfully started up after cultivation of denitrification biofilm and using it as inoculum. The transition of Anammox from denitrification was accomplished within 85 d. Anammox process was found suitable to remove ammonia from sludge dewatering effluent. The effluent ammonia concentration was detected to be 23.11 mgN/L at HRT of 28 h when influent ammonia concentration was fed 245 mgN/L, which was less than that for the national discharge standard Ⅱ （25 rngN/L） of China. Volumetric total nitrogen loading rate was up to 584.99 mg TN/（L. d） at HRT of 17 h, while influent concentrations were kept 243.25 mg NH4＊ -N/L and 288.31 mg NO2^- -N/L.

Application of organic polymeric flocculants in centrifugal dewa-tering of oil refinery sludge

In order to evaluate the applicability of the organic polymeric flocculants(OPF) in the treatment of oil refinery sludge, experiments were conducted to show that OPF have better performance of flocculation than inorganic flocculants. Both the anionic and cationic OPF have satisfactory flocculation efficiency in oil sludge treatment, but the latter are more cost efficient. Among the over 20 types of flocculants tested, 2 OPF(CPAM 2 and HPAM 2) were selected as the treatment agents, based on their good treatment performances, oil resistance and economic feasibility. It was demonstrated in the industrial scale centrifugal dewatering experiments that the application of either CPAM 2 or HPAM 2 could achieve high treatment efficiency of the oil sludge dewatering and reduce the COD of centrifugal liquid to less than 1000 mg/L.

Solidification Efficiency and Mechanism of Conventional Curing Agents for Sewage Sludge Stabilization and Dewatering

One of the challenges faced by sewage sludge treatment and disposal is its higher water content,and how to efficient dewater those hazardous materials properly is welcome in practice. This study stabilized the sewage sludge via the using of conventional curing agents and calcined aluminum salts,and the corresponding dewatering mechanisms and structural changes of the stabilized sludge were further comparable analyzed.Experimental results showed that wollastonite and kaolin exhibit a relative higher dewatering efficiency as compared to other conventional curing agents; however the releasing rate of heavy metals of Cu,Cr,Ni for kaolin solidification and Zn,Pb for wollastonite solidification is higher than the sludge samples solidified by other curing agents. For comparison,the sludge samples solidified by calcined aluminum salts (AS),calcium ash,Mg-based curing agent,tricalcium aluminate( C_3A) show a lower heavy metals leaching potential and unconfined compressive strength. In addition,the economic characteristics and local availability of AS,calcium ash,C_3A and CaO makes it have a broad prospect in extension and application. These findings are of great significance for stabilization and dewatering of sewage sludge.

Enhanced dewaterability of waste activated sludge by UV assisted ZVI-PDS oxidation

Ultraviolet(UV)assisted zero-valent iron(ZVI)-activated sodium persulfate(PDS)oxidation(UV-ZVI-PDS)was used to treat waste activated sludge(WAS)in this study.The dewaterability performance and mechanism of WAS dewatering were analyzed.The results showed that UV-ZVI-PDS can obtain better sludge dewatering performance in a wide pH range(2.0-8.0).When the molar ratio of ZVI/PDS was 0.6,UV was 254nm,PDS dosage was 200 mg/g TS(total solid),pH was 6.54,reaction time was 20 min,the CST(capillary suction time)and SRF(specific resistance to filtration)were decreased by 64.0%and 78.2%,respectively.The molar ratio of ZVI/PDS used in this paper is much lower than that of literatures,and the contents of total Fe and Fe^(2+) in sludge supernatant remained at a low level,as 3.7 mg/L and 0.0 mg/L.The analysis of extracellular polymeric substances(EPS),scanning electron microscope(SEM)and particle size distribution showed that the EPS could be effectively destroyed by UV-ZVI-PDS,the sludge flocs broken down into smaller particles,cracks and holes appeared,and then the bound water was released.At the same time,the highly hydrophilic tightly bound-EPS(TB-EPS)were converted into loosely bound EPS(LB-EPS)and soluble EPS(S-EPS).During sludge pretreated by UV-ZVI-PDS,positively charged ions,such as Fe^(2+),Fe^(3+) and H^(+),produced in the reaction system could reduce the electronegativity of sludge surface,promote sludge particles aggregation,and then enhanced the sludge dewaterability.

Systematic assessment of dredged sludge dewaterability improvement with different organic polymers based on analytic hierarchy process

Organic polymeric flocculants are commonly used in improving dredged sludge dewaterability, but less attention has been paid to residual water quality. In this paper, the effects of cationic etherified starch(CS) and poly-dimethyl diallyl ammonium chloride(PDDA) on dredged sludge dewatering efficiency and residual water quality of Baiyangdian lake were comprehensively investigated and evaluated by analytic hierarchy process(AHP). The results indicated that PDDA had stronger electrical effect and flocculation performance compared with CS, resulting in more efficient dewatering performance. PDDA can reduce the pollutants of discharged residual water, while CS significantly promoted the increase of NH_(4)^(+)-N and NO_(3)^(–)-N in the residual water. The increase of NH_(4)^(+)-N in the residual water of CS was due to the release of dredged sludge, while the increase of NO_(3)^(-)-N was introduced by CS leaching. AHP showed that PDDA performed better in flocculation treatment of dredged sludge than other organic polymers. This work provides a method for optimization of flocculation treatment for dredged sludge dewaterability.

