Recycling of wood chips and wheat dregs for sludge processing.

A Buchner filtration study was conducted to investigate the effect on sludge dewatering of adding organic waste solids (wood chips or wheat dregs) to sludge after chemical preconditioning (with ferric chloride or alum). Increasing the dose of wood chips or wheat dregs enhanced sludge filtration performance and increased the energy content of the filter cake, but did not consistently increase the total filtrate removed. The additional filtrate removal was found to balance the inert solids load only when the chemical preconditioner used did not result in sufficient coagulation of the sludge and the skeleton builder dose was low (< or = 90%). Accordingly, various dose ranges of wood chips and wheat dregs are suggested for different sludge management schemes.

Nutrient removal from polluted river water by using constructed wetlands.

The Erh-Ren River is one of the most polluted rivers in Taiwan. Although its flow rate is relatively low, the rate is still beyond the capacity of any traditional water treatment facility. A pilot-scale constructed wetland (CW) is the attempt used to purify the highly polluted river water and to collect data for the construction and operation of a full-scale system in the future. This article reports the results from this initial stage of our research work. During the study, the most efficient nutrient removal occurred between April and October. The monthly average removal rates of chemical oxygen demand (COD) ranged from 13-51% of ammonia-N (AN) from 78-100%, and of orthophosphate (OP) from 52-85%. After November, input COD levels increased, and the monthly average removal rates of ammonia-N dropped to 16% and of orthophosphate to 13%. The dramatic changes in removal efficiency suggest that the macrophytes in the CW had a direct influence on the water treatment and that the change of seasons and the quality of the river water inhibited the growth of the macrophytes.

Characterization of denitrification and nitrification in a step-feed alternating anoxic-oxic sequencing batch reactor.

This study was conducted to characterize the denitrification and nitrification in a bench-scale sequencing batch reactor operating with a three-stage, alternating anoxic-oxic sequence and step feed (SAOSBR) for treating synthetic wastewater. The results of long-term operation and dynamic studies showed that the SAOSBR increased the availability of organic matter in wastewater for exogenous denitrification in anoxic periods, and subsequently allowed nitrification to occur under a lower organic loading in oxic periods. Comparatively high kinetic rates of 1.2 to 6.6 mg nitrate/g mixed liquor suspended solids (MLSS) x h for denitrification and 1.0 to 2.8 mg nitrogen/g MLSS x h for nitrification were found in dynamic studies. With sufficient influent organics and alkalinity, complete denitrification and full nitrification could be achieved sequentially in the alternating anoxic and oxic periods, resulting in an average total nitrogen removal efficiency up to approximately 90%. Alkalinity recovery because of exogenous denitrification was experienced, and a minimum influent alkalinity to total Kjeldahl nitrogen (TKN) ratio of 2.4 was required to reach complete TKN removal. The pH value would be a better parameter other than oxidation-reduction potential or dissolved oxgyen to determine the completeness of nitrification and denitrification in the SAOSBR.

Using seafood waste as sludge conditioners.

In this study, three kinds of seafood wastes (shrimp shell particles, oyster shell particles, and internal bone particles of squid) were added to dewatered sludge preconditioned with chemical conditioner (alum or ferric chloride). The specific resistance of sludge dewatering was calculated to evaluate the effectiveness of sludge dewatering. The result showed that adding chemical conditioners alone caused noticeable pH decrease and resulted in a conditioned sludge with poor filterability. The addition of oyster shell or internal bone of squid to chemically preconditioned sludge efficiently improved sludge dewatering. This result was possibly due to both the availability of alkaline and the function as skeleton builder provided by these two waste solids. Particle sizes (0.59-2.0 mm) of oyster shell and internal bone of squid were found to have insignificant effect on sludge dewatering.

Studies of the inheritance of seed qualities and the exploitation of F2 heterosis in low gossypol strains in upland cotton.

Twenty cross combinations were made with 4 recessive glandless lines (gl2gl2 gl3gl3) used as females and 5 dominant glandless lines (Gl2eGl2e Gl3Gl3) used as male parents to estimate the genetic variance components of kernel oil and protein content of seeds, oil and protein index, and kernel index using a genetic model for parents, F2 and F3. The results showed that all the analyzed traits were mainly controlled by additive effects. Oil content was controlled mainly by maternal additive effect, and other traits by direct additive effect. The average heterosis of F2 over mid-parent based on population mean was -1.99% to 1.11% for all these traits. It suggests that little inbreeding depression exists for F2 and F3 seeds. There were 75% and 60% of the F2 and the F3 combinations in which open-pollinated seeds contained gossypol levels lower than 0.4 gkg-1. This result indicated that it is possible to screen and select high yielding F2 hybrids with a gossypol content lower than the regulated criterion and without lowering seed quality.

Enhancing the dewaterability and amenability of sludge for subsequent stabilization processes by using organic waste solids as conditioners.

Dual-material conditioning of sludge was evaluated using a chemical conditioner (either alum or ferric chloride), followed by a physical conditioner (either wood chips or wheat dregs). The combined effects of the conditioners on the dewaterability of the sludge with vacuum filtration and the amenability of the resulting sludge cake for subsequent stabilization processes were investigated. Results showed that the specific resistance of the conditioned sludge was effectively reduced when the dose of wood chips or wheat dregs was increased in each dual-material combination. From the results of analysis of solids in the cake, the filtered sludge cake with either wood chips or wheat dregs conditioning in higher dosage resulted in lower moisture and higher volatile combustible solids content. Accordingly, sludge conditioning with these two materials substantially increased the heating value of the dewatered sludge. In addition, wood chips are the most widely used bulking agent, and wheat dregs could be suitable to act as amendments in sludge composting. These results indicate that these two organic waste solids could replace a significant portion of the chemicals now used for sludge conditioning to improve the dewaterability of sludge and the amenability of the resulting sludge cake for incineration and composting processes.