Effect of vacuum degree and aeration rate on sludge dewatering behavior with the aeration-vacuum method

Due to large-scale dredging operations, a large amount of sludge is inevitably produced. Large areas of land are occupied when the dredged sludge is discarded in the disposal site as waste material. The sludge dewatering with aeration-vacuum (SDAV) method is suit for treating the sludge with high water content and high clay content in the disposal site. The water in the sludge can be discharged out. The volume of the sludge can be reduced quickly, and the recycling of the land can be accelerated by this method. Most importantly, this technique is an efficient way to deal with clogging problems when pumping water from high water content, high clay content dredged sludge. Vacuum degree range tests, the aeration rate range tests, and the influencing factors of sludge dewatering behavior tests were conducted with a self-developed SDAV model test device. Sludge samples were taken from the South-to-North Water Diversion East Line Project in Huai’an White-Horse Lake disposal site, Jiangsu Province, China. The optimal range of vacuum degree and aeration rate were obtained through the test results, and the mechanisms for how the two factors work and how they affect the sludge dewatering behavior were analyzed. The suitable vacuum degree range in SDAV is below 50 kPa, and the suitable aeration rate is about 1.0 m3/h. The low-vacuum degree contributes to reduce the ad-sorption effect of micro-channels on soil particles in filter material and to maintain the arch structures. Aeration has the effects of expansion, disturbance, changing Reynolds number, and dynamic sieve separating. The pump quantity of water per meter of filter tube (m) has different change rules as the vacuum degree changes under different aeration rates. The reason is that the formed arch structures’ conformation and permeability differ greatly under different combined-conditions of vacuum degree and aeration rate. The optimal combined-condition for dewatering the sludge is 35 kPa with 1.0 m3/h.

Novel cationic polyamidine:Synthesis,characterization,and sludge dewatering performance

In this study,a new and facile route was employed for synthesis of polyamidine with abundant cations and attractive five-membered ringlike structural unit.N-vinylformamide and acrylonitrile copolymerized firstly to form intermediates,and the intermediates were processed with hydrochloric acid to produce polyamidine.A series of polymerization conditions（e.g.polymerization time,temperature and dosage of initiator） were optimized through productivity,viscosity and cationic degree as evaluation.SEM analysis illustrated that the amidinization process could reduce the size of spaces between molecular and created compact structure,which would contribute to good flocculation performance and high viscosity.FT-IR,XPS and NMR spectra presented a rather clear structure of polyamidine.34.3%of sludge was sedimentated through the flocculation of polyamidine in the early stages.In contrast,only 6.8%of sludge was sedimentated by polyacrylamide.The moisture content in dehydrated floc could be reduced to 77.7%when 60 mg/L polyamidine was added.These results demonstrated that the polyamidine showed a great potential in the practical application of sludge dewatering.

Optimized production of a novel bioflocculant M-C11 by Klebsiella sp. and its application in sludge dewatering

The optimized production of a novel bioflocculant M-C11 produced by Klebsiella sp. and its application in sludge dewatering were investigated. The optimal medium carbon source,nitrogen source, metal ion, initial pH and culture temperature for the bioflocculant production were glucose, NaNO3, MgSO4, and pH 7.0 and 25°C, respectively. A compositional analysis indicated that the purified M-C11 consisted of 91.2% sugar, 4.6% protein and 3.9% nucleic acids（m/m）. A Fourier transform infrared spectrum confirmed the presence of carboxyl, hydroxyl,methoxyl and amino groups. The microbial flocculant exhibited excellent pH and thermal stability in a kaolin suspension over a pH range of 4.0 to 8.0 and a temperature range of 20 to 60°C.The optimum bioflocculating activity was observed as 92.37% for 2.56 mL M-C11 and 0.37 g/L CaCl2 dosages using response surface methodology. The sludge resistance in filtration（SRF）decreased from 11.6 × 1012 to 4.7 × 1012m/kg, which indicated that the sludge dewaterability was remarkably enhanced by the bioflocculant conditioning. The sludge dewatering performance conditioned by M-C11 was more efficient than that of inorganic flocculating reagents,such as aluminum sulfate and polymeric aluminum chloride. The bioflocculant has advantages over traditional sludge conditioners due to its lower cost, benign biodegradability and negligible secondary pollution. In addition, the bioflocculant was favorably adapted to the specific sludge pH and salinity.

Techno-economic analysis of sidestream ammonia removal technologies:Biological options versus thermal stripping

Over the past twenty years,various commercial technologies have been deployed to remove ammonia(NH4eN)from anaerobic digestion(AD)liquors.In recent years many anaerobic digesters have been upgraded to include a pre-treatment,such as the thermal hydrolysis process(THP),to produce more biogas,increasing NH4eN concentrations in the liquors are costly to treat.This study provides a comparative techno-economic assessment of sidestream technologies to remove NH4eN from conventional AD and THP/AD dewatering liquors:a deammonification continuous stirred tank reactor(PNA),a nitrification/denitrification sequencing batch reactor(SBR)and thermal ammonia stripping process with an ammonia scrubber(STRIP).The SBR and PNA were based on full-scale data,whereas the STRIP was designed using a computational approach to achieve NH4eN removals of 90e95%.The PNA presented the lowest whole-life cost(WLC)over 40 years,with£7.7 M,while the STRIP had a WLC of£43.9 M.This study identified that THP dewatering liquors,and thus a higher ammonia load,can lead to a 1.5e3.0 times increase in operational expenditure with the PNA and the SBR.Furthermore,this study highlighted that deammonification is a capable and cost-effective nitrogen removal technology.Processes like the STRIP respond to current pressures faced by the water industry on ammonia recovery together with targets to reduce nitrous oxide emissions.Nevertheless,ammonia striping-based processes must further be demonstrated in WWTPs and WLC reduced to grant their wide implementation and replace existing technologies